stunthanger.com
Electric Stunt => Gettin all AMP'ed up! => Topic started by: Target on September 12, 2015, 12:47:51 PM
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I realize that this will likely vary from design to design, but what are the "standard" mods that folks in the know will do to a kit while building for a dedicated electric stunt plane?
I have an RSM Thunderbird 2 kit that I would like to build and could use tips to end up with it at a nice light RTF weight. I'm also aware that some designs lend themselves to conversion better than others. If it doesn't look like I can build it light electric, then I will go with glow... But I would rather go electric. Since there is little or no real vibration, I would think I could "get the lead out" on the build and end up light.
It is my intent to finish the plane with an iron on covering, blasphemy, I know, but....
Any suggestions appreciated.
Regards,
Chris
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If it was made for the pipe you can cut allot of fuselage off the bottom.
MM
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Get rid of the maple motor mounts, go with 1/64 ply doublers, use a composite of 1/16 balsa and 2 pieces 1/64 ply for the LE bulkhead. Mold your balsa rather than carve it, watch how much glue, especially epoxy you use. Cover the wings and stab with Monokote or Ultracote. Taper your control surfaces, go with 3/32 control horns if it is a 40 size stunter, etc. Cut off the extra lengths of wire for the electrics, use a lightweight CF prop and spinner. Use those thin very light weight wheels, Don't have excess lengths to your metal hardware, no pilot, no instrument panel, use contest wood, build up your flaps, stab, and elevators. Go ahead and build up the vertical fin too! Wrap your lead outs to the minimum of AMA specs, and keep them as short as possible, use the lightest weight line clips too. Hollow out wing tips, enlarge holes in bulkheads and wing ribs without weakening them, use the heavier balsa on the outboard side, minimum size fillets, minimum number of hinges to be safe, CF push rods with ball links, CF bell crank, and last of all use a light weight tip weight box!
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Wow, Crist.
I'll keep those things in mind.
Anything else, LOL?
That's a great list, thank you.
Where do you buy the skinny wheels from?
Kind regards,
Chris
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I'm sure Crist didn't intentionally leave it out but good lightweight batteries such as Thunderpower or Hyperion HV series will also help, remember with the HV batteries you will also need a charger capable of charging them to full capacity.
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Wheels
http://www.maxxprod.com/mpi/mpi-29.html
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Get rid of the maple motor mounts, go with 1/64 ply doublers, use a composite of 1/16 balsa and 2 pieces 1/64 ply for the LE bulkhead. Mold your balsa rather than carve it, watch how much glue, especially epoxy you use. Cover the wings and stab with Monokote or Ultracote. Taper your control surfaces, go with 3/32 control horns if it is a 40 size stunter, etc. Cut off the extra lengths of wire for the electrics, use a lightweight CF prop and spinner. Use those thin very light weight wheels, Don't have excess lengths to your metal hardware, no pilot, no instrument panel, use contest wood, build up your flaps, stab, and elevators. Go ahead and build up the vertical fin too! Wrap your lead outs to the minimum of AMA specs, and keep them as short as possible, use the lightest weight line clips too. Hollow out wing tips, enlarge holes in bulkheads and wing ribs without weakening them, use the heavier balsa on the outboard side, minimum size fillets, minimum number of hinges to be safe, CF push rods with ball links, CF bell crank, and last of all use a light weight tip weight box!
H^^ H^^ H^^
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I make a balsa plywood fuselage (1/8 vertical between 1/16 horizontal) using contact cement!
Spars do not need to go all the way to the wing tips!
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Thanks Crist, John and William.
R,
Chris
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My experience is that electric firewall & battery tray installations are typically lighter than beam mounts. Case in point: I converted a ARF SV-11 fuselage by removing the beams and installing the firewall & tray and netted a 21 gram savings. Of course, if scratch built I would have used thinner doublers, etc as Crist pointed out. I also like lite ply instead of birch ply where prudent. If you cannot use thinner doublers then consider cutting lightening holes in them
A VERY important consideration is the arrangement of the components. in addition to all the operational aspects (function, serviceability & such) this is vital in assuring you can achieve your CG with minimal ballasting. The T-bird has a long nose & short tail, I would be worried about it going nose heavy. If you can take a 8-10oz lipo and slide it a couple inches fore/aft you can make a big effect on the CG. I notch out the wing LE as deep as feasible and build in reinforcements. Then I also try to keep the battery tray open all the way to the back of the motor.
Selection of components matters. Test flights on my newest bird revealed it was tail heavy and that the battery was larger than needed. Luckily this airplane has a front mounted motor so I was able to swap in the next size larger motor and the next size smaller battery to move the CG forward AND score a 19g total weight save - not a bad trade!
Given the mission of a CLPA bird I would urge avoiding extremes in structural changes. We still need the airplane to be adequately strong and stiff. It still comes down to common sense light weight building techniques (go study a Crist Rigotti build thread), same as if you were using IC. In this regard, the use of iron-on covering is a good thing...
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Thanks Dennis.
I learned the notched wing LE/open bulkhead lesson on my arf oriental. I "almost" did that mod to it, but decided not to, and have some regret about my decision. I'm still a little nose heavy and have 3/4 oz tail weight installed.
For that plane, I'm looking at a lighter battery (I'm using 1650ma of a 2700 battery), but it is as far back as it'll go now....
I'll look the plans over more carefully as I prepare to build and see if I can save weight north of the cg so as not to have the same issues.