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GP Slowpoke Balance Question

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GP Slowpoke Balance Question

Old 07-26-2004, 02:47 PM
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Metastable
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Default GP Slowpoke Balance Question

I just finished a GP Slowpoke .10-.25 kit and have a question regarding balancing. Before I bought the kit, I read a lot of posts about how bad the balance was, and that some people were putting as much as a pound of lead in the nose (insane). Now that mine is done, I found that it takes a 12oz Coke sitting on the glowplug to balance this thing. I was very careful to build the tail as light as possible, knowing there would be a problem.

However, I have found that the balance point location is very sensitive. If I move the balance point from 3-5/8" from leading edge to 4-1/4", the plane balances. I have everything as far forward as I can get it, with the heaviest items all the way forward.

So here is the question(s): Should I load this thing up with lead, or will it fly ok with my 25LA and 9x6 prop? I mean, 12oz of extra mass is insane and I don't want to be strapping a brick to this thing. Also, how will the plane balance be affected with the 6oz fuel tank when going from full to empty? Seems to me that there will be a significant shift in balance since the CG is so touchy on this model.

Any helpful comments would be appreciated.
Old 07-26-2004, 06:13 PM
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DaveB
 
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Default RE: GP Slowpoke Balance Question

A 12 oz. Coke bottle seems like a lot, even if the bottle is empty.

I built the "Poke" per the plans and powered with the OS 26FS 4 stroke. I had to add weight to the nose, 2 strips of lead about 2 inches each as I recall. The lead I used was the typical stick on strips produced by Great Planes and others. I don't think that amounted to more than an ounce or two at most. Something isn't right here, so please double check the balance. I usually find the balance point is on the main spar. Check it out at that point and see if you get a better result.

I would discourage you from flying the "Poke" with all that extra weight.

Good luck.

DaveB
Old 07-27-2004, 12:09 AM
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Metastable
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Default RE: GP Slowpoke Balance Question

Thanks for the reply DaveB. I also consulted my local hobby shop, and they suggested that the CG should typically be 1/3 of the wing depth back from the leading edge. Since the bottom of the wing is 14" deep, I figure this suggestion would put the CG at about 4-2/3" back from the leading edge which is right in line with your suggestion (main spar is at 4-5/8" ). The kit calls for CG to be 3-5/8", and as the kit was built, it came out to 4-1/4".

I was able to overcome the balance issue with a little statics (mass X distance).

1) Replaced rubber tail wheel with light weight foam wheel.
2) Replaced lightweight plastic spinner with brass spinner.

Both of these things made a huge difference in CG and were nearly equivalent in effect to the Coke can counterweight without the side effect of adding more mass.

Thanks again for your input. I'll test fly it this weekend. [sm=thumbup.gif]
Old 07-27-2004, 10:14 AM
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Bax
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Default RE: GP Slowpoke Balance Question

As a note to add...if a model is within the maximum weight listed in the model's spec sheet when ready to fly, then the amount of weight you may have had to add to the model for balance purposes is irrelevan. The SloPoke usually needs weight in the nose because it has such a short nose. Imagine one of the WWI models with the rotary engine, suchas a Fokker Eindekker, or a Sopwith Pup, or one of the Nieuports. I've seen models of those with well over a pound of weight on the firewall because of the short nose.

As long as the all-up weight is within bounds, and the model balances, then what you had to add where is not relevant. Since you were able to balance the model by adding a minimum of weight by moving equipment around inside the model, even better!

The designed balance point is at 3-5/8 inches aft of the wing's leading edge at the fuselage. Balancing the model farther aft will make it more sensitive to pitch inputs, and may make the model difficult to handle. Of course, you can adjust where the model balances to suit how you like to fly.
Old 07-27-2004, 01:32 PM
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mancha
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Default RE: GP Slowpoke Balance Question

Metastable:

I fly mine with a Magnun 30 4-s 10X6 and 3 oz of weight right against the fire wall, big rubber wheels!
it flies great, soft landings even with strong head winds. It is balance as recommended.

the weight difference between a LA 25 and the Magnun 30 4-s is not that big, recheck your balance, probably was wrong!!
Old 07-27-2004, 02:29 PM
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Metastable
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Default RE: GP Slowpoke Balance Question

Thanks for all of the input guys. The brass spinner and lighter tail wheel had a huge impact on balance. I think the key was to appropriately add or remove mass from the extreme ends of the plane. I got it within spec without having to add dead weight (aside from the heavier spinner).

Looking forward to the maiden flight!

Thanks again.
Old 07-27-2004, 02:58 PM
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mancha
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Default RE: GP Slowpoke Balance Question

Tell us how you did.
Old 08-02-2004, 05:06 PM
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Metastable
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Default RE: GP Slowpoke Balance Question

First flight was ok, but not spectacular. Despite being within balance tolerance, it still flew tail heavy. I'm going to move the CG forward a little more to fit exactly on the design point. I can do this by moving the engine forward a little more.

I can't imagine flying this plane with anything less than a 25. Control was "interesting" since it only has elevator/rudder. I didn't feel comfortable flying/landing this model, so I am going to modify the wing to add ailerons. I saw in other threads that others have added ailerons to either the inboard or outboard wing sections. The inboard modification would be simple--does anyone have a good reason for one over the other?

Also, are there any other recommendations for modification?
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Old 08-02-2004, 05:22 PM
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famousdave
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Default RE: GP Slowpoke Balance Question

To me, that plane would be scary without ailerons!! Like a one-arm man in a wheel chair.. .then again, I don't think a plane is a plane without ailerons!!

I had both the .15 and the slow poke 40.. both were nice planes - I sold them as my flying style changed with my experience level..

Both models needed a ton of lead in the nose. I want to say the little one had 6oz and the bigger one had 11 oz. All I know is that it was a lot, but both came in within max weight and dead on CG.

It is critical that you balance this model on the CG in the manual, especially if you don't have ailerons. Stability is lost exponentially with each 1/4 inch of CG back. This is a very easy flying plane, it should glide forever and be extremely easy to fly. I have used this plane as a trainer for new students, that is how easy it is to fly.

As far as wing mods - on a plane that size, use a single servo center mounted and inboard ailerons, they won't be as effective, but they will work for what you need.

I tried to find some pics I had of my Slow Poke, but I cannot find them... I used inboard ailerons - it was a simple mod that took me 1/2 hour... of course, the covering was not on yet...

DP
Old 08-03-2004, 02:26 PM
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mancha
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Default RE: GP Slowpoke Balance Question

I am in love with the 3 channels slow poke, I really like tyhe way it flys, with the dihedral it has it can fly well with out ailerons, try to find the balance where you feel confortable before you chop and rebuild.- if you are looking for a .25 range plane with aileron try the Kadet tail dragger, at the end it will bring more joy to you than the modified poke.
Old 01-27-2011, 12:31 AM
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vrfpvflyer
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Default RE: GP Slowpoke Balance Question

I have the slow pole 15. Where is the CG on it? Is it 1/3 or 1/4 from leading edge of wing or?

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