Sport 40 transom mounted strut

[Samuel Hagan JR]

So far the testing on my new hull has proven no advantage. I have had to downsize the prop from what I ran on my previous boat. I will be putting the strut back under the boat. I believe that the cushion of air under the transom helps hold the prop up better.

When you mean cushion of air under the transom are you talking about the airtraps under the boat or the very back. Is that why some guys have those long 1/8th inch runners on the rear bottom.

The cushion of air as I describe it is the air passing under the hull. As the air passes under the boat, the boat is held up. The way that the bottom is shaped will reflect how the hull handles. Most Sport boats have a flat bottom for the rear half of the hull and that is probably the best scenario for holding the rear of the boat up at speed. The air traps down the side will help hold the air under the hull.
Take a look at the modern hydroplanes of today that run the props farther behind the transom. They have also recessed the transom and run the sponson canoes and rear shoes as far back as the prop for support.

My Sport 40 doesn't have a tunnel underneath or belley pan. It's completely flat. I'm guessing with today's speeds and motor technology, the cushion isn't needed as much as it used too. I have my strut mounted underneath but I have the drive dog 1/4" past the transom. I was told about a half in past the transom help speed some but anymore then that it lost speed. I might try mounting it on the rear for shits and giggles but I don't want to cut up a shaft just to try it out.

 

[Robert Pickard]

Let me ask if i took my sport40 which the strut is mounted on the bottom and ran in a IMPBA event will it be legal

 

[Ray Sametz]

Let me ask if i took my sport40 which the strut is mounted on the bottom and ran in a IMPBA event will it be legal

YES

 

[Robert Pickard]

Great because i have a few races in Georgia i want to go to plus S.C. next year

 

[El Zorro]

Does anyone bother to actually READ the Rule Book anymore? I don't understand why people come on this site ( or other sites ) to find out what the rules are when they can get on the IMPBA website and read it for themselves in black and white. And as far as the strut on the transom rule for Sport 40 goes, if you bothered to look it up in the Rule Book you will notice that ALL of the Sport Hydro classes allow the strut to be mounted on the transom. Makes things a little easier for the people who build and run Sport Hydros. And as you can see with some of the past posts there doesn't seem to be any advantage to where the strut is mounted. Do like the guys that always run fast do: go to the lake and test, test, TEST!

Dick Tyndall

 

[Jerry Dunlap]

Does anyone bother to actually READ the Rule Book anymore? I don't understand why people come on this site ( or other sites ) to find out what the rules are when they can get on the IMPBA website and read it for themselves in black and white. And as far as the strut on the transom rule for Sport 40 goes, if you bothered to look it up in the Rule Book you will notice that ALL of the Sport Hydro classes allow the strut to be mounted on the transom. Makes things a little easier for the people who build and run Sport Hydros. And as you can see with some of the past posts there doesn't seem to be any advantage to where the strut is mounted. Do like the guys that always run fast do: go to the lake and test, test, TEST!

Dick Tyndall

Here's a fast Sport 40 that belongs to someone capable of reading the rulebook.

JD

 

[Samuel Hagan JR]

This thread got off topic quick. Can someone clean it up.

 

[tom galdys]

IMHO, Take the time and put it under the boat. Matt Smith outran the Canadian boats in Ottawa with their off the transom struts and I just finished doing some incredible racing with him in Elmira. Both of our boats are(I shud say were,I had a catastrophic failure. My right sponson broke off and is hanging by threads)set up the same and run fast and on rails. Both are PT boats. Good job Phil. Tom

 

[Don Ferrette]

It all depends on the boat, some like the strut under the boat (like Phil's hull, I tried it both ways) and some like it on the transom (ML Boatworks). There is no substitute from test time at the pond to know which set up is best for you.

 

[anthony_marquart]

Does anyone bother to actually READ the Rule Book anymore? I don't understand why people come on this site ( or other sites ) to find out what the rules are when they can get on the IMPBA website and read it for themselves in black and white. And as far as the strut on the transom rule for Sport 40 goes, if you bothered to look it up in the Rule Book you will notice that ALL of the Sport Hydro classes allow the strut to be mounted on the transom. Makes things a little easier for the people who build and run Sport Hydros. And as you can see with some of the past posts there doesn't seem to be any advantage to where the strut is mounted. Do like the guys that always run fast do: go to the lake and test, test, TEST!

Dick Tyndall

Here's a fast Sport 40 that belongs to someone capable of reading the rulebook.

JD

Looks like you are about to loose your cowl in that pic,..

 

[El Zorro]

Had a boat go across the top of mine before this picture was taken and knock the cowl loose. We had some tape on one side to help hold it down. Need to rethink holding the cowl down on this one. This MLboatworks GP400 has a transom mounted strut and runs pretty good. Phil Thomas' Sport 40's seem to run best with the strut under the boat. The design of the boat will have a lot to do with where strut needs to be to get the best performance from the boat.

Dick Tyndall

 

[LarryConrad]

All my question is why not keep both NAMBA and IMPBA rules the same on the sport boats makes it hard when a NAMBA memeber goes to a big IMPBA JMHO

Both organizations allow strut placement either under the hull or on the transom, NAMBA allowed transom mounted struts on sport 40's prior to the IMPBA membership voting in favor of allowing it.

Let me ask if i took my sport40 which the strut is mounted on the bottom and ran in a IMPBA event will it be legal

Yes, but you would not be able to enter the race unless you comply with the rules requiring membership in the IMPBA, or paying a $10.00 fee with proof of a valid membership in another organization, as stated in the IMPBA rule book on page E 6, III, Insurance.

 

[Robert Pickard]

I know about the fee Larry i was in IMPBA in Michigan and i have a up to date NAMBA card

 

[sebastiencaron]

Hi guy's, the high point boat of the D1 series are a Phil thomas sport 20 electric with the strut behind the transom. He are the fastest P hydro boat of the D1. I confirm you that the PT hull can run with the strut behind the transom.

I don't want to start a debate, but Matt Smith don't outran the canadian boat in Ottawa race. I finish with the same amount of point in sport 40. Both boat have a similar performance. But i agree with Tom, Matt have a good boat.

Sebastien