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Old Aug 29, 2004, 11:38 AM
solo6796's Avatar
United States, TX, Richmond
Joined Aug 2003
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Bird of Time ...One more Time

Finally getting around to building my BoT. Got the Dynaflite kit and it's all true....kinda crappy wood and stuff. Got George Voss's fiberglass fuse and laser cut ribset and all new wood.

Incorporating a bolt on, 3 piece wing with spoilers.

Using Womack's bolt beam made with .060 carbon,and balsa shear web buried in a laminate of 3 kit ribs from the Dynaflyte kit. The rest of the ribs are Voss's laser cut set of the original Thornburg plan. Upper spar is 3/8 spruce, doubled, with .007 carbon laminated in between and capped with CF at approx.010 thickness (from Don Cleveland, the stuff he uses on the Avenger wing) continuous. Three piece wing. Single spar on the bottom capped with a laminate of .007 carbon tape. 3/8 hard balsa shear webs throughout and wrapped in Braided kevlar cord .025" dia, 5 yards per side. The dihedral brace is 1/8 plywood, extending 12" per side on the leading and 9" per side trailing.

Should be strong enuf. Outer panels and tail feathers are done. Using George Voss's fiberglass fuse, narrow version.

Got to have the spoilers, working that into the design. Estimated maiden in 2-3 weeks.

I thought the spar looked decent enough, just had to post it. This assembly weighs in at just shy of 5 oz.

AJ
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Old Aug 29, 2004, 11:43 AM
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United States, TX, Richmond
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A couple more........
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Old Aug 29, 2004, 01:25 PM
WGH
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Iowa
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Doesn't that big hole in the middle of the spar weaken it?
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Old Aug 29, 2004, 01:31 PM
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USA, TX, Houston
Joined Mar 2004
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BOT Again

It looks great Alan. You are leading the building again like you did with the Hawk.

I have the RCM plans and plan to buid the 3 piece wing version someday soon. I will be folowing this thread and looking at the pictures. Gosh, there are so many projects waiting to be started!

Tommy L
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Old Aug 29, 2004, 02:12 PM
solo6796's Avatar
United States, TX, Richmond
Joined Aug 2003
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Quote:
Originally Posted by WGH
Doesn't that big hole in the middle of the spar weaken it?

No, I've seen Jack Womack's setup withstand a full pedal launch and hard zoom. Mine may not be THAT strong, but I expect it to handle a hard launch.

The plywood dihedral brace is filled with 3/8" vertical balsa shear webs and filled epoxy. I tried to stress it, and there is no flex. The three spars are over and under the bolt beam, and the CF is one continuous piece from panel tip to tip.

We'll see soon enough........

AJ
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Old Aug 29, 2004, 02:16 PM
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United States, TX, Richmond
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Tommy,

Let's go Flying!

AJ
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Old Aug 29, 2004, 08:09 PM
WGH
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Quote:
Originally Posted by solo6796
No, I've seen Jack Womack's setup withstand a full pedal launch and hard zoom. Mine may not be THAT strong, but I expect it to handle a hard launch.

The plywood dihedral brace is filled with 3/8" vertical balsa shear webs and filled epoxy. I tried to stress it, and there is no flex. The three spars are over and under the bolt beam, and the CF is one continuous piece from panel tip to tip.

We'll see soon enough........

AJ
Ok, looking good!!!!
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Old Aug 29, 2004, 09:37 PM
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Athens, LA, United States
Joined Apr 2002
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Solo:

Looking good!!

Mine is completely ready for finishing tonight. In fact, I have been working on it tonight. Waiting for epoxy to cure now. I expect to post some more photos of mine this week and will maiden it soon.

I am going to try to cover the fuse with Ultracoat. If that doesn't work, I'll paint it. I'm gonna start on the fuse because it isn't as straight forward as the wings and tail surfaces.

I'll keep your build in my favorites.

EJ
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Old Aug 29, 2004, 10:28 PM
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United States, TX, Richmond
Joined Aug 2003
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ejett,

Thanks, I've been watching your build and can't wait to see it all together. I have the ribs and webs in the left center and working on the right side now.

I noticed your stab pix and am worried that your pivot tube may be too short. I would make it long enough to get passed the first set of capstrips (ribs). That way, the load will be carried over a larger area. I saw a guy at the Mid South blow off his stab on launch. He had made it light, but the pivot receiving tube was only about 1 1/2" long. The stab broke at the end of the tube, between the first rib and the inner end.

I know it's a little late for that, but it might be a little weaker than it should be......

AJ
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Old Aug 29, 2004, 11:15 PM
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Athens, LA, United States
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AJ

You have a good point. I don't think I will have a problem on my ship because it is not intended to be used on a winch.

Based on your comments here though, I will make another set when I build the BotF version, I hope to build next. It would definitely need to be strong enough. I don't like the little 1/16 wire at the front either. I will go with at least 3/32 with 1/8 for the pivot pin. I'm saving my FG fuse for the BotF version.

Keep up the good work on yours and thanks for the heads up on the tube.

EJ
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Old Aug 29, 2004, 11:17 PM
B for Bruce
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The 'Wack, BC, Canada
Joined Oct 2002
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If you're going to redo the stab pin and receiving tube linkage here's what I did with my BoT. The longer tube in the fin totally eliminates the wobble that comes from wear or play at the fin with the usual short spaced plates or short tube.
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Old Aug 30, 2004, 10:27 PM
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United States, TX, Richmond
Joined Aug 2003
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Got the center section ribbed and webbed and bottom sheeting done. Laid it out on the couch, and started making those glider sounds in the living room.

Spoilers are next, then sheeting, and sanding, sanding, sanding........

AJ
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Old Aug 30, 2004, 11:06 PM
Think Thermals!!!!
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Costa Mesa, California
Joined Mar 2004
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Quote:
Originally Posted by WGH
Doesn't that big hole in the middle of the spar weaken it?

Yes. However the center is so over built it most likely will not suffer a failure. I sure wouldn't cut a hole in mine. There are other ways to provide sufficent structure to anchor the wing to the fuse.
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Old Aug 31, 2004, 04:10 AM
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Houston Hobby, Texas, United States
Joined Oct 2003
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Jack's green BOT

That big hole in the middle of the spar makes little if any difference at all. The load is carried by the .060" thick carbon fiber spar caps which are held apart and parallel by the balsa spar. 1/16" thick carbon fiber x 1/2" wide, top and bottom spar caps, will carry a huge load. The hole is placed at the nuetral point that carriers little if any stress.
AJ is using Jack Womack's details. I have seen Jack go for full pedal launch and zoom off the winch with his BOT more than once. I wouldn't bet against the system, it works.
I dug up a few old pictures of Jack's green BOT which now belongs to Walter Higgens.

RBeach
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Old Aug 31, 2004, 06:43 AM
solo6796's Avatar
United States, TX, Richmond
Joined Aug 2003
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Comon' guys, that hole ain't so big.......

The spars/shearwebs carry the load. Without them, the plywood brace would splinter easily.

Anyway, I guess I'll find out soon.......

AJ
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