seaplane trimming
05-05-2009, 09:05 PM
#1
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seaplane trimming
i have read that the extra drag created by the floats may require nose up trim to compensate, so my question is how to overcome this. Can I remove some of the nose weight without an adverse effect on stability (CG)? Pic included so you can see how much trim were talking about here. Forgot to mention that the cg is at the forward in the acceptable range.
05-06-2009, 08:23 AM
#2
RE: seaplane trimming
The plane needs to balance in the same place with or without floats, so you can't just arbitrarily remove weight.
The best thing to do is: With the regular gear in place (assuming you have flown this plane before) mark where it balances.
Now, swap the gear over to floats.
Pick it up again where you marked the CG. If it needs to be re-balanced, add the weights to the FLOATS. This way, when you swap the gear for floats and vise-versa, you won't have to re-balance all the time.
As for trimming, fly it first and then decide if it needs trim.
The best thing to do is: With the regular gear in place (assuming you have flown this plane before) mark where it balances.
Now, swap the gear over to floats.
Pick it up again where you marked the CG. If it needs to be re-balanced, add the weights to the FLOATS. This way, when you swap the gear for floats and vise-versa, you won't have to re-balance all the time.
As for trimming, fly it first and then decide if it needs trim.
05-06-2009, 08:48 AM
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RE: seaplane trimming
Not to second guess MinnFlyer, because he is absolutely correct, but did you check the incidence of the wing compared to the floats? If you're getting out of whack there, it can cause a trim issue and basic instability.
05-06-2009, 10:08 AM
#5
RE: seaplane trimming
FLY THE WING! Never re-balance the aircraft for the mode of flight (Land or sea). The wing determines the CG and that should never change. If water handling is a problem, you may have to move the floats fore and aft to adjust the CG over the step.
05-06-2009, 06:50 PM
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RE: seaplane trimming
I think you guys are missing the point here. I have flown this plane many times on land with the cg at the same spot and it did not require any up elevator trim for straight and level flight. So I have to think that the aerodynamics of the floats are pulling the nose down. Float incidence is at 1.8 degrees and flys off the water with a touch of up. So back to the question, if I reduce float to wing angle closer to zero might this trim issue also be reduced. Also, what effect would result in raising both alerions a little. Since dropping flaps lowers the nose.
05-07-2009, 07:33 AM
#7
RE: seaplane trimming
I understand the situation. Let me see if I can shed some light on it for you.
First, you are adding a ton of drag to the bottom of the plane, so requiring some UP trim is not unusual by any means.
The incidence of the floats does very little in the air, but it does a LOT on the water. So theoretically, you could point the nose of the floats up to help lift the nose of the plane, but by the time they were tilted enough to help, the plane would be pointing down when it sat in the water and you'd never get airborne.
Since you say that the plane takes off with just a little UP elevator, I would say that the floats are set exactly right. I wouldn't change them at all!
But now I am a little perplexed... You say that when you drop the flaps the nose goes DOWN? This is highly unusual. Adding flaps should increase lift, and very often we will turn the aileron clevises in 2 or 3 turns on a float plane to do just that - add a little more lift.
So if I were you, I would at least try dropping the ailerons a tad and see if it helps. But if you're stuck with having to keep some UP trim in it, don't worry about it. As long as the plane flies good, who cares?
First, you are adding a ton of drag to the bottom of the plane, so requiring some UP trim is not unusual by any means.
The incidence of the floats does very little in the air, but it does a LOT on the water. So theoretically, you could point the nose of the floats up to help lift the nose of the plane, but by the time they were tilted enough to help, the plane would be pointing down when it sat in the water and you'd never get airborne.
Since you say that the plane takes off with just a little UP elevator, I would say that the floats are set exactly right. I wouldn't change them at all!
But now I am a little perplexed... You say that when you drop the flaps the nose goes DOWN? This is highly unusual. Adding flaps should increase lift, and very often we will turn the aileron clevises in 2 or 3 turns on a float plane to do just that - add a little more lift.
So if I were you, I would at least try dropping the ailerons a tad and see if it helps. But if you're stuck with having to keep some UP trim in it, don't worry about it. As long as the plane flies good, who cares?
