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Model weight specification

Old 05-29-2013, 06:05 AM
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Taxus812
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Default Model weight specification

is the model weight specification typicaly the weight of just the airframe or the aproximate weight of the assembled aircraft, motor and radio equipment ?


(I did see one listed as apromate flying weight so I assum that means fully built)




Old 05-29-2013, 06:27 AM
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FlyerInOKC
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Default RE: Model weight specification

It is the all up weight with the exception of fuel if a glow or gasser is used.
Old 05-29-2013, 06:27 AM
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LesUyeda
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Default RE: Model weight specification

Depends on how sneaky the manufacturer is. Frequently an estimate of all up, ready to fly, using standard components, Your mileage may vary. I have seen some, where the box of wood provided weighed more then the advertised all up weight. Kind of hard to get there from here.

Les
Old 05-29-2013, 06:40 AM
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Default RE: Model weight specification


ORIGINAL: LesUyeda

Depends on how sneaky the manufacturer is. Frequently an estimate of all up, ready to fly, using standard components, Your mileage may vary. I have seen some, where the box of wood provided weighed more then the advertised all up weight. Kind of hard to get there from here.

Les

Unfortunate but so true. I generally consider the weights specified as being minimum.
Old 05-29-2013, 06:43 AM
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Default RE: Model weight specification

Building techniques also affect the weight. I like to add a little modification here and there or reinforce something I don't like so I have a tendency to get a little heavier than advertised.
Old 05-29-2013, 07:17 AM
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Default RE: Model weight specification

I like to leave as much in the box and on the shelves of the LHS as possible, so my stuff comes out on the light side of the kit manufacture's specifications.

Bob
Old 05-29-2013, 07:47 AM
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Show off!
Old 05-29-2013, 07:59 AM
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Bax
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Default RE: Model weight specification

For all the kits/ARF's I'm familiar with, the weight range in the specifications is the recommended ready-to-fly weight of the model. For engine-powered models, it is without fuel, but electric models do include the battery packs.

Kits can weigh more in the box because there is a lot of extra wood that's not used (all the wood holding the die-cut pieces, and the centers of ribs and bulkheads, and sticks and sheet you'll cut down). You'll also wind up carving and sanding a lot more wood off the assembled airframe. Don't forget about the packing material that won't be used. ....And, yes, there are some kits that have such dense wood that you're not going to get the airframe anywhere close to the recommended weight range. If you can, talk to the kit maker about that.
Old 05-29-2013, 10:38 AM
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Taxus812
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Default RE: Model weight specification

Im way over what they say this cub should be (http://www.hangar-9.com/Products/Def...ProdID=HAN1500).The original spec stated it would be 6 - 7 lbs flying weight (with a saito .56 FS) . I weigh in at 8.5lbs with an OS .72 FS supass II. The .72 is heavy (20oz) but not that much

I was a little worried about being so much over so I did a wing loading calculation.The wing cube loading puts me at about 9.3 (wing loading at 22oz/sq.ft)so it should be ok.




Old 05-29-2013, 12:23 PM
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Gray Beard
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Default RE: Model weight specification

Wouldn't worry about it as a cub has a bunch of lift. Being an ARF there isn't a lot you can do about it other then strip the covering and start lightening. Last one I built was the Goldberg Cub and it was heavy at 8 pounds with an OS .91fs. As a 40 size plane I thought it was heavy but the wing is built like a tank and it has a lot of ply in the build. In flight it is perfect though. The .91 was the only engine the fellow I built it for had but a nice .46 two stroke would do just as well. He added floats and figured he would need the extra power anyway, I don't think so but you use what you have.
Old 05-29-2013, 06:55 PM
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52larry52
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Default RE: Model weight specification

If you have not yet C/G balanced the Cub and it is nose heavy with the four stroke .72, then move the RX and battery to the rear of the plane's cabin area to achieve C/G balance without adding any additional dead weight. Move the parts that have to be there to balance it if possible. Keep the amount of non functional added ballast to a minimum. Use a light weight spinner and a wooden prop to take a little weight off the nose if that helps. In any case at 8.5 lbs a J-3 cub of that size will fly fine. If you are putting a pilot in your plane, a J-3 Cub gets flown solo from the back seat. Enjoy...

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