Strut on a Catamaran

[tjcast]

Hi All,
Right to the point, In general how does strut depth and angle effect the ride attitude of a Catamaran (mainly P and Q classes)?

Thanks for any input.

[TRUCKPULL]

Tom
If you are using the new ABC props, you need some down angle on the strut, about two to three degrees more then an Octura.

Larry

[tjcast]

Basically what I'm looking for is:

1) not changing anything else but strut depth, how does that effect the ride attitude of the boat? deeper does what? shallower does what? and

2) not changing anything else but the angle of the strut, how does that effect the ride attitude of the boat? positive angle does what? negative angle does what?

[Fluid]

1) Strut depth: set deep the boat rides lighter; set shallow settles the hull.

2) Strut angle: set prop end up raises the bow; set with the prop end down lowers the bow.

3) N, P, Q, T all react the same.
.

[tjcast]

1) Strut depth: set deep the boat rides lighter; set shallow settles the hull.

2) Strut angle: set prop end up raises the bow; set with the prop end down lowers the bow.

3) N, P, Q, T all react the same.
.

Thanks, that's what I was looking for. Re-affirms what I thought.

[MikeP323]

Just One problem

1) Strut depth: set deep the boat rides lighter; set shallow settles the hull.

2) Strut angle: set prop end up raises the bow; set with the prop end down lowers the bow.

3) N, P, Q, T all react the same.
.

Lordy I hate to show my ignorance like this but N,P,Q,T, all react the same. Could you please help me out with what
you are talking about here. I understand numbers one and two but came up with nothing on No. 3.

Thanks

[TRUCKPULL]

N,P,Q,and T are different classes and sizes of boats for racing.

Larry

[MikeP323]

N,P,Q,and T are different classes and sizes of boats for racing.

Larry

Thanks - I am just a club racer and so only recognize P and P limited, Q, and Offshore. Then we have several classes with club rules such as
Hydro and Outrigger. And Unlimited which is a "run what ya brung" open. Anyhoo I did get confused with the N and T which are foreign to me.
Thank you for the comeback.

Mike

[longballlumber]

1) Strut depth: set deep the boat rides lighter; set shallow settles the hull.

2) Strut angle: set prop end up raises the bow; set with the prop end down lowers the bow.

3) N, P, Q, T all react the same.
.

Thanks, that's what I was looking for. Re-affirms what I thought.

This response is somewhat perplexing for me. So generally speaking, if a Cat is blowing over regularly your suggesting that raising the strut would settle the boat down?

I agree with the statement about angle...

In both cases, if you put the prop deeper in the water it’s going to lift the transom and lower the bow. Again these are general ideas. Obviously boat balance (CG), and prop type will also need to be taken into account.

[zooma]

Sounds like the same technique for setting up a mono. All my monos have TFL stingers. I'm having a lot of trouble eliminating chine walk, because I can't raise the prop without also making the angle too positive and thus lifting the bow too much.

[martin]

Sounds like the same technique for setting up a mono. All my monos have TFL stingers. I'm having a lot of trouble eliminating chine walk, because I can't raise the prop without also making the angle too positive and thus lifting the bow too much.

Yes raising the center line of the stuffing tube higher up the transom on a mono helps with chine walk, as it puts the hull further into the water. Something that is difficult to achieve with just trying different angles on the stinger without upsetting the boats running in other areas.

[Shooter]

This response is somewhat perplexing for me. So generally speaking, if a Cat is blowing over regularly your suggesting that raising the strut would settle the boat down?

I agree with the statement about angle...

In both cases, if you put the prop deeper in the water it’s going to lift the transom and lower the bow. Again these are general ideas. Obviously boat balance (CG), and prop type will also need to be taken into account.

I have to agree with Mike on this one. I think he accidentally typed it backwards. A deeper strut will lower the AOA and settle it down. Shallow strut will increase AOA and lighten it up.

[dasboata]

if you lower the strut in the water it will push the bow down,, I run my struts hi and try to bigger props,,for blow overs adjust with the angle

[madmikepags]

If you lower the strut and the angle is zero,(as I always have my struts on my cats), you're boat will be less stable, regardless if its pushing he nose down a bit. If you look at the rear of the boat and picture the rear edge of the sponsons and the center of the prop as three points of a vector, if the center point is lower than the outside points the center acts as a rocker point for the other 2 points to rock back and forth, like a see saw. If you raise the center point above the other 2 points they wont rock back and forth, thus making the boat more stable. Another important note is that as you start to raise the strut higher than the edge of the sponsons you are also getting less prop in the water. People look at my Q Cat sometimes and are shocked to see a 457/3 or even a 460 sometimes. well when the strut is 3/4 of an inch above the rear of the sponsons you need to get more prop in the water to get it MOOOOvin.