need to add weight question
#1
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I need to add weight to the tail of my newest addition cox .09 medallion powered, can i add weight to the bottom of the elevator next to the fuselage,without hurting flight cariteristics?Or add the weight on the fuselage as shown in pictures?
Last edited by jayseas; 01-21-2014 at 11:14 AM.
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#8
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I have added 1.5Oz to the tail, the c/g is now 1 1/4" aft of the t/e of the wing.I will go fly like this and see how she does.Ship weighs 11.5 oz total.
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I would not glue the weights onto Elevator, because the Elevator can break off at fuse Joint easy after hard landings.
I also would split the amount of weights in half and fix it on left and right side of the fuse.
I also would split the amount of weights in half and fix it on left and right side of the fuse.
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It's not suprising that it's come out nose heavy, that's a long nose moment and a short tail moment. If it were me I'd probably shift the engine back a little if I could, ditch the spinner (too much weight out on the nose) and maybe go to one wheel, or none if you fly off grass.
The lighter the better!
The lighter the better!
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Probably a good idea to ditch the spinner but not much weight there, but it all adds up i suppose.If i have to i can shift the eng aft some and go with a different shape tank.But first some flight test.
thanks guys for ally your comments.
thanks guys for ally your comments.
#16
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I think a better solution would be to saw the fuselage off, in front of
the tail segment, make the cut 45 degrees, not 90 degrees. Then
splice in a fuselage extension, bringing the elevator hinge line back
to the neutral point of your pushrod. You'll still to have to add tail
ballast, but maybe only 1/3rd as much. The prior suggestions that
have you relocate the engine further back is also a good Idea.
Frankly I think the best plan of action is to cut away the wing, stab
and elevator ; and build a new fuselage with the relocated engine
and lengthened tail moment. This way you may not have to add any
weight; resulting in a lighter and better flying model.
An easy way to determine nose and tail moments is to locate the
components on the 3/8" fuselage sheet, that is, place the engine,
fuel tank, completed wing, and empanage into postitions that render
the balance at approx. 15-20 % of the wing chord.
Just looking at your model, it's difficult to determine span and wing area.
It looks as if you based your model on a Ringmaster Jr, which has 195sq"s
wing area. If you can keep the total ready to fly weight under 12 ozs,
you will have a nice flying airplane. There's lots of weight saving things
you can employ on your next model. Leave off the landing gear, spinner,
use a lightweight covering, and finish. Also, hook up a Balloon tank, which
feeds at regular atmospheric pressure, not a pressurized bladder. Good Luck;

Tony
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Tony alotm of what you save makes sense but leaving of landing gear and such i can't do. i fly alone.I will fly as is first to see what's up.But as you stated. i will keep the cutting the fuselage in mined.Thanks
#18
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Well it's been awhile but, what i ended up doing is shortened the nose went to a 1 OZ tank, pushed tank and eng back 3/4" With 1 oz of weight to the tail.CG is just shy of 3/4" aft of l/e.
Last edited by jayseas; 03-01-2014 at 01:24 PM.
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#21

My Feedback: (1)

Excellent now its back into a reasonable range. I may I would like to talk about main gears. I understand why you have the mains so far forward in an attempt to protect the prop and possibly prevent flop overs, Heck in the days of the old timers before there was much RC a lot of airplanes did this too and for the same reasons.
But do understand and this applies to RC also that when the mains of a conventional gear (tail dragger) is so far forward from the CG that this will promote landings that are what I would characterize as 'boingers' or crow hopping. The very best place for the ease of landings is for the wheels footprint to be exactly under the CG as many early American full scale gliders. But of course this makes it hard on propellors so somewhere just forward of the leading edge will actually improve your landings with minimal flop overs.
Moving those wheels back and say getting rid of that plastic spinner which always looked cheezy to me anyway should just about eliminate the need for that pesky lead peeking out from under that tail.
John
But do understand and this applies to RC also that when the mains of a conventional gear (tail dragger) is so far forward from the CG that this will promote landings that are what I would characterize as 'boingers' or crow hopping. The very best place for the ease of landings is for the wheels footprint to be exactly under the CG as many early American full scale gliders. But of course this makes it hard on propellors so somewhere just forward of the leading edge will actually improve your landings with minimal flop overs.
Moving those wheels back and say getting rid of that plastic spinner which always looked cheezy to me anyway should just about eliminate the need for that pesky lead peeking out from under that tail.
John
Last edited by JohnBuckner; 03-01-2014 at 06:42 PM.
#22
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Hi John, the ideal location for a wheel is not directly under the CG!
The ideal location for a wheel or wheels or even a towhook is 15 degrees
in front of the CG.This has been a known trim for quite a few decades.
I first heard about the 15 degree location in 1958 when I built my first
A1 Nordic glider . I then noticed that most of the top stunt flyers located
their landing gear very close to that same 15 degrees.
Tony
The ideal location for a wheel or wheels or even a towhook is 15 degrees
in front of the CG.This has been a known trim for quite a few decades.
I first heard about the 15 degree location in 1958 when I built my first
A1 Nordic glider . I then noticed that most of the top stunt flyers located
their landing gear very close to that same 15 degrees.

Tony
#23

My Feedback: (1)

I was talking of the wheels foot print in relation to the the CG and was not talking about towhooks at all. Now in terms ease of landing and the least tendency to porpose or bounce a CG wheel is indeed the best location and I learned this in the late fifiies and sixties flying a number of wonderful and rather vintage for the time old ships even then such the Baby Bowlus, Pratt-Read and even a Leister Kaufman, full scale ships and all had the single main gear very close to the CG.
The further you move that main gear forward (taildragger) the more directionally unstable the airplane will become and the more pronounced will become the tendency to bounce on anything less a perfect touchdown. Now Obviously you must have the main gear further forward than a glider to keep the propeller off the ground.
Also my whole point is the OP's gear is excessively forward and simply moving it back a little would eliminate that lead!
John
The further you move that main gear forward (taildragger) the more directionally unstable the airplane will become and the more pronounced will become the tendency to bounce on anything less a perfect touchdown. Now Obviously you must have the main gear further forward than a glider to keep the propeller off the ground.
Also my whole point is the OP's gear is excessively forward and simply moving it back a little would eliminate that lead!
John
Last edited by JohnBuckner; 03-01-2014 at 09:51 PM.
#24
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Thanks for your comments guys. i like the way the plane looks with the wheels set forward,also with ground i have to fly over and land on it helps to keep it from flipping over on takeoffs and landings.I agree the big red spinner has got to go, it's being changed to a smaller yellow one.Again thanks for all your comments, i don't post often, but when i do i get get some good advice from the site.
jim
jim