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Need Comp-Arf cosmetic repair technique help

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Old 10-06-2010, 10:47 PM
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Zeeb
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Default Need Comp-Arf cosmetic repair technique help

Okay I know you're not supposed to post the same question/thread in different forums, but I posted in the GS Aerobatic forum and I'm not getting any input so I thought I might try here....

I dumb thumbed my 2.6 Comp-Arf Extra into a small tree on landing the other day and have a new right stab and right wing since those were hurt pretty good. Stab is junk and wing might be repairable, but I just ordered a new one. The fuselage came out unscathed except for a broken wheelpant. The left side horizontal stab has some areas where basically the gel coat is gone, that elevator has a small spot on top where a stick went into it and the left side wing has a small hole in the leading edge where a stick went into it.

Since there are no soft spots around those areas, I'm thinking I could just do a cosmetic repair on those items? The biggest spot is in the stab with a small chunk out of the top of the surface and some scratches/chips on the underside. That area in the pics is about the size of a dime. The spot on the top of the elevator is about 1/4" square, the wing leading edge is about the size of a pencil eraser.

Since I'm not really into adding weight especially on the elevator and I don't want to get into a whole fiberglass repair "make it look perfect" mentality on this, I'm thinking I could just fill the holes with say some epoxy/micro balloon mix or even Hysol might work. Smooth off the area with one of those body filler spreaders and just use some touch up paint on those areas? I got the matching paint when I ordered the wing and stab.

How 'bout it guys; will such a plan work or do you have other suggestions?

The pics below are:
1. horizontal stab bottom about 4" out from fuse.
2. horizontal stab bottom about 9" out from fuse.
3. horizontal stab top about 9" out from fuse, this is the biggest hole
4. left elevator top
5. left elevator top close up
6. left wing leading edge out about 20" from fuse.
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Old 10-07-2010, 06:30 AM
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Default RE: Need Comp-Arf cosmetic repair technique help

http://www.rcuniverse.com/forum/m_3379769/tm.htm


The search function in this forum will bring up many techniques.
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Old 10-07-2010, 07:10 AM
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Default RE: Need Comp-Arf cosmetic repair technique help

Hi, you can dribble some thin cyno in the cracks and push them together. There shouldn't be an issue with the foam. It's cyno proof foam.
Check though just in case.
Then as you say you can mix some laminating resin and micro balloons into a fairly thick paste and push it into the damaged area.
I would tape over the filler till it sets and then take off the tape and rub it down
If you are going to paint it then the micro ballon mix is not good to paint onto so use a thin skim of car body filler. This is heavy but ok if you are only using a skim it gives you a good surface to rub down to.
Then preferably give it a coat of primer filler 2 pack paint onto the filler, rub this down after a day or so and paint it. Try not to rub through the color that Comp ARF applied as it will become porous due to the paint being the gel coat.
Obviously check the structure for any internal damage.
If you have a hole then you can make a shape of plywood or balsa which is slightly larger than the hole. Place whatever shape you have made over the hole and cut around it with a scalpel. This gives a perfect fit and you can then glue this in place and fill and paint it.
Hope you understand all that.
Jim
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Old 10-07-2010, 09:43 AM
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Default RE: Need Comp-Arf cosmetic repair technique help

Jon595,

I did try the search engine, but didn't see the 5 year old thread you linked to. It's got some good information and I may try using it on the wing I replaced as it has some structural damage.

Jim,

Thanks for the thoughts; I'd pretty much written off cyno as I figured the foam in the elevator wouldn't tolerate it but maybe I can check the junk horizontal stab and see what happens. I really want to keep that elevator repair light as it wouldn't take much extra weight on a control surface to induce a flutter. I hadn't thought about using some small wood pieces to fill a portion of the holes, good idea. I'd also forgotten about paint not sticking to the epoxy and was actually thinking more about using Hysol since it's eaiser to work with and doesn't run like epoxy, maybe a nylon body filler "spatula" spreader and just bring it up to the surface in a couple of layers as it sets? Since that stuff is basically a glorified epoxy, is the paint going to have the same issues with not sticking?

If these were larger areas or more visible I'd spend more time and do things as I would for a fiberglass repair on a full scale cowingling inlet or something, but since there doesn't appear to be any structural damage in these areas either I'm more concerned about sealing the areas than the final finish appearance. Worst case scenario I guess I could get another stab and elevator from Comp-Arf but those puppies are about $200.00 each plus shipping and it takes about 3 weeks for stuff to get here from Thailand.
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Old 10-07-2010, 04:36 PM
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Default RE: Need Comp-Arf cosmetic repair technique help

Personally, i would do atleast a surface patch on any damage on the leading edge extending past the damage 4 to 6" along the span of the leading edge, and 1/2 to 1" past the damage going chord wise. if that damage on the leading edge isn't patched correctly, you could find yourself spending ALOT more money for an entire new airframe b/c the stab or wing decided to part ways with the internal structure. you have to remember that the majority of the strength in a Comp-Arf airplane is in the skin of the component, not the internal parts, so if you damage the skin, you've weakened the entire structure. so not repairing it correctly could be a recipe for disaster.
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Old 10-08-2010, 03:02 AM
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Default RE: Need Comp-Arf cosmetic repair technique help

Hi as Invertmast says it's a good idea to glass over the repair with lightweight glasscloth, or I think that's what he said.
Many foams now seem to be cyno proof, I have a Chinese foamy thing that I thought was poystyrene but I can't sand it and it takes cyno and car body filler without any effect, probably EPP or some other foam.
Comp ARF foam was always cyno proof. I worked there for a while so I have a little experience of the materials. They could have changed them of course since I was there.
You can probably see the internal structure by looking down the root rib.
Hope you get it fixed.
Jim
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