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Nose down trim on float takeoff

scotthayd

Registered User
I have been experimenting with float takeoffs and wanted to report an observation.

First I should say I'm flying a stretched pacer aka Bushmaster with a 180 hp motor and 2440 floats, standard pacer tailfeathers.

I have found that if I make a standard takeoff (trim neutral, one notch flaps, hold the yolk back until the second rise then ease forward until you gain some speed then let if fly off) when heavy I have to push the nose over after the second rise. I'm working on developing the right touch for that push over the top.

I have experimented with trimming all the way forward. When I do that I don't have to push the nose over, and I also get a significantly shorter takeoff run. I'm not sure why that is, but it really seems to work.
The only downside I have noticed is that after takeoff I spend a lot of time cranking on the trim.

I have a couple of theories on why a forward trimmed takeoff may be shorter.
1) Maybe it noses over with a more proper amount of force after the second rise with forward trim. I try to push it over gently when trimmed neutral, but it can be hard to judge.
2) Maybe the nose up forces of neutral trim plus yolk full back are higher when trimmed neutral, and I'm dragging the float heels too hard. Would a neutral yolk through the second rise would have the same result as forward trimming?
3) Maybe the forward trim is pushing the nose lower when running on the step, getting me deeper into the "sweet spot" than I normally get with neutral trim. It's psychologically hard to push the nose forward when you're running on the step. Harder than just releasing a little back pressure.

Whatever it is, if I'm loaded heavy I get up on the step and off the water sooner if I trim the nose all the way down.
Interested to hear other people's opinions. Also wondering if this works on wheel takeoffs.
 
Trim in right place, my Bushmaster takes off by itself, no pushing to get it on the step, it finds the right attitude, up and then lowers by itself to the sweet spot, fully-loaded or light. Don't ask about aerodynamics, I can't explain it. It's close to a no-hands take-off.

I lengthened a Tri-Pacer by 25 inches, took off turtleneck, added 15 per cent to tail feathers, Smith wings, 0-360 and Vetterman exhausts, 2250 Eddy Peck floats. An ordinary pilot, I imagine to myself the floats and exhausts favour performance.
 
scott, Perhaps I'm not understanding you correctly but it sounds as though you are letting the floats get well into the second rise before you push forward. Do you know what causes that second rise? It is the aft section of the bottoms getting sucked into the water by the water being accelerated on the bottoms. That suction is drag. You should be letting the nose down at the very first hint of that second rise if not just before. If you do it this way you will not have to push the nose down, you will be letting it down. If you have to push the bows down to get on the step you are retarding the acceleration because you are pushing more water. When you let the bows get too high you are creating water drag due to the high angle between the keel line and the water surface. The 2440s have a short straight section of keel before it starts to curve up towards the bow. The means that the sweet spot is very narrow when compared to other floats. This also means that you have to let the floats do their job without forcing.

What gross weight are you running on those floats when you are having these issues? What are you calling heavy?
 
I suggest you do two things. Go to a big lake and find your minimum power takeoff. After that? Add sandbags to mimic your loads and do the same thing. It'll teach you a lot about your plane, your trim, and your technique.
 
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