Bracket theory

[bly]

Originally Posted by workinpr0gress

Bly, do they give a trim/tilt range in deg.?

Carmen said he would call the factory. I am getting nothing but irritated here. See you bruce.


This is my new retractable carbon fiber riggers I am prototyping. Then I have to come up with a name for the new company? Nobody has a cam clamp retracting rigger like these. The best of the best.

[gofastsandman]

Originally Posted by bly

Carmen said he would call the factory. I am getting nothing but irritated here. See you bruce.


This is my new retractable carbon fiber riggers I am prototyping. Then I have to come up with a name for the new company? Nobody has a cam clamp retracting rigger like these. The best of the best.

Black Magic.

[FishStretcher]

So I was wondering if anyone wants to trade some aluminum MIG welding for my leftover 5086/5083 alloy? I would prefer to TIG tack weld it/ seam seal it on the outside, and MIG it inside, but I don't have an aluminum MIG machine, especially one that can do 1/4". All I have is a steel MIG and a nice TIG unit- welding inside a bracket with a TIG torch won't be fun.

Someone in MA/NH would be good.

[Bigshrimpin]

fs - take a look at this design from potter. If I were ever to build another bracket . . . this is the design I would pick.

minimum setback . . . allows tabs . . . easy build.

[thehermit]

That would be killer on your boat Big ;-)

[FishStretcher]

Too many ideas!

That is certainly interesting. I don't find it exactly attractive, but I can see the practicality. I wonder if the water separates off the transom enough to reduce the drag with such a short extension?

Originally Posted by Bigshrimpin

fs - take a look at this design from potter. If I were ever to build another bracket . . . this is the design I would pick.

minimum setback . . . allows tabs . . . easy build.

[Bigshrimpin]

It's similar in design to how intrepid builds their transom.

I'm not sure what you mean by this question . . "I wonder if the water separates off the transom enough to reduce the drag with such a short extension?"

you see any high performance racing boats or bass boats with 30" setbacks? nope! Most jack plates are 10" maximum. The bracket is 4" off the water when you are running . . . so it's a non issue. The reason the current armstrong, hermco, stainless is deigned the way it is now is so you can convert/retrofit an i/o and get full tilt of the outboard with a nice swim platform. None of the popular brackets are designed with performance in mind.

[FishStretcher]

Ok, that makes more sense. Although I had heard the line about "running the outboard in clear water is more efficient and faster". Maybe this small separation is enough. Or maybe it is an imagined effect?

Originally Posted by Bigshrimpin

It's similar in design to how intrepid builds their transom.

I'm not sure what you mean by this question . . "I wonder if the water separates off the transom enough to reduce the drag with such a short extension?"

you see any high performance racing boats or bass boats with 30" setbacks? nope! Most jack plates are 10" maximum. The bracket is 4" off the water when you are running . . . so it's a non issue. The reason the current armstrong, hermco, stainless is deigned the way it is now is so you can convert/retrofit an i/o and get full tilt of the outboard with a nice swim platform. None of the popular brackets are designed with performance in mind.

[martin]

Originally Posted by FishStretcher

I did some stress analysis on a 24" bracket with (importantly) a center rib in the flotation volume.

The center rib helps a lot.

The loading is for 5 Gs. (not 10) Plus full thrust from a 100 hp outboard. Something sort of like the loading you might see landing after skipping off the top of a wave.

The deformed shape is magnified 50 fold so you can see what happens.

A rib that goes from the real transom to about halfway between the lower two outboard mounting holes seems to be an important structural feature.

Yield strength for this aluminum is ~180 MPa, but repeated stresses above 50 MPa would be a bad thing, in very general terms. I expect the loading from the outboard holes to be much lower, as the stress is distributed along the casting, not just inside the bolt holes.

FishStretcher
What are the psi stress point on you annalsist.. I have twin out boards on a bracket and need to know what stress he bracket can take.. 30 inch set back.. ..1/2 inch back plate 1/4 " platform and side and bottom.. 1/2 inch 3 " inch angle .. 6061t .. You can see bracket on my other post 76 23 seacraft thanks Martin

[gothog]

my boat has that bracket . i just posted in the photo forum