Admittedly, I can't say that EVERY Herr Aqua-Star has peoblems taking off. Only every one I have ever seen. All four of 'em. Each of those refused to take off because the nose plowed under water as soon as a little power was added. So, when anyone tried to take off, the nose submarines, the prop gets into the water, and it makes a big spectacle spraying water and slowly churning around on the surface.
The "as designed" nose is very slender. The thrustline is elevated so it gets a lot of leverage to force the nose down. Since the nose is so slender, the leverage from the thrustline can force it right through the surface of the water. Here is the factory ad photo.
Two owners of these little aardvarks have called Herr customer service, and tell me that Herr claims never to have heard of the problem.
I discussed this with several of the owners. Herr adds downforce to the motor. Every full-size seaplane with a high-mounted motor uses upthrust to counteract the nose-down effect of the offset thrustline. Still, wedging in some upthrust was not enough to keep the nose on top of the water.
This is where you decide whether to assume that the manufacturer sold a kit that will actually ROW. If you hang on to this assumption, it will waste a lot of time. You can't move the cg aft and still have a flyable model without major redesign. We tried adding a lot more elevator travel so the propblast can lean on the elevator to help hold the nose up. As soon as the prop hits any water, it slows down, and the elevator force is lost. Besides, too much elevator would make it squirrelly if it ever DOES ROW. So the only thing left is to figure out a way to add buoyancy or hydro-dynamic lift to the nose.
Our club president here, Ralph Swank, added plywood foreplanes to the nose. These are essentially like splash deflectors, but they are roughly the size of half a silver dollar on each side of the nose. These work adequately. As soon as the thrust starts to push the nose under, these have enough force to prevent it from going deeper while deflecting any spray from the prop. If I can get pics of Ralph's mods, I will add them to this article.
Fred Thompson (Not the Movie Actor/Senator from Tennessee) was having a submarining problem with his Aqua-Star, and added a supplemental hull. This makes the whole hull wider, so it has both more floatation and it lifts and planes the airplane at a slower speed (quicker takeoff).
Here are Fred's remarks:
"I finished the alterations to the sea plane and flew it 3 times so far and each time it took off from the water in about a 60 foot run
with about a 4 Mph breeze. The alterations do not seem to change the flight characteristics at all except for the extra up thrust
which required a little bit of down elevator trim at full throttle and seemed to be ok at 1/2 throttle also.
As you can see the down angle on the pod is [not] what Herr originally designed into it. It was at 3 degrees down thrust.
It is now at about 5 degrees up thrust. Also I put on my norvel 074 not that it's needed it but my 061 is being used on another plane.
The 074 is fine. The Balance point that Herr designed still works fine on my new front hull design. I'm using 3 standard Futaba
servos, a 7 channel receiver, and a 600 ma battery pack.
I hope that the other guys who have this sea plane can use the information and get theirs flying off the water also. "
Contact Fred at: n4ntp@netzero.net
Good News! In the interest both of fairness and progress, I dropped an email on SIG's website. They responded immediately and advised me that they have a "fix". They snailmailed me the "Aquastar Additional Instructions", also known as "Herr Engineering Corp. Kit #502 Aqua-Star Correction Sheet, Revision #5" and granted permission to place it here on the website
Click on the image for a full-size illustration, then right-click on the image to "save picture as". Use your favorite image processing program to fit it onto a printed page, or just us it as "notes".