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Author Topic: Not so much building, more like rebuilding techniques!  (Read 1275 times)

Offline Matt Brown

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Not so much building, more like rebuilding techniques!
« on: July 27, 2017, 12:09:00 PM »
A few months back I was putting in the maiden flight on a profile plane I picked up at a swap meet.
Flight started out okay but I thought the engine was a little rich. After am minute or two it was about right. I flew through quite a few maneuvers and noticed it continued to get a bit leaner. Another minute or so and it was really lean. As the plane came into the wind once, I saw a bit of flutter on the stab. Did it again the next lap. I started doing some hard climbs and dives as it came into the wind to let the elevators add some stiffness to the stab. This worked for several laps without any flutter. Next time around was too much or I just didn't have enough control throw in and it fluttered big time, snapping the outboard half of the stab off. The plane took an instant dirt nap.
Wing was fine but nose broke off where the doublers ended and the stab/elevators were toast.
Back at home I made a new stab and elevators. I also cleaned up the nose break as best I could while leaving as many of the splintery pieces in place that would mesh back into place. I put it back on with 30 minute epoxy. It went back in mesh very well, within less than 1/32" from original position.
Any suggestions on additional strengthening methods? It just seems like losing the one piece fuse is a lot of strength lost. I considered cutting away the top 1/4" and laying in a piece of spruce to bolster the joint but not sure I'd be gaining that much. I do not know the internal structure of the wing but I considered some hardwood dowels going down into the the wing center section.

Ideas?
Thanks, Matt
« Last Edit: July 27, 2017, 01:21:46 PM by Matt Brown »
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Offline Target

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Re: Not so much building, more like rebuilding techniques!
« Reply #1 on: July 27, 2017, 01:18:51 PM »
Is it a profile fuse, I assume?
If so, I would add some hardwood rails outside the engine bearers if there is room, or if not at least add a plywood tripler on each side of the fuse to cover the break and extend past a ways.

On the stab, I would add a hardwood or CF tube the same thickness as the stab, ahead of the hinges enough to not disturb the hinges (assuming nylon pin style hinges). I would extend the stiffener about 2/3 span on each side and obviously use a continuous piece.

You are on your own on the wing. But you get the idea from the above ideas.

Your dirt nap comment made me laugh out loud, and I needed that, thanks! LL~
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Regards,
Chris
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Offline Matt Brown

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Re: Not so much building, more like rebuilding techniques!
« Reply #2 on: July 27, 2017, 01:24:43 PM »
Quote from: Chris Behm on July 27, 2017, 01:18:51 PM
Is it a profile fuse, I assume?
If so, I would add some hardwood rails outside the engine bearers if there is room, or if not at least add a plywood tripler on each side of the fuse to cover the break and extend past a ways.

On the stab, I would add a hardwood or CF tube the same thickness as the stab, ahead of the hinges enough to not disturb the hinges (assuming nylon pin style hinges). I would extend the stiffener about 2/3 span on each side and obviously use a continuous piece.

You are on your own on the wing. But you get the idea from the above ideas.


The stab and elevators were toast. I made new although the only balsa I had on hand seemed a bit too light. So I didn't have a repeat crash, I glassed the stab with 3/4oz cloth. I think it will be plenty strong now.


Matt

Your dirt nap comment made me laugh out loud, and I needed that, thanks! LL~
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Offline Steven Kientz

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Re: Not so much building, more like rebuilding techniques!
« Reply #3 on: July 27, 2017, 04:13:42 PM »
I would use bamboo skewers  in predrilled holes to secure the nose. Drill at an angle from the broken piece thru the new glue joint. Bamboo is really tough/stringy. You could use CA, I use Sigment.  You've seen my crashes and rebuilds.

Steve
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Steve Kientz
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Offline Steve Helmick

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Re: Not so much building, more like rebuilding techniques!
« Reply #4 on: July 29, 2017, 06:53:23 PM »
In the great English model magazine Aeromodeller, there was an article devoted to the subject of repairing. The author advocated keeping all the pieces and gluing them all together, then splicing in new wood to replace all the little bits.  D>K Steve

PS: I like the idea of the bamboo skewers...just use chopstix on the fuselage splice, with epoxy. Drill the holes a wee bit oversized, so you can get the glue full depth. 
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