stunthanger.com
Electric Stunt => Gettin all AMP'ed up! => Topic started by: jjorgensen on November 24, 2011, 02:35:01 PM
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Here is my funfly airplane for the Minneapolis Piston Popper's Jan. 1 get together. Arrowind 2215/20 motor, 8-6 prop, 3S 2100 mah lipo, 16oz.
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I LIKE it! Looks like a real nice build, and Larry Renger's designs all fly great. You should have plenty of power too. Have you flown it yet?
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Great job! ;D
Tell more about construction? Did you get a set of laser cut parts or cut your own? Were there any glitches in the construction that I should fix? What lines do you plan to use?
At 16 ounces it is about double the weight of the original, but that just brings its wing loading (cubic wing loading) in line with regular stunters. I am dying to know how well it carries that much weight, and whether the structure is adequate to do so.
My very best wishes to you for your first flights!
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I blew up the plans from the magazine and cut my own parts. The only problem area I had with the construction was connecting the outboard trailing edges with the straight piece that the elevons attach to. It seemed very weak to me so I ended up using my hinge slotting tool and inserting a 1/64th piece of plywood to reenforce the joint. That stiffened everything up nicely. I think the front turbulator spars could be a little thicker also, but that's just my preference. I have used similar turbulators in free flight models but they are delicate and easy to break just by picking the plane up by the wing. I'm going to start with 40 foot lines. I had this same power package on a 1/2 A Pathfinder that flew a little fast, so I'm hoping it will be ok with this design. Hopefully I can get in some trim flights before Jan. 1 if the weather cooperates.
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I agree on the spars. Adequate for performance but a pain when handling the model. In the past they were even SMALLER! The weight penalty of going bigger is negligible, so I will. Good call, thanks. H^^
As far as the trailing edge thing, the sheeting is really the source of strength in that area, and the stresses are pretty much taken by the spar and ply bellcrank mounts.
How did the Lucky Boxes and control link work out for you?
The power system you quoted sounds like at least equivalent to a .10, probably a .15. I would set the power fairly low for first flights, and maybe only 1 minute or less duration. It took me quite a while to find the right handle spacing, balance point and control horn length. Doing a full 5 minutes, then needing a new battery when you found out what you need to know in a couple of loops is a major bummer.
Once you find that sweet spot, though, competition beware! HH%%
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By the way, did you scale the model up to my 250 sq.in. size or go larger?
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I scaled it up to the 250 square. It may be a 1/2 inch longer wingspan, but it is very close. The lucky boxes seem to work fine. I left a little slop so they move more freely. In fact, I upped the trailing edge from 1/16 to 3/32 so I have 1/16 piano wire inside 3/32 lucky boxes. Same with the rudder and fill in pieces on the fusalage side. That accounts for a little weight gain, but the majority is in the battery. It wasn't clear to me from the plans how to join the trailing edges so I ended up with a butt joint just outside the sheeting which is why it appeared weak. Even with gussets it had to much play for my taste, so I put in the plywood biscuit. I'll keep the initial flights short till I get a feel for it.
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I just ran some quick calculations and it appears you have the power of a .15 which is 3 times the power used on the original model. Combine that with double the weight, and I predict that you can easily tear the model apart in midair! ~^
Hate to be gloom and doom, but since you haven't flown it yet, I suggest finding a much lighter, lower power system for it. Sorry. :(
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You can always reduce the prop load and reduce the horsepower!
#^
Dean P.
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For 1cc stunt, we use 15 Watt-Hours total battery capacity as the limit. Andy Borgogna's Baby Pathfinder hits that limit and flies very well indeed. The system mentioned above is over 25 Watt-Hours. My Electric Baby Flite Streak only needs 9.8 Watt-Hours.
Reducing the power is simple, but it doesn't reduce the weight until you re-equip. Of course, running the existing motor on a smaller prop will allow a smaller battery, and that would be a huge help.
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Yes, but in the meanwhile even more weight can be reduced by shedding the wings at high speed!
Of course I'm not being serious ... there is no substitute for lightness, but at least the ship could be flown safely for now.
take care,
Dean
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Has this been flown yet? I'm really eager to find out how it goes! #^
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Is the weather that bad? We want to hear your flight report. #^