IMCub

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So I'm thinking of getting a Tequilia Sunrise with a OS.25 FX and have the idea of putting a single large float under it like a Kittiwake (or the Kingfishers?), keeping it balanced when at rest with a couple small wing mounted floats.

I looked at the programs for calculating single and dual float dimensions on A.T.'s link page ... when I plugged in the length of the TS into the single float program, and I plugged in the length of a .40 trainer into the dual float program, I found (much to my pleasure) that the dimensions are pretty darn close to each other.

It seems like I may be able to use a single 40 size float under a TS and have it just about right.

Is this a good or bad idea?

If a good idea, does anyone know what the vertical relation ship between the wing mounted float and the center float should be? I suspect both floats should be free and clear with the plane up on the step, but that's just my gut feel.

Thanks for any and all feedback!

Cheers!

Cub

JohnBuckner

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On any single float or flying boat design that uses wingfloats if the floats are not well clear of the water on the step at takeoff or landing is inviting violent water loops. With that arrangement if the wings were not perfectly level say at touchdown a premature wingfloat strike before the hull will present problems. The only exception to this would be an aircraft with hull sponsons like the early Dornier boats or the Boeing 314.

The TS as a single float ship should work fine. Just consider setting up a slight list with one float just out of the water when the airplane is at rest.

John

IMCub

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John,

This is something I've been thinking that I really want to do and just needed a little encouragement in the form of positive feedback. Thanks.

On the other hand, I now have a mental picture of seeing wing, water, tail, water, engine, water ... all rotating very fast!

By just out of the water, are you talking half an inch or an inch ...

Again, Thanks!

Dave

JimCasey

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When I had a Kittiwake, I had a heck of a time taking off with the wingtip floats installed. I removed them and was able to take off a much greater percentage of the time. I also learned that using almost any rudder on takeoff would cause the float to catch an edge.

My friend Ralph has a Laker. He had a waterlooping problem on takeoff and cured it by attaching extensions to the wingtip floats so the wings could not deviate much from level on the takeoff run.

Do I have a point? Maybe.
Either be able to keep the wingtip floats completely out of the water on takeoff, or make it so that when they touch they cause very little drag. By Ralph's modification of extending the floats, they touch very gently before the plane gets significantly out of shape. I would also bet that a v-bottom float would work better because it can slide a bit without digging in. The float on the Kittiwake was flat-bottom.

It will be a cool-looking airplane. Cover it to look like a Grumman Duck. Prewar color scheme.

IMCub

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So it sounds like the little floats need to be on retracts. Just kidding ... sort of.

If I go with this, it I'd better be pretty good at landing the little plane with level wings before I take to the pond or I'm going to spend a lot on time doing retrieval duty in the boat.

I'm thinking maybe it was a Grumman Duck that I thought was so cool on the old war movies. Big engine, passengers in the float?

Thanks for the info!

JimCasey

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Duck was used in Black Sheep Squadron, and a peter O'Toole movie called Murphy's War.

more pics: go to google, click on "images" and search on "Grumman Duck"

IMCub

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Yeah ... That's it! Jim, you are a wealth of information. Thanks!

scale only 4 me

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Well there are three things to consider when setting up tip floats, all very important
First; Buoyancy. The floats need to have 100% reserve buoyancy.
That is if the weight of the wing tip on the water is 8oz the tip float needs to be able to float 16oz. This way the wing tip will stay afloat easily while taxing and wing tip won’t sink into the water. I see this allot and the guys wonder why they can't get on step.
Second; Angle of attack. The tip float needs to be set up at an angle that will allow them to act like water skies. If the don't have enough angle they will want to sink/dig in the water when you add throttle and do that water loop thing. Also stopping the plane form getting on step,
Thrid; Height off the water, very important! You want the wing tip floats to be completely out of the water while on step, but when taxing to be low enough that when one is in the water the other is just barely out of the water. If the tip floats are to high out of the water it makes for difficult taxing and you get the water looping again.

If you're going to try it on your T.S, I suggest you set it up so your tip floats can be adjusted to find the perfect angle and height. It should work fine with the right set up.

Have fun

IMCub

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100% reserve bouyancy ... just like a pontoon boat, but of course! Angle of attack! I never would have thought of it.

I'd give you at least a buck for your 2 cents so you can keep spreading the joy to other would be mono-float plane'ers!


And I do appreciate you're willingness to share your knowledge with ARFers like myself. I've tried building, but I'm REALLY slow. I've been flying for 6 months, but the first kit trainer I started in 1987 still isn't finished! LOL.

BTW, a very nice collection of planes!

Cheers!

Cub

JohnBuckner

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Cub, you don,t have to be an ace pilot or have retractable tip floats, its just a real bad idea to set tip floats at the water when on the step. I have watched countless wild rides over the years at float flys from airplanes set up this way, look at it this way it may work at takeoff (usually you are closer at takeoff) but you gotta land some time and that is usually further out all the while trying to keep from diggin a tip. Just to set your mind at ease just look at some old movies or photos of the big boats and they all will set dead in the water with a wing down and the opposite tip float well clear.

Scale_only has also offered some excellent parameters for other tip float considerations. Don,t let any of this deter you it is entirely possible and done right should be a fun little ship.

John

PeterC

This last summer I saw the Martin Mars flying boats moored at Sproat Lake on Vancouver Island. At rest there was a definite list to the plane and I'll bet one tip float was at least 6 feet out of the water. That is one HUGE plane. Anyone tempted? I have three views somewhere.
To IMCub a TS or any other conventional plane on a mono float is just like a flying boat except the plane now has two fuselages, one that floats and one that sits above it. Same rules apply to both.
Peter

IMCub

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Holy Smokes! I did a quick look on google ... an RC plane with the wing tip 6 feet out of the water and a 60 meter wingspan! How big of RC planes do you Canadians fly?

Sorry Peter, i couldn't resist. Our club has a bomb drop contest during the summer ... maybe a water drop would be in order ... hmmmm ...

Thanks for the advice everyone. I'm liking the idea more and more all the time. And yes, I'll keep the wing floats clear when on step!

Cheers!

PeterC

That was just a small one, you should see the one that crashed.

scale only 4 me

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Cub,
Your more than welcome. you'll find most modelers are more than happy to pass on thier knowledge to new comers to the hobby.

All those things I mentioned I learned the hard way, experimentation and asking questions.

By the way, a Mono hull or single float (if set up right) IMHO will have better water handling than a twin float set up. One big plus with a single float set up is, the wind can't flip over the plane, been there seen that.

Have fun and welcome to the hobby!

JimCasey

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SO4M raises some interesting points.

My own (qualitative) experiments would tend to verify that the tip floats need buoyancy. In the seaplane I am playing with now, I initially put big floats out on the tips, integrated with wingtip plates that also extended above the top surface of the wing. That wing had a really ugly stall, so I grabbed another old wing I had, with a known gentle stall, and grafted that in place. Instead of tip floats, I used hydrofoils on that one. THey kept the plane rock solid after the plane hit about 5 mph, but it didn't taxi well since the lift of the hydrofoils went away at taxi speed.
Then I made some floats to replace the hydrofoils, but they were small. They would be forced underwater in a crosswind, so it was better than the hydrofoils, but still inadequate.
So, I will go back to larger floats.
Now the question of reserve buoyancy: THe tip floats' normal load is zero. But they DO have to be big enough to keep from being submarined when the plane gets hit with a crosswind 'cause when the wingtip is in the water it causes more drag than the rudder can overcome.

I will disagree with SO4M on one point: A monohull/seaplane WILL blow over if the conditions are right. I have even seen the ultimate high-wind tolerant plane (Northstar) flipped by a crosswind gust. High-wing, light planes are worse, Low-wing planes are better. Seaplanes count as low-wing planes because the wing is close to the water, and if the tip floats are floaty enough, they'll keep you out of trouble like outriggers on a canoe.

scale only 4 me

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I have to disagree with you here Jim
The tip floats do have a load to carry. In most single float or mono hull designs,(DOXs excluded) If you set the plane in water it can't help but fall to one side or the other. the weight I refer to is the weight required to keep the wing tip from entering the water. the above "8oz-16oz ratio" is just an example, in most cases it's much less. the point is, for good taxing caricteristics and getting on step quickly the tip floats buoyenacy is very inportant. your hydofoil experiment comfirmed that. The point is to not let the wing tip be able to sink or plow into the water.

I should have said the mono hulls and single floats set ups have less of a tendency to flip over. Sure, any plane can be flipped over in enough wind. I mis-spoke. but where typical dual float planes are grounded due to wind and choppy water. My kingfisher just plows right through.

JimCasey

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Not to argue, but explaining what I meant: The entire weight of the plane is borne by the center float/hull. If it flops over to one side, it's difficult (but not impossible) to predict the amount of force required to support the wingtip. It ain't much. Especially if, when the plane is sitting at its static waterline, the wingtip floats will just touch the surface.

Static tip Floatation required would be pretty close to the weight of the airplane times the height of the center of gravity above the water level times the sine of the angle the plane rocks over , all divided by the lengh from the centerline of the airplane to the float.

I find that more force /floatation is needed to oppose crosswind forces since they are inherently unstable: once the crosswind starts to lift the upwind wing, more wing area is presented and more force is generated which lifts the wing even more......
THe only thing to prevent wingtip dunkification is an adequately floaty float. I'm not sure how to quantify just how floaty is enough. It's probably overly simplistic just to say twice the static load on the float.

But at least you have a rule of thumb, and I don't.

scale only 4 me

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We're on the same page, just speaking a different language

My Basic rule for visually calculating tip floats size/ buoyancy
In swimming pool conditions no wind
If the tip float sinks more than half way into the water, it's too small. Being a Carpenter not an engineer, I usually do a lot of experimenting to find the right size for things.

There was a great series of articles a few years back on float design in M.A.N. Showed that equation you describe. It was a great source of information for someone new to float flying.

get em wet just not to wet

IMCub

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Well, it sounds like you two really are agreeing, so I guess I'll cancel my planes for building that wind tunnel to determine rollover forces due to side winds ...

SO4M ... another gem ... more than half submerged requires a bigger float ... I can work with that.

Any suggestions on shape? I've seen both long and narrow and short and wide.

I was thinking that long, tall and narrow would be good ... sort of like a flat spar buoy. It would avoid unwanted wing action due to little waves and but would provide more buoyancy as needed (the move the plane was rolled over, the more of the float would come into play.) Based on Jim's comments, I probably wouldn't have it go all the way up to the wing forming an inverted winglet.
As always, I'm open to suggestions.

JimCasey

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My "INITIAL" try at wingtip floats were a lot like the tip floats on a Seamaster. They worked well, and I don't recall ever having a waterloop because of them. I do remember some wingtip-first landings that ended happily.
Those were balsa-skinned foam blocks, glued to the bottom of the wing. 2" wide on a 10" chord wing. 2" high at the rear, curved up to meet the leading edge. The actual tip plate followed the bottom contour of the float, but extended 1/2" above the upper surface of the wing.

I wondered if the tip design had anything to do with that particular wing's evil stall characteristics. That's why I fooled around with other designs. I think I'll try 'em again on the new wing.

scale only 4 me

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IMCub,
based on a visual guess of a Tequila sunrise, I'd say tip floats should be around 1.5"-2"wide and tall and about 5"-6" long.
The shape is really only important for aerodinamic reasons.
styrofoam is good because it easy to shape. A mostly flat bottom surface that rounds up in the front and rounds down in the back would be fine.
My first single float set up consisted of this same shape. See the EX-230 in my gallery. very quick and cheap. it was held to the wing with packing tape.

One more thing to keep in mind when you're shaping the floats. Keep the bottom edges sharpe/square. you want sharp edges so the water will spray off the floats not rap around them/ come up the sides.

IMCub

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Hey Jim,

It sounds like you are a strong believer in that old saying "If at first you don't succeed ... stall, stall again!"

I'd don't quite follow what you did on the wing tips/top ... but if I'm visualizing this correctly, you started with a 2 in wide x 2 in tall x 10 in long block of foam and put a curve to the front end. Correct?

Was this on a low wing plane? I'll bet it looked cool and it would certainly get you more buoyancy when more was needed.

I'll take your advice on using some seamaster floats, but if I get caught taking them, I'm sending the owner your way!

Cub

JimCasey

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>>but if I'm visualizing this correctly, you started with a 2 in wide x 2 in tall x 10 in long block of foam and put a curve to the front end. Correct? <<
Nearly.
I curved the top of the block of foam to fit the bottom surface of the wing. Then I contoured the bottom surface of the block to plane on top of the surface of the water. Zero thickness at the front, 2" high at the back, continuous curve.

The plane is a .40-size seaplane, so the wing is not very high off the water. Your TS lower wing would be a litle higher.

IMCub

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Peter, I know you thought he saw some big float planes, but maybe you should come down to McMinville ... Last night I saw the footage of the Spruce goose (really the Birch Goose) flying. I've never notice before how far out of the water it's wing floats were ...

SO4M ... I checked out your EX-230 ... very nice. Looks like your wing tip floats are a lot more stable than what I had planned ... thanks for the ideas.

PeterC

IM
Am interesting float plane that was around a few years ago was the old GeeBee Mallard. It had tip floats that looked like foam coffee cups squeezed a bit flat with pllywood bottoms glued to them at a positive angle of attack. Positive and progressive floatation right down to where the wingtip went under, Not very aerodynamic, (but nether was the rest of the plane) but they worked quite well. I guess it was just a spin on the Seamaster concept which also work very well. Unfortunately, like aerodynamics, hydrodynamics don't scale well either. I guess the best solution would be to cobble up (quickly) some tip floats and see how they work; if they are too small, build bigger ones. I guess it is safe to say, err on the large side.
Peter