After camping Goat work

The first annual Memorial Day camping trip is over and the 10 miles we hiked on Sunday is still hurting my calf muscles ... wow.

Goat is for some reason back on the front burner. I decided today to work on the tail struts. After cutting and filing the four pieces, I fitted one end of each and have yet to cut the struts to length until I do the final alignment against the vertical tail. I also should note that Aircraft Spruce did not have 3/8 x 0.035" in stock, so I used 0.058". This puts more weight in the tail, which is never a good thing, but the extra security feels nice.

I also assembled the whole aircraft (minus wings) in the apartment again. This included finally drilling holes in the upper vertical tail attach point to accept the upper pin; this tube end was replaced when I mis-drilled the original, so I took my time. Now I can fold up the vertical tail and use the real forward pin to attach it to the lower, rotating vertical tail part from G4T14. Two birds with one stone.

The control lines are currently simply a tied up messy bundle and rather stretchy. I really should use the quick links and at least make my temporary lines the right length. I just noticed in the picture that the right rudder line is running beneath the wrong tube. Remember this setup is temporary. Also temporary is the lower attach pin is shown here as a 3/16" bolt before getting stepped up to the correct 1/4" diameter.


Oh I also took a shot on Friday of the horizontal tail ribs still with peel-ply. I'm really dissatisfied with the finish of the blue foam compared to the pink foam. I think the bond is roughly equivalent, but the finished rib in blue foam sure looks comparatively awful. It's all hidden by covering in the end of course...

More ribs

What can I say? I've not been working much on Goat recently. Sadly, the Sandlin main site is down too :-( Instead, I've been making composite discus-launch glider pods and just starting to make molded horizontal tail mounts. The techniques have certainly been perfected by others, but I'm finding it rather rewarding to improve my own skills. Each fuselage is taking about an hour of prep, an hour of layup, and a half hour of cleanup. The tail mounts are still slow, with only one flyable part out of the mold thus far. Thought I'd share a picture of the current inventory, which doesn't include the two I've given away to friends.

I did do a little work on Goat today and over the last week between test flights at work. I finished putting the other graphite rod in the long rib blank and sometime over the week cut and installed the four remaining ribs. Yesterday, I wrapped the ribs with fiberglass tape, using 3M Super 77 to make the process easier. And this afternoon, I cut eight strips of peel-ply and epoxied all the ribs. A little cleanup a few hours ago and the horizontal tail is looking rather complete!

I know I shouldn't, but I looked into covering a bit. A coworker recommended the full Stitts Polyfiber treatment as the best investment ... but it's sooo expensive, on the order of the price of materials in the whole airframe. I'm wondering if I'm reading too much into the process, but I haven't found a great tutorial online to review and see if I'm just being overly conservative. Suggestions are welcomed. I have a long way to go before covering.

To do:
* finally remake the last two cabane truss members I've been meaning to do
* make a jig and try bending a new keel tube, make a replacement fuselage carry-through assembly and match drill several existing bolt locations
* drill the top tail attachment in the re-built upper tail tube (*mega alignment needed*)
* finish gluing the foam crush supports in the vertical tail
* final drill the vertical tail lower control rod guide and rivet it on
* make the horizontal tail struts

That's plenty for now...

Mmmmm, Ribs

I stole some time from my take-home final and worked on Goat over the last week (?). I can't really remember when I did this work, but I have a few pictures.

To the left is how I'm making ribs now. I cut a several foot long piece of 1"x1" pink foam, made a slit for the carbon cap, and glued each long cap in at once. The picture to the left shows the first of two caps getting bonded in the slot, this time with West Systems resin. The board and PC power supply are simply to keep the part straight as it cures. To the right is one of the completed ribs, installed near the tip of the horizontal stabilizer. I bonded the unfinished rib to the leading and trailing edges and added a wrap (with 3M Super 77) of fiberglass cloth. I have yet to put resin on this cloth (like I showed for the rudder ribs) instead waiting to have all eight horizontal stab ribs ready for that stage at once. Now I simply need to make six more foam ribs...

I had some leftover curing epoxy from another project, so I started gluing in the tail anti-crush foam blocks. These go between the 1/4" x 0.035" truss tubes on the vertical tail. This is the aft-most lower corner block bonded in place.

These foam pieces see virtually no loading that I can think of. Maybe they see some shearing from torsional twisting of the whole vertical tail ... but the fabric will probably take most of that load. I think they're mostly to keep the covering from dimpling the thin truss pieces in. So, I didn't work too hard on getting a super-uber-bond.

I did remember to take a finished shot of the lower horizontal stabilizer control rod guide bushing support structure. I mentioned I believe last post I added an additional wrap from what I had a picture of.

You can see the PVC bushing (white) held firmly between the two 1/4" x 0.035" truss members and with two layers of 1" fiberglass tape wrapped around the trailing edge tube, all of this supported by a foam stand-off. I'm quite a happy camper with this arrangement.

Tail work

I'm back ... slowly.

I did some work on the rear tip of the vertical tail, namely on the elevator control linkage area. I added the PVC guides between the rear 1/4 x 0.035" tubes. Instead of just making a slurry of epoxy, I manufacturer a couple foam stand-offs to tie the guide tubes to the structural member. I 3M'd some 1" wide fiberglass tape around the foam, PVC, and aluminum tube, then I added some thickened epoxy to fillet the sharp intersection of the 1/4" tubes, then I 3M'd another glass wrap around the whole thing, on the outside of the fillet. I mashed epoxy into the fibers and thoroughly wet out enough to practically see through the fiberglass tape. A simple layer of peel-ply and clamps to ensure the fabric fit down in the fillets nicely, let cure overnight, and admire the handiwork. I'd say these aren't going ANYWHERE without some severe hammering. I remembered to add some shims/spacers inside the guide tubes while I was doing this bonding, so both guides are parallel and in good alignment. It's super smooth motion. Yes I couldn't resist putting the horizontal stab back on and seeing how the elevator stick felt ... 'bout the same as before.

While I had epoxy on the brain, I finished off the rudder ribs. I did two at once, pushing epoxy through the fibers of the 3M'd fiberglass tape, then using a wrap of peel-ply to get a nice finish. In the morning, I pulled off the peel-ply and knocked down the edges with an 80 grit sanding block. Two evenings' work, and the rudder is as good as done!

Oh I just checked the pictures of the elevator guides above. I guess I took the photo between layers. You can see the flox fillets around the 1/4" tube before putting the final wrap over them. Take my word for it, the next wrap actually went on rather well (3M is great stuff).

William-T-Pique through the Panama Canal!

Slightly off topic, but I very much enjoyed reading Alan's boat-building blog for both his previous projects. Currently, he is sailing around the world and just made the trek through the Panama Canal! The crew is keeping a wonderful news site of their progress with an educational spin: Eye of the World/

I took screenshot videos of the boat passing under the Centennial Bridge and moving through the first Miraflores lock.





Awesome job Alan!

I'd really like to hear from anyone reading this ... I opened up the comments to anyone with or without signing in to whatever account thing this site has. Just a few words of "hello" or "having fun reading" or even "I have a hanger and towplane and a trailer you're welcome to use." I'm just curious who all is reading.

So I caught up on some other pressing stuff around the house & office, so I decided to do a little assembly work this morning. Notably, I installed the elevator control line pulleys sometime earlier this week while it was raining.

Now, I also made the control linkage part to connect the sliding tube to the elevator itself. Well, um, there is no elevator per-se. I haven't yet bent the 3/8" tubes to make up the trailing edge for the elevator. Despite this, the elevator leading edge is done and hinged. So it's a little anti-climactic. But now I have another moving part!

The bottom of the control linkage shows off more of the temporary work back here. The marine pulleys from Harken are rather smooth and very nice actually. They'll do much better with larger line. The control tube guides will also do much better when they're bonded to the structure with epoxy and cabosil. The foam anti-twist supports will be nicer too without the wrap of electrical tape, so look out for that to happen when I mix up some big batch for doing ribs in the next month.

Speaking of ribs, I did a little work during the last snow storm to attach the horizontal stabilizer to the vertical tail, necessitating some filing of aluminum and using the die set from Harbor Freight.

That's all for now!

Harbor Freight is my friend

I have heard the name Harbor Freight before, but hadn't ever really looked into them. With the snow finally plowed enough to get out, venturing to Harbor Freight was on the list! Their prices on tools I have bought before were generally half what I paid ... meaning a half-hour drive to the store is worth the savings. I bought several random things, including a tap & die set to make the quick-pins for Goat. I already modified the horizontal stabilizer AN3-30A bolt to accept two lock-nuts (low profile ones) and trimmed it to 1-1/8" long. Now my previously jury-rigged bolt actually stays in by itself! I was thinking hard about getting a drill press for making all those sheet metal parts a bit easier, eventually deciding against it since I'm almost done making those kinds of parts, heh.

In other news, I started a jig to re-bend the keel tube. I have to find some fine-grained sand to stuff the tube before I try to bend it this time. I have been told that will dramatically help reduce the kinking, along with a good jig of course.

No pictures this time.

I did give a go at sleeping inside that igloo by the way. Unfortunately, I didn't put in a secondary vent hole, relying simply on the main entrance for ventilation. After about two hours outside, I woke up extremely light-headed and abandoned it... I was quite warm, I think my CO2 was just not escaping enough without that vent. DOH.