I tried to fly my seaplane. I suspect that water spray may be killing the engine.
Is there something I should do to reduce the likelihood of water spray entering the carb? Do you recommend an air filter or ?

This is a 6 foot "Wave King" seaplane; high wing, with the engine in a pod above the wing in tractor. There is a float under each wing.

Engine is a Webra blackhead 61 with a 10/8 prop. On shore performance is flawless, but it flamed out on the water.

It was windy (16mph) and the plane weathervaned. Turning by blipping the throttle was the only option. Turns generated a substantial water spray. You can see it and hear it hit the prop. There is a spinner, about 2.25 inch.

On a prior outing with dead calm conditions, engine never died in 10 minutes of taxiing.

I have no water rudder.

I would appreciate any guidance here. This is my first seaplane in 18 years of rc.

If water is hitting the prop, it will rob a substantial amoung of power from the engine.... the easiest fix is to install spray rails on the side of the hull to deflect the spray sideways, away from the prop... It the engine is exposed, it doesn't hurt to have an air filter (Bru-line makes some), but it will not protect against a heavy soaking of water.....

Taxi with full up elevator. If you add 3 or 4 clicks of power your prop blast hitting the elevator will raise the nose. Higher nose-less spray. You will probably also notice that the plane weathervanes downwind when you do this . You can steer with the throttle. Less: weathervane upwind. More: Weathervane downwind.

Spray deflectors are another handy mod you can do to your plane. 1/4" wide rails at the edge of the bottom, angled down 30-45 degrees. When the spray scooting out the side of your hull hits the deflector, it will be pushed down. Inerestingly enough, this adds to the lifting force of the hull and gets you up on step more quickly.

Also, the blipping of the throttle is causing the nose to "dive" into the water further compounding the problem. High mounted engines like this will tend to make the nose dive. So, smooth throttle applications and the up elevator should make a difference. As the model gets on the "step" you can ease off the elevator and the tendency for the engine to push the nose down will decrease with speed of the airplane.

I want to follow up on the spray rails.

When you refer to "edge of the bottom" I presume you mean just above the water line?

This plane has a molded plastic hull. Molded into the hull is a bumped out "v" ("<" in cross section) which runs from the tail forward, ending just a bit forward of the propeller. Floating, this is just above the water line.

The wing floats have no such feature. They are shaped like, for lack of a better description, a common rowboat. I believe a fair amount of the water is coming off the fuselage side of both floats. It sounds like a spray rail on the inside of each float would be prudent.

What kind of material, with what shape, do you use for the rails? Perhaps a plastic extrusion, with an obtuse angle cross section?

The edge of the bottom is where the bottom meets the side of the fuselage/float. Here is a pictire of the installed spray rails.

Another way to accomplish the same thing is with triangle stock. Either way they are installed near the nose-where the spray squirts out from under the float.

Jim: Thanks for the sketches. Now I understand.
Spray rails it shall be.

Go Navy--(that's hard for me to say, being ex-USAF). Here's a pic of a spray rail to go along with Jim's diagram. Your pontoons shouldn't need one, but the main sponson (fuselage) should get them on both sides, from just behind the point of the bow to about 2/3 of the way to the step.

Khodges: Great pics. Thanks a lot. Now I can make them look reasonably "scale".

They must work...is that the carburetor intake at the six o'clock position beneath that radial?

Okay; Bru line filter is on its way, and spray rails will be added. I think I will also add small water rudder (per other threads in this forum) so I can steer this thing without needing to "blip" (= temporarily blast) throttle. (I'll save the other turning methods for later in the learning curve; These water take offs are a whole new program.)

Hold full up elevator till it gets on step. Advance throttle gradually to avoid "nose diving"

Great help guys, thanks a lot.

Better hurry. In Wisc the lakes will freeze back over again in a couple weeks. :-/

Jim: We do get our full spectrum weather here, no doubt about that.

I took a day off from work (trying to keep my priorities right) and installed the water rudder and thanks to some 35 year old lithoplate, installed the spray rails.

We are expecting a heat wave tomorrow, maybe 70 degrees, and the Wave King will again try to rise and shine.

Now if I only could figure out this digital camera business, I could post a pic of my work and let you experts throw stones at it.

Again, thanks to all for the advice.

Status Report:

Further tests on the water indicate the spray rails as installed are not doing much good. I will try to modify them.

After a flameout, we finally got the plane on step, but I failed to promptly go to neutral elevator.
We were airborne but stalled.

The wing floats fill with water that splashes against the underside of the wing. That will have to be corrected.

The more I look around, at full scales and other rc flying boats, I've come to the conclusion that the hull design on the Wave King
may not be the best.

Most flying boats seem to have a significant portion of the bow above waterline at rest. The Wave King has all but the very end of the bow in the water. I think this makes it more likely that it will plow with the slightest chop.

Do you know of best design practices for seaplanes in this regard?

Perhaps I should reshape the bow to allow more of the planing surface to extend above water?

I picked up a Wave King at a garage sale this last summer and have begun to build it. There are a few things about this kit I don't like such as the tip floats. How on earth can you butt join two pieces of plastic and make a watertight seam? At the same time you have to fasten a wire mounting bracket to them. Instructions are really vague about this. Just a couple of drawings of the finished product.
I have been using Polyurethane glue for most of the wood to plastic assembly, it seems to provide a pretty good bond. One change I am going to make is that I am going to make it a twin engine job. This seems a lot easier than the pod provided in the kit. That big bow wave scares me. I am going to mount the engines as high as I can and incorporate a couple of degrees of up thrust to help them clear the wave. If there is a problem I will add the spray rails as per Jim Casey.
Are there any more of these planes out there? It is quite an attractive design which only a moulded plastic or fiberglass hull can provide.
Peter

Peter: I haven't seen one of these for sale anywhere in the last seven years.

Regarding the wing floats: You must have a plywood piece inside the plastic to anchor the floats. And, the plans don't mention this, but you will want to seal the float "strut" at the top so water spray does not fill the float. This is learned through experience.

But, I have a suggestion for you. Peruse what I posted on RC Canada this morning and the single reply:

http://www.rccanada.ca/bb/viewtopic.php?p=254980#254980

I think you might avoid trouble if you discard his wing floats in favor of a float which does not ride in the water but above it, and hits the water only if a wing dips.

A lot of the water spray I experience comes from the wing floats.

Absent some other suggestion, I intend to 1) remove his floats and see if the plane still rides above the "water line" molded into the fuselage, and if so, 2) create new wing floats placed closer to the tips and which do not ride in the water.

If I was building anew, I would extend the nose an inch or two and extend the curved bottom upward to enhance getting on the step. I would also build the spray rails as suggested above. Good luck determining the cut of the metal to follow the curve and still project at a 45 degree angle outward. (I learned this through experience.)

Oh, I highly recommend a simple aluminum piece in the rudder for a water rudder.

I had some issue with the skimpy plans and the angle on the stabilizer. The formed plastic saddle was vague as to the location of the stabilizer. Following advice from others in this forum, I raised the trailing edge of the stabilizer and carefully made sure I had the incidence shown on the plans.

I also checked the balance and found I was a bit nose heavy. I moved the battery back so that might help this create break bonds with the water.

It looks great in the air. It is not a floater, though it is gentle.

You have covered a lot of the things that have concerned me about the design. I think I am going to make some new tip floats and mount them further outboard. I have seen many full size sea planes and they all have tip floats in which only one touches the water at one time. I don't kow how you plan on stretching the fuselage
I set the stab incidence as per the moulded saddle. It seems to look about right and the polyurethane glue seems to be doing it's job. If I move the motors as far forward and as high as is practical I may not have a severe water spray problem. If I do I'll add spray rails.
AS you stated this is a pretty rare design and I'm not aware of any others. The plans for mine seem to be for a smaller version which was 40 powered. The instructions call for a 2-1/4" spinner but I'm sure I could easily use a 2-3/4" one. Also the wing shown is tapered where mine is constant chord.
I'll post a picture when I get a bit further along.
So many planes, so little time.
Peter

Peter:

I'm not sure how I would extend it either....maybe a balsa block with fiberglass. My plans were half size. One problem is the space available for a fuel tank. I could only fit a six ounce. Good thing the Webra is thrifty. I am running an 11/7 and turning about 11,800. Good luck!