N79FT A Skybolt Story
|On:||Jul 03, 2015|
|Tags:||9891U, mechanicing, fiberglass|
In the past 7 months I have been busy building... the crib for the baby. Almost non stop evenings, 4-6 hours a day: the result is good, but this is a "Skybolt Story", not a "Bed Story": so no, I won't post all my projects here :).
Also, it seems like next 2-3 years will be mostly furniture building for this guy.. Oh well.
Meanwhile, I was able to put in a few hours into fixing up the coves in my wingtips where all the lights are.
If you recall, I have made strobe shields quite a while back, but I haven't fixed up the coves. I was waiting for the shields to be painted.
Well, they were during the cgr-30 install, and then I was working on the crib.. So finally, the time has come.
Look at what I had to start with.
Sad sad wingtip
Another sad wingtip
First, all the lights came out. The old plastic lenses went straight into the trash bin. Then, came off the foam padding that goes in between the lens and the wingtip.
All opened up
Cleaned and sanded
I think the above was about an hour of sanding. All old paint came off. Also, the broken rivnut went out (did you notice it? That extra hole was what someone has drilled and used a sheet metal screw to "fix" it instead of drilling out the broken rivnut).
Finally, masked with the first set of masking tape. I was set to repaint the coves.
Masking the edges
The other wingtip was even worse. The cove itself had a huge "dip" in it. Also, some "genius" decided to screw #10 screws straight into the fiberglass... Some threads were all torn up, and I decided to install rivnuts all around to make sure the tips match.
Just disassembled, note the large dip in the nav light area
In with Bondo! Lots of sanding! Oh man, I hate sanding...
Bondo, and sanding...
Phew. Quick fit of the strobe shields over the rivnuts, needed to enlarge the holes...
Fitting holes in the strobe shield
And we're ready with the second one.
Now, I wanted to clean up the nav lights housing as well. Originally I wanted to paint both cover and base, but once I cleaned up the base, I decided to leave it as is: apparently, it was nice and shiny after all that 40 year old corrosion cleaned off of it!
Nav lights covers. Second one was cleaned up as well
Cleaning nav lights bases. Shiny!
Came out nice after painting!
Then, final masking, and painting. Damn! That didn't go so well. I didn't notice a fairly small dip in the other tip's cove, and the Bondo'd one got some pinholes. Time was running very short so I ended up leaving that as is.
Right wingtip cove, painted. See the dip now?
Left tip. That one with pinholes :(
Once the paint was all dry came the time for fitting the foam padding and lenses. And here, I made a fatal mistake: I have installed the padding first. That makes fitting of the lens virtually impossible (at least, for me).
That had produced an unsightly gap of about 1/8 inches. Oh god! I had no spare lenses, and I had to put the plane back together not to screw my partner who needed the plane soon. Very soon.
... I ended up screwing him anyway 'cause somewhere in the middle of me fitting that first lens Max was born and I was knocked out for 5 days ...
... just in case you're wondering: 7lbs 11oz, 20 inches, June 25, 2015, 10:35 am ...
... I still haven't had any chance to get another lens, so I decided to put it back together as is as a memory of me being stupid. Maybe I'll buy another set from Ken in another year or two; and also fix all the dips and pinholes ...
Fitting the foam padding
Fitting the foam padding (back side)
Top/front lens fitting
Bottom seams: see the unsightly gap?
I was much smarter with the other lens, and made sure to fit it before I put on the foam padding, and it came out perfect.
Fitting other lens. See no padding?
Padding on: and some holes in, too
The other side
Then, I've put the lights back in, permanently screwed on the lenses, and I was done!
Installing the nav light base
Much nicer than before, but with some problems. Still, much nicer than before.
Till next time (which-I-dont-know-when-will-come)!
|On:||Dec 10, 2014|
I'm done with my longest airplane project so far! No, it's not for the Skybolt, it's for my Cheetah. But it's an important one and was a great fun to tackle.
So, without further adieu...
The Cheetah never had an engine analyzer -- and I elected to get one, full blown, replacing all the standard engine gauges. I ended up picking the EI's CGR-30P because of it's roundness, compactness, and me generally liking EI a lot.
So, late August, it was Christmas. I got the box, that had a lot of boxes, with boxes, and boxes inside -- lots of stuff. Probes, aggregator box, wires...
First thing I did was put everything together on my dining table, just to make sure I understand the wire-up and that it works. I have even blown into the fuel transducer and was satisfied seeing it registering some "flow".
On the bench
And then, the install. The problem was, I also wanted to fly in between, so I had to plan the install in stages and make sure the airplane's flyable in between.
First thing was running two out of three wire harnesses thru the firewall (all temp probes, and all pressure and flow transducers). I found a spot on the inside of the firewall for the box, and made sure I had enough length to run to the "aggregator" box.
Reused existing hole, new grommet
Wires bundled neatly for running thru
All wires are thru
.. and neatly tucked away
The hole with the wire harness sealed
I was planning to fly out to friend's hangar and work on the probes install there. The luck did not cooperate -- very sluggish pull-thru on the engine start and heavy discharge right after on the ammeter hinted at the alternator failure.
Sure enough, it was. I ended up unbuttoning the cowl at the FBO I was hangaring at.
That day, since the cowl was off and out of the way, I decided to continue and wire up as many probes as I could.
The CHT probes, lubed with anti-seize
The EGT and CHT probes on one side
Probes on the other side
Then, came the time of connecting the probes to harnesses. As you saw on the pictures, probes have dinky little wires that aren't protected in any way. I asked EI if I should special-treat them in any way and they said no, but I still decided to get some fiberglass firesleeving from Grainger, and tucked them neatly away. Liked this much better!
Connecting the probes. Notice the barrel connectors staggered, and fire sleeve
Sleeved and tucked away.
Sun was setting down at that time, and I called it a day.
We replaced the alternator in the field, but I kept the cowl open to wire up the rest of the probes.
Installing and wiring more probes
I decided to install pressure transducers on the engine mount tubes using clamps, to keep them close to the engine outlets and hose lengths to the minimum. Consulted with EI again, and they said that's an okay idea.
Oil pressure transducer
Oil pressure transducer wire-up
Fuel pressure transducer
Fuel pressure transducer wire-up
That was it. I didn't install the fuel flow transducer yet.
Next, came closing that cowling, and a big break due to weather, travel, and life....
This time it was a day to install the "aggregator box". All the probes feed into it, and there's a single wire that connects the box to the display of the engine monitor.
I didn't know what the exact length of the screws to mount it would be, so I decided to buy a bunch of different ones. Didn't have any way to measure the firewall thickness.
All that hardware
First hole in the firewall
The "aggregator box" installed
That was a short day 'cause I had some things to take care of in the evening.
So finally, it was time for a bunch of work behind the panel. Before then though, I decided to make a little panel insert that will hold the annunciator LEDs, the USB port, and the display dimmer.
As usual, played with the layout in Solid Works before I liked it. Decided on a 2 inch hole and fiddled with locations until I was happy. And then, used the final drawing as a template!
Painted. Also painted the panel covers
I also painted the panel covers that I took so long to figure out how to make.
Finally, back to the hangar! This session took 2 days actually :). It was the time to install, wire up, re-position all the gauges on the panel, and such.
The old CHT, EGT and hobbs were to go. Clock was to be relocated to the position it's visible at (it was right under the panel eyebrow before). Davtron OAT/PALT/DALT/Volts gauge was to be relocated to another spot in the panel to free up space for CGR-30 auxiliary panel I made in the previous session. And, most of wireup had to be done. Harnesses connected to the box, ran to the display, and power.
Box installed on the firewall, with harnesses coming in
Behind the panel, sometime in the middle
Ring terminals for power
Auxiliary panel installed
P-leads connected to mag inputs
And then, it was time for the first checkout.
I pull the plane out of the hangar, and hook the rest of things up with test leads.
Turn the enigne on, and observe!
We're on! Oh, wait...
You see the problem? Yes, right mag is dead! Oh, and the old tach (I had one of those fancy Horizon P1000's that tells you if a mag is dead) is showing everything's okay. And, the engine starts doing this rattle sound, and quits. WTF?!
Thoughts about grounding something I shouldn't have grounded (ie, a plead) cross my mind. Then, thoughts about a loose screw somewhere next to the ignition switch crosses my mind.
I re-try. Same thing. Engine starts, runs a few seconds, and dies off. WHAAA??!
... I decide to go take a bathroom break. On the way back, another thought crosses my mind.... I get back, practically running, get into the plane - and sure enough! Fuel selector is "off". I switched it off the day before, before getting behind the panel. Just in case :) Phew.
The "right mag" problem doesn't go away though. I start diagnosing -- touching input wires to different pegs on the ignition key -- no matter which mag it is, "left" is okay and "right" is dead. Uneasy thoughts about a dead wire in the harness and having to undo the whole thing start crowding me... But, I decide to dig a bit deeper. Success!
Can you spot the problem?
Left mag RPM raw signal value
Right mag RPM raw signal value
Bingo! A call to EI, and a quick configuration update fixed that one.
It was that time to go to Fletcher's and continue working on it there. Plus, my new wheelpants were ready!
Before I went though, I had to make one last missing bit. A bracket for the ammeter shunt. Did that at the home shop; and did it in a couple different widths to see which one fits better. That bracket was supposed to plug the hole left after old engine gauges removal, and hold the shunt.
By the way, I decided to wire the shunt into the battery leads. First of all, that's how Grummans are wired by default; and second, it actually shows you the actual discharge when you're on battery -- a good thing! It doesn't show the true load when charging the battery though -- just the charge current. That's okay though, as long as charge current remains positive I know my alt is okay.
Two shunt plates
With the shunt
My makeshift paintbooth for painting these little boys
All that bending, sanding, filing, and drilling took about a couple hours in the shop.
Onward - to Fletcher's!
We've measured lengths for all the new hoses; and decided to change all of them -- mine were manufactured 15 years ago. Also, found a small oil cooler leak, and decided to replace that bad boy. Oh, and I was finishing up behind the panel while David's guys were working on fitting and trimming my wheelpants.
I took out all the gauges, unwired everything that was to be removed, and installed the shunt... Then, it was time to call that a day since Clayton was supposed to fly me back, and I didn't want to make him go back after dark.
Shunt attached to the bracket
Installed. The bracket replaced old engine gauges.
Shot from behind the panel
I drove up to Fletcher's to finish up some more work behind the panel.
My new wheelpants, all painted!
Oil temp probe installed and safetied
Display installed on it's final place
Starting to wire up the shunt
When trying to do the shunt, I realized that I didn't have the right size terminals, and the big enough crimper... Oh well, left that over to another day
Final panel, with CGR and all the holes plugged
All holes left after oil and fuel lines removal patched
Also that day, I felt a blast and wanted to do more -- so decided to do the last finishing touch and clean up the oxidation off of my mixture knob. Acetone, baby!
Last one! I arrived about a week later, to find the pants installed, oil cooler installed, and all hoses hooked up. John also hooked up the fuel flow transducer. And I made sure to have that crimper and right size ring terminals.
Battery wire ring terminal crimp
Shunt wired up
After that, we decided to temporarily hook up the cowling, and do the weight and balance, the right way. Too many changes. New oil cooler, new wheelpants, new gauge.. Plus, I know this particular airplane was never weighted at the factory, so why not.
Speak of unusual attitudes! One wheel on the scales.
And another. "Pull up, Jimmy!"
On scales. Leveling.
... and then, it was the moment of truth, sort of. Final checkup. Rolled her out of the shop, fired up, and...
Shutdown.. checked all hoses -- a little drop of the oil on the oil cooler inlet. John said there was some oil in the hose, to wipe out, and try again.
Did just that. Fired up, and.. fuel pressure shows 0. "Oh shit!"... You guessed, right? Fuel switched off, again! Damn, that thing actually works!
I suppose I have to give some final thoughts.
Here's what I like about the gauge:
Here's what I didn't like:
Overall, I love it. Great gauge, and I will be putting that on the Skybolt! :)
|On:||Nov 23, 2014|
|Tags:||CAD, lower wings, ailerons, ribs|
No posts about the Skybolt doesn't mean that there was nothing done :). Yessir!
I was redrawing pretty much everything I did in the first few months of modeling the lower wing; and that ate up a bunch of time and didn't actually produce anything to show. But damn, did it suck up time!
I ended up re-doing:
Especially with ribs, the problem was that I did them while learning SolidWorks -- which led me to sketching them in AutoCad first (I used to hate doing curves in SWX.. now I hate Autocad, but that's another story :)). That made them virtually un-tweakable; and "tweaking" the verticals, which I had to do after confirming drag wire interference, proved to be virtually impossible.
So, I decided to clean it all up. Oh yeah, and I have moved that interfering vertical.
The brand-spanking new set of ribs:
Master sketch, off of which everything else was derived
Butt Wing Rib
Typical Wing Rib
One of the many sketches that go into a rib
Rrriiibbzzz!! Oh, wait...
And then, only then, I could go on to finishing the tip rib and the aileron tip rib.
For tip rib, I used the positioned tip bow to project the cuts onto the surface of the nose block. I'll explain this technique in a bit with aileron as illustration.
Tip rib, with all the cuts that will match the bow perfectly
Tip, and other ribs, on the spars, and tip bow
And then there's the aileron, it's bow, and tip rib.
I started with a "placeholder" that was the inboard (full size) butt rib. Then, using the tip bow, I drew a couple of "guide curves" and projected it on a couple planes, corresponding to ribs, giving me two different profiles.
Projections, and helpers
Guide curve and loft profile
Then, I set up my loft, and voila!
After that, I drew the butt rib. In the previous post, I said that it is supposed to be a touch larger profile than the tip wing rib; but that ended up not being the case -- in fact, it's a touch smaller and somewhat "hides" in the aileron well area. I decided not to mess with that...
Tip rib sketch, derived from the "regular" rib, and the tip bow "intersecting" with it
Aileron tip rib model
And here it is, in all it's glory, with the bow, tip rib, with everything matching perfectly. Note how the tip bow of the aileron changes shape along it's length -- that will be a hard one to hand-shape when making it...
Aileron on the wing
|On:||Oct 24, 2014|
|Tags:||9891U, mechanicing, sheet metal|
No Skybolt news, you say?
Well, with dead alternator, tons of work, and unfinished install of a gauge that is supposed to keep you informed about your engine, not much time for the Bolt.
I love to fly at night. It's just something out of a different world, something... else.
There are a few things that are extremely important at night. Most importantly, the old "See and be seen" rule.
To be seen, you need blinking lights on your airplane, nav lights, ideally a landing light, and such.
To see, you need to retain your night vision. That means, no bright white or any color light besides something like red or blue. Otherwise, your eyes readjust for "daylight", and you are at good odds of not seeing other blinking lights... like the ones on an airplane you might fly into!
You see, I don't have strobe shields on my plane. Take a look at the picture below, and imagine you sitting in the cabin.
Strobe Shields on a Grumman
You see that vertical little metal "fin" I circled? That's what blocks you from seeing the strobe - a bright flashing white light. If that metal fin is not there, you basically get blinded every second or so.
It's so bad I ended up flying with strobes turned off a couple times I was up after dark. I figured, just one beacon on the tail and no strobes is better than a blind pilot.
And especially now, when the weather in Texas is so nice and night flying is just calling and calling and calling, that became a priority project.
So, on to it!
Those shields go under the wing tip light cluster lens, and the spot they're supposed to go into is curved. Shields themselves are nothing but a curved L - angle out of aluminum.
So, I needed a stretcher.
Prepared one of the wingtips:
Wingtip light cluster with the spot where the shield goes cleaned up.
First, I decided to make a test piece to get some practice. Never used a stretcher before.
We start with a simple L-angle. I used 6061-T4, 0.025 thick.
And then, stretch-check-stretch-check... Not bad at all. Just takes time.
Close enough for a prototype.
You can see on the pictures that the stretcher leaves pretty deep "scratches". On the prototype, I tried sanding them out -- only to get my metal turn paper thin.
On the real one, I decided to fill them up with Bondo.
So, bought some, and made myself a pattern too -- which I printed full size.
To do that, asked Adam, the guy who bought my 28797's share (thanks again, man!) to take some pictures of strobe shield on his Tiger.
And then, just drew around it in Solid Works. Turned out nice.
Sketching around the photo in SWX.
Note the tape measure above -- I first drew a line 6 inches long and scaled the photo until that line matched 6 inches on the tape measure. This way I ensured proper scale.
SolidWorks part for the Strobe Shield
Drawing of the part for the patterns.
So with those patterns printed out, I went to town.
First thing I noticed is that curvature on the wingtip I was working on doesn't match the pattern :). Of course. They're all different (and by the way, on the other wingtip it matched perfectly. Go figure.). I wanted the pattern to primarily get the general shape right.
So, here I am stretching my L shaped angle, and... SNAP!
So now, bend another L angle, deburr, clean up, size... sigh.. I went much much slower...
I think, getting it perfect took around 3 hours of careful work. That curve gets aggressive towards the end. And, when I was almost done.. snap! I tore it up again, this time the very tip.
Luckily, it actually still was long enough (I started with a piece longer than necessary), so I was able to get away with this tear. Phew.
Cut to about the right size
Next, came a lot of sanding, filing, and emery-clothing to get it to the right shape. And then, the holes.
Those had to be duplicated and match up with the existing holes in the wingtip, so I made a simple hole duplicator. No, I'm not paying 10 bucks for that thing!
Homemade Hole Duplicator
And, we have the holes.
Finally, I filled all the scratch marks with Bondo, sanded it down, and called it a nite. I think it was around 3 am then :).
Next day, the other wingtip.
Notice that this one has rivnuts and not just holes. I now have a theory why this plane is missing strobe shields.
I think the guy who tore all the threads in the fiberglass wingtip and installed those rivnuts (remember, the other one doesn't have them?), was too lazy and didn't want to tweak the holes in the strobe shields to match with the rivnuts. That's my guess.
Initially, I thought about making oversized holes in the shield, but that would put one of them too close to the edge. Then, I tried filing the rivnut down a bit, but decided that I'm not gaining much there, and that notching the strobe shield base would be best. That's what I ended up doing.
I made just the first notch, and to stretching it was!
When it was close to the other rivnut, I notched area around it.
Secont Notch - close!
They came out perfect.
And then, tons of filing, shaping, sanding, Bondoing, sanding, washing, and...
They're not quite complete yet. I'll have to clean up the rest of black tape from under the wingtip lenses and replace them with new ones, but that'll come after painting the shields. I'll ask Dave Fletcher to paint them into the same Imron he's gonna use for the (now soon to come) wheelpants.
And you know what.. that was fun!
|On:||Oct 07, 2014|
No posts for 1 month and 5 days! Holy cow.
That's all been eaten up by a couple projects. One of them ended up being a complete redraw of all airfoil sections on the lower wings on the Skybolt; and nothing to write about (no pretty pictures, very routine work). Just lots and lots of cleanup.
Another one... was me following an old Russian tradition.
You see, during long winter months Russians' desire for fruit and vegetables (and mushrooms) is satisfied with pickled everything. Cucumbers, tomatoes, cabbage, grape leaves, dill (!), apples, garlic, fish (haha :) ), and other things which I don't know English words for.
My genes are calling. It's fall, and I had to pickle me something.
It was.. a disassembled Lycoming for the Skybolt!
Some weeks ago, a gentleman posted on the Forum about him selling an O-360-A4M, all overhauled, yellowtagged, and such, by Superior; with higher compression pistons from ECI, with everything needed to put it together minus the sump and accessories, for a very attractive price.
Best part was, it was disassembled, so I am to get all the fun putting it together without the disassembling and sending parts out for overhaul (and well, paying for that too :)).
In short, it was a great deal.
The problem? Well, I will not need it for quite a while. 10 years maybe, if I go with the speed I'm currently going at.
I figured, assembling and pickling it after would be a bad proposition. A much better one would be to pickle it part by part.
As usual, started with a thread on the Biplane Forum.
At the end of the day, I ended up using three things.
Phillips 20W-50 Anti-Rust Pickling Oil
Good' Ol' STP
Cortec CorrShield VpCI-368
This latter substance is amazing. It's mineral spirits soluble, moisture displacing spray-on stuff that can protect up to 2 years in outside (!!!) storage. I'm storing the engine parts inside my house, so I figured it will do very good for a much bigger number of years.
It sprays on, and then dries over a couple days to consistency of candlewax. A bit sticky, but very tough. They claim it's scratch resistant.
Just in case I missed something or ended up scratching it off; I decided to also put a thick layer of Aeroshell grease on everything that's covered with CorrShield. Just in case.
It showed up!
For smaller pieces, I first wanted to put them in sealed sandwich bags, with some STP / Oil 50-50 mix, and squeeze all the air out.
New connecting rod
Now in the baggie with STP/Oil Mix
Gears and bits
.. all bagged up
But after them sitting like that for a couple days, I didn't like how all the oil drained to the bottom of the baggies. So instead, I submerged everything in 2 oil/STP baths.
Piston pins, gears, rocker arms, misc accessory case things in oil/STP bath
Pushrods, piston rings, tappets, etc in oil/STP bath
At this point, I ran out of oil and STP... And I had too much of CorrShield and grease -- and, after playing for some time with CorrShield and seeing how tough it is, I decided to use it on everything that didn't get into oil baths; even on smaller parts.
One of the jugs
Jugs, right side up and tops CorrShielded and greased.
Some more small pieces stored "dry", covered in CorrShield and grease.
Thru studs and pushrod tubes
Bearings, oil pump housing and minor pieces
This project took a couple weeks worth of evenings; and now my inner Russian is completely satisfied with his stash of pickles!
|On:||Sep 03, 2014|
|Tags:||sheet metal, cgr30, mechanicing, 9891U|
So on the Cheetah side, I am slowly ramping up for replacing all the engine gauges that I currently have on the panel with the CGR-30. I got it at Oshkosh, and finally, the box arrived a couple weeks ago.
Ain't she a beauty? Assembled on the bench for testing and familiarizing myself with it :)
Ain't she a beauty?
Because of it, I will lose a few 2 1/4 inch round gauges, and I decided to make some covers for the panel, not to have unsightly holes in it.
Of course I could've bought them from Spruce or whatever, 5 bucks a pop, but if you know me, I would rather spend hours making something I can make. Besides, this is a nice first sheet metal exercise :). And, I wanted a nice domed bulge on each one of them. Just Flat wasn't enough.
So, I got to it.
First iteration was making a jig that would sandwich the sheet between two boards, with holes over and under the metal. Then, I would press a "piston" thru the holes using my vice as a press. Pictures are better than a thousand words.
Three piece jig + soon-to-be-'piston'. Oak boards sandwich the sheet between them. Ply plate has the "piston" and is used as a backing plate for it.
That didn't work out. Vice jaws are not perfectly parallel, and the "piston" is not exactly the same diameter as the holes -- so it gets misaligned, even though there are four guiding bolts in the corners... Here's the jig assembled, and one of the first tries.
I think I tried it two or three times, with the same result.. no matter how much I tried to align the "piston", it would make a bit more pressure on one side of the jig than on the other, either resulting in a tear, or in an uneven "bulge".
Out of desperation, I took a piece of metal, laid it over one of the holes in the oak jig board, and started banging away - and was surprised! I was getting almost what I wanted, just not clean enough.
I tried sandwiching the metal between two plates and banging via the top hole - and made a fairly nice bulge! The edges weren't very clean, but I reasoned that if I opened the top hole up a bit more, that would give me access to the edge, and I will be able to bang on the edge a bit more, defining it better.
Ha! No. Same stuff.. I was able to make a fairly nice bulge, but the edge will be all "torn" and ugly.
Bulge is there, but the edge is god awful
I also tried putting a profile on the bottom, "die" plate of the jig, with a very sharp edge and curvature under it.
No luck. I think I spent a couple hours, making over ten "bulges" and trying different hammering techniques...
All those tries.
The Two Hammers
So I gave up, and emailed Bill Rose, the gentleman who gave me all the SolidWorks parts for standard HW, and, in general, helps me a bunch with my silly SWX and other questions, for advice.
Bill suggested using MDF for the jig instead of oak. Apparently, irregularities in wood grain would make it hard to define the edges uniformely. He also suggested using corking tools akin a big "chisel" on the edges to better define them.
..and.. it worked!
The third jig is ugly, but it works. Upper hole is enlarged just to get access to the edges (I didn't bother making the top hole concentric with the bottom or even round; there was no need).
The third jig
I used the two-headed plastic/rubber hammer's rubber head as a corking tool, lightly hitting it with the plastic mallet, and having it slide from the edge into the center of the bulge.
This bulge still has some "orange peel" on it and needs to be smoothed out, but the edges are very well defined!
Check out those edges!
But of course, I screwed up again - the hole in the bottom, "die" plate of the jig, is of a wrong diameter (I used the wrong holesaw). But hey, at least I think I figured that technique out!
Good evening in the shop tonight :).
|On:||Sep 01, 2014|
|Tags:||CAD, lower wings, ailerons|
Another week and a half. Did a ton of little things; each one of which took a ton of time, with seemingly little result... I guess, devil's in the details.
It's constant tweaking and tuning of things that takes a bunch of time. But, at this point, most of the rough things are in, and it's that tweaking and tuning that's left to do...
Finished all the drag wires. Initially I did an incorrect layout from the standpoint of which wire passes over which (or under which, depends on how you look at it). Apparently, I came across a definition of drag/anti-drag that's exactly the opposite of how the plans define them... Sigh.
Wires have to cross inside the drag wire blocks and inside the spar; so one has to go over and one under, like this (lots of transparency here):
Drag/Anti Drag Wires Crossing
That's the pattern I did wrong; causing some interference with the bellcrank and heavy interference with rib diagonals.
Thanks to my original post on drag wire blocks interference in the aileron bay, and the picture Ward posted in that thread, I figured the wires pattern out. Switching it around made for much better clearance!
Also, my original problem with aileron interfering with the drag wire blocks is apparently no problem at all - I'll just relieve them (rasp, file, sandpaper, whatever) to provide clearance.
So, here's what the wing looks like right now:
Latest wing with all the drag wires
... and then, something I spent quite a number of hours on. You see, I want to sheet the inside of the aileron bay with curved piece of 1/16th plywood, supported on braces joining ends of the ribs together.
A few pictures below show the idea:
Aileron Bay Sheeting. Grain orientation is off, I know :)
This shows the support brace between ribs, just one for now.
Aileron Bay Sheeting, showing the support brace.
This is all very rough. The problem though was this.
Here's how it looks from the wing tip side:
Aileron Well, looking from the tip, zoomed out
Aileron Well, zoomed in.
See that clearance??? 7/64ths between the aileron tip and the nut! So even before I started figuring out the best spline curve for that sheeting, it was obvious that it won't clear... 1/16th ply + 1/16th gap is already a 1/8th, or 8/64ths!
Asked the Biplane Forum folk in the same thread... And, separately, actually figured it out - it was suggested to use two thin jam nuts there instead of a thin + regular nyloc.
That cleared a lot of space up!
Finally, some clearance!
I was thinking about modifying the tails of the wing ribs in the bay area to support this sheeting.. But, even with thin jam nuts, the bay is still very tight. Given that I won't be able to build exactly to perfect dimensions, I finally decided not to bother, and just build in place (and then we'll see what clearance I really will be able to get :)
Backup plan? Have some drag wire hardware protrude into the bay, and sheeting be not "in front of it", but somewhat behind it (closer to the main wing spar). Something like this.
And with that, I moved on to
Added all the hardware to the aileron hinges. Cleaned up most of the compression plates (doublers) to go around the compression struts and drag wires.
Oh, and apparently, my aileron hinges were drawn a bit wrong (and had that unsightly early model of Fafnir rod end I have thrown together). Fixed that. Made them pretty green color to celebrate the occasion :).
All pretty and correct hinges with HW
Compression plates relieved for the struts and drag wires
As I expected. Drag wires don't clear rib's diagonals in some places.
Station 24 vertical and diagonal interference.
Hale Wallace in his notes suggested to relocate station 24 vertical to 23 3/4, 1/4 inch forward (or "left" in the above picture). This will make the diagonal more steep, and clear the drag wires. I'll have to do that.
Another nasty. I was ready for this, and, sure enough, the bellcrank/idler pushrod doesn't clear the compression struts. The idler will have to be made lower; Steen bends them downward and I will see if I can avoid that by just moving it down a bit (and moving the idler arm down on it's bushing).
Pushrod not clearing compression struts.
So, I started looking at relocating that vertical first.
My ribs' models are the first ones I did in Solid Works; and they suck. They are made off of sketches created from converted AutoCAD files, with lots of ugly things in them. They are practically unmodifiable. Back then I thought it was easier to draw things in AutoCAD and import them to SWX - oh, what an idiot I was :).
Also, while looking at things, it became clear that they also are not sitting right on spars (not symmetrical to spars' center plane basically).
It feels like I will end up re-drawing them from scratch, and doing them as proper assemblies this time. We'll see.
It might well be that the problem I was having with aileron-to-other-ribs-alignment will go away, and no holes will need to be relocated...
It's annoying, but at this time I am so much better with SWX than back a year ago when I was doing ribs. Still, Le Sigh.
I've been putting this off, since those tip ribs are not dimensioned on the plans, and aren't a standard airfoil. They're supposed to create a nice transition from the main wing panel into the tip bow, creating some nice curvature.
I had the wing tip rib drawn up approximately, just as a placeholder.
Yesterday, I did an approximate aileron tip rib as well. Cutting it out of the plan and super-imposing two patters on one another helped! Plans are off (dimensions marked on them are not matching the dimensions measured off of them), but at least they're off uniformly within one sheet; allowing me to do this. It shows what's where.
Tip Rib, cut out - finally, some physical work on the "plane"!
Well, for one, it became obvious that the top aileron skin on the leading edge will have to create a compound curve going to the tip rib.
Searching thru the Forum, and reading things showed that apparently it's not that big of a problem. Gradual gluing and lots of clamping pressure should solve that one. :)
And then, there's the overall tip rib shape.
This is all very early with no "trimming cuts" made, obviously.
If you think about it, the aileron tip rib is supposed to be a bit "beefier" ("taller") than the wing tip rib. The tail of the aileron tip rib in the place where it's touching the bow should be 3/4 inches tall (so that it's flush with the bow).
All that will create nice smooth "flow" of curves from the last "full size" airfoil section (created by the wing rib and the aileron rib) into the tip ribs and tip bow.
So, first thing I'm not sure about is how good my tip rib (wing rib that is) is. I think the aileron tip rib should "play off" the wing tip rib's shape... In fact, if you lay a straightedge between the tip rib and the aileron rib with aileron positioned at 0 degree deflection, moving that straightedge should define the form of the aileron tip rib. I will do just that, later, lofting the surface that will "cut" the aileron tip rib out (and use a real straightedge with some sandpaper glued to it to shape the actual aileron's tip rib). I love it how CADing makes you think about these things!
But! That requires me to have a nice wing tip rib. Which I don't have. So to that task then, first.
Skybolt plans have the general outline and no grid on them. It's not a standard airfoil. Hmmm...
Last time I did it, I took dimensions off of plans. It turned out a bit off shape-wise if compared visually to the plans, so I tweaked it a bit. I still don't like that tip rib.
To the Firebolt!
Firebolt, by the way, is Skybolt, "improved" (and by that I mean added weight). Fuselage is a few inches longer, and hardware is all different; but basic wing design and overall things are the same. It makes it a great reference to read thru and see how things are done there.
Firebolt's wing tip rib is located at the same station as Skybolt's. That gives me some hope :).
Firebolt plans are also off (print dimensions not matching actual on sheets), but at least they have the grid -- amount of error accumulated over 1 inch of measurment hopefully is negligible. We'll have to see.
Dimensioning the Firebolt plans
And after going thru about half of that dimensioning, I decided that it's actually time to write this B-Log post, and take a break :).
I'll be bending some more sheet metal tomorrow. Post on that coming up!
|On:||Aug 28, 2014|
|Tags:||tools, software, website, SWX|
Thanks to Bill Rose of the Biplane Forum fame, I have a lot of SolidWorks models of various hardware and other common airplane things.
I just recently have set up a page where you can grab all of them. Models are hosted on GitHub, so you will always get the most recent version.
The page is going to be linked in the Resources menu on the left. Click here to go straight to it.
|On:||Aug 21, 2014|
|Tags:||CAD, lower wings|
Past few CAD sessions were drag wires and compression struts...
Typical wire blocks look like this:
Drag / Anti-Drag Wire Block
One interesting thing is that those interfere with aileron's leading edge in the aileron bay if left as is...
Block interference in the aileron bay
Again, asked guys on the Forum. Looks like just relieving them should work.
It's also clear that they interfere with the control system. Well, Ill have to adjust that when I finish the wires' models.
Meanwhile, added all the compression struts and working on the drag / anti-drag wire alignment and layout (they have to cross in the middle of wing bays, so I have to figure out what goes on top and what goes on the bottom). HFW did a good starting layout in his addendum to Plans, so going off of that for now.
Not much more to tell, so Ill just post two more pictures :).
Drag / Anti-Drag Wires hardware
Drag / Anti-Drag Wires in the first wing bay. Second bay is being modeled
|On:||Aug 18, 2014|
|Tags:||9891U, flying, stories|
After I posted my story on removing the footstep to Grumman Gang mailing list, Ken Blackman of AirMods NW fame wrote me an email.. He recognized the plane, and apparently he flew it back in the 70s and had a great story to share... Here it is, below.
Ken Blackman's Story
...we were so desperate for airplanes we were picking up "drop-outs" from other dealers canceling orders when they came available and this plane was one (sans the little tanks) we bought while at the 1977 Dealer Convention. We has also agreed to purchase a '75 Traveler "Repo" from Grumman Credit that a dealer had faulted on. It was in Oklahoma City. Maynard took airlines to OKC to get the Traveler and I was going to fly the Cheetah to San Jose, drop it there, and fly the AA-5 on up to our facility at Everett, WA for needed mechanical work and sale prep. (We had a much better maintenance facility at my end of the operation) I was within a half hour of leaving when the delivery center paged me to the phone. It was Maynard and he was asking me to come to OKC and pick him up at the Traveler was a total piece of crap.
I flew there and we stayed overnight to get a got early take-off the next day. This was in January and there had just been a minor snow fall all through our intended route through Albuquerque and on west to California. The weather was clear the next day and winds were forecast to be light & variable. There was a big high pressure coming into the NM area so we figured we would make ABQ the first leg, refuel, and on to Prescott. The 37 gal. usable put us on a thin edge for the first leg but we figured we had close to VFR reserves. Tracking the VORs, measuring the distances and doing the math I was maintaining a steady 145 to 147 MPH and flying at the higher altitudes we were getting real good economy. From Tucumcari to the next VORTAC I calculated 146 MPH and the previous leg was 147. Marking the time from that one to the next one would require a certain number of minutes enroute so we continued along in smooth air. Maynard was sound asleep in the right seat. When the stopwatch showed we should be arriving at the next fix the "TO/FROM" didn't flip. I waited another couple of minutes, then started looking at my chart and the ground for references. (Lots of luck over the desert.) I woke Maynard up wrestling the chart and he asked what was going on. I explained we should have been at the check point 10 minutes ago but weren't. We both started looking for ground references and finally found two roads that intersected along our route line and identified we were still a good 25 miles from the VOR.
I called Flight Service and was connected to a briefer in ABQ. I explained our situation and he said there as a weather phenomenon occurring called a "Venturi Effect" I had never heard of. The high pressure area coming into the ABQ area was causing wind to flow into the lower pressure area we were in and, coming through the Sandia Gap east of ABQ, set up a headwind that dissipated just east of our position. We had a head wind of nearly 50 MPH! This definitely put Albuquerque out of range but retreating to Tucumcari would not work because we would lose the wind very soon and not have the push needed to get there. Santa Fe was possible as we would be flying about 80 degrees to the wind direction and it would dissipate before we were half way there but it was a stretch and they were having snow pellets and possible freezing rain in the forecast. Looking at the chart I found a dirt strip at Kline's Corners right along a freeway and cross road intersection. It was within our range so we headed for it. Arriving at the intersection and identifying it we could only find a ragged old windsock on top of a collapsing building in the middle of a lot of snow. "NFY"
We flew low over the cross road but there were power and phone lines that would prevent landing on it. There was the freeway and an underpass where that cross road went over it. There was a Chevron gas station there with the on-ramp to the interstate and traffic was light. We made a low pass to check for obstacles and it was good for about a half mile past the on-ramp. We made a left hand downwind and tried to set up a landing but there were a couple of cars we were concerned about followed by a couple more that we didn't trust to not panic and run into us if we landed in front of them. We went around again and had a similar problem plus two cars were coming down the on-ramp. We were flying on the tank that read the most fuel and, about the time we turned downwind, the engine quit! Switched tanks and decided we were committed this time. There was a Semi just going under the overpass and another one a mile or so behind it. Trusting that the driver of the 2nd one would not run is over, we settled down to land about where the on ramp joined the freeway.
We taxied off the main lanes to the shoulder and turned 45 degrees to the left and shut down. The Trucker pulled his rig up to block anyone from hitting our plane and got out his flairs. "What'd ya do, run out of gas?" he asked. "Nope, but close. If you think you are going to run dry, for God's sake, land before you do!" I replied. About that time a state trooper came flying off the opposite set of freeway lanes, bounding across the dirt, snow covered median and blocked the right lane of the highway. He had picked up the CB call from the trucker. After explain our situation to him he asked if he should call a tow truck... "NO!!!" I asked if he could just block traffic back of the in-ramp and we would taxi it up to the gas station. He did and we did. (I had to zig-zag through the edge of road snow markers but made it fine.)
This was before EAA was working with MO-GAS and we didn't know how it would react to it. We decided to use the higher octane unleaded so stuffed a hose in each tank and filled it up. The cop blocked off the freeway again and one of the guys from the station drove his pickup to park under the power lines and turned on his flashers. We taxied back to the underpass to give us a little more runway I did a run-up only to have the engine run very rough. We thought the car gas might be causing this then realized we were about 7,000 ft, MSL, and full rich was not the correct procedure. Leaned it out half way and run-up was fine. Take off was long but we were well above the power lines and on our way to ABQ. The damned thing ran better, and burned a little less per hour with the car gas. We decided to park it in ABQ and get a good dinner and night's sleep before flying on the next day to San Jose.
We decided to leave the plane at RHV and I flew a used trade in 2 place on home. The owners of Bede Micro (Keith Henshaw and Rod (his partner)) were close friends of Maynard and had become so with me. They developed the Honda Turbo conversion for the BD-5 and stretched the fuselage. They had a facility to help people build their BD-5 kits with their tooling and fixtures and assistance. They were talking about getting a Grumman for their running around and bought '91U soon after it arrived.
There was a good article about Keith in Sport Aviation, I think the January or Feb. issue this year, about his achievements in supporting the BD aircraft and development of the Honda powered version. (He passed away last winter in his late '80s.)
Well, now you know the bit of history of your airplane that is not in the log books.
© Copyright 2014-2015 "N79FT". All rights reserved.
This construction log only shows how I did things during the construction of my Skybolt. These pages are for information and personal entertainment only and not to be construed as the only way, or even the perceived correct way of doing things. You are responsible for your own construction techniques.