Bracket tub shape opinions

[1bayouboy]

I really appreciate the discussion guys.....

The pics of the seamark look like the tub's bottom is straight back from the transom, parallel with the boat's keel. Not sure the distance up from the bottom. The outline I have is 3 1/2 inches up from the bottom on the center 21 degree deadrise panels, but only 1 1/2 inches above the middle 13 degree panels. I can vary it in any way, but I wanted the max flotation I could fit. I thought the effect should be similar to a stepped bottom.....but what do I know....it's my first attempt.

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.

[1bayouboy]

Looking at the D&D page, it looks like the top of the bracket where the motors mount is supposed to be 28 1/2 inches above the boats bottom in line with the motors. That's moving the motors up 3 - 3 1/2 inches....but I thinki t assumes the anticavitation plates will be below the bottom of the bracket.

[warthog5]

The pics of the seamark look like the tub's bottom is straight back from the transom, parallel with the boat's keel.

That is correct from what I see too, thus it has more flotation.

The flotation can be deceiving for us average Joe. it's not until this stuff is all mounted and floated until you get a better understanding.

Let's look at the side of the tub alone. Where will the waterline be?

Upon first looking at it will it be 3in, 4in or 5in from the underside of the platform?

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. So we want more area that will be submerged to help the boat sit level.

That means a wider and deeper tub. It also means more volume going aft of the transom.

From this:



To this:

[1bayouboy]

And it looks like if that motor was trimmed all the way down, the anticav plate would be just about at the keel of the bracket....

Nice that the bracket has a prop pocket for the trolling motor...

[SCSeacraft]

Give me a shout if you need another set of hands,as long as one of them has a cold one in it of course!

Here are some pics of your junk from Bobby G's Place, thought you might want them.



You may need to change her name to "Playmate" after the stack of 1978 Playboys that came out of her!

Donnie

[1bayouboy]

You're on there SC.......I think the beer to epoxy ratio is 1/1...

Some quick calc's....with a 28 inch setback and a width of 52 inches that'll be 1456 square inches...or 10.1 square feet. So for every inch above the sloped bottom it sinks in the water, that's 0.84 cubic feet...which is 50lbs of flotation. The V bottom is about 8 inches down from the corner so that should be equivalent to 4 inches for the area
which would be 200lbs of water. So I should have 400-500 lbs of flotation...... The old water line on the transom was about 18 inches up from the keel which would give me 14 inches or so of bracket in the water. I think I need more beer to think about this any more...

[SCSeacraft]

Why don't you just go buy the aluminum bracket I have up at Bobby's place and be done with it??
Donnie

[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

[warthog5]

HeHe You bring up even more question's Chuck.

How does the anti cavitation plate look when your on plane?

Is it underwater or even with the surface. Do you get a bunch of spray off of it?

In the last 2 pix's. from what you stated look's backwards to me. I realize the boat is in gear in the bottom pix.

It's hard to see in this pix, due to the Black color. I have aprox 4in between the water surface and the bottom side of the 2in band around the swim platform when the boat sit's at rest.




Now let's forget the bottom of the bracket for a sec.
With a stright edge extended out from the keel of the boat. Measure from the top side of that stright edge to the anti cavitation plate. What that figure?

[1bayouboy]

Hey SC....where's the fun in that... but really...what kind of bracket have you got??

Good pics Chuck...that bracket looks great....and good questions. and thoughts. I was going witha thru hull but leaving a little room might be a benefit later. I think the wide tub is going to have enough flotation.