Rudder Questions / Length to Transom?

[rcboatlover]

I'm building two Dumas boats this winter, one is a sport 40 hydro and the other is a 36" SK Daddal for .40 sized engines. I'm thinking of buying Speedmaster rudders for the boats, but which one should I buy? So far it looks like the .45 rudders are what I need, but they come in four different lengths. The leading edge of the rudder to the transom range from 1 1/8" to 3 3/4" How do I figure out which one I need?

Also is there going to be a problem if I move the strut from the bottom of the SK Daddal to the back? Dumas has it set up for a non adjustable strut, but I want something that I can adjust. I'm thinking of getting a Speedmaster VM-1 strut for the back. It's a Small Strut for .187 cable with a round bottom.

I need to know ASAP. I plan to order this weekend.

Thanks Dale P.

 

[PHIL THOMAS]

I'm building two Dumas boats this winter, one is a sport 40 hydro and the other is a 36" SK Daddal for .40 sized engines. I'm thinking of buying Speedmaster rudders for the boats, but which one should I buy? So far it looks like the .45 rudders are what I need, but they come in four different lengths. The leading edge of the rudder to the transom range from 1 1/8" to 3 3/4" How do I figure out which one I need?
Also is there going to be a problem if I move the strut from the bottom of the SK Daddal to the back? Dumas has it set up for a non adjustable strut, but I want something that I can adjust. I'm thinking of getting a Speedmaster VM-1 strut for the back. It's a Small Strut for .187 cable with a round bottom.

I need to know ASAP. I plan to order this weekend.

Thanks Dale P.

Dale, The sport 40 boat will have the strut under the boat this is a rule that is followed for racing, if you wont race it do what you want but the boat runs fine with the rear of the strut just at the back of the tramsom. You dont need the 40 rudder for the sport 40 or the SK,, the speedmaster long 20 rudder is best, not the small hydro one. Also there is two length mounts for these get the short one for the sport 40

The vm struts have a long extension behind the strut blade that can be trimmed off.

Setting up the SK with the strut on the tramsom is ok if you want to use the long extended VM strut you may want to get the longer mount for the 20 rudder also.

I have never seen a SK setup like that but it should work ok. I think that the deeper the strut the more it wll lift the boat so try to stay about as deep as the original setup. Also the SK had a small turn fin on the bottom to keep it from sliding too much. Good Luck PHIL

 

[rcboatlover]

Hey thanks for the help! I was wondering if the 20 rudders would work.

I plan to keep the strut under the Hydro, I built it with the standard dumas strut, which is already adjustable. I'm only moving it on the SK Daddal with the speedmaster strut.

Do you really think I need the extended strut though? The original design calls for the prop hub to be 2" from the transom. I fugured it would be best to keep it as close to the transom as possible.

 

[Flyin Rat Sass]

the dumas hardware is a joke .years ago i ended up (after trying everything)running the prop 3/4 submerged.the most important thing with this hull is to have a small(1/16" to1/8") convex curve in the contact area(measured forward from the transom).otherwise the trim tabs will only have two settings...#1...too wet, nose plowing...won't plane.#2...massive wheelies.This curve allows adjusting to a point in between that in glassy water condtions only the back 2 or three inches are wet.

good luck

 

[rcboatlover]

Yes I fully agree, the Dumas hardware is crap! Glad to see I'm not the only one to put the strut on the back of the SK Daddal. I just can't see mounting a fixed strut to the bottom. Remember PJ's Little Rascal last year? He had to tare it apart because the Dumas suggested strut angle wasn't right. I think the Speedmaster hardware will look nice too!

Thanks for the tip for the bottom. Is that a OS .65 in yours?

 

[Flyin Rat Sass]

No Problem ,glad to help (this is the only area that i have some experience)I had to order my kit direct from Dumas.you may end up wanting to angle the prop up a little as i did with my first one (my hull was a little too flat and didn't want to "air out").you will find that these are a little difficult to setup ,between trim tabs prop selection,prop depth and angle,hull shape ect there's a lot to sort out(I enjoyed the learning experience) oh yea thats an O.S. 81 vr-m

:blink:

 

[Propjockey]

You just HAD to bring up Hydro-plow, didn't ya?! LOL!

Yes, definitely get some kind of adjustment in the strut set-up.

 

[rcboatlover]

Don't worry PJ, my Little Raskel just sits on the shelf. I got it to run, but not that well. I'm still thinking on letting it go on E-Bay!