# Transom forces with a sterndrive

Discussion in 'Sterndrives' started by Alumination, Jan 20, 2016.

1. Joined: Oct 2013
Posts: 84
Likes: 2, Points: 0, Legacy Rep: -7
Location: Knoxville, Tennessee

### AluminationJunior Member

The part of the transom where the sterndrive will mount will still be at the standard 12-14 degree lean back angle. The rest of the transom will be "reversed" or "rocket ship".

2. Joined: Aug 2002
Posts: 16,836
Likes: 1,734, Points: 123, Legacy Rep: 2031
Location: Milwaukee, WI

### gonzoSenior Member

I see. So it will be kind of a vee?

3. Joined: Oct 2013
Posts: 84
Likes: 2, Points: 0, Legacy Rep: -7
Location: Knoxville, Tennessee

### AluminationJunior Member

I'm not visualizing what you mean by a "vee".

A transom which looks like this but with a center section angled opposite.

4. Joined: Aug 2002
Posts: 16,836
Likes: 1,734, Points: 123, Legacy Rep: 2031
Location: Milwaukee, WI

### gonzoSenior Member

It's a vee sideways. You have the standard 14 degree so the transom shield works without modifications and the reverse transom for looks. It is a simple solution.

5. Joined: Oct 2009
Posts: 5,229
Likes: 634, Points: 113, Legacy Rep: 1485
Location: Midcoast Maine

### DCockeySenior Member

The car analogy for your question is the forces the drive wheels exert on the car structure, not the aerodynamic forces which would correspond to the hydrodynamic forces on a boat's hull.

For engineering design purposes you will need to include the "steady state" forces originating from the propeller thust and other hydrodynamic forces on the submerged portion of the I/O unit, both going straight and turning, and the dynamic forces originating from the boats motion as it goes over waves, etc. If the boat will be trailered then the dynamic loads due to the motion when the trailer goes over a bump, etc need to considered.

6. Joined: Oct 2013
Posts: 84
Likes: 2, Points: 0, Legacy Rep: -7
Location: Knoxville, Tennessee

### AluminationJunior Member

Exactly.
But since that transom won't be one continuous flat plane from gunwale to gunwale I am wondering how to best go about compensating and/or improving the design of the transom in the areas where it is most important and necessary.

Sure most boats have a similarly designed transom to which an outboard or sterndrive gets mounted, however the transom wasn't originally designed as the optimal way of doing this, the transom was already there as it encloses the stern of the boat. Also most typical transoms are beefed up on the inside, tied into the stringer system, floor, etc.

Have you ever seen a diagram showing how a sterndrive or outboard acts on a boat? How the power is transferred? What type and direction the forces are applied etc. ?

Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.