Graupner Eco Manta rebuild

[larryrose11]

Hello all,
IM rebuilding an old Graupner Eco Manta.
I was wondering about the driveline. They use submerged props, and usually a straing shaft, angled downward.

I had this boat running last season, It ran pretty wet with the straight shaft. I was unnhappy with how much water came up the prop shaft, which was stock. I would like to install a 3/8 flex shaft / teflon liner, and use the 4mm threaded shaft so I can use the ECO props I have seen.

Here is my question, why the straight shafts? I have seen an example of a shaft on an eco hull that is horizontal:

http://www.eco-idc.de/offizielle-meisterschaften/em-2000/fotos/eco/ECO470.JPG

Is there an advantage that Im not seeing with the straight shafts, angled downward?
If so, what is a good angle to ues?

As for motors, I have a TP2935-5Y, 3200kv, 1300Watt I was going to use on 3S lippo. Is a 60A ESC too small?
Thanks,
Larry

[larryrose11]

I got a reply from Gromov about what angle to use, 11-12 deg, but no reason why.
The rules for Eco class state that the prop must be submerged, and not extend past the transom.
So, If a prop is submerged, and under he boat, I suspect that a prop shaft that is horizontal would cause the boat to flip backwards when on plane.
A negative strut angle would help that, but 11-12 degrees down? Is that too much?

I dont doubt Gromov opinion on the matter, he is a race winner:
2010 in FSR E class, the European Championship in 2011 in ECO expert, ECO MINI expert classes....
BUT, IM a scientist and a research engineer, so I need some explaining.

I could build something with some adjustment options tho....

[Southwest]

I have a 19" eco by Hoph Boot with a slanted wire drive shaft and i saw where an eco in a video had a 2600kv on 3S = 28860rpm on a 27 or 28mm prop and it moved great. I'm going to try a .o98 liner for my wire drive for water control. I like your picture with a cat or rigger drive horizonal drive. Trouble is find exact angle and like you mention the 11-12 degree down angle. I have a mono that has straight shaft most of the way to coupler except for the last 1 1/2" which is .130 cable and is smooth . The dog drive end has 1 straight bearing and a flanged bearing. The flanged is next to the dog drive. Also 1 straight bearing about 1" from the other straight bearing. This would control water. Many years ago, i built x-boxes and was told to have x-boxes props about 1/8" from bottom of x-box for a smooth ride and it worked. Weight distribution or CG is the KEY. What keeps bearing in place at dog drive is the actually the dog drive.