Prop Depth

[sport hydro]

I am running a Dumas 1/8 scale Circus hull painted as the Miller High Life, w/CMB67 green head. I run the strut with the centerline of the shaft just below the rear shoes.I run a X457 two blade detounged and can mill real slow and have good but not great speed. If I put a 1455 three blade cupped and worked over by Mark Shouland, I get about 3-5 miles faster but have to mill at almost half throttle. When running a lifting prop, should I change the strut depth either shallower or deeper?

 

[Hydro Junkie]

All boats are different, as Mark reminded me a week or so ago. Your best bet is to scribe a line on the strut at the present setting and experiment from there. If changing the strut doesn't work, you'll know where to reset it to

 

[Greg Hahn]

Sport,

running a lifter on that boat will be a real challenge with the boat properly ballanced C/G. If you can get it to launch (and that's a bigg iff) it will have to mill fast. The best performance I ever got out of that boat was with a de-pitched ABC 5569 three blade or a straight up 457. Also that boat will run and turn better without the rear shoes. The full scale boat ran both with and without the shoes, I don't know why.

I always liked the boat and the paint scheme so I ended up scratching one from newton plans and heavily modified the sponsons and bottom and it is now my main scale boat, it runs great.

good luck

 

[sport hydro]

Sport,

running a lifter on that boat will be a real challenge with the boat properly ballanced C/G. If you can get it to launch (and that's a bigg iff) it will have to mill fast. The best performance I ever got out of that boat was with a de-pitched ABC 5569 three blade or a straight up 457. Also that boat will run and turn better without the rear shoes. The full scale boat ran both with and without the shoes, I don't know why.

I always liked the boat and the paint scheme so I ended up scratching one from newton plans and heavily modified the sponsons and bottom and it is now my main scale boat, it runs great.

good luck

Thanks Greg. I agree with the paint scheme, thats why I built one. I can get it up on plane with the lifting prop, but like you said, milling slower than half throttle will stall the motor. I'll look at removing the shoes and picking up an ABC prop to try.

 

[Martin Lovsund]

Hey that's my boat and photo...kewl, love that paint scheme as well. Ed when I was running that boat I could not get the 1400 series props to launch at all. It ran best with the strut at 1-1/8" deep and a detounged x457 at 4.5" cup. The front sponsons were modified a bit and they were 1-1/8" deep at the rears as well so on the setup table it was dead level. I had to add about 3/4 lb of weight to the sponson tips and the canard flaps were up some also to keep it on the water.

Martin

 

[sport hydro]

Hey that's my boat and photo...kewl, love that paint scheme as well. Ed when I was running that boat I could not get the 1400 series props to launch at all. It ran best with the strut at 1-1/8" deep and a detounged x457 at 4.5" cup. The front sponsons were modified a bit and they were 1-1/8" deep at the rears as well so on the setup table it was dead level. I had to add about 3/4 lb of weight to the sponson tips and the canard flaps were up some also to keep it on the water.

Martin

Yea, I grabbed the wrong one out of my folder. Ican get it on plane with the 1455, but it takes about half a straight away and alot of fenessing the throttle to get it to go. I do run the flaps up even with the deck at the back of the flap. When you say the sponsons were modified, did you add material to them or remove material? I have about 1lb in the nose of the boat.

Here is my boat.

Miller_Racing_1.bmp

 

[Martin Lovsund]

Nice shot, looks great. When I was building the boat John Finch had a really good running Dumas kit and he said to add some depth to the rear of the front sponsons. Can't remember exactly but think it was 3/16" at the sponson trailing edge tapered up to nothing at the step. Boat ran great for years once I found the final setup.

 

[sport hydro]

Nice shot, looks great. When I was building the boat John Finch had a really good running Dumas kit and he said to add some depth to the rear of the front sponsons. Can't remember exactly but think it was 3/16" at the sponson trailing edge tapered up to nothing at the step. Boat ran great for years once I found the final setup.

Thanks again, I will try that. I'll make some add on tapers and try them.