Build a transom bracket?

[Tampa Bay Mike]

 Has anyone either built or considered building their own transom bracket similar to an Armstrong? I'm enclosing the transom on my 77 22-2 using 1 1/2" Coosa and have been considering building one while I'm at it.

[mshugg]

Some have tackled it.  I can’t think of which rebuilds though.  There have also been some built over on Classic Seacraft. 

My only concern would be weight.  Fiberglass is heavier than aluminum to get the same strength.  I know that if I were doing it, I’d be so paranoid about strength that I’d tend to overbuild, making it even heavier. 

[RickK]

One of our members, Daytrip, has built a bracket on his Bertram conversion over on Bateau2.com - he's an engineer so he can probably help with any calcs on lever and moment and other stuff I can only spell.
https://forums.bateau2.com/viewtopic.php?f=10&t=59473

[Tampa Bay Mike]

Well, I guess it's nice to know that I'm not the only one who is crazy enough to consider doing it.

If I do decide to try it, I would probably use Coosa to keep the weight down as much as possible. It would be nice to be able to blend it all together, and saving some of the $$ that Armstrong wants wouldn't be a bad thing either.

And Rick, thanks for the link. Looks like I have some more research to do.

[Tampa Bay Mike]

 Ok, so I've still been toying around with this idea in my head lately so I decided to make a rough prototype over the weekend with this piece of coosa that's taking up room in the shop. The idea from here would be to clamp it all together with some thickened resin, fillet the inside corners and round off the outside ones, and add about 3-4 layers of 1708 inside and out. I would also add in the bottom piece, and was thinking about spanning the width of the transom on the top with a piece of 1" honeycomb, or the like, to make the swim platform. Then I would glass and bolt the entire thing to the transom.





It's about 21" deep as-is so I can still add a jackplate. I made the outside face flat for now but it looks like I may need to recut it at an angle but that's easy enough to change if needed.

Oh, and right now I only have about an hour into this and a couple of deck screws holding it all together so don't think you'll hurt my feelings if you tell me I'm out of my mind. 

[RickK]

Mike, have you spent any time looking through Daytrips' rebuild/stretch of an old Bertie? At this point in his stretch he is building the bracket:
https://forums.bateau2.com/viewtopic.php?f=10&t=62908&start=80#p433731

Here is a link to the last Bertie he rebuilt/customized and also built a bracket - on both he tied the bracket into the stringers.
https://forums.bateau2.com/viewtopic.php?f=10&t=59473

He's a member here also but I think he spends more time over there.

[Tampa Bay Mike]

Yes, I did read through most of that first build. I meant to say thanks for the link. That's what gave me the idea of adding the platform across the top. I think it would add a lot more area for bolting to the transom. I will check out the other link too, and anything else I can find before I commit to this.

[RickK]

Daytrip is an Engineer and thought out the best approach and something called "the moment" is important with offset. He tied into the stringer system so his entire thrust system (engines, bracket and platform) are pushing directly into the strength of the hull.
I know that companies like Armstrong make brackets that will tie into a strong transom and we have plenty of members with them.  As long as you have the transom worthy of this (I think you do) then I would consider a bracket.  Can you build one of the caliber of Armstrong?  Read Daytrips threads about building the bracket portion.  You could also PM him and ask him to give some advice here on the thread.

[mshugg]

No, you are not out of your mind, but as Rick has much more diplomatically pointed out, there is a lot of stuff in bracket stuff. First, you are starting with a hull that was designed when outboards weighed significantly less.  Add to that , you want to place a heavier outboard significantly aft of the transom altering the designed trim of the boat.  Not trying to rain on your parade, just suggesting that there are a many considerations.

Your tub looks small, not much bigger than the bolt pattern of a standard outboard. That doesn’t allow for the distribution of force for a heavier outboard located 21” aft of the designed transom.  Second, the small tub, does little in the way of additional flotation.  Look at the tub on an aamstrong bracket.  It’s much bigger to offset the weight of heavier outboards.  Armstrong uses aluminum, which is lighter than fiberglass in terms of strength. Even with Coosa core, glass will be heavier requiring even more flotation.

Again, I’m not trying to piss on your parade.  Just suggesting that you learn from other’s lessons.  Use a larger tub for more flotation and for greater distribution of force.  And definitely angle the aft end.  You’ll want that negative trim.

[Tampa Bay Mike]

Thanks for the replies, and no offence taken. I knew there was a lot to this that I didn't know yet.

Seems like there are a few things at play now that will probably help in my decision. First, I dont feel comfortable enough to try extending the stringers through the transom. That's quite a commitment for an unknown. As for the tub size, it was as big as I could make it with the amount of coosa I had left over. Could I buy another sheet to make it bigger? Sure. Would I end up with more money in materials than if I just bought an Armstrong? Maybe, which makes this all a moot point. Could I use a cheaper core to do it like honeycomb or a lower density foam and still have enough strength? That I don't know. Could I use a combination of things? Again, not sure.

So that's pretty much where I'm at. I don't think its completely out of the question, but it's just a matter of can I do it safely and without spending more than it's worth.

[RickK]

I agree it's a lot to think about. My biggest concern would be my expensive motor falling off 

[Capt. Bob]

This was taken from our Gallery. There are other photos there showing how it was built into the transom. You're beyond that point now but interesting anyway. Clicking on the pic will take you to the Gallery for more shots of the bracket.



https://classicaquasport.com/smf/index.php?topic=2547.msg16637#msg16637

I realize it's not an Aqua. I believe there was a rebuild here that showed a fiberglass bracket molded into the transom but I can't seem to find it.

Good luck.

[mshugg]

That is some awesome craftsmanship!  The finished bracket looks amazing.  I couldn’t find a build thread for it, though.  Is there one?

[Capt. Bob]

There was a build thread but I'm not sure it was this hull. I'll keep looking.

[Capt. Bob]

Here is one but still not the one I remember. It is the Apollo thread with bracket shown above.

https://classicaquasport.com/smf/index.php?topic=12744.msg128871#msg128871

Unfortunately, this rebuild thread ended before completion.


https://classicaquasport.com/smf/index.php?topic=9164.75