Mark's Mean Machine

[Rocstar]

This will be a single motor sport cat powered by a Castle 1515. Because of the shallow tunnel and where I wanted the strut to mount, the bracket and strut itself had to be modified. The real estate available on the transom for mounting hardware is limited because of the shoebox design of the hull. I shortened the bracket to move the prop closer to the hull, and notched the strut to clear the the upper deck.










The hull comes with factory installed carbon fiber from Aeromarine, but I added another layer.

[srislash]

That'll firm her up. Looks clean.

[nate]

Im trying to decide where to put my rudder, its a speedmaster .21...its going to be a pain..

[tlandauer]

While I am not in this league, I and a few others found that the rudder pictured is too short, the boat will spin out easily, unless the modified strut helps that.

[Rocstar]

While I am not in this league, I and a few others found that the rudder pictured is too short, the boat will spin out easily, unless the modified strut helps that.

That's interesting. The rudder extends about 2.5'' below the strut, unless it's not wide enough. I'm interested in what you found that works.

[properchopper]

Joel,

Looks good so far - agreed that the top deck overhang yields a small landing pad for the hardware feet. I ran into the same sitch in a recent MM build with Spd hardware. Had to lengthen the strut slot as well to get enough vertical adjustment to keep the prop from being oversubmerged.

DSC05345.JPGDSC05343.JPG

I agree with Tim that a decent amount of rudder is key to avoiding spinouts - I like the Spd .21 because it's ultra-long and can be trimmed to suit. Then again there's other ways to skin (turn) a cat : (I did this to my beater MM for the L + R turn Offshore course at Winter Warmups). Worked great but lots of drag kept the speed down a tad

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[properchopper]

Im trying to decide where to put my rudder, its a speedmaster .21...its going to be a pain..

Spd makes a center mount bracket for their 60/90 hardware - might be adapted to give you another choice. Either way you may need to shim the lower hull to get a flat surface big enough to accommodate the mounting foot.

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As it turns out, I originally had the idea of going twin with my beater MM using SV27 struts & spec motors but it didn't go that way. Yours should be a nice runner -

[tlandauer]

While I am not in this league, I and a few others found that the rudder pictured is too short, the boat will spin out easily, unless the modified strut helps that.

At first I used this but spin out was a problem:http://www.offshoreelectrics.com/pro...d=ros-spdr-005
then I went to this and instantly it was gone:http://www.offshoreelectrics.com/pro...d=ros-spdr-001

[Rocstar]

[ATTACH=CONFIG]112273[/ATTACH][ATTACH=CONFIG]112272[/ATTACH]

Thanks Tony, I may be making a change.

[Rocstar]

At first I used this but spin out was a problem:http://www.offshoreelectrics.com/pro...d=ros-spdr-005
then I went to this and instantly it was gone:http://www.offshoreelectrics.com/pro...d=ros-spdr-001

Thanks for the input.

[Greg Schweers]

The reason this boat spins out for me is when I come into a turn at full throttle I have to let off the throttle for a second (let the boat set down). What's happening is that there is very little boat in the water going down the straight, then you try to turn and nothing happens - so you give it more rudder and the boat spins out. I have very little throw on my boat. Adding a long rudder is basically slowing the boat down. I did add a very small fin to the side of the strut, which did help with the high speed turns. The easiest way to put hardware on the boat is to use Jeff's FE-30 hardware. You do have to cut the slot on the strut, drill 2 holes and you're done. If I build another cat, I'll build the sprint cat. Same bottom, different top, but weighs 6 oz. lighter.

[tlandauer]

The long rudder should be cut ,less than 1 inch. The threshold of between spinning out and not is not so much. IMO the longer rudder will not add that much drag if trimmed to the exact sweet spot.
Another suggestion is to use a strut with a skeg. but I have no first hand experience in that. That seems adding drag as well.
I agree with what you said, just want to clarify my thoughts here.
Cheers!

Sent from my Droid using Tapatalk 2

[Rocstar]

Motor and mount ready to rock...








Hatch bolts and seal installed...

[Rocstar]

Taking some advise and swapped out the rudder for a Speedmaster 21. It's way too long, but the water pickup is high enough that Mark can trim as needed.

[kfxguy]

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