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Platform to bracket layup question
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So I am at the point that the bracket tub is out of the mold.
Attachment 22892 Attachment 22893 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. |
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 |
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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. Attachment 22905 Attachment 22906 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. Attachment 22904 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. Attachment 22903 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. |
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). http://www.classicseacraft.com/commu...3&d=1611433206
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http://www.wellcraftv20.com/gallery/...188_Medium.jpg
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. http://www.wellcraftv20.com/gallery/...195_Medium.jpg |
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FWIW - I still have that bracket and there are no stress cracks at all even after the guard rail test.
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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? |
http://www.classicseacraft.com/commu...5&d=1611433341
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. http://www.wellcraftv20.com/gallery/...7/DSCN5898.jpg |
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keep in mind however you decide to do it that your outboard mounting bracket needs to fit over the clamping board with some room to spare should you need to lower the engine which would be highly unlikely...does this make sense? strick |
When you cap the bracket with the swim platform mold you'll have the 4 layers (you already laminated) + "mud" + the thickness of the swim platform cap (another 5 - 6 layers of 1708). That make 9 or 10 layers of glass. Does that address your question?
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Another note . . . See the front lip on the Hermco bracket.
http://www.wellcraftv20.com/gallery/...rmco.sized.jpg This was a trick Hermco used with his caps to stiffen up the swim platform area. We didn't learn this until much later on. Please ignore the "hard edge" label . . . that was label for another bracket conversation. |
Yes, the transom of the bracket. After I test mount it to the boat and feel good about my height and such, I plan on trimming the board to the blue lines, give or take. Of course that means that there will be no glass on the edges. I can obviously seal with neat epoxy. I guess I was not realizing that the "hood" on the platform was structural. I figured it was just to minimize fairing, being that it was just puttied to the front of the clamping board.
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we had many pictures and even some diagrams of the Seamark brackets but it still did not answer all our questions as we could not see it from every angle as to how they were built.. I found this picture of the first one I built...all epoxy...over kill to say the least but I ended up hanging a Brand new Suzuki 250 on that boat after the Yamaha kept giving me trouble. strick |
Reading this again . . . The sides of my transom core were beveled and glassed only top of the core was exposed until it was mudded/capped with the swim platform mold. The seem edges were sealed and glassed on my last bracket.
http://www.wellcraftv20.com/gallery/...5399_Small.jpg http://www.wellcraftv20.com/gallery/...5401_Small.jpg |
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"Potter puttied his decks and top caps to his transoms in much the same way... trying to free the two joined parts has annoyed many a seacraft restorer.."
Some of that is my concern. On mine when I tried to remove the in floor live well it was potter puttied to the hull. One good pull with a pry bar and the whole thing just popped right off. A couple other places there was putty a chisel under an exposed edge and the whole pool of putty just came off intact. Now granted it was poly based putty and I am using epoxy but... Anyway I'm going to do a little more head scratching and see if I can come up with a plan. I don't want to reinvent the wheel but I am willing try something different if it has merit. |
Hermco ground and glassed this seam.
https://pro2-bar-s3-cdn-cf6.myportfo...1b7907ca725555 https://pro2-bar-s3-cdn-cf.myportfol...4159515d0bd6a4 |
Ok thanks guys I understand.
Really appreciate all the information and pictures you both posted! I will make sure I post pictures of what I do. Once I get the tub mounted and double check all my height measurements Ill cut the transom to the right height and then start on the platform mold. |
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I had found this picture of a Hermco platform a while back. I thought it was a pretty good shot of everything going on.
Attachment 22913 I do plan on glassing the front of the platform to the tub. Right now I have 7/16" of glass for a hanger rail at top of the front of the tub as well as around the perimeter where the bolts will go thru. It is about 5" wide. So I'll have plenty of glass at the top to bevel and glass the platform to it. I was planning on two full height box stringers about 3 1/2" wide, similar in construction as the ones in the boat. Do you think that will be adequate? |
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While I have been scratching my head. I broke out the plasma cutter and started making washers. 304 stainless 5/16" thick 2 x 2 3/8". 36 of these and that should take away another 12 lbs or so of buoyancy.
Attachment 22914 |
Having a plasma cutter at your disposal is super helpful. You are a lucky guy. If you use 5200 b/w the boat and the bracket, you almost don't need any fastners at all (not that I would trust it). Getting the guardrail tested bracket off the seawolf was brutal. With all the fasteners removed, I lifted the entire stern of the boat (with a hoist) and hung it in the air for a week trying to break the bracket free. I think you could have driven the boat full speed with no fasteners and the 5200 would have never come free.
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The guy from Santa Cruz fiberglass Hawaii did just that and it still did not break loose
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36 bracket to hull bolts?
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If you use 5200, prep with acetone, not alcohol, as I believe that inhibits the cure.
My T-top aft feet are bonded to the deck with 5200. Technically a G10 pad bonded down and the feet screwed to that so as to not penetrate the deck. It works for towing at close to triple digit speeds. It's a whole different thing from Potter putty. I do the same thing for all the transom transducer mounts- I bond down pads with 5200 and screw to that. It's underwater, so it's only ugly on the trailer. |
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