Bracket mock up
 

I cut some cardboard into the shape of what my bracket should end up. Its rather large. :nice:

Its 41" wide, 17" tall, and has a setback of 30". Totally submerged it will provide about 850lbs of floatation. Assuming my waterline stays the same, about 10" will be submerged. So that is about 550lbs of floatation.

First pic, the sharpie lines are where the outside of the stringers are. My plan is to extend the stringers out the transom and build my floatation box off the extended stringers.

http://i272.photobucket.com/albums/j...bracket001.jpg

This is the basic bracket shape. I cut it too tall, so i just dropped it below the hull for now. Ran out of light and i will cut it correctly tomorrow. That is a 2' level on the top for reference to size.

http://i272.photobucket.com/albums/j...bracket002.jpg

http://i272.photobucket.com/albums/j...bracket003.jpg

http://i272.photobucket.com/albums/j...bracket004.jpg

What do yall think? The outside edges of the bracket will be flush with the bottom of the hull at the strakes, and the bottom of the bracket will be flat. I will have 5" between the bottom of the boat and the bracket.

I think its the best compromise for the most floatation and also keeping the basic purpose of a bracket. RidgeRunner linked a site, http://www.hermco.net/ thier design has the most floatation, but i believe their design does take away some of the performance aspects of a bracket as they dont "swoop" up any.

Looks like you will have a lot of flotation. How close to the bottom of the boat will the bottom of the bracket be?

Should be 5". Badnews. We just got a rain storm and my bracket fell apart, i guess i need more duck tape. :you:

being that i converted my v to a bracket, i would shorten the set back to just what you need to tilt motor. You really don't need to lift motor up all the way up. further back adds more leverage on transom and changes the center of gravity quite a bit. I always wished i went shorter with mine, but i bought a used Armstrong and beggars can't be to picky! But are building so you can do what you want. but looks good from here!!

I'd agree with MJ, make it shorter. I'd also make it taller, the biggest mistake in converting a boat to a bracket is mounting the motor too low. You also need to make sure you have a clean break(step) with the hull bottom. If you don't it acts like extending the hull length, which will add a lot of drag

The "clean break" area on my Stainless Marine bracket and the swoop are the precise areas where Hermco fills the gap.(Big Shrimpin's brackets too) By closing in a little more of that void on the underside of the bracket, they add floatation.
I don't think they go so far as to hurt the performance. Water rises as it leaves the rear of the hull but I watch where the water hits the lower and I know there is more room to add some additional floatation below the waterline. I was thinking of starting at 1.5" from the bottom at the transom with a swoop that winds up approx 2 to 3" higher than where I have noted the water hitting the lower unit. (Now there is 6" to 7" from the bottom of the bracket at the rear to the waterline on the lower) If it was 4'wide that would be a couple extra square feet of floatation at rest and yet completely out of the water on plane AND being 4' wide the boat would certainly be more resistant to transom sinkage when there are four people standing at the transom. LOL.. It would need to be light enough to reap the benefits yet strong enough to withstand the beating of a barely used 300XS Merc. :oh: Umm , did I stray?

I thought that the bracket being longer than mounting the engine on the transom helped the boat ride better in seas?

I have heard the opposite. I can't tell any detriment but I never rode in it before the bracket was installed.

I guess there is a point of diminishing returns.

longer makes it harder to steer i think. reverse is tuff to steer even on the sea ox, also when adding bracket you need to add a inch in height for every 6" of leanth. and as stated above a bracket should be at least for a 25" motor! shorter and it will get wet from following seas, some times getting swamped!

To test how the boat will ride with a heavier motor i am strapping a 30gallon livewell onto the bracket. If it rides good with then it will stay there. More room in the boat. As far as bracket height, my motor mount is five inches taller than the top of the bracket. I was thinking that running the edhes of the bracket flush with the strakes would help with any porposing issues. Ridge do you have any issues if you dont use tabs?

30 gal tank is ok for the test but its not going to show right, cause it will not fix the center yof gravity that is going to change when weight gets moved further back past transom.

Hmmmm. MJ that may be a good thing. My Mercury 200 is a 2.5L with a 25" shaft approx 395lbs.

I thought it was 1" up for every 12" back??? If that is not the case then i need to go back to the drawing board. One reason for trying to keep my bracket low is I am planning to install a port side transom door. I dont want to be trying to haul a tourney winning shark up 12" to get it over the bracket platform. Might not do the full width platform across the transom. I agree with Ridge 100% on the Armstrong design, they lose some valuable floatation with the sharp angle. How much of a clean break do i need from the strakes to the bottom of the bracket? Or can i get by with angling the bottom of the bracket just a tad, I would not lose as much floatation, but should still keep the bracket out of the water when running.

Ridge later on down the road i may go to a bigger motor. One reason for such a big and beefy bracket. I am also on the lookout for trim tabs, if i have the room to mount them.

Just turn it into a 23'....

http://www.thehulltruth.com/boating-...-4-stroke.html

Jason do you get on THT (the hull truth)? theres a guy on there building a Dusky he is very good with brackets and has actually started building his own for sale. His screen name is EDWARDPIC look him up he knows his stuff about bracket design, he could answer some design questions for ya.

No Kracker, i don't get on THT alot. Heck i dont even have username on there. CTerrebonne it will be a 23 after my bracket. :beer: 25 if you count the motor. 26 if you count the bow pulpit.

Just a thought, if i take pics thru out the build and document everything is it possible to get an inspection and possibly raise the hp and capacity ratings? The bracket will be a part of the hull not an add on? What do yall think? Or am i wasting time with an inspection?

Softy inspection is great to have, and they will leave you alone on the water! But they are not going to change the original capacity plate, don't waste your time.

I agree with MJ on capacity plate, that isn't going to change. Which is why I don't have one... OOOps!

Ridge i think mine is about to fall off. On a side note, a V20 has less capacity than an 18 Fisherman. How the heck is that possible.

Just a guess, but it seems to me that if a V20 and an 18 fisherman both have the same amount of flotation, then the 18 would have a greater capacity simply because it has less weight due to no superstructure. Like I said, it's just a guess, but it seems logical.

I just re-read all the posts in here. I never needed the trim tabs. No porpoising issues at all unless you overtrim the motor.. But they are nice and should have been original equipment IMO.

Good to know on the trim tabs. How much setback is your bracket Ridge?

Stainless Marine 30". Moved fuel tank and console forward a tad and installed a 13gallon fresh water tank in the dead space under the floor in front of the fuel tank bulkhead, moved the batteries under the console. The modified console is a heavy SOB, despite the fact that I cut off the bench seat/storage off the front and use a 94 QT Igloo in front of the console as a seat. IN other words I tried to adjust the balance of the boat to compensate for the 30" setback. It works best with the 400 lb motor it was intended for, not ideal with the big motor.. 24" to 26" would probably be better.

Gotcha. I was thinking about moving my fuel tank forward, but not 100% dead set on it yet. I also have a water tank from the Sportsman. Plus one 27 gallon tank, maybe one more if i can find one for a good price. I was actually planning on installing the extra fuel tank in front of the stock tank. But i have a thru hull fitting with a water pickup about eight inches from the cabin bulkhead. I will have the cap out of the boat so its easier to do any modifications. But i also want to foam any unused areas. If i use the water tank it will be in the cabin. All the way forward.

I believe that is true, but it is proportional to the hull length. A 30 foot boat can take more setback than a 20 footer.

If you study the "go fast" guys, they seem to like around 24" of setback on a 20' boat...and they have tried everything to get 1 more mph out of their boats.