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Building Tips and technical articles. => Building techniques => Topic started by: Jonathan Chivers on April 29, 2013, 01:06:58 PM
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Hello all,
most plans give an indication of how much weight I should put on the outside wing, but how do you know if this is right for your model, lines, wind etc?
Related to this, when converting an I/C design to electric, does the placement of a battery on the right hand side of a profile fuselage change this?
If this has been covered before, please point me at the right link.
Jonathan
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Again,, searching on the forum for "tip weight" will give you a weeks worth of reading,,
MY method to bench trim is to set the airplane up as it will fly,, level wings, put my scale under the outboard tip, add lead till that wingtip "weighs" between 1.25 and 1.5 ounces,,
then flight testing will give info for further adjusting.
It may be a real benefit for you to search using something like "trim chart Paul Walker " which should net you a plethora of info on how to trim and why,,
Good luck,
have fun,, the research is almost as much fun as building and flying,,
well for me anyway,, but I am a bit ,, different LOL
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The key word in Mark's post, if you've been asleep for the last 30 years, is "adjusting".
Make a weight box, and plan on fiddling with the tip weight.
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Guys will give you well-explained, completely bogus "theoretical" advice on this subject. I'd start with a lot and remove it a little at a time until the airplane flies best. A weight box is nice, but it's handier to stick a lump of modeling clay (if you drive on the right side of the road) or Plasticine (if you drive on the left side of the road) to the wing tip.
The farther to the outside you put the battery, the less ballast you'll need.
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Guys will give you well-explained, completely bogus "theoretical" advice on this subject. I'd start with a lot and remove it a little at a time until the airplane flies best. A weight box is nice, but it's handier to stick a lump of modeling clay (if you drive on the right side of the road) or Plasticine (if you drive on the left side of the road) to the wing tip.
True, but a weight box is prettier in the end.
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Only if yu can't tell it is there. LL~ LL~ LL~
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Jonathan, keep in mind that leadout position, tip weight, and warps all interact. Set the initial leadout position using a leadout calculator(Line III or similar). Even Wild Bill Netzebands nomographs from the 1960's American Aircraft Modeler articles work well enough. Way too much leadout sweep will make the outboard tip drop(roll away from you) in both inside and outside loops. Tip weight does the same thing.
Warps are different. If the plane tends to get light on the lines on inside corners it is rolling left. If it gets light on outside corners it is rolling right. The only way to really tell, unless you've got years of experience, is to do some large inside and outside loops. Gradually tighten them up until you start to feel a difference between them, if any(lucky you). It's best to straighten the whole wing if there is a warp, and it can be done. A plastic film koted wing can be twisted and ironed. Fabric and dope cand be done with heat too, just takes more. If the wing can't be straightened and the warp isn't crippling, twisting the flaps like ailerons usually works OK. The flaps can correct smallish warps. A badly warped wing will always be warped. Twisting the flaps can make it flyable, but it will always have idiosyncracies you'll have to watch out for.
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I use BBs in an adjustable weight box. I start out with a number of BBs based on engine displacement. 5 for an 049 airplane and 40 for a 40 airplane. That seems to be enough for safe. If needed I add or remove BBs 5 at a time until I get it to suit me. S?P
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I use BBs in an adjustable weight box. I start out with a number of BBs based on engine displacement. 5 for an 049 airplane and 40 for a 40 airplane. That seems to be enough for safe. If needed I add or remove BBs 5 at a time until I get it to suit me. S?P
This is a great idea Jim! I think I am going to use it.
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Thank you for everybody's replies.
Jonathan