Madcow wood questions?

[AfterBurners]

Here are a few pictures of my Madcow Jayhawk. I'm ready to paint it and after wet sanding the fin / wings the wood grain shows through and badly. These grooves are pretty deep. When I used the wood filler and primer I never noticed the imperfections. Everything looked great! When I bought the kit also I noticed the wings were pretty warped. In all fairness to Mike he offered to replace the wings but I had decided to go ahead and build it and the wings were already mounted the best I could align them.

The issue with wood was also pretty noticeable on some of his other kits I built. The Scooter and also the 4" Patriot. Is there reason why the wood is like this other than just poor quality?? As I mentioned it looked fine after I use the wood filler and primer and sanded the kit. It's also noticeable on the winglets. This is going to be a flyer so I have really no concerns cosmetic, but I might consider building another one, just don't want to deal with it again. I've wet sanded wood before in the past, but never had too many issues with it. BTW - MC BTW makes great kits and has some awesome designs...could be just bad wood batch?

 

[Steve Shannon]

I don't think this is necessarily caused by low quality wood. Here one possible explanation: When you sand an edge it removes more material than sanding on the flat, resulting in revealing the end grain of the wood. On top of that you wet sanded it. Water soaks into exposed end grain fastest. The water soaked into the exposed wood, causing swelling which exaggerated the grain and possibly warping.


Steve Shannon

 

[MikeyDSlagle]

Yep, what Steve said. My Cowabunga did the same thing when wet sanding. Water got to the wood. It looked just like that. Talk about frustrated. I have since been more careful and haven't had it happen again. Not to say it won't in the future. I let mine dry, re-painted and sanded it down again. Took quite some effort but it looks great now.

 

[rharshberger]

I don't think this is necessarily caused by low quality wood. Here one possible explanation: When you sand an edge it removes more material than sanding on the flat, resulting in revealing the end grain of the wood. On top of that you wet sanded it. Water soaks into exposed end grain fastest. The water soaked into the exposed wood, causing swelling which exaggerated the grain and possibly warping.


Steve Shannon

Its delamination of the outer skin due to water. Very common on hobby grade plywood which uses thinner outer skins and glues that are not waterproof/resistant.

 

[AfterBurners]

I get the wet sanding part but I barely wet the surface. It was more like mud sanding. Anyways thank the feed back. At this point I'm not going to waste any time sanding it down again and again, besides it will be a frequent flyer. It's a great kit!.

Seeing that others have had issues with MC kits, but I think it's just plywood in general I think I'll pass on purchasing anymore plywood type kits.

I think I'll spend a little more and go with better quality material or different alternate material like fiber glass.

 

[tomsteve]

having done a crapton of woodworking and cutting plywood over every thickness from 1/8 up to 3/4", id say im lookin at tearout from cutting. ive usually gotten the tearout when cutting against the grain of the top plys, which looks like what you have. its not a sign of poor quality ply. could be fed too fast through the saw. could be dull blade. could be not enough teeth on the blade.

if it is delamination from wet sanding, its understandable- plywood used for rocket kits isnt usually waterproof.

 

[Banzai88]

I get the wet sanding part but I barely wet the surface. It was more like mud sanding. Anyways thank the feed back. At this point I'm not going to waste any time sanding it down again and again. Seeing that others have had issues with MC kits I thinks I'll pass on purchasing anymore. I think I'll spend a little more and go with better quality material or different alternate material.

Hate to tell you this, but I've had the very same issues with Apogee parts, Binder, LOC, Estes, and North Coast wood. It's water on the wood.

I sand the wood to 400 grit, seal it, prime it, then wet sand the primer. No more issues.

 

[AfterBurners]

I might try fiber glass if its worth the extra dollars and weight?

 

[mikec]

having done a crapton of woodworking and cutting plywood over every thickness from 1/8 up to 3/4", id say im lookin at tearout from cutting.

Madcow's stuff is all laser-cut.

Just don't wet-sand plywood. I've never once had any urge to do so.

 

[AfterBurners]

I don't think this is necessarily caused by low quality wood. Here one possible explanation: When you sand an edge it removes more material than sanding on the flat, resulting in revealing the end grain of the wood. On top of that you wet sanded it. Water soaks into exposed end grain fastest. The water soaked into the exposed wood, causing swelling which exaggerated the grain and possibly warping.


Steve Shannon

Steve some of these imperfections appears on flat surfaces that are not near any edges, but it's not as noticeable.

 

[Incongruent]

Steve some of these imperfections appears on flat surfaces that are not near any edges, but it's not as noticeable.

Primer is porous, to aid paint adhesion, but this which allows some water to go through it.

 

[o1d_dude]

Wet sanding plywood is not something I'd recommend.

Finish it first (sand, seal, prime, paint, sand) then wet sand if you want.

 

[AfterBurners]

Wet sanding plywood is not something I'd recommend.

Finish it first (sand, seal, prime, paint, sand) then wet sand if you want.

Now you tell me LOL

 

[dr wogz]

ditto with all the above. But as far as the warping issue, I have the Sea wolf, and I had a significant warp LE tip to TE. About a 1/4" bow along the length of 3 of the 4 main fins. Now, they are about 22" long at the root! But still a very noticeable warp even to the unaided eye.. They were replaced free of charge (minus shipping though). It does happen. It's wood!

 

[Lowpuller]

I would add that I love Mad Cow kits and their service is awesome. However I have only built their fiberglass kits.

 

[AfterBurners]

I agree Lowpuller. I wasn't questioning the kits, just the quality of the wood. Yes they have EXCEPTIONAL service!!! When I got home from work tonight I decided to spend an hour and fill in and sand down those imperfections (Caused by me of course) and primer the area. I used Elmer's "Purple" wood filler some 220 and 320 and now I'm back to where I started with a primer kit ready for paint. Tomorrow I'll go back over some the areas with a rubber grip and clean up all the tight corners and edges. Put one more light coat of primer let dry and just use a scotch bright pad or some 800 and then lay down the white.

I'll post some pictures here when I'm done. Thanks again guys for your feed back.

Hasta LaPasta