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Mark Boesen's

Nice original Babe Bee from a Super Cub 105, late fifties.



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Grounded the Fleet

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Grounded the Fleet

Post  batjac on Fri Feb 13, 2015 1:52 am

Well, after flying the Traveling Engine with a balloon tank, I got the urge to try a TD and balloon on my BTC-4B plane.  So, I pulled off the Medallion and wedge tank and replaced them with a TD.049 and a balloon, and put 42’ lines on.  I also moved the pushrod in one hole to give the elevator more throw.  It took a few tries, but the TD fired up.  It could have used more time tweaking for best needle setting, but oh well.  I should have bench run it first, but it was clear yesterday morning, so I rushed to get it in the air.  Here’s the video of the flight (watch it in large screen for the payoff shot):



I over-controlled the launch.  I guess one hole in on the horn gave more control than I thought.  It made tighter loops than I expected, but with a couple more flights I would have gotten circular loops down, I think.  It did fine on the first three loops, but when I gave it up elevator for the fourth loop, that was when the fuse and wing went their separate ways.  I didn’t do enough straight and level laps to get a good 10 lap speed average, but my whiz wheel says that after the engine unloaded, it was doing 61MPH.  I love playing with new toys.

And, this did actually do a good thing.  It validated the whole BTC concept.  I didn’t even feel bad that the plane crashed.  A little chagrinned, but not upset at all.  I built it knowing it would eventually crash, but I was more kinda thinking of a figure 9 or something.  Well, lesson learned.  The basic BTC design is okay for reedies, or a milder Medallion, but not for a hot TD.  

The glue joint didn’t fail on the plane, the wood of the fuse failed, taking the wing and the top part of the fuse with it.  Ah, well.  A quick fix.  Well, okay, so I threw it in the trash can at first and was going to just move on.  But, that would have been a waste, and against the BTC spirit.  So I fished the parts back out of the trash can.

It really was a quick fix.  I just carved the fuselage top and the balsa fillets from the bottom of the wing and sanded it smooth.  Then I carved and sanded the remaining top of the fuse to a clean shape that I could glue a canopy to.  I grabbed a scrap piece of ¼”x1” trailing edge stock and cut to shape for the canopy.  The stab broke loose, so I carved and sanded the remaining fuse balsa from the stab and got it ready to glue back in.

I drew a line from front to back, ¾” up from the bottom, to ensure the wing and stab were in line.   I took a piece of 4” airfoil shaped balsa left over from the wing construction and traced around it for the wing cut out.  Then, to strengthen the tail where the crash had ripped out the balsa, I grabbed a ¼” stick of scrap spruce and cut out slots in the fuse for the stick and the stab using the pencil line for a guide.

I cut the hole for the wing in the fuselage and sanded the top center of the wing to cut through the clear sealer for a good glue joint.  I glued in the wing, the stab/elevator, and a new fin.  Glued on the canopy, made a new pushrod, and sat back to look at what I’d made.  I didn’t think to take any pictures while I was rebuilding, I just wanted to get the thing rebuilt quickly.  

So, it went from this:



To this:




I like the new look.  If I ever build another BTC-4 variant, I’ll do a mid-wing like this.  It really wouldn’t take any more time to do it this way.  Now to make up a bladder system for the TD and it’s ready to test out.


I grounded the other BTC-4 and put glass reinforcements on the fuselage to wing joints on both sides of the fuse.  That plane’ll not be coming apart now.  I’ve change the product engine on it out for a built up Killer Bee copy and see how it does.  I’m looking forward to that.  Especially now that I know how little it hurts to crash.  I’ll push more and hopefully learn faster than I am now.


Unfortunately, I won’t have time to get in another flight before I have to leave town, so the test flight will have to wait until I get back.

The Revisionist Mark
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Re: Grounded the Fleet

Post  pkrankow on Fri Feb 13, 2015 8:05 am

That's a looker now!
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Re: Grounded the Fleet

Post  RknRusty on Fri Feb 13, 2015 10:11 am

It was needled fine at takeoff. and unloaded to full speed in the air, but something about the fuel feed changed. Have you got a picture of your balloon setup?
Rusty

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Re: Grounded the Fleet

Post  roddie on Fri Feb 13, 2015 10:54 am

Nice tight loops though!! I hope the re-build flies as good. At least the reinforcement of the others shouldn't have changed the c of g. I agree.. cutting a wing-slot as opposed to a high-wing mount wouldn't require much more time. A canopy definitely looks nice though.. and you could easily add them to the other high-wing versions to dress them up a little.. Thumbs Up

Did you ever fly the BTC-"twin" with the R/L-hand props?
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Re: Grounded the Fleet

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