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Old Aug 31, 2010, 01:34 AM
Master of the Wind
G Norsworthy's Avatar
United States, CA, San Jose
Joined Sep 2008
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Whoops!
Caracho-Pike Perfect repair double header

I came over to poach a thermal, thought I was higher, entered to circle in the same direction, and the unthinkable still happened. No rain of parts but both took it pretty hard. The Caracho is definitely repairable, the PP is a toss-up between repair and replace. I have both parties sitting here but will start with the Caracho since it needs to get back in the owner's hands ASAP.

Spent 2 days reading up on the repair threads. The small LE dent is no problem, no worse than the Parker dent in my Opus. The other side has a broken bottom spar and lots of skin delam. There seem to be two general strategies to skin repair, Bob McGowan's pick and CA, and the square cut and replace method. We will probably use a combination of both here.
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Old Aug 31, 2010, 01:49 AM
Master of the Wind
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United States, CA, San Jose
Joined Sep 2008
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There is always a need to see some progress. Started with the fuse wrinkle. Alternated between CA and wet permagrit grind and found a glass/kevlar layup underneath. Cut down to but not through the kevlar and took the paint back a bit. Made a bandage of uni carbon followed by 1.5 oz glass, wrapped it in Accuply release film then blenderm tape, tight but not tight enough to collapse the boom. Should be ready to fill and sand tomorrow.

Moved on to pick and fill on the small dent. Pulled up the skin and used CA to attach any delams. Filled in the missing area with balsa. General strategy was to end up slightly low so that the affected area can be feather sanded then back filled with carbon/glass cloth and filled back up to the airfoil shape without cutting any more fibers than necessary out of the patch.

Spent a little time picking and CAing on the bad side where things go back together nicely. Fortunately the center mount and joiner boxes were not damaged. Took out some of the shear web and ground (with vacuum) the spar out where it was broken, as the wrinkled fibers were preventing fitting things back together straight.

Tomorrow will pick up a few more clamps and prepare to glue the spars back to the shear webs. Still pondering how to match that salmon color...
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Old Aug 31, 2010, 02:00 AM
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Jyvaskyla, Finland
Joined Aug 2003
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All parts, also center panel look repailable. Spar is ok, but damage like that is almost impossible fix to like new condition.

Here are some pics from my Aspire center panel. Just to inspire you... the plane was damaged in Turkey WC 2008, and repaired in 1 hours time using just CA, x-acto knife and Vladimir Ava d-box material. The result was perfectly flyable and plane is still in use (although I sold it). Small irregulalities in airfoil do not affect performance in thermal flying. They might hurt distance performance, though.

Just make the repairs strong and beware warps







Later I laminated some carbon to wing underside, to make it stiffer torsionally and in landings.

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Old Aug 31, 2010, 02:26 AM
I do this for fun!
Sunshine Coast, Australia
Joined Sep 2004
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I've repaired a lot worse than that on a Caracho and a Shooter and had them fly as well after as before. I'm sure you'll do a better job than me

Ken.
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Old Aug 31, 2010, 03:23 AM
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Jyvaskyla, Finland
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Quote:
Originally Posted by skyboyken View Post
I've repaired a lot worse than that on a Caracho and a Shooter and had them fly as well after as before. I'm sure you'll do a better job than me

Ken.
Yes, the pics in mail #2 look like perfect repair job. Perfect will become "perfect" again
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Old Aug 31, 2010, 01:36 PM
Martin
USA, CA, Piedmont
Joined May 2005
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Repairs

AirCraft Spruce has a great two part light weight filler that works perfectly for the finishing work on these repairs. It is easy to apply, dries very quickly and sands mooth.
Mart
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Old Aug 31, 2010, 03:12 PM
Master of the Wind
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United States, CA, San Jose
Joined Sep 2008
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Thanks for the encouragement. Nice graft, Tuomo. Mart, I will look into that filler as there will be some filling. Couldn't resist and unwrapped the fuse on the way out this morning. Came out really nice with the skin faired down under the patch. If I knew how to paint I think I could hide it.
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Old Sep 01, 2010, 01:44 AM
Master of the Wind
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Scored some foam and assorted syringe parts dumpster diving, and picked up two more clamps on the way home. Also a turkey baster to go with one of the tips, but that was not needed yet.

Fixed the skin and hinge line behind the spar with CA. A little ripply but it will have to be patched with cloth and filled anyway. The big job was to glue the spar back to the shear web. First I picked and cut out as much of the splooge fillet as I could get to. Then a dry fit with the clamps. Looked pretty good. Then I used the plastic tip on the syringe to inject epoxy as far back as possible into the shear web and spar joint, which is pretty wide. Put in a little extra for good measure. Clamped it down and went after the other side top with 3 oz carbon and 1.5 oz glass with release film, foam rubber, and books. The LE and TE sight straight. Next will be to feather the bottom spar and replace it with tow, then sister it with graphlite and epoxy/chopped carbon in place of the splooge.

This repair is going better than I thought, but then I haven't started trying to restore the airfoil yet. Looking at the PP maybe isn't as bad as I thought but still worse than this one and gives me a stomach ache.
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Old Sep 02, 2010, 01:03 AM
that's gonna hurt...
USA, CA, San Jose
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Greg - good of you to help out Ken this way. I know he'll apreciate getting back in the air.

Bruce
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Old Sep 02, 2010, 01:12 AM
Master of the Wind
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Did the spar tonight. Feathered it down with a dremel sanding drum and vacuum. Not sure how wide is necessary but it is about 2.5" total. Next inserted the missing piece of shear web with splooge. Then back filled the missing spar area with tow, above the skin level. Will somehow need to cut that back down but will think about that when the times comes. Finally added 3 pieces of graphlite to sister the top spar just in case buried in splooge, and 3 pieces of graphlite to bridge the LE, which will be much stronger than pure splooge. No pics since I can't work and shoot at the same time, and it got warm again so I have to work fast.

Started sanding and filling the fuse bandage. This part looks pretty good.
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Old Sep 03, 2010, 01:31 AM
Master of the Wind
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Cut a window in the newly repaired skin behind the spar so I could access the top skin and glue it back together without so much distortion. Found that the rear of the shear web was not well clamped like the front, leaving a small bump at the rear of the spar that I will have to sand out of the skin. Not too bad but annoying. Back filled it with splooge. Spent some time fixing the remainder of the attached skin. Filled the dent on the other side, should be ready for block sand tomorrow. The filler is good stuff.

Got the fuse sanded and ready to paint. Can put this away for now.

PP is another story. Looks like the spar is broken on top but not on the bottom. However like the Caracho it is detached from the shear web. This one has less crunch in it and goes back together very cleanly. Any opinions whether I could clamp this together and then run CA down the interior to soak the joint between the spar and shear web? The alternative is to inject epoxy again but there is much less access as the cutout is smaller and it looks like the split runs pretty far toward the center section. Another idea is to CA as far as I can go and feel the heat when it kicks. Beyond that drill micro holes just in front and behind the spar and get more CA in where it did not reach.

The other problem is that unlike the Caracho even with the crunched part of the LE skin cut out the LE's do not line up straight. That means there is twist or distortion somewhere in the wing. The top skin behind the spar is wrinkled so I am thinking of cutting a window right from the start to get access to the bottom skin, which is much less wrinkled. The foam used in the PP is much harder to piece back together than the balsa in the Caracho.

Think I will sleep on this one and take another look after I cut away the crunched spar tomorrow.
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Last edited by G Norsworthy; Sep 03, 2010 at 01:34 AM. Reason: idea
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Old Sep 03, 2010, 12:34 PM
F3X
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Costa Mesa, CA USA
Joined Jun 2001
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When you splice the spar do the outside repair as you described and try and taper it 10:1 .10 thick cap so 1.0inch scarf each side of the break.
Also since you have access take out the shear web under the scarf and add uni to the inside spar and then add back a shear web of vert balsa and glass the sides.
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Old Sep 04, 2010, 01:24 AM
Master of the Wind
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United States, CA, San Jose
Joined Sep 2008
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Good idea. Looks like the spars are under control.

The SuperFil is good stuff. One round on the pole dent and I can see this repair will disappear with a little paint. The other side, well we will see how good I am, or how much patience I have. Put balsa tabs on the skin and replaced the triangular patch on top. Then added tabs to the cutout for the new skin. Had a great idea put together from ideas here to curve a piece of balsa with water using an intact section of wing. It came out good but it appears that the skin is not 1/16" balsa. Need to go out tomorrow and pick up some 1/32". It might actually be 1/20 but a little thinner with 3 oz carbon skin and filler should bring it back pretty close to original.

Cut a window behind the spar on the PP. Ground out the buckle on the top spar and now it does not look so bad. Peeled it up and did the syringe trick again to glue back the shear web. That part is really clean. Unfortunately the foam core transmits shock pretty far from the impact point and does not go back like balsa. Getting the skin back where it belongs is going to be a challenge, since some of the spongy part goes all the way to the tip.
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Old Sep 05, 2010, 01:26 AM
Master of the Wind
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Joined Sep 2008
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Got the Caracho buttoned back up. Will need some filling and sanding, and the repair area may be slightly thicker than the rest of the wing, but we will see what we can do. Used the dremel drum and vacuum to feather the skin over all the seams. Laid in 3 oz carbon cloth in front and 2 layers of 1.5 glass behind the spar. Let that cure with release film, foam, and books on top. It followed the contours pretty well. After that the first layer of filler. Tomorow the top.

PP got the spar feathered back the 10:1 plus a little. Went deeper right over the break. Cut 3 different lengths of carbon tow to fill the gap. Wet it out, not dry at all, and let it cure with books on top. Actually looks pretty good. May not even be much over.

Spent the rest of the time picking and glueing skin. The foam is very porous and CA does not kick very fast in it like it does in balsa. Don't quite understand why it bonds skin in seconds and airplane in minutes even if you rub it. I will have to live with wrinkles in the skin. No way I am cutting that all out and replacing it. Probably would not be any better anyway.
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Old Sep 05, 2010, 02:57 AM
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United States, CA, Fremont
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Looking good my friend. Hope to see this (PP) back to air soon.

-Kai
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