Bracket tub shape opinions

[1bayouboy]

Still gathering materials but meanwhile devising a plan for the mold. After looking over all the pics I could find, I decided I want to try for maximum flotation and looks.

So I enlisted some help from the capt and traced the hull bottom then cut it out so I could have a visual aid...

Some help from the capt....



Getting the bottom traced



And here's the shape so far..the inside of the blue tape....it follows the 21 degree panel and blends over into the 13 degree panel. Maximum width is 52 inches. The flat section of the tub's keel is 3.5 inches above the flat section on the hull's keel to leave room for a garboard drain. I think I left enough room on the sides for tabs....and I can also put a little slope on the sides. I should be able to mount the motors on 30 inch centers.....a couple of inches wider than stock....and which right now is looking like it will be twin 140 zukes.
The mold building will be a little tricky but I think I have a plan to keep the front and back parallel and at 13 degrees while I get the sides and bottom fixed in place. I'll know if it works in the next couple of weeks as I try to build it. It should have a lot of flotation. I'm still considering the setback....I'd like to keep it as short as possible and still be able to trim the motors all the way up. I'm not sure the distance from the inside of the transom to the end of the cowling on those motors....if somebody knows please chime in.

[Old'sCool]

Nice Captain!

[warthog5]

1bayouboy Glad to see some Class pix's.

Call Brownspoint Marine and have them send you the PDF "Setup File".
http://www.brownspoint.com/index.htm

The imfo is not in the factory manual.

[other tom]

...

[strick]

Looks like you are on the right track. I think you are looking at a 26-27 inch set back for Zuke 140's. Bigshrimpin knows...we designed his for a single 140 Zuke. Maybe he will chime in. Were will the anticavitation plate on the motors sit in relation to the bottom of the bracket's transom.

strick

[1bayouboy]

Seems like it should be about even with the bottom of the tub as long as it's no more than an inch above the boat's bottom per foot of setback. The bottom of the tub at the engine mount centerlines is two inches above the bottom of the middle bottom panel. If I use a 30" inch spacing on centers it puts the motors just about even with the first chine. Not sure if that's good, bad or indifferent.

[warthog5]

The motor's will be much higher than that.

[1bayouboy]

Thanks guys....that's exactly the kind of discussion I wanted before I start sawing MDF....

Here's some outlines....My question is should the anticavitation plate be above the bottom of the bracket. I know on the brackets that angle up you can mount the motors higher and not hide the prop behind the bracket, but on a bracket that follow the line as the boat's keel all the way back it seems like I shouldn't get the anticavitation plate above the bottom of the bracket....just like on the boats transom. I can get the motors higher by moving them out from the center somwhat which I'm doing. So the red line is the motor and cav anticav plate; the orange line is the bracket's transom, blue lines show spacing in inches....I threw it together and it's not square....when I draw the pattern on a drawing board it will be.....

[strick]

Ideally you want it were the red lines are. The anticavitation plate on my suxuki is right at the bottom of the keel of the bracket....just like if you had it mounted to the transomon the boat. Mount the bracket so you have the anticavitation plate 1 inch up for every foot of set back. Thats the starting point. You may have to raise the engine even more so I would make sure that once you mount the engine you have room to move it up or down and still have the anticavitation close to were the red lines are. But what the hell do I know I'm just a veterinarian. Maybe someone who knows what they are doing could chime in. Gotta get to work.

strick

[strick]

I could run the 21 degree deadrise portion farther up before the transition to 13 degrees. I avoid trying to slope the tubs bottom upwards as it goes back just because that seems harder to lay out in a way to build a mold.

I like that idea. It might provide a little more flotation. You can make a more dramatic reverse chine in it also if you want. I think the seamark has a bit of a reverse chine in it. Lets keep in mind that the shape of the flotation chamber is as imortant for boyancy as is the size. My bracket down side up.



I snapped a couple pics of the motor today to see exactly were my anticavitation plate sits. It is actually about 1.5-2 inches below the keel of the bracket.

The point here is, that anything above the waterline just add's weight and has no effect on flotation to help the boat sit level. Only what is submerged does have a effect.

Looking back I probably could have made the sides of my flotation chamber deeper thus providing more flotation. Also I probably could have mounted the bracket 1.5 inches lower.

Here are more pics:



Make sure you leave enough room for your transducer if it is going to be a transom mounted.



make sure that you can stand on it and have dry feet....



Why in this photo does it appear that the bracket could be mounted a little lower....



while in this photo it looks like the bracket is mounted just right....




Theres a lot for you to consider. It hurts my head to think about it.

strick