propeller tipspeed

[Christian Lucas]

Yes ,there is no sonic boom in water ,must be terrible for all kind of animal in the water.

i have some options to go. 1. is the high rev inrunner. 2. is a high rev outrunner using a Halbach magnetsystem and a carbon can . 3. is a outrunner rev about 25000 rpm under load and gear it up with a epicyclic gear 1:5 from Kontronik . Propeller ,i will custom made it like in the pic from laserlito or in wax and than by dentiststeel .For the boat i start a tread in the outrigger Hydroplane Forum.

 

[lohring]

Hi Tim,

Yes,a wige style without a wing in the mid section.This Job have the sponson to do as they create enough lift by them self. Maybe i make the sponson holder not from a carbontube inplace can be a copter rotorblade that work for start as a hydrofoil,lossing it's lift when out of water.

We've done a lot of work with wings and surfaces in ground effect. The goal was to keep everything out of the water. Because boats are limited to water propellers for record attempts, there are several problems. Too much lift on the transom lets the prop blow out. Too much lift forward causes blow overs. Stability is the big issue. We found that surfaces in very close ground effect with air traps have great height and directional control. The air pressure under the surface blows a trough in the water that guides the direction of the surface. Small changes in height cause big changes in lift, but the changes aren't as big as a planing surface experiences. This gives somewhat of a shock absorbing ride in rough water.

Wings running a little higher generate a lot of lift, especially with air traps, but are unstable. Increases

in height cause a big center of lift movement toward the front of the wing, causing a blow over. Our record holding gas sport hydro needed spoilers on its forward wing to stop this. See the picture below. Air trap experiments on our gas hydros often resulted in too much lift in the aft section with the prop blowing out. It's a delicate balance. We ran adjustable wings on the sponson tubes to generate down force when we needed it. The drag of these wings in air aren't significant compared to the 800 times greater drag of the same surface in water. Below is a scale model of a proposed electric hydro designed to lift lead acid batteries. The full scale boat was never built because lithium polymer batteries allowed power to weight ratios better than the

we used to set the record.
Lohring Miller