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Building Tips and technical articles. => Paint and finishing => Topic started by: wwwarbird on March 13, 2014, 10:05:31 PM
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I started in last night on repairing the Avenger that I picked up in Milwaukee last November. I purchased it second or third (or maybe fourth) hand. I understand that it was originally built by Dave Trible, and I think he powered it with a PA .40. Through my historical investigation I'm pretty sure it hasn't flown or even had an engine run in it since Dave let it go. Talking with Dave I guess he had put very few flights on it himself as the .40 didn't have quite enough power for the 63-1/2" span bird. It sounded like it was one of those flew it a few times and hung it on the wall kind of things.
When I got ahold of the model the underside of the wing had some light damage, nothing structural, just a bunch of hangar rash holes in the covering from being banged around by the previous owners. I'm going to patch and touch up the wing first and if that goes well I then plan to add a few 1/2 bulkheads in the belly and close up the pipe tunnel. I'm going to mount a Saito .62 on the nose so the tunnel won't be necessary. I suppose I could make a torpedo and stick in there... ;D
More Avenger info here: http://stunthanger.com/smf/index.php?topic=33240.0
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Looking good!
Marcus
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Looking good Wayne. I'll be watching. I've not forgotten about getting those old drawings to you. I'd like to get the chance to work them over a little and make a copy. In the near future I'll get to it. I want to see your finished work here and know how she goes with the four stroker. If I did that today I'd put a .61 or even .76 in it but the problem there would be fuel capacity. Would have to rethink the tank compartment. Eventually I will because a future project will have similar issues.
Dave
Addendum; when you close up the pipe tunnel be sure you leave some opening to allow the air coming in the front cowling aperture out at a somewhat expanded rate. If you'll look into the front you'll see the effort to get air out faster than it got in. This is the secret to getting these basketballs through the air.
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Dave,
I'm going to put a Dubro 6 ounce clunk tank in it and will be running muffler pressure. I don't have one here to try but I actually think an 8 ounce would also fit in the airplane with no modifications at all. The cowl mods shouldn't be too big of a deal but I'm going to finish the other work first. My only concern at this point is whether or not the exhaust pipe will reach outside the cowling, it's gonna be close.
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I've got all of the patches on the wing, lightly sanded with just a couple of coats of clear on them so far.
Now it's time to see how closing up the pipe tunnel is going to go. I attacked it tonight and so far it's gone way easier than I expected. First I made up four bulkheads to give me something to glue the "plug" onto, and also to support it's shape while I push everything into place when it's time to glue. I also sanded all around the perimeter of the existing tunnel opening in the belly to give a nice square edge for the "plug" to mate up with. This also gets things down to fresh wood for the gluing process later.
It pays to save good scraps. I had a nice piece of pre-molded 1/8" balsa left over from back when I scratchbuilt my Helldiver. The radius was almost exactly what I needed for the plug. I'd figured beforehand that my biggest problem was going to be cutting the "plug" to the proper overall shape to minimize any filling later on. I was worried about it because the sides of the tunnel opening are not really parallel, and are also little bit wavy from front to rear. Just in time, my brain suddenly spit out a GREAT IDEA!!! First, I cut a length of the pre-molded piece slightly wider that necessary. Then, I sat it on top of the tunnel opening and carefully "mashed" all the way around it a few times to put a reference groove on the inside for cutting the piece out. I was only able to get away with this technique because the fuselage sides are very stiff on this model, I'm not sure I would have tried it otherwise. (After digging into it I'm thinking that Dave must have glassed the fuse?) I lifted the piece off and flipped it over and holding it into the light just right (shadowing) I could see enough of a groove that I could "trace" it with a fine line pen for my cutting reference. This worked out very well, it just took a little time sanding after that to get a perfect fit...
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It fits! o2oP
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You're going to have a winner there.
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You're going to have a winner there.
Dave gets the credit for this one Doc, I'm just blowing the dust off it. ;D
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Got the tunnel piece glued in last night using 30 minute epoxy. Tonight I was able to get it all sanded and faired in and then put on two coats of 50/50 clear. I think I might put a piece of carbon veil over it next, I'll decide after a little more sanding. y1
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Some good work going on here. Keep it going.
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...added a layer of carbon veil tonight. It overlaps the seam by about 1/8" to a 1/4" all around the perimeter. This will help speed up the finish prep and also add some integrity to the spliced in piece. ;D
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Looks like a shadow line of a torpedo....looks good as is! H^^
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And I was thinkin' that a little propeller and some fins on the back of a tuned pipe would look pretty cool. Too late, I guess. H^^ Steve
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I was able to get some paint work done on the Avenger tonight. From what I understand, this TBM was originally painted with Sig dope. For the "fix" I started with Brodak Insignia White and started adding their Polar Grey until I got as close a match as I could sneak up on. I sprayed everything in with my small airbrush and it went pretty well. Next will be feathering in the edges with some 1500 or 2000 grit and then painting in the rest of the bar on the "Star and Bar" wing insignia. After that I'll reconnect the panel lines and finish it off with some clear... ;D
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Damned fine job. H^^
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That looks great and I think David will be proud of yah.
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That looks great and I think David will be proud of yah.
Thanks guys, it's getting there, I'm just plugging along... :)
Hey Doc, are you going to make Polk City? Hoping to see you, Jim, and maybe even Dave there. Maybe you guys can set up a caravan? ;D
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I'm impressed by your work. Looks like you'll have a fine looking model when you're done.
Thanks for the repair photos.
Charles
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Still up in the air about the Polk City contest. It would be great to get up there again, even just to spectate.
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...the latest from the Grumman "Ironworks"...
Tonight I started filling in the "Star and Bar" insignia, next step will be doing the blue outline.
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Another area that required touching up was the "glass" for the ventral gun position. Dave did a great job when he originally detailed this airplane. y1
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...finished up the insignia tonight. Unless I screw something up I'm all done with the color painting. I just have to finish tidying up the ink lines and then shoot some clear over the repaired areas...
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While the insignia is drying I've started in on plugging the front of the pipe tunnel at the firewall. First, I scraped away and sanded some of the old fuel proofer (epoxy?) in the area. Then I made a filler bulkhead out of 1/8" lite ply. Once I finalize the fit I'll scuff sand and clean the entire engine compartment, glue in the filler piece, and then coat the entire compartment with 30 minute epoxy. ;D
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Thankfully, the top of this bird isn't needing too much attention. The only critical thing really is an open bay puncture on the top of the inboard wing. The overall diameter is only about 1/4" and with a tiny crack shooting off it to the rear that was just beginning. I figured trying to patch and repair it would result in a more noticeable blemish so I just dribbled in a spot of 30 minute epoxy with a toothpick. Hope it works!
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Shot what should be the final clear coats on the Avenger resto/mod/repair over a few sessions last night and this morning. I'm not impressed with my ink work, but it is what it is. I'll let it dry now for at least a week to get good and hard and then I'll try my hand for the first time at a little dope finish rubbing and buffing. Usually I just spray the final clear, let it dry, and then call it good on the finish. Dave had this thing so polished up though that I have to try my best to blend it all in as best I can. I really hope to achieve the same original overall shine to further disguise the repairs, we'll see how it goes. :)
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While giving all the touch-up paint work a chance to fully harden before I try my hand at some polishing, the past few nights I've been whittling away on the cowling for the Saito swap... ;D
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Finally, all done and ready to fly. I'll still try to do a bit more polishing on the bottom of the wing, but other than that we're ready to go...
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Just add fuel... ;D
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Outstanding work Wayne!
Derek
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Now, that is pretty cool. How's it fly?
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Way cool!!!!!
Marcus
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How's it fly?
Dunno yet, maybe this weekend, maybe.
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Wayne that looks fabulous!! Great workmanship! Please fill us in with your flight report.
Dave
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Hi WWW,
Outstanding repair work!! It REALLY came out really nice!
BIG Bear
RNMM/AMM
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Nice work Wayne, It looks really good! H^^ H^^
Can't wait to see some pic's of it outside at the field! y1
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Well, I thought I was done repairing this thing. It was too windy for any test flying but I had it with at the Polk City, IA contest this past weekend to show it to some folks. When I was loading things up to leave on Sunday I managed to bonk myself a nice new hole in the top of the outboard wing. Stupid mistake!!! HB~>
Tonight I started in on the new repair...(insert Powell "sigh" here) :(
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Yeah, things happen. I tell people I do more damage on the ground than I do when I'm flying. Try a door knob on a plane that had never been flown yet. Didn't know if I should cry or stomp it on the ground.
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Wayne I'm sorry to see the mishap. This is how I learned not to carry ink pens in my shirt pocket. I can only guess exactly how I got that shade of blue but it's not as dark as the Sig dark blue so I think I added black to their medium blue. I'd mix tiny amounts until I got close. When it dries it goes a shade darker. On a semi-scale you might mask off a square or rectangle and make it look like battle damage repair if you couldn't match it exactly. Could even leave it 'bare aluminum'. Years ago I saw a number of war birds including a TBM come in here locally to a restorer covered in bare patches.
These old dope finishes can get real brittle. I think I made it worse in earlier days because I used solely acetone as the thinner. It dried the dope out more than usual. Now I use laquer thinner and a little retarder. I've thought about reviving a couple older airplanes and decided I will spray on a new clear non- tautening coat. I'd thin it with a mix of 50% acetone to soften and penetrate the underlying coats and 50% retarder to allow the dope to dry slowly and glossy. A few drops of light machine oil in the dope should plasticize it and keep it from going so brittle again. Either the oil or make the thinner a three way mix including laquer thinner. I do think some acetone would be needed to get that old dope to soften. You could then re-rub it if you wanted. We'll try it sometime.
Dave
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However this patch comes out, that airplane is saweeeeet!! You do great work, my friend!
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Outstanding effort, Wayne...and Dave! Great looking ship!
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Thanks for the info and tips Dave, we'll see how it goes. There might be something to your acetone theory on this older dope finish, this thing is really brittle. y1
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If you can buy rejuvenator in smaller quantities than gallons, give it a try and see if it doesn't restore the flexibility of the old dope. (No, you guys cannot use it on ME!) I haven't used any for years, so can't tell you how available quarts might be. Try Aircraft Spruce and other full scale shops for it.
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I actually have a brand new pint of Brodak rejuvenator. I've never used the stuff on anything before. I'm not planning on trying this on the Avenger but I've often wondered if you could just hang up an older model, spray the whole thing with a good even coat or two of rejuvenator, and "bring it back to life". Has anyone here ever tried that process? If so, what kind of thinner/rejuvenator ratio would be best?
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I've done it on full scale, but never a model.
Check the container for suggestions on the ratio, and if there are none, I would experiment with a 50-50 mix first, then go whichever way seems best if that doesn't work well for you. If it stays stiff, reduce the rejuvenator to get more penetration. The other way, back off on the thinner a bit.
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Well, I finally got the Avenger finished up...again...
As kind of an experiment I did this last (hopefully!) repair with a small brush, sanding it smooth between every coat of clear, color, and the final clearcoats. The final sanding was with 1500 and then I finished it off with a good buff with some silver polish. The shine came out nice and even with the rest of the plane. A little half circle crack showed up once it got filled with the polishing compound, I didn't know it was there until then, I'll just have to live with it. It's pretty weird that it cracked though because it's in the freshly painted area. The repaired blue spot is actually a much closer color match than it appears, for some reason the spot brightens up in the photos. Anyway, I just mixed it as close as I could get to Dave's original color, it looks pretty good from across the street.