RE: DERIVATIVE, New 2X2
 

Thanks Bob,

The idea is to pass on knowledge and knowhow. To me, that's the main purpose of having the forum in the first place. Folks have forgotten that was the original purpose of the WWW, being used amongst the scientific community.

BTW- Part-All is magic stuff as release agents go. Only needs two coats and a light polish

RE: DERIVATIVE, New 2X2
 

Whaddya suppose this is?

RE: DERIVATIVE, New 2X2
 

A piece of fanfold shaped to serve as the pipe floor. Glassed and vacuum packed; worked out rather well.

Actually, fanfold stock will be sliced with a hot wire, sealed and used in fuse construction just like Herex. Haven't done it yet but I will to see how strong. The pipe floor was a good first step

RE: DERIVATIVE, New 2X2
 

A photo of it in situ would be nice. I can't quite picture it.

From my very little experience with the ES pipe, it seems to me that the pipe tunnel separator/insulator doesn't require a very robust material as long as the airflow through the tunnel is adequate.

RE: DERIVATIVE, New 2X2
 

I'll take a couple snaps tonight and post. I think the foam will work out well for noise too. It's similar to 2mm depron without the paper, but sealed with the glass on the pipe side. Turns out this stuff is very resilient

When completing my Aesthesis fuse, the pipe floor that was used (glassed balsa) weighed 3-4X as much (about 75 grams) as the glassed foam does (20 grams)

RE: DERIVATIVE, New 2X2
 

Lessee if these come through. RCU postings have been a bear lately

RE: DERIVATIVE, New 2X2
 

Bob, make better sense?

RE: DERIVATIVE, New 2X2
 

Made significant progress on Delta over the last couple weeks. Here are some pics.

The way I build wings and stabs is to first set the foam up with it's socket before sheeting. Socket installation uses subspars that surround the sockets and extend to the sheeting. This technique forms an "I" beam structure and is much stronger and actually lighter than other popular techniques such as false ribs at the ends of sockets. This enables the use of lighter materials elsewhere in wing or stab construction

RE: DERIVATIVE, New 2X2
 

The sheeting is 1/32" sanded and measured with calipers to assure the lightest possible structure that has adequate strength and stiffness. Carbon veil under the skins improves stiffness. Epoxy is used.

The easiest way to set up a vacuum bag is to turn it inside out and install the breather stock. I usually use paper towels for breather but I had some felt fabric on hand from lining a wing case so i used that instead this time around. The pink plastic is perforated anti stick film.

The seals were purchased from ACP. The vacuum adapter from AS&S. ACP also sells vacuum adapters but at 50$ each they are pricy. Aircraft Spruce sells a larger adapter for around 7.50$ so I bought a pair and cut then down. Works great

RE: DERIVATIVE, New 2X2
 

Matt,

Sorry I haven't checked on your progress lately - what a lot you've gotten done!!

The pipe tunnel separator looks great! Very light and functional, however it looks as if the pipe is going to be tough to access.

I see the lord mount on the front neck of the pipe... how are you securing the "stinger" tail?

Hard to believe you got a 55cc completely under the hood of that cowl with only a little header sticking out. I guess that with the soft mount the finished header cutout will have to be a little bigger.

I like the way you did the wing tube socket. Looks much stronger having contact all along the socket. That looks like a thinner airfoil compared to most these days.

RE: DERIVATIVE, New 2X2
 

It is designed to be as accessible as practical. The pipe/header are easily removable/installable as a unit, even with the engine mounted

The pipe mount is at the approximate cg of the pipe. It is the only one used..... the pipe is never supported anywhere else in my soft mounted set-ups and is allowed freedom to oscillate. Carbon pipes survive well and headers don't break unless I screw something up. Such was the case with the very first header I built for the DLE....there was no flex in the header's goose neck and it broke at the flange. My current header is flexed at the gooseneck and has survived about 4 galons of flying. The header was purchased from DA. The Teflon tape covering the gooseneck doesn't survive the exhaust. But I've devised a better alternative to teflon tape which survives much much better. I started using that same technique to couple header and pipe and it is working well so far

It's a stab actually. The section is 9% at the root and tip with area of 260 square inches. Weight including the carbon tube is 3.6 ounces. That's the same as a 500 square inch wing panel weighing 7 ounces which is where mine usually come out before finish

The header will be concealed at the chin cowl. I don't like exposing any parts of the nose if I can avoid it.....

RE: DERIVATIVE, New 2X2
 

Uh, I'm having a brain freeze.... what is this 'fanfold' material you are using?

RE: DERIVATIVE, New 2X2
 

Foam, blue or pink; Home Depot....

I have the stab set in the fuse. I will post a few snaps tonight. My fixture is a simple piece of 1/16" lexan. I will explain more with the photos.

BTW - I always set the stab first to make certain it is square to the fin; then align the wing to the stab. It is the easiest way to do alignment of this type

RE: DERIVATIVE, New 2X2
 

Matt, how thick is this fanfold layup you're using? I'm surprised it's stiff enough for flooring useage
Mind sharing what weight glass you used in this layup

RE: DERIVATIVE, New 2X2
 

Well, foam by itself is not particularly stiff but how stiff does it have to be to guide airflow? It is not a structural part of the model and nothing will touch it. Depron, 2mm thick, would do the same job. I cut the fanfold foam to 2mm thickness from the original 7-8 mm thickness with a hot wire and laminated 3/4 oz glass to one side, the pipe side. Then I epoxied it in the fuse; pro bond or gorilla could have been used also to bond the foam to the fuse....Simple, effective, super light, adequately strong. It is lighter than 1/32 laminated balsa by about 1/3. Tried it both ways, opted for the foam

The structural component will be the one piece servo tray that will essentially cover the whole canopy area. I will be laminating honeycomb stock for that job. The wing tube socket will be attached to the servo tray producing a monocque structure. My expectation is that this model will fly for 2000 flights just like my last one, unless I dumb thumb it; with the DLE55 up front

RE: DERIVATIVE, New 2X2
 

The sheet of clear plastic has served well over the years. I've drawn a "T" on it to help align the fin's post center line with the stab's TE center line. It is flexible enough to bend around the slightly extended post. That's usually around 1/4" - 1/2" on most models so it doesn't lose any alignment bending around a bit.

I have another where I've drawn several horizontal lines to help align the anhedral stab on Aesthesis a couple years ago. Worked as expected. The stab support crutch inside the fuse is lite ply. It extends 12 1/2" from rudder post forward, past the front base of the fin to provide much needed strength in this routinely weak area in most composite fuses.

Here's a simple way to make your own stab adjusters. I started with a short section of phenolic stock, 1/4" ID by 3/4" OD. Cut the sides, drilled and tapped for 6-32 set screws and voila. It took all of maybe 15 minutes to shape the pair. Each weighs next to nothing (2 grams). Gorilla glued in place

RE: DERIVATIVE, New 2X2
 

Matt, Excellent work! It seems you are nearing the finish line on this project.

Looking forward with great anticipation to seeing the final result - hopefully this summer!

RE: DERIVATIVE, New 2X2
 

Thanks Bob, I am shooting to have it completed before the summer....This great weather we've been having has cut into my building time, LOL. I've flown more this winter than I've flown in the summer it seems

Anyway, Stab weight plus elevator to this point is 54 grams per side, 1.9 ozs. I'll detail the covering next where I will be doing a different technique than the norm. All glass of course

RE: DERIVATIVE, New 2X2
 

Here's a different technique for glassing skins.

Prep the balsa with a fine sanding as though you were going to cover "normally".
Seal the balsa with nitrate, hair spray etc. I used hairspray this time.
Prepare 015 thick mylar skins; cut the skins very close to the surface perimeter. I left 2mm margin all around
You may wax the inside of the skins. It isn't absolutely necessary but if you want to make certain of release, wax
Spray the inside of the mular with primer. Or alternately, paint may be used. I used KlassKote epoxy primer, 2 light coats, and let it cure
Apply the fiberglass, carbon veil, silkspan or whatever reinforcing stock you like. I used 0.6 oz glass cloth
Apply the epoxy. I used Pro Set 125 resin 229 sloooooww hardener. A a 1" brush and a foam roller work great
Cover the stab, wing, rudder. etc. I used blue masking tape to hold the mylar in the right place
Place in vacuum bag and draw vacuum. I used about 8" Hg negative or about 200 mm Hg vacuum. About 4 psi neg

RE: DERIVATIVE, New 2X2
 

Wow, you've taken the idea I was planning to try and tried it.

Well done, the finish looks superb.

RE: DERIVATIVE, New 2X2
 

Thanks.....I will be pulling the covered stab out tonight. I will post photos.

I tried the technique on a rudder many years ago and the result was a heavier part than I wanted. I had not used the foam roller on the rudder and left too much epoxy behind. The foam roller provides for much more even and very thin coverage. Using epoxy paint will probably work well too, but I have not tried that yet. Renegade when you try this approach, why not try epoxy paint and report back?

Each stab half picks up the minimum weight, around 3 grams for the glass cloth and around 6 grams for the epoxy. The only other variable is the primer. I'll see what the final pick up was when I remove from the vac pac. A guy I know tried the approach without a vac pac (he used lead shot bags) and his results were somewhat variable. A vac pac makes this job straight forward

RE: DERIVATIVE, New 2X2
 

Had a problem with my epoxy cure....DRAT!!! Experienced a set-back last night....

Comes with the territory of driving on unchartered roads. When you are trailblazing, sometimes the trail gets you and sometimes the blaze

RE: DERIVATIVE, New 2X2
 

Just left things alone for a few days to figure out how to salvage the stabs. The epoxy cured more fully and was able to remove the mylar from one panel with minimal damage to the surface. The other panel was damaged substantially but I managed to salvage that panel also. Had to refinish part of that sheeting on one panel.

More importantly, the key lesson learned was that the mylar and the epoxy paint I used (KlassKote primer) had to be more compatible with one another. The mylar prep simply was not sufficient. I opted not to spray PVA on the waxed mylar sheet before spraying the epoxy paint (primer), a mistake.... Spraying paint first on the cover requires PVA barrier for best results. Knew that of course but rushed myself...dumb!!

Since then I acquired teflon sheeting for the wings and rudder. Teflon is bullet proof.

I also completed the landing gear strut build for the plane and am in process of fitting. I'll post pics of the gear detail soon

RE: DERIVATIVE, New 2X2
 

Matt, did the mylar not release?

RE: DERIVATIVE, New 2X2
 

I think the mylar would have released epoxy alone. Mylar was waxed with 2 coats of Part-All as I do most of my mold surfaces and I normally also PVA the surfaces, something I did not do here. KlassKote primer stuck too well to the waxed mylar which caused the glass to lift in places. Teflon sheeting will cure that issue.

My landing gear clam shell molds are teflon lined. These work perfectly; no additional prep required