Bracket placement question
 

I am beginning to build the mold for a bracket for my 23' cc. I intend to build a "Hermco" style twin bracket, so no rise front to back of the keel of the tub.

My question is how far above the boat keel/transom does the bracket need to sit. I have seen everything from 2-5" referenced. By my calculations the bracket will displace 1500 cubic inches, so about 55 lbs per inch of depth at the waterline of the tub. I would like to have the bracket tub 3" above the keel/transom, because I think this will allow water to pass, for the most part under the tub at speed, eliminating the trim tab effect. Does this sound appropriate or do I need to go higher and loose some flotation? One plus to going higher is that I would have room for the transducer mounting brackets under the tub. At 3" I will build a small pocket into the bottom leading edge of the tub for the brackets.

I have the instructions Don sent me when I ordered the XL (twin) bracket for my 23' if you want that.

That would be a fantastic starting point. Thank you. I sent you a PM.

Take a look at this.

http://dadmarine.com/twin.html

I always try to make them as low as possible to gain the most floatation at rest. You can always taper the tub to keep the rear from dragging on plane if you go super low but most will clear high as they are with no taper or "rise" as you mentioned. A lot of brackets do have some built in rise or taper. On a 23 it is not as important to gain maximum floatation as if you were trying to do a bracket on a 20 with an heaver outboard so take outboard weight into account also. A light single wont need as much as heaver twins. If you want to maximize floatation go low if that is not your concern you can come up a few inches...