Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Hey, nice Stits..

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Old 06-25-2009, 11:35 AM
  #1  
MJD
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Default Hey, nice Stits..

Yeah, well.. [X(]

I decided to cover a Screamin Demon in Stits fabric, aka Ceconite or Poly-Fibre, as an exercise in toughening up the outer skin. Although it takes a fair bit of clear to seal it up, done right the weight uptake is small. I used the lightest of the three regular aircraft grades, one intended for ultralights and experimental aircraft up to a certain wing loading. It could be used on the tail surfaces of a homebuilt light plane for example, but only if it is experimental since cert'ed aircraft require one grade up. Nonetheless, it's tough as nails in contrast to most model coverings. Stupid easy to apply too:

- two good coats of nitrate around the perimeter
- 1 light mist coat 3M-77 over the nitrated bits
- lay precut fabric over the area
- pull out smooth and rub edges down which will stick nicely with the 3M 77. You don't need to pull tight as it shrinks like the dickens.
- dope the perimeter down by brushing through the fabric. Once 2-3 coats have been applied around the perimeter to lock it down and have dried..
- shrink with a 350F iron (I said 350, that's what you use) while moving back and forth between sides to keep tension somewhat even - i.e. avoid warps, but I had zero trouble.

Now play your favorite drum riffs on the wing while you psyche up for sealing with nitrate and a brush.

I only applied nitrate around the very perimeter, then shrunk it down smooth and did final trimming. Then, for the coup de grace or so I hoped - with the fabric stretched tight over the whole airframe, I then brushed laminating epoxy over all the center section sheeting, LE and the inner 2/3 of the tips. This was my attempt to "glass" the center, LE etc. in one shot with the covering material. I am happy with the result - the skin is tough as nails, the open bays are as tight as I would dare have them, and I think it needs more ribs and spars for shape next time.

After sanding off any rough spots in the epoxy (not much) I then attacked sealing it with clear nitrate. A few quickly brushed on coats and ome gentle sanding about every other coat and voila. It sounds like more work than it is - brushing on thinned nitrate in summer is an exercise in painting faster than the stuff dries, or almost anyhow. Quick job, then I let it sit outside for a while.

As it sits here, with elevons fitted - using continuous hinge made from heavy fabric and a dremel slotting saw - the airframe weighs about 14.5 ounces, and is almost ready for primer, once the fins are cured and bonded on and glassed in place.

I really don't like iron on coverings much, but I use them all the time. I like not worrying about sealing edges and sticking to oily bits and ooh the iron's too hot and oops, it doesn't stick to that very well, etc. If I could finish an airplane by dunking it in a tub I'd get off on that.

But painting satisifies me, I enjoy the process as the finish gradually gets nicer and nicer, or that's the plan at least. It feels like modelling, and iron on feels like take-out food by comparison.

Oh yes, I did add a center section hand-hold about 4-1/2" wide, and narrowed the elevons a bit. And noticed afterwards I had forgotten to relocate the servo mounts outwards, now to deal with that.

MJD



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Old 06-25-2009, 01:13 PM
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combatpigg
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Default RE: Hey, nice Stits..

Looks great MJD!

Iron on is a pain to keep up with for me. I'm not as handy with a rag between flights as some guys. Either way, high speed lifts the slightest flaws. I've gottn to the point of using clear packing tape over seams before they have a chance to lift, but it looks crude.
We'll see how your method shown here holds up to the test of time. Is this the approved method?
One thing is for sure, this is the only way I would ever do a diesel project ever again. Fabric and paint. I'm not sure how anything other than dope works with fabric, such as being prone to cracking or even making the fabric brittle?
Is a drop or 2 of castor added to dope considered OK?
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Old 06-25-2009, 02:02 PM
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Default RE: Hey, nice Stits..


ORIGINAL: combatpigg

Looks great MJD!

Iron on is a pain to keep up with for me. I'm not as handy with a rag between flights as some guys. Either way, high speed lifts the slightest flaws. I've gottn to the point of using clear packing tape over seams before they have a chance to lift, but it looks crude.
We'll see how your method shown here holds up to the test of time. Is this the approved method?
One thing is for sure, this is the only way I would ever do a diesel project ever again. Fabric and paint. I'm not sure how anything other than dope works with fabric, such as being prone to cracking or even making the fabric brittle?
Is a drop or 2 of castor added to dope considered OK?
Yeah, you can do that to plasticize it a bit, helps reduce overall shrinkage and increase flexibility. Full scale rag wings are painted using either dope, enamel, out-of-the-can polyurethane, or two part polyurethane finishes, I think that's about it. Aircraft finishes are generally formulated to be flexible because everything on an aircraft flexes somewhat anyway and is also subject to continuous thermal expansion and contraction.

You can easily see the nitrated perimeter versus the epoxied areas, with a funky transition area between. It's all stuck down very tenaciously. Now I have to cover the elevons, not having done that first; doh! No big deal, nearly as easy.

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Old 06-26-2009, 03:46 PM
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Default RE: Hey, nice Stits..

The tip fins are glued on and fairing puttied, waiting for me to get up the next wave of ambition to glass them to the tips. Hmm, better take a picture and post it, supposed to do that first dummy.

I decided I need to redeem myself from the NC rally issue, and will do that as follows: I will dedicate this evening and the weekend's spare time to a particular project I have been itching to get at; making the plug to mold a glass/epoxy top cowl for the Screamin Demon, engine, tank and all. I think they all should have one, side exhaust or rear, but I might be accused of bias on that subject, and rightly so. But seriously, this is an accessory I am itching to be able to offer because I think it's frigging cool. I'll post a sketch of a couple of ideas I had in mind for ridicule, kind of an open forum think tank R&D session without coffee and peanuts.

Mike D.
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Old 06-26-2009, 03:58 PM
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Default RE: Hey, nice Stits..

I decided I need to redeem myself from the NC rally issue,
Huh
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Old 06-26-2009, 05:08 PM
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Default RE: Hey, nice Stits..

I'd be interested in a cowl, but no coffee?!? Okay, I'll take a beer.[sm=spinnyeyes.gif]
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Old 06-26-2009, 05:26 PM
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Default RE: Hey, nice Stits..

What about covering with 21st Century iron on fabric, I've got two unopened rolls of the stuff, what are the drawbacks, I've never used the stuff.
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Old 06-26-2009, 05:39 PM
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Default RE: Hey, nice Stits..

That's what the bottom of mine is covered with. It's tough stuff, though I thought a little more shrink tension would be nice, but maybe I was lazy smoothing it out. It seems to be up to it so far. I love it on sport models. I'd be curious to hear from someone who used it 100% on a delta. I thought it might be the bee's knee's because of its toughness.

Mike D.
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