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.