I just went out to fly my float plane for the first time after replacing the fuse yesterday. I have the same setup as I did on the previous identical plane. This plane now needs a VERY long take off run. I managed to get it airborne only once. What the heck happened? Can you tell by the pic if I have something screwy?

It sounds like your wing may have a negative incidence angle when the floats are "up on step". In this configuration the wing is pushing down rather than lifting. Try making the front mount longer which will raise the nose of the plane......Seaplane

I suspected that. I have the tips of the floats pointed down so that they are not parallel with the fuse but maybe I need them down even more.

Hard to tell from the picture without a side view but it appears that you have excessive wing to float decaledge which makes it difficult to actually get on the step. In other works you only need two to four degrees positive wing incidence to the float top decks.

Another factor that is not visable is the CG to float step relationship on that airplane the aircraft CG with the floats should be up to but no more than 3/8ths inch in Front of the step, never put the CG behind the step.

Either one or a combination of both is the problem.

Johhn

It could be an illusion, but by drawing a line from your forward support (which appears to be at the "step") up the side of the fuse. you may have the floats mounted too far forward. I can't see it too clear?!

Roger

Are those Gee Bee floats? See lots of other threads on them! Even if they are set up perfectly they are still difficult to unstick. A few ripples in the water helps them break loose. I have had them in the past and they were always frustrating. The problem stems from the fact that the step is rounded. A sharp cut off seperates the water cleanly and allows planes to take off easily. Also, when in doubt, add more power.

I'll get some better pics to clear things up. Till then, I'll stick with the ol' Seamaster.

This thread is a good example of the many theories and wives tales you will hear about float set up. It helps to remember that model float planes require a different setup than full scale.

Gee Bee floats are definately a big part of the problem. They have no flat planing surface, so their angle on the water has to be controlled by the elevator. If you can keep the top of the floats parallel to the surface of the water while the airplane is gaining speed, you can get them off the water quite easily. But let the angle change so that the front or rear portion of the float bottom gets into the water and the drag will slow you right down. (Or cause a water loop.)

The fact that you have a flat bottom wing complicates things because flat bottom wings fly with the bottom of the wing at a negative angle to the direction if travel. Set up the way you have it, you will have to give the airplane a fair amount of up elevator to get it to run properly on the center of the floats and that will increase the drag on the airplane to the point where you can't get up to flying speed. On the other hand, if you don't give it any elevator, the airplane will try to level itself and the nose of the floats will dig in.

When all else fails, try setting the top of the floats parallel to the top of the stabilizer. This will let the airplane run along the water in it's normal flying attitude without elevator input, while the floats are approximately centered and causing minimum drag. Once flying speed is acheived on the water, slowly feed in up elevator and she will take off.

Jim

You are correct. They are definately not easy to set up. I must have just got lucky the first time. I'm gonna keep trying.

Just by looking at your picture I can tell you the lack of any visible engine will certainly increase your takeoff run. In fact it will make it almost infinite!

Peter

Kneeslapper!! I put an OS .46 on the plane and it does move quite a bit faster now!

The absence of the cowl makes the floats look like they are mounted way too far forward also.

OK, I was out of town, and unable to browse the forum.

Glad somebody spotted that there was no engine.
You also need a WING. It's a primary consideration in becoming airborne.

Just as an experiment, try sharpening the back of the step of the floats. GeeBees are limited by the manufacturing process in how sharp they can be . Maybe some epoxy on the back of the step, and sand it flush with the bottom in front of the step. Or, re-skin the bottom of the front half of the floats with some really thin plywood and PFM.

Don't horse back on the stick when you're trying to take off, just a tiny bit of back pressure after you get up on step. If the backs of the floats dig in, it's just like dropping anchor.

A float plane's take-off is no different than a land based plane.
It must be able to rotate in order for the wing to lift the plane of the water/ground at a given speed,
At a slower speed more angle is needed. At higher speed less angle.

First assuming your step is in the proper range

If the afterbody (part of the float from the step back) of the float won't allow the plane to rotate easily, it will take much more speed in order for the wing to make lift at the flat angle of attack

Think of it this way
Imagine a Taildrager with a vey tall tail wheel that held the tail up so high the plane is almost at flying additude (you may have seen this at you land feild)
Well the plane may never be able to rotate enough in order to come off the ground.

A float plane will act the same way if the tail is forced to stay high by the afterbody of the float

Thats why those land speed record cars never leave the ground. Put their mains close to cg and they would launch.

It's all about the angles, Well the cg/step location is very important aswell.

Shim the front gear in small incriments until you find the perfect angle and you'll be Golden!

P.S. I wouldn't ever use Gee bee floats (rounded edges issue), but I have seen guys use them with ok results on lite aircraft. Good Luck

Here is some pics. What do you guys think? (the cg is marked with a black line under the wing)

Howz it look?

That should work if you're carefull with the elevator. Use a little up elevator to hold the float tops parallel to the water as the speed builds up and the airplane will take off by itself.

If that doesn't work for you, start shimming the REAR strut until the airplane will run along the water with no elevator input. Then a little up elevator at the right time will take it off.

Do not shim the front strut. You already have the wing at a high angle of attack. Any higher and you risk taking off before you reach flying speed, followed by the inevitable tip stall-splash.

Jim

My observation of the pictures tells me that the floats are too far ahead (step to C/G location) and also very minimal size wise.
It's hard to judge where the step on Gee=Bee floats is because of the tapered step. I always used to make it around 50% of the step zone.
Peter

One issue that has not been addressed here is that more float is not always better. If a float is too long the aircraft can't rotate. One test is to set the plane on a table. with the wing incedence at zero push the tail down as far as the floats will allow. If you can't get at least a +7 degree incenence as measured at the wing the floats are too long or not properly mounted.

I set mine up with 1 or 2 degree positive wing when the float is level .

Last of all 86 the GEE BEE floats. I have been float flying for 30 years and have seen only very light overpowered planes work with these floats. They look like a quick and easy way to get into float flying, but there are several problems with their basic design, the step being the biggest. The rounded edges on the bottom of the float are also a problem, that edge should be sharp. I learned this the hard way too!

He also has very little or no float in front of the prop. You are right that the floats are probably too small for the airplane.

Sawyer

Don't move the floats back any further, that would make it even more likely to dig the tips in.

Jim

Ok, i'll take your suggestions and move the floats around. Maybe they are too small but they fall into the weight range of the plane??? Thanks and keep them coming.

I'm sorry Mike but I think you will still have a problem no matter where you put those floats. If you send me your e-mail I will send you a copy of an article I wrote on "What I wish I had know when I started float flying." There is also a source for bullet proof floats in all sizes in the article.

That sounds great! My email is: [email protected]

Send it to me, too. I will stick it in the Florida Float Flyers' website.

[email protected]

One more thing I see from your photo is the cg location
Now I know everyone is differnt on this issue.
But I like to set my planes CG on the AFT end of the range.
That mark, if that's your CG, is a little on the forward if not infront of the CG range, Moving the CG back a little will help it rotate as well,
Almost all kit designers set the CG on the main spar or visa versa, the mark in your photo looks like it's infont of the spar about 1/2" or so, I'd move the CG back to the spar (ckeck you instruction book to be sure) And I think you'll be happy with the way the plane becomes more responsive.

God luck

That cg is by the book and it is correct. When this plane was land-borne, I moved the cg behind that mark and it was very uncontrollable. These Tiger Trainers acually require a great deal of nose weight.