Bracket theory

FishStretcher · #1 10-11-2011, 09:56 PM

From what I can tell, all the (flotation) brackets all have centrally mounted flotation volumes. And no flotation out at the edges.

It seems like at rest, some flotation under the wide swim platform would help lift the outboard out of the water even more. Why isn't this done? Is the issue making the boat roll in a sea that was coming at an angle to the stern?

Or is there some other reason, like practical construction issues, or something else?

strick · #2 10-11-2011, 11:37 PM

Most of us will have trim tabs that are in the way. Also the shape of the hull rises as you move outboard so it would not add a whole lot of flotation. Once in a while you will see folks that have added large flotation/storage boxes on the outer transom edges of their 20 master anglers. The motor is transom mounted....Their trim tabs are mounted inboard to those boxes. Finally it would look ugly having a bracket that looked like that.

strick

Bushwacker · #3 10-11-2011, 11:40 PM

Don Herman told me that Potter set the Hermco bracket tub width to leave room for a retractable swim ladder under one side of the swim platform. However he said very few folks are actually installing such swim ladders (but I did!), so he's thinking about making the tub wider, taking it out to line up with the second step to accommodate the heavy 4-stroke motors.

Capt Chuck · #4 10-12-2011, 08:41 AM

Correct Denny!, I did also

FishStretcher · #5 10-15-2011, 10:15 PM

Thanks. I think I will weld on some stepped side flotation to my bracket before I install it. Maybe not out to the edge, though. That's why I am drawing up the transom now, so I can fold some more aluminum.

FishStretcher · #6 11-11-2011, 12:04 AM

So far this is what I am thinking of. I still have to fab the stepped side boxes out of 5083 or 5086 and weld them in. That's a 20" motor (I think- top of mount, to anti ventilation plate) on a 20 foot hull transom. I may more accurately model the Master Angler transom later.

77SceptreOB · #7 11-11-2011, 01:39 AM

nice drawing!!

Sea Addict · #8 11-11-2011, 03:19 AM

Yeah bitching drawing...

bly · #9 11-11-2011, 08:43 AM

is there much floatation Volume compared to the extra weight of the wider bracket? Or are we going to extend the bracket to the full width of the transom and have a lengthened stepped boat hull instead. We could also bolt a piece of styrofoam onto the top of the trim tabs and maybe add a little floatation to the heavy stainless trim tabs. What about the loss of floatation because some brackets are pitching up away from the plane of the bottom too much?

FishStretcher · #10 11-11-2011, 08:55 AM

If I manage to get the height of the bracket right, then the extra volume was worth another 140 lb of flotation, if I remember correctly. On a 6 foot wide bracket with 30" setback, the extra "boxes" leave ~8" of width on each side for trim tabs.

The story is: I bought someone else's custom aluminum bracket and I want to modify it for more flotation. He seems to be a very talented metal fabricator/artist.

The bracket needs a little work with the bridgeport and plasma cutter first, it weighs a bit more than I like at about 135 pounds and is probably overkill, with 1/2" plate in places, 1/4" everywhere else. I think I can add the boxes on the side and get it down around 105-110 lb dry. I don't think I can modify it to be a lot lighter (if at all) than a fiberglass bracket, but it is what I have. Maybe with a design from scratch with some thinner sheet, but I am not doing that. Plus a thinner wall makes it more susceptible to failure when it eventually does corrode.

I think with the steps, it should still be far enough in height from the planing surface of the standard hull to be dry when on plane.