Strut position

[sebastiencaron]

Hi, i'm member and secretary of hydroplane club in province of Quebec. It's Modeleur marin du Quebec. Almost of the boat in the club have a strut behind of the transom. I will like to know if it's legal for the Namba and Impba. If not, i will like to know the difference between the strut behind transom and strut under the boat. What is the advantage or disadvantage for each position.

Sébastien Caron

 

[Hydro Junkie]

Have you checked out either group's rulebook yet? They are very precise on what's legal and what's not. You can look at the NAMBA site at http://www.namba.com and the IMPBA site at http://www.impba.net.

In the IMPBA, the strut must be under the hull in all classes except Sport 20 The rules on scale, Sport 40 and Sport 20 are in the IMPBA rulebook, pages H-4 through H-8

NAMBA allows the drive dog to be one drive dog length behind the transom in all sport classes, meaning the strut must be under the hull. The rest of the rules are in section 20 of the NAMBA rule book.

The advantage of having the strut mounted on the transom is that it's easier to adjust and, in some cases, it makes it easier for the prop to carry the back of the boat. The advantage of the under hull strut is that the boat looks more scale and the prop isn't as exposed as it is in the transom mounting. This makes the boat slightly safer to handle while running on the beach

 

[Kez]

Salut Sebastien,

When I lived in Montreal in the 80's and early 90s I used to watch you guys race...I remember it was Coteau du lac (or sur la lac?) I also attended the Valleyfield Regatta.

The strut location has been a topic that comes up every few months. I mount the strut through the floor for two reasons;

1. It is more scale looking as HJ pointed out.

2. I believe it is stronger to mount the strut through the floor. If I mount the strut to the transom, I will have to really beef up the transom as you will be bolting the rudder to it as well. Imagine all the holes you will have to drill in the tiny piece of transom..

kez

 

[P THOMAS]

Hi, i'm member and secretary of hydroplane club in province of Quebec. It's Modeleur marin du Quebec. Almost of the boat in the club have a strut behind of the transom. I will like to know if it's legal for the Namba and Impba. If not, i will like to know the difference between the strut behind transom and strut under the boat. What is the advantage or disadvantage for each position.

Sébastien Caron

Hello, Sébastien

Your group in Quebec has there own rule for strut that is more scale to the boats you are modleing.

Both NAMBA and IMPBA sport40 rule the strut is to be under the boat.

IMPBA sport20 can be stup with the rear mounted strut.

I think there is not any real big advantage to either setup, but it is easier to install and adjust the rear mounted struts.

I think the under the hull strut does lift the rear of the hull better than the strut/prop further back does.

Phil T

 

[sebastiencaron]

At this time, everyone don't find any advantage or disavantage on the performance for both position. If is just to make boat more scale, why the both position are not accepted on NAMBA and IMPBA??? :unsure:

Sébastien

 

[Bill Gibson]

At this time, everyone don't find any advantage or disavantage on the performance for both position. If is just to make boat more scale, why the both position are not accepted on NAMBA and IMPBA??? :unsure:

Sébastien

It is a very good question....I guess it comes down to the position of the sanctioning body...some feel that there is a performance advantage in positioning the prop farther behind the Transom of the boat and some feel there is not...Im a NAMBA member so i dont know if there is or isnt, as my struts go thru the bottom of my sport hydros as per the rules...dont think id be real happy if it was allowed as if there was any real advantage, i would have to redo my sport hydros to be compeitive....maybe thats why NAMBA doesnt allow it...just guessing....one thing i find a little odd is why IMPBA allows the strut to be positioned behind the transom on Sport 20s, but not on Sport 40s...as they are all sport hydros...im not knocking the IMPBA, as i was a member for years...great organization...i just dont quite get that part...