I recently bought a new plane to replace the old ugly U.S. Air Core 40 Trainer. you know? the heavy corrugated plastic trainers. I put floats on the old trainer plane along with an Irvine .53 engine and a 10x6 prop. I cant seem to get it off of the water at all I got it off once but it instantly stalled and fell to the water. please help me. Do I not have enough power? You'd think that a .53 would be enough power to get a .40 size plane off of the water. Could it be my prop size? or a balancing issue? or maybe the floats aren't in the right spot?

Your floats should be set up so the step on the bottom of the float is 1/2"-1" behind the CG. The top of the floats should be parallel to the centerline of the fuse and wing saddle; this setup should prevent the plane from lifting off until it has reached an adequate speed.

But the plane doesnt even lift off of the water. Ive only gotten it to lift off once Will moving the floats solve this problem or does it just not have enough power?

Change only one thing at a time!
Get the floats on properly, and go fly.
Then....

As said, one thing at a time. Then I'd try a larger lower pitch prop, like an 11 x 5 or a 12 x 4. Assuming you have clearance.

I have used my Irvine .53 in three planes (Sig Four-Star, H9 Twist 3D and World Models SkyRaider Mach II), and the APC 12.25x3.75 is - in my experience - the best prop for max power at low speed. 11x5/6 or even 10x8 will give you more speed but not as much pulling power. The Irvine is ported for torque rather than high rpm. It seems to like the larger props. APC 12x6 has become my favourite size for general flying. A 10x6 is probably smaller than you would want for flying a float plane.

Water has a lot of stiction to it. Proper float setup is a must. The power should be fine but in your case the model was likely horsed off the water with too much up elevator and this led to a rapid rotation to a stall at low speed once the floats did break free.

Sure, sticking a .90 on the model would let you get away with this sloppy setup but it's hardly the elegant answer. The model will still struggle to break free but the extra power would just let it "helicopter" away from the crude takeoff.

The real issue is your float setup. Assuming a proper float design then the location of the step is critical. Proper float design is also critical. If you just whipped up your own then there may also be issues with the floats.

Pics of the floats and how they are setup on the model? Try to give us a telephote side view. Telephoto since it flattens the perspective and we can see the wing and floats with more accuracy for placement and angles. Prop it up on the edge of a table with the wing level and shoot as directly in line with the side as possible.

I'm not quite sure what your ground clearance is, but a 12x4 would be my first choice. A 10x8 or 11x6 would probably work too.

I have a 10x9 on it right now, Im going to see if the floats are positioned wrong first. then I will see if the prop isnt the problem if it is the prop, I will try a larger prop. thanks, Ill let you know how it goes.

BD,

Float design and mounting is critical to success. Some things are obvious, others not so much. Borrow a digital camera if you have to and post front, bottom, and side view of your setup. It's the only good way folks will be able to help you.

Multiflyer

Montana- you may just plain ol be too durn heavy- once you get the floats set right - step under cg and a slight down angle to th plane's nose setting on the water -- try this:
on a calm day try a full power tke oof with only enough elevator to bring the plane up to apparant level position - if it is not too heavy it will , at that point , gradually take off .Adding more up elevator will just dump it back into the water.
larger props don't make more power -they make less -
leave it a bit rich and try a APC 11x6 these won't split when the water hits em
unless that engine is cranking 12000 -it ain't at full power.
Are you flying from a mountain lake (high altitude)?
I was born in Moiese- and that is a lower alitude -for some of Montana-
more altitude and you get less power - so you can't swing larger props and the plane must be lighter -
flatlanders really have to se how much this affects things to really appreciate it.

Find Chuck Cunningham's write up on float design & set-up.

This links to the Cunningham article referenced.

You probably need more positive incidence-especially with a heavy plane. Top of floats level, bottom of wing tilted UP 2-3 degrees.


http://www.flyinglindy.homestead.com/skisandfloats.html