"pocket" transoms

[RTN]

In referance to "pocket" transoms like those found on flats and bass boats.....what is their purpose.

[DaveB]

I think that they increase buoyancy aft (allowing for larger engines) and increase the running length facillitating planing (providing more lift aft, preventing squatting)... Could be wrong though... just my 2c

Dave

[cyclops]

Sounds right to me. The closer the engine moves to the center of a boat, the larger the engine weight range it can safely handle.

[mackid068]

Pocket transom? As in a small transom?

[RTN]

I must be using the wrong terminology. What I am refering to is the "pocket" section on the bottom rear of the hull.

[cyclops]

Everybody, I am referring to a POCKET TRANSOM as used in a inflatable boat. The 2 side tanks extend way past the engine to stabilize the boat in all weather conditions.What are you talking about?

[cyclops]

OK, I think you are refering to TUNNEL DRIVE as used on VERY SHALLOW running boats. They go easily in 6" of water at wide open throttle.

[cyclops]

They are without a doubt THE BEST boat on tidal flats. Do you need some web stes to check out?

[RTN]

Cyclops has it figured out. It's not actually a tunnel hull. Is the purpose of the pocket hull to allow for a higher mounting of the outboard?

[cyclops]

Actually it is to run the props in a very WET mode of surface drive. Boat stopped, the prop is submerged. Race it up and the boat lifts on to a plane. Speed increases and the prop maintains suction and thrust. Carefull adjusting of motor height is required as boat load changes. Still, it will not suck all the bottom up like a true jet pump drive will and destroy it self. 1 Aluminum and spare prop is very reliable, out and back if you get careless.

[PowerTech]

pockets are the funk on fast flats boats.in lets more water get to the prop with the motoer higher like the other dude said.the pocket is a bite taken out of the transome doun were the drain plug is.A hydrolic jack plate and a pocket is the way to go for great speed and shalow water running.My old budy jon put a pocket and a pad on his hydrostream to get rid of the hook and that thing hauled ass.I got a old hews bonefisher with no pocket but I think the new ones have them.

[cyclops]

Web search. flats boats Plenty of companies with all the features. Enjoy

[RTN]

As I understand it then the pocket actually directs water upward to allow the motor to be raised and still run without cavitating. How high can you raise the motor before loss of performance?

[PowerTech]

I don't know how high you can go up .some one may want the model of your boat and motor tipe to tell you something about that or a measure of the pocket or something.Or maby there is a general rule of thumb But I don't know.What I do know is hydrolic jack plates kick ass and you can adjust them on the fly for the optimum hight for plaining or high speed and with the trim adjust on the engine and a jack plate you can tune that baby rite in to the sweat spot when ever you want.

[cyclops]

You are getting the idea of it. Take a 6" deep puddle of water. Start a powerfull wet/dry floor vacume cleaner. Move the hose end to the water surface. Nothing happens till you touch OR submerge the hose end. Then you can raise the hose end ABOVE the water surface. Touchy but DOABLE. In a OB boat you can eliminate MOST of the lower unit body drag. More efficient and faster. More prop protection with simple hull design. It works.

[Reese]

Sorry to jump in....what you guys are talking about is called a "notched transom". As previously mentioned, it does help to get a cleaner stream of water to the prop helping efficiency, but the real purpose is to increase the fulcrum effect at top speed without sacraficing hole shot.

For example a 20 ft. bass boat with a notched transom of 10" along with a setback plate of 10" will have a total setback of 20". Upon take off, the notched section is under water and the boat behaves as if it only had 10" of setback. Once the boat plans the flat keel begins to raise the boat and the CG begins to move towards the transom near the notched section.

At speed, this setup will require less trim from the outboard allowing greater power to be directed towards forward motion. This also explains why 280 hp outboard bass boats routinely hit 100 mph.

[texas nitro]

can anyone help? :confused:
pocket tunnel taking on water between transome and engine bracket and will not plane properly

[Corpus Skipper]

engine bracket ???? Set back bracket, jack plate????? If either of these are the case, a tunnel extension will solve that problem. As far as planing, I think you were in another thread with that one http://boatdesign.net/forums/showthread.php?t=7664