Strut location on a Sport 40

[Kez]

This topic may have been discussed before but I could not find a related thread.

What are the advantages and disadvantages of mounting the strut through the bottom and bolting it to the transom? Intuition tells me that transom mount would place the prop further back, effectively lengthening the hull, and probably would result in a better handling/performing boat.

Maybe there are disadvantages that I have not thought of.

I wonder why the sport hydro rules required that the drive dog can not extend beyond the transom?

Thanks,

Kez

 

[Brian Schymik]

FYI, in IMPBA the strut on a sport 40 MUST be under the hull. No option here.

Brian

 

[Eric Bourlet]

FYI, in IMPBA the strut on a sport 40 MUST be under the hull. No option here.

Brian

Same in NAMBA

 

[AFIRacing]

I thought Namba Revised the rule to read ::The drive dog may be one drive dog length behind transom of the boat Revised 2/28/05

Steve H

 

[P THOMAS]

I thought Namba Revised the rule to read ::The drive dog may be one drive dog length behind transom of the boat Revised 2/28/05

Steve H

SO wouldnt the strut have to under the hull? B) The Namba and Impba rule is the same on this just worded differently.

 

[RaceCraftBearings]

I thought Namba Revised the rule to read ::The drive dog may be one drive dog length behind transom of the boat Revised 2/28/05

Steve H

The drive dog is not part of the strut therfore is not part of the equasion of this subject.

 

[piper_chuck]

FYI, in IMPBA the strut on a sport 40 MUST be under the hull. No option here.

Brian

Same in NAMBA

So, the "disadvantage" of mounting the strut on the transom is that the boat wouldn't be legal for either NAMBA or IMPBA.

 

[SayMikey]

FYI, in IMPBA the strut on a sport 40 MUST be under the hull. No option here.

Brian

Same in NAMBA

So, the "disadvantage" of mounting the strut on the transom is that the boat wouldn't be legal for either NAMBA or IMPBA.

You are correct Chuck,when the sport 40 rules were written we tried to stop the intrusion of rigger style hulls from sneaking in the class. Many attempts were made to get around the rules by filling inbetween sponsons. You have to remember back when,sport 40 hulls were mostly Dumas hulls and 35 mph was fast. The rules as written have served the class well and its been the biggest class in Evansville since we started our club in the early 80s. I even know where the first hulls are today 4 muesem quality boats that rival any scale boat ive ever seen. And I am the 2005 IMPBA scale concourse winner so detail is someting i know about. Thank God most sport40 guys today just paint there own scheme,my sport40 was built to stick in turn one with anyone and has a few scars to prove it....Mikey

 

[Kez]

Thanks all for stopping by. But I have yet to hear an answer to the original question: Would transom mounting the strut have a performance advantage over through-hull bottom mount? If so, I would like to know the reasons. Has anyone tried this?

Reason for this post is that I am building a sport 40. I would not mind if I can not enter it in sport 40 class. Getting the most out of the hull is my goal. I am trying to decide where to drill holes for the strut.

Thanks,

Kez

 

[Eric Bourlet]

I was hoping that Mark Anderson would chime in on this and hope he still does. Mark did some testing with one of his Mutt II hulls a couple of years back. According to him it did not make any difference in the performance i.e. lap and heat times, but did make setting the boat up a little quicker to get the setup right. Mark holds the NAMBA strait line, two lap and has held the fastest heat racing record so he should know.

To be candid when there was a group pushing to change the rule in NAMBA, I spoke against it and Mark was in favor because of the results of his testing. I won't go into my reasons here as that is off topic for this thread.

 

[ken stang]

Kez

You can bolt the strut on the inside of the transom and go through the bottom of the boat. that way you can also bolt it on the back side of the transom.

 

[Brian Schymik]

Well, setup is easier if it is on the back, with one real asset to this method. Replacing the stuffing box is really hard if the strut comes out the bottom. :angry:

But Mark Anderson told me the same thing Eric stated. There is little performance to gain. These boats are already Easy to setup, regardless of where you put the strut.

60 mph is often seen out of these boats, with the strut underneath. I think that is great performance.

Brian