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Stuntman23 build - Finally working instead of talking

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Stuntman23 build - Finally working instead of talking

Post  RknRusty on Sat Aug 15, 2015 8:53 pm

I wouldn't even know how far back to look and see when I started talking about replenishing my 1/2A fleet... possibly last November after the Carolina Gang's 1/2A Day. The idea is to bolster my small Baby fleet with three Stuntman23s that are surprisingly capable aerobats and can also endure novice pilots, or whomever I foist the handle upon. And it was a great excuse to check out the new Michaels craft store in my neighborhood. They have good balsa, except it's too consistent, like most of the sheets came right out of the sawmill together. So templates are officially on the table, as well as an old Stuntman of Watt's and my old Green Death, later known as the chopper, after being aggressively shortened... and became a delightful flyer. And testbed for learning Tee Dees, balloons, tanks, and bladders. I remember flying it one day and seeing a pair of steel hemostats flapping in the wind Lol. Hadn't quite gotten the hang of it yet.

I found a couple of 1/4" fuselage sheets that had tight grain and seemed hard enough. I also found one at home that was very hard, but only long enough for two radial mount fuselages. The modern beam mount won't work with the short planks, but the Goldberg method would work. But I'm not wild about that design for a couple of reasons. For one of my models, I might go radial mount with a screw-on aluminum backplate mount for a Medallion. One of the models is going to CEF member Rat9000, who has been incredibly patient with my herky jerky schedule. Fair warning, if I bust a Stunter between now and the Criterium, there will be further delays. Regarding the fuse; I want to implement one of Ken Cook's enhancements and rip the fuse and insert a 1/8"x1/4" strip of spruce from the firewall to the tail. This will help prevent the fuse from breaking  behind the wing. I don't have any 1/8 spruce, and didn't think to look at the store. If it isn't available, I could use plywood. What about a 1/4" x1/16" strip of carbon fiber? Maybe I could use CF for an embedded spar on the wing.

I'm pretty happy with the 1/8" wing sheets, except it would have been convenient if I could have gotten 6" wide sheets, rather than 4". The chord is 5" or 5.5", I forget which. But splicing gives me the opportunity to stiffen it with a spanwise spruce spar, and/or find a good combo of grain that will compliment each other in a strengthening fashion. Lots of you guys can give me tips on splicing the wing together. I would appreciate any input on how to do this.

The 3/32" balsa for the stab/elev. are excellent, nice and firm but not too heavy. I'm trying my best to build it light in the tail. I've gotten lucky in the past. The Refried Bean, Lil Satan, and Oriental didn't require any weight at all to trim.

Here's what I got drawn today.


Below is a picture showing how the Goldberg kit spliced the wing. Of course the chordwise splice is just so they could fit it in the box, so I will not be cutting it there. But the spanwise splice is the one I'll need y'all's advice on.

Should I cut it straight along the probable CG? I doubt if I could do a staggered joint without hopelessly botching it. It'll certainly be straight if I embed a 1/8"x1/8" spruce or ply spar. What about a Carbon fiber strip rather than wood? Or is that going to be structurally helpful at all? The more I think about a spar, the less I think it's worth the trouble.

And when I finish this project, the one I'm really excited about is the Hyper Viper profile for my Conquest .15 CL engine. bounce Yeah yeah, talkie talkie...
Rusty

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Re: Stuntman23 build - Finally working instead of talking

Post  Ken Cook on Sat Aug 15, 2015 9:18 pm

Rusty, the problem that occurs with wings like that is the flexing that takes place in hard maneuvers. Personally I wouldn't go through the trouble to finger joint the wood like the kit. It's a silly idea and a good glue joint which is straight is equally efficient at least for this purpose. A strip of 1/8x 3/8 bass down the center carefully fit and glued would be more than adequate. It can also if adequately placed provide a through hole for your bellcrank. Making the tips out of the same material by running the strips of bass perpendicular to the wing directly on the tips will also prevent cupping which can also take place with wide wings like that. This is especially notable if you were to dope a wing like that. Many will paint a wing like this underside and topside and leave the plane sitting on a bench to dry. The underside solvents are trapped under the wing while the topside readily gasses off resulting in the top drying faster which shrinks placing a curl into the wing. I constantly monitor the doping as it's drying flipping things over and insuring equal coats onto top and bottom.

The nice thing about bass is it's straight grained and a razor plane can take the material down in just a few passes resulting in less sanding which can also warp things. I use the carbon fiber exclusively nowadays as I found that I can't come close to strength using anything else. Say bye bye to a broken fuse with little to no weight penalty. I have also glued balsa directly to arrow shafts which is extremely light and amazingly strong. They bury directly in a piece of 1/4" balsa and go undetected.
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Re: Stuntman23 build - Finally working instead of talking

Post  pkrankow on Sat Aug 15, 2015 9:54 pm

CA glue sticks to carbon fiber like nobody's business. It is crazy how strong that bond is. Some CA battens are really a good choice for stiffeners, if you choose to go that route.

Finger joints are there so a 12 YO can get the wing built right. Since you are gluing then applying the template this is not necessary.

Spruce is much superior to bass if you have it. I have used spruce and it was a delight to work with. Bass might plane a little better, maybe, but spruce takes loading and flex much better.

Phil

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Re: Stuntman23 build - Finally working instead of talking

Post  NEW222 on Sat Aug 15, 2015 10:01 pm

Nice. Now as for adding to the wing. When I build these little 1/2a flat wings, I used 3" wide balsa and put a 1/8" x 1/8" spruce spar spanwise myself. My last plane, I had put a spar in the center as well as on the leading edge. The weight penalty was small, and it seemed to take MY landings better than that of just balsa.
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Re: Stuntman23 build - Finally working instead of talking

Post  RknRusty on Sat Aug 15, 2015 10:07 pm

Ken Cook wrote:              Rusty, the problem that occurs with wings like that is the flexing that takes place in hard maneuvers. Personally I wouldn't go through the trouble to finger joint the wood like the kit. It's a silly idea and a good glue joint which is straight is equally efficient at least for this purpose. A strip of 1/8x 3/8 bass down the center carefully fit and glued would be more than adequate. It can also if adequately placed provide a through hole for your bellcrank. Making the tips out of the same material by running the strips of bass perpendicular to the wing directly on the tips will also prevent cupping which can also take place with wide wings like that....
So Bass for the wing spar and tips. That's good, I have that on the shelf already

Ken Cook wrote:The nice thing about bass is it's straight grained and a razor plane can take the material down in just a few passes resulting in less sanding which can also warp things. I use the carbon fiber exclusively nowadays as I found that I can't come close to strength using anything else. Say bye bye to a broken fuse with little to no weight penalty. I have also glued balsa directly to arrow shafts which is extremely light and amazingly strong. They bury directly in a piece of 1/4" balsa and go undetected.
And CF to stiffen the fuse. Putting a round hollow arrowshaft into the ripped fuse; do you mean I should rip it and then gouge a trough into each face to enclose it?
Thanks,
Rusty

P.S. It looks like your engine finally left Columbia today, so it's on the way to PA now.

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Re: Stuntman23 build - Finally working instead of talking

Post  RknRusty on Sat Aug 15, 2015 10:09 pm

Boy, I got good replies while I was responding to Ken. Thanks, guys, I'll read over all of it and ask questions if necessary.
Rusty

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Re: Stuntman23 build - Finally working instead of talking

Post  getback on Sun Aug 16, 2015 7:26 am

Glad your able to get back to this project , I like the stuntman 23 for what it is and have a lot of fly time in on them there is some good ideas here for the improvement of the wing cupping and fuse breaking right behind the TE . using the arrow shaft .. I would personally take the fuse and rip it just deep enough for the arrow to in bed into flush and glue in with CA being its lighter than epoxy , but that's just me ! my SM 23 that's not broken has wing cupping and don't fly like it use to and that's why it sets , With a finished wing I don't know if I could get it out probably since it already has repaired cracks in it . You are inspiring me to do some repair on it the time I flew it with the medallion on it it really moved out good . And about those flying Hemi-Stats lol! . Eric Laughing
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Re: Stuntman23 build - Finally working instead of talking

Post  Ken Cook on Sun Aug 16, 2015 8:09 am

One thing to remember, without all of the above mentioned, the plane will fly just fine. I don't like the mushing out in the hard maneuvers so I go the extra distance. I don't know about the Brodak kit due to never building this particular kit other than those that have participated here. A simpler approach is to use strands of carbon tow down the sides of the fuse CA'd to the side. While it doesn't offer a sleek finish, it will provide a lot of strength. A good solid piece of C grain however will provide great strength provided it doesn't weigh as much as a 2x4. If a bit more strength is required, a few coats of thinned dope will certainly up the ante. If even more is desired, silkspan the entire wing. Rusty, I don't go through the trouble on 1/2A's to rout out a concave groove for the shaft. I build my flaps on full size stunters using the concave groove. The arrow shaft becomes the leading edge of my flap. I use a a whiz wheel on the Dremel to cut my hinge slits.  I will V out the 1/4" balsa, glue the shaft to the stock if it's on the bottom or just place it directly down the middle. I usually sikspan or place iron on covering over it. Yes, if you look for it you can see it. If that's not something you prefer, a router table combined with a cove bit will readily give you a perfect fitting groove. I have Bob Zambelli's Stuntman. He probably doesn't even remember but I received it about 16 years ago and it flies superb. It's hideous the old bird. The saw marks are still on the slab as nothing was sanded, essentially stock kit with no replacement and a slap and dash paint job the way it was done by many of us in our early building stages. I love that little plane. Oil soaked to death but still going strong. All of the above advice offered is all true. I can say use what you have and started turning fast little circles. Ken
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Re: Stuntman23 build - Finally working instead of talking

Post  RknRusty on Sun Aug 16, 2015 9:46 pm

Ken, good point on the possibility of my overthinking this project, I'm famous for that. I am definitely going with arrow shaft, or hobby shop CF strip or tubing in the fuselage, but I'll probably keep the wing simple, or only do one with a basswood strip. I plan to run Medallions on the two I keep.
No progress today, burned a whole Sunday at my M-i-L's house. DAMMIT! lol!

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Re: Stuntman23 build - Finally working instead of talking

Post  pkrankow on Mon Aug 17, 2015 12:29 pm

RknRusty wrote:
No progress today, burned a whole Sunday at my M-i-L's house. DAMMIT! lol!

Sounds like my last two weekends.

You are making me want a Stuntman. I just cut templates from Outerzone and put the wing together in paper.
http://outerzone.co.uk/plan_details.asp?ID=4338

But paper is all I get right now. Too many other projects right now, and I am behind on house cleaning.

Phil
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