Has anyone built and flown this plane? I have, but I am having some problems with it.

This plane was very easy to build. I built it with half the dihedral in the plans. I used Hitec 81MG servos and a Magnum .15 engine. I added 1/2" to the rudder and 1/3" to the elevator. I used angled balsa stock for the ailerons--same width--just tapered. I sealed the aileron gap.

Once in the air the plane flies easily at half throttle.

Takeoffs are a problem. The plane plows through the water. With full up elevator, much water still hits the prop and slows or stops the engine. I shaped the nose of the plane per the template provided. I think I should have left it flat on top--more like a boat. I have yet had a totally calm day to try taking off. Can I add some strakes to the sides to get it up on plane faster and to keep it from plowing through the water?

After several failed takeoff attempts, the fuselage is full of water--about 1/4-inch. The wing saddle is tightly sealed with silicone. To seal the hatch up front, I use waterproof tape. I don't know how to seal this thing any better. The water must be pushing past the silicone seal. Do I need to build some sort of deflector before the seal? Do I need to seal the receiver and battery in a plastic bag? They are mounted off the floor of the fuselage.

Landings are very easy.

When I do a loop the Magnum .15 wants to die at the top of the loop, but it slowly recovers its rpm. What's with this? Too lean? I tried richening the main needle some.

I read you post this past week and noticed no one replied to it. I thought about it all week and decided I'd try to address some of your issues regarding takeoffs, water handling, and waterproofing, but will leave the engine questions to someone with more expertise.

Regarding water spray getting into the prop, let me start off with two words:

"Chine rails".

The problem you are experiencing is common with model seaplanes of the "flying boat" or "flying hull" or "planing hull" type. When you accelerate the water is forced out from under the hull and up and back into the prop. What you need to do is redirect that water and you do that with "chine rails". The chine of a hull (whether it's a seaplane or a boat) is the point or area where the hull transitions from the SIDE to the BOTTOM. This is called the "chine line". By adding a rail or strip of material to this line, you can change the direction of the water as it moves out from under the hull.

I have attached a drawing I hope will be easy for you to follow regarding how to do this.

I once highly modified a Jetco Navigator from a single-channel rudder-only model to a 4-channel model. I built it as a true amphibian - with knock-off landing gear for use on the ground. The tail wheel strut incorporated both a wheel and a water rudder for steering. This model worked exceptionally well but suffered from the same problem you describe - the spray was always getting into the prop, slowing the engine down so I couldn't take off. A friend with boat building experience (full size boats) told me about "chine rails". They were not difficult to install, and refinishing to that area of the model was minimal. The chine rails made all the difference in the world! Takeoffs were never a problem after that.

You mentioned not having a "totally calm day" to attempt a takeoff. Believe it or not, most seaplane models don't do well on calm water, unless they are extremely overpowered. Takeoffs are easier on water that's a little rough. Also, use "up elevator" only enough to get the model up on the step, then go to "neutral" and wait until it's moving at a good clip before adding "up" to come off the water.

Regarding your problems with water getting into the hull, would it be possible to seal the hatch and access everything only through the cabin? The more openings you have, the greater the chance of leaks. I even put my aileron pushrod exits on the TOP of the wing instead of the traditional bottom location. Same with the rudder and elevator - TOP pushrod exits (above the stabilizer) instead of underneath. All pushrods were the "tube within a tube" type - no open oval holes in the fuselage with a bent wire pushrod for seaplanes!

Here's how I sealed the opening (cabin) in my model but I believe you could use this for a hatch, too. I could never get silicone to stick to a painted surface - it would always let go sooner or later (usually sooner). This method works for me. Using an awl (or small drill bit), make a lot of holes AT DIFFERENT ANGLES in the top of the cabin (wing seat). Cover the bottom of the wing with Saran Wrap. Make sure it's wrinkle free - smooth it out and tape it down (tape outside the area where the wing will mate with the cabin). Put a good bead of silicone on the top of the cabin and WORK IT INTO THE HOLES you punched with the awl. Immediately put the wing on and fasten it (whether it's rubber banded or bolted). Let the silicone cure completely. When you remove the wing and the Saran Wrap you'll have perfect seal that matches your wing exactly. The holes that you made at different angles, "nail" the silicone gasket to the wing saddle so it doesn't separate later.

I always wrapped my battery pack and receiver in a plastic "baggie" with rubber bands put on tightly around where the wires exit. While I have had excellent results keeping water out of my model using these methods, I want to say that no matter how carefully you waterproof everything, at some time YOU WILL get water into the hull! It's a fact of life. It's the nature of model seaplanes. When it happens, your receiver MAY short out. But, not to worry. I have found that you simply need to take the receiver and battery pack out, drain the water out of the model, and lay the electronics out in the sun to dry for a little while. Once everything is dry, you just put it all back in, the electronics start working again and you're back to flying!

By the way, while on the subject of waterproofing, there is one more area you need to be concerned with and that is windshields. They have a nasty habit of "caving in" under pressure from all that spray that hits them. Most model seaplane kits compensate for this by design or providing heavier windshield material, but if you are scratch building, make sure you use a little heavier acetate and that the construction around the windshield is very strong.

Here's another image, this time a top view:

And here is the Jetco Navigator I mentioned above. This model was originally designed and kitted as a single channel (rudder only or rudder with "kick-up" elevator). No provision was made for a throttle and the recommended engine was .074 to .10.

My modifications included:

* Using spruce for wing spars instead of balsa (spruce is 10 times the strength but only 4 times the weight of balsa). I felt it was needed to handle the extra weight and power load.
* Redesigning the wing for ailerons (including differential due to the flat bottom airfoil).
* Completely redesigning the power pod and it's pylon to include a built-in fuel tank with clunk (had to custom make out of tin stock to fit the profile of the power pod). Designed for a Fox .25 R/C engine. This meant the throttle linkage had to be routed through the pylon. The throttle servo, along with the aileron servo, was located in the wing center section.
* Redesigning the stabilizer for a full elevator (rather than the small "kick up" type).
* Designing a tail dragger type landing gear (rather than the tricycle arrangement shown on the plans) to take advantage of a combination tail-wheel/water rudder of my design for steering.
* And of course the addition of the chine rails that made for really easy water handling.

linclogs,

Awesome response!

Thanks, I will try the chine rails. I think this will help solve the problem. I think I also need some sort of deflector on the deck in front of the prop like those on small wet sailboats (sunfish n laser). This is a really small plane and it doesn't take much of a wake to put water over the bow.

I made a couple of flights yesterday on calmer water. The .15 is enough power to get it off the calm water. It, however, still plows throught the water. I think if I do the chine rails right it will help lift it out of the water under power and keep water out of the prop.

The engine seemed to run fine yesterday with power throughout the entire loop. I must have had it too lean or something before.

I did split S, immelman, and some inverted flight. Rolls are slow and require some down elevator correction. Wind was about 10-15 but coming from the shore so the lake was calm on my side of the lake. At half throttle and 10 mph wind the plane is a very easy flyer. When the winds started to reach 15 and gust, I had to add 3/4-full power and the plane was a little twichy when hit by gusts. I think it would have been even more twichy if I had built in all the dihedral they said to in the plans. I built in 1/2 what it called for.

The plane is a little on the small side to see. My plane is white with a flourescent red tail and wing. If it were not for the flourescent red, I might not be able to fly it.

Your plane is really great looking.

Thanks again.