Platform to bracket layup question

[take a potter]

So I am at the point that the bracket tub is out of the mold.





I have not trimmed it yet, nor have I cut the clamping board down to the correct height or mitered the sides of it. I am trying to get my next steps clear in my mind, but don't feel like I have the best plan.

Right now the inside of the clamping board only has 4 layers of glass on it. I was thinking that after I test mount the tub to the boat, with just 3 bolts, I could trim the clamping board and template the platform.

However, maybe someone who has done this before can give me an idea as to when to glass the rest of the inside of the clamping board. I am assuming that I need to grind back the glass on the outside of the clamping board and run the final layers of glass around from the front to the back.

How do you handle the angles, I will need to cut darts in the fabric to make it wrap but obviously this weakens the laminate, do you just do the same offset seams as anywhere else? How much glass should be on the top and angled sides of the clamping board? My plan was 3/8" of glass on each face of the clamping board. Ie. how many layers thick should the wrap be?
Then once that is done how many layers of glass do you run up the front of the clamping board from the platform? And do you wrap it over the top also, after grinding what you just wrapped when you tied the front to the back?

I guess what I am asking is what is the best way to tie everything together and not mess up any more of the nice surfaces that came out of the molds than necessary?

Seems a shame to lay glass on the top of the platform after it comes out of the mold but can't seem to come up with an alternative, I am hoping that I am missing something because I am too deep in the weeds.

[strick]

You are going about it a little different then they way Tim and I have done it in the past so I dont think I can be of much help...we used to build complete one off molds where you make the two parts tub and swim platform then lay them up as you would any other fiberglass part..."gel coat then glass" and then attach the swim, platform to the tub...we used to have lots of pictures but they are gone now as are most pictures from years ago on the internet...if you are worried about glassing the corners just put some fillets in....maybe Bigshrimpin will chime in if you can get him to put down his metal detector for 2 seconds

strick

[take a potter]

Originally Posted by strick

You are going about it a little different then they way Tim and I have done it in the past so I dont think I can be of much help...we used to build complete one off molds where you make the two parts tub and swim platform then lay them up as you would any other fiberglass part..."gel coat then glass" and then attach the swim, platform to the tub...we used to have lots of pictures but they are gone now as are most pictures from years ago on the internet...if you are worried about glassing the corners just put some fillets in....maybe Bigshrimpin will chime in if you can get him to put down his metal detector for 2 seconds

strick

Well that's not good... I was not trying to do it different than Strick, at least not up to this point.

I think it is my description, that may be flawed. I laid up the tub in a one off mold, and was planning to do the same with the platform. Specifically to get the lip of the platform nicely radiused.

Here is the way it looks now out of the mold, I still need to add glass to the inside of the clamping board. Right now it only has 4 layers.




I have seen many, including you Strick that included a "hood", for lack of a better term, with the platform layup. This "hood" then becomes the front and sides of the "clamping board".

The hood would be in the shape of the clamping board, the blue tape in this pic.



I guess I do not understand the value of the hood. I assumed the core at the back of the tub was laminated front and back and as part of that the sides were wrapped with glass also. Since you can't wrap the sides when the tub is in the mold, or maybe you can and I did it wrong, then you wrap them after trimming the top of the clamping board once it is out of the mold.

So with all that said, why not just make a platform with a lip and then glass that to the tub and run some glass up the face of the clamping board?

One of the problems I have read about is stress cracks at the forward corners where the clamping board meets the platform, because of the sharp angle. So I was thinking of running my platform to the back edge of the clamping board and curving it to meet the desired depth of the platform. Like this but also having a radius at the front corner of the clamping board.



So this is what I was trying to figure out, how to tie/glass the platform into the clamping board? Without creating a fairing nightmare. As part of that process I was trying to come up with a layup schedule. Like how many layers of glass need to wrap around the sides/top of the clamping board? And if I layup my platform with 2 layers of 1700 on the top of a 1/2" marine ply core, how many layers of glass would you wrap from the platform up the front of the clamping board? Are 2 layers of 1700 attaching the platform to the front of the clamping board enough?

The other parts of the platform will be glassed to the tub, the front will get glassed to the front of the tub after beveling the outside front of the tub. For the sides I created flanges when I laid up the tub and I'll glass those to the bottom of the platform. Plus glue it down with potter putty on top of the stringers.

[Bigshrimpin]

[Bigshrimpin]

To minimize flex make stringers inside the bracket as tall as possible. You can also glass the swim platform to the bracket from the inside. That will add additional support at the area you are describing. You can also add upside down knees inside the tub to support that area . When laying up the swim platform, use 1808 or 1708 and don't skimp of the swim platform layup (6 layers).

[Bigshrimpin]

On this bracket I cut the pieces and used 4" and 6" 1708 tape in the corners. That makes the layup in the corners twice as thick.

[Bigshrimpin]

[Bigshrimpin]

FWIW - I still have that bracket and there are no stress cracks at all even after the guard rail test.

[take a potter]

Thank you @Bigshrimpin for the pictures and the results of the impressive test.
So seeing all of that I still think I have the same question. Before you install the platform with what I am calling the "hood", have you laid up a full complement of glass on the inside/front and sides of the clamping board? Or does the "hood" when it gets glued to the clamping board take the place of laying up glass on the front and edges?

[Bigshrimpin]

Just so we are on the same page with terminology . . . this area outlined in blue tape you are referring to as the "clamping board"?

If so 4 layers is plenty if your plan is to make a swim platform mold.