Question for Boat Builders

[nbass]

Most commercial boats are built with about a 15-degree transom angle. We have seen hydro transoms built with a wide variety of angles all the way out to 21-degrees. What is the purpose for such a variation from what seems to be a standard? Can the same purpose be attained with a 15-degree angle?

Thanks,
Neil Bass

[reed28n]

Transom Angle

The only purpose of the transom angle variation is to locate the gear case a desired distance from the trailing edge of the boat.

There are a number of factors that go into the angle. Not all boat designs will perform at the same angle tunnel, step or flat bottoms could use a different angle. It is something that needs to be tested with driver and motor set up.

[bill boyes]

By increasing the angle of the transom you effectively move the motor back to increase the distance from the rear of the boat to the nose of the the gear case. You can do the same thing by adding material(Wood, Metal) to the outside of the transom.

[Bill Huson]

and the extreme . . .

I built a CSH with a chrome moly tube motor board thinger that could be moved fore and aft to experiment. Started out with that sucker way, way back. An unwise experiment because: 1) the boat itself was an unproven design 2) the Yamato was fresh outta the crate and didn't have the lower unit worked. Not only scared me but everyone on the race course - Like whoa! Where's that boat going next?

I still think repositioning the motor board is better than radical transom angles. I believe Bill Giles built CSH boats with the motor board stepped back from the normal position at the end of the afterplane.

[Team B&H]

Motor/prop location is determined by transom position and transom angle. You can change either or both to get the motor/prop where you want it. If you want the motor/prop farther aft, you can build the boat with either more transom angle or move the entire transom farther aft or do both. There is no magic angle as the angle alone does not mean much except for A boats where you need lower angles so the motor can be kicked in without bottoming out on its own brackets.