DrYankum

My Feedback: (11)

To the seaplane gurus with lots of experience: Is there a general rule for establishing the wing incidence on setting up floats. I'm doing a KMP Beaver and with the hardware used that it already predrilled, the floats with the top of the float set at Zero gives the wing a 5 1/2 degree positive incidence. Reading some posts on this site says that that setting is too much positive and that the plane will have a tendency to take off prematurely before achieving proper ground speed. It was suggested that 2 to 3 degrees is the correct setting. I've seen other sites that talk of 7 degrees being correct.
Any thoughts and comments about this matter?
Jerry

Newc

I've found that 1.5 to 2 degrees works well. An additional comment for you to consider as you add floats to your plane...Have the CG correct for the plane as it is flown on wheels. Then, when setting up for floats, in establishing the CG of the plane on floats do so by adding weigh to the floats, not to the plane. In this way you are always assured of the correct CG no matter which configuration you are flying and don't have to worry about adding weight when changing, etc.

bralex

My Feedback: (1)

Jerry,

As far as I know, the 2-3 degrees are correct but the reference point is the datum or thrust line of the airplane. 2-3 degrees off the datum line gives the floats a slight downward angle from the fuselage/datum line. The datum line is an extension of the crank shaft of the engine.

seaplane

Jerry, I've found that the plane, when on it's take off run, will dictate the float's incedence rather than the floats dictating the plane's incedence. When the floats are at high speed, they will (by design) teeter on the step. If you have the nose of the floats down too much, the plane (if trimmed out correctly) will try to attain level attitude which will push the nose of the floats down. This will result in uncontrollable high speed steering. You can prove this out by adding up elevator on the take off run to push the back end of the floats down and lifting the nose end. The steering will get better, but too much up elevator could result in premature lift off or the back end of the floats dragging and slowing the plane down. I would suggest you start out with 2-3 degrees positive wing incedence when the tops of the floats are level. Don't forget that floats will tend to stick to the water especially on dead calm water. I've seen this happen and the pilot right away thinks the setup is wrong. A little head wind and some ripples will help a great deal......Seaplane

JimCasey

My Feedback: (1)

There IS a school of thought out there that the top of the float should be parallel to the bottom of the wing--if you have a flat-bottom wing. Another school of thought is that the incidence of the stabilizer should match the top of the float. Dangerous if you have a plane with a flat-bottom wing and the stab is in the wing downwash and mounted with positive incidence. (Goldberg Eagle).

I went reactionary when I built my telemaster, and the wing is a good 5 degrees positive. It works fine, but as seaplane said, tune the incidence for what works on your plane. I set up a super stick with zero-zero once, and it was hard to get off the water without drooping the flaperons.

A couple of degrees is about slap-dab in the middle of the safe range.

Augie11

I'll throw in a vote for 1.5 to 2.5 degrees. I've never seen a reference (or aircraft) set up at 7 !

Chip_Mull

My Feedback: (1)

Two or three degrees at the most. Remember what angle you want the floats to be in a landing attitude. If the plane or you like to land at a flat attitude and you have 7 degrees built in, the nose of the floats might try to dig in on landing. The floats should be either flat or a degree or two positive on landing.

CG is more important and should be on or slightly forward of the step. Re-read the "Newc" reply about balancing.

On take-off in a full scale plane on floats there's a "Sweet Spot" you're looking for. It's when the aircraft is just balancing on the step with no drag from the bow or dragging the heels in the water. With enough speed and flying the "Sweet Spot", that magic thing happens. You shouldn't have to fly at max speed to lift off and you shouldn't need a lot of up elevator.

I used to challenge the peanut gallery on the beach to shout in unison when they all thought my Seamaster had left the water. I didn't have to pay up once! Fly it off and be smooth about it.

cyclops2

There is NO incidence or COG problems with a Flying boat.

Chip_Mull

My Feedback: (1)

That's true! End of problem.

DrYankum

My Feedback: (11)

Yeah...a flying boat would not have that problem.I've got a partially framed up Anderson Kingfisher that'll be pulled around by either a G-26 or a Quadra 35, but that wont be ready until next season. Mean time will fly the KMP Beaver at the pond at Joe Nall, among other sites.
Thanks for all your info...I will be setting the floats up with so that the wing has a 2 1/2 degree positive.

Chip_Mull

My Feedback: (1)

Couple of suggestions for the Kingfisher. A friend of mine and I built two of them several years ago. When I first started I contacted Jerry Nelson about his Kingfisher and went to visit him in Reno. Jerry suggests an additional 20% surface area on the vertical fin which he incorporates into his drawings. I flew an old Champion model of the Kingfisher at Clearlake and I would have to agree, it needs it. Also, the Kingfisher has a lot of drag so carry power on the landings. It likes to drop in like a greased brick deadstick.

Jerry was a great help with the Kingfisher. We would have never gotten as far with this project without him. He's a great builder and a good friend.

They all seem to come out a little on the heavy side so go for the most power you can cram in because you're limited on props.

Here's a shot of my quarter scale Kingfisher.

JimCasey

My Feedback: (1)

>>>There is NO incidence or COG problems with a Flying boat.<<<<

That's only true if the FB is designed and assembled properly. The Herr Aquastar, for one, needs a lot of modifications and tweaks to its design for decent surface handling. As-designed it is more of a bad atomizer than an airplane. Add power, The nose goes under, the prop gets water from over the bow, and there's a big cloud of spray where the airplane should be. And when this happens, a lot of water gets inside and if by some miracle you get it airborne you will have MASSIVE CG problems when you start to climb and the slug of water rushes to the tail.

It can be fixed, but you imply that Flying boats are automatically perfect due to their floating hull design which is just not true.

The aquastar really needs a wider forebody to the hull (the patch is spray rails), and it needs more upthust, and I'd bet a round of cold brewskis that it would be happier with more wing (and stabilizer) incidence.

cyclops2

There are 2 cures for the water sloshing around.

Build better. Do not have open cockpit windows.

Build all seaplane fuselages, out of a solid piece of blue foam.

britbrat

You want a BAD flying boat? Try a Lanier Seabird [sm=thumbdown.gif]

cyclops2

Anyone ever see a good Kyosho PBY ? I only saw the high speed tugboat version. 2 plowed a lot a had to be hand launched. Was that normal for them ?

britbrat

Sounds like a real PBY with dead turbo's.

freebelle2

My Feedback: (1)

Our club members from Northern Ontario Canada fly a lot of float equipped models because that is the normal situation in the full size plane world up here. The rules we follow here sets the wing incidence between 2 to 3 degrees of positive incidence on the wing to float level position ie wing is higher at the front. The CG in relation to the float step is extremely critical. The rule is that an imaginary line is drawn from the CG position at the bottom of the wing of a high wing plane at an angle of 7 degrees (perhaps the 7 degrees mentioned earlier but applied to the wrong situation) back from vertically down. The step should be on this line wherever it is located below the plane in its mounted position. This is a suitable position to have minimal float contact but still control when the plane is ready to lift off. The float should have a step which is straight across the float and not pointed as some. The step also must be deep enough to float the plane near take-off with the tail part of the float out of water. This normally means a step of 1/2 to 3/4 inches. The length of the float is also important. It should be between 75% to 80% of the length of the fuselage and the step located so that in its proper position as mentioned before, leaves about 3 inches in front of the prop. If there is not enough float ahead of the prop there is a tendency to dig in when landing and taking off which gives a lot of spray and creates multiple problems. The floats should be mounted with about 2 inches of clearance from the prop. Normally the width between floats centres should be about 25% of the wing span. The centre of the floats would normally about the position of the wheels. The floats also need to be mounted almost parallel to the centre line of the plane. A little toe-in can be tolerated. The power should be applied slowly on take-off and up elevator applied to get it up on step then almost neutral elevator until lift-off. It is critical especially if there is above five knots of wind to keep the plane within 10 degrees of straight into the wind. Otherwise if a wing starts to lift early it is hard to prevent a tipover.

Chip_Mull

My Feedback: (1)

Best description I have seen on float set-up! I just realized you can't just print a reply or am I missing something here?

Chip

Newc

The Ontario explanation is a good one. It's very much like the oft quoted Chuck Cunningham article, eh?