Custom Fiberglass Extended Swim Platform

[tpenfield]

Ted, you could simply under-skin

I possibly could, except I'm not exactly sure what that means . . . Would it be creating a smooth 'skin' for the bottom of the platform as I am doing with the top side of the platform?

One of the challenges in the design has been providing enough tilt & turn room for the B3 outdrives. I had been figuring on fairly shallow (1-2") ribs front to back in order to provide rigidity to the platform, while allowing space for the extremes of outdrive movement. Perhaps more of a foam filled 'sandwich' would also work, instead of ribs. :noidea:

 

[Scott Danforth]

by underskin, yes

or wait until you try it to see if the swim platform drags coming out the hole

 

[tpenfield]

Thanks, Scott. The idea of a skinned underside has got me thinking about some different ways of doing things on the underneath structure.

Perhaps I can use some pour-in foam, carve it to shape after it cures, then fiberglass over the carved foam to make the’skinned’ underside.

BTW - I have a doubter or two offering comment on the other aforementioned forum. Warnings of ruining the stern of the boat and having structural problems. Not any detail behind the comments, just caution flags.

Am I missing something? :noidea: I can’t see that this would lead to structural issues, and as long as it is done right should be beneficial not detrimental.

 

[chevymaher]

There are always people who know nothing on forums. But they played a expert on TV. Boats come with them from the factory. They don't spontaneously combust. I think you will be fine.

 

[Scott Danforth]

Ted, maybe they stayed at the holiday express last night.

the key is to make sure you tie the upper near the rub-rai / cap joint and tie the struts into something solid and make sure that they are properly sealed.

I would thru-bolt a clevis mount, seal with 5200, then run your struts up.

 

[tpenfield]

Ted, maybe they stayed at the holiday express last night.

the key is to make sure you tie the upper near the rub-rai / cap joint and tie the struts into something solid and make sure that they are properly sealed.

I would thru-bolt a clevis mount, seal with 5200, then run your struts up.

Being a newbie over there, I have not called anyone out, as in asking to see their Holiday Inn Express receipt

When you say "thru-bolt a clevis mount" . . . you mean through the transom (right?) Depending on the location along the transom, there are enclosed/foam filled chambers along the outer regions of the transom. So, those areas would not be conducive for though bolting. If I can get just inside of those area, then I could certainly do a through bolt.

I had planned on a lag bolt there, but a thru-bolt would be better in situations where the platform is catching some water.

 

[kcassells]

OOOOhhhhhhhhhh the Pain of it all! People and opionions...oooh tte pain!
Keep on kickin Ted...you are on the right path grasshopper!

 

[oldrem]

When I remodeled my bathroom, there were a couple naysayers on the tiling site that said some of the things I engineered would need replacing in a year or two. Those items are still rock solid - that was in 2006.

 

[tpenfield]

Yup, I was thinking that these folks were armchair experts, but just wanted to check.

Meanwhile, I have done some checking on how Formula attaches the ESP's to their boats . . .

Here is an example of a factory platform:



And here is the view from underneath . . .


Looks to be a full cantilever, no struts. I have looked at pictures of many others, as many as I could find. . . no struts.

Doesn't looked skinned either. Formula offers either a ladder or a folding swim step underneath with their ESP's.

The attachment looks to be around the perimeter of the mating area, and nothing else. It must work though . . .

I've sent out a call for pictures on the Formula Owner's forum to see if I can get some more details

 

[oldrem]

What you can't see is all the clear packing tape holding it :laugh:

 

[tpenfield]

What you can't see is all the clear packing tape holding it :laugh:

Does Gorilla Tape come in white ?

 

[Scott Danforth]

Does Gorilla Tape come in white ?

5200 comes in white

 

[oldrem]

Does Gorilla Tape come in white ?

Actually, YES https://www.amazon.com/Gorilla-Tape...coding=UTF8&psc=1&refRID=HG303KNFJDFCTB8MK9SZ

 

[Mad Props]

Ted, judging by the picture you posted, it looks like they did what I always wanted to try if I made a swim platform... my guess is the stainless bar running around the perimeter most likely extends in through the hull several feet and is fastened inside the engine area somehow. So it IS cantilevered, but it's got a ton of area/bearing surface inside the hull.

plus it's probably got 10lbs of 5200 between it and the stock platform lol.

 

[Grub54891]

If you are worried about bolting through foam or soft areas, you could drill the holes larger, fill them in with an epoxy, cabosil, or fiberstrand mix, then drill the correct size and install a good backer plate on the inside.
That should be done with most any screw hole. Most rotted transoms are because the holes were not sealed correctly.

 

[tpenfield]

Ted, judging by the picture you posted, it looks like they did what I always wanted to try if I made a swim platform... my guess is the stainless bar running around the perimeter most likely extends in through the hull several feet and is fastened inside the engine area somehow. So it IS cantilevered, but it's got a ton of area/bearing surface inside the hull.

plus it's probably got 10lbs of 5200 between it and the stock platform lol.

Actually, the big stainless steel bar stops about 1" short of the hull (if you look closely at the picture). So, it does not provide any sort of cantilever. All the Formula ESP's that I have seen are the same way.

Formula's secret sauce must be something other than the SS perimeter bar.

 

[Chris51280]

If the back platform has ribs underneath and would be rigid within itself, the only stress you see is the top being pull forces and bottom push forces. the top isn't the problem since it is fastened with the extension to your current boat platform. the problem becomes with the height to length ratio and the momentum you get. If you look closely, the platform is bolted underneath against the hull. This also keeps it from spreading apart when load is applied on the top since it will most likely spread due to the curved hull and forces need to go somewhere. Newtons law. I don't have your overall dimensions but this should explain what I mean.

There are platforms overhanging the grand canyon and don't have any supports underneath

 

[Chris51280]

I would put a grid system underneath and closing it up like a box with the cross members attached to the bottom cover plate. You can slot the plate where the ribs are and use peanut butter to glue it together and fill the gaps. You have enough height to make it this way. the outer black squares are bolt on areas. not sure how your boat looks like where you want to attach it.

 

[tpenfield]

The shape of the platform is probably the biggest factor contributing to the strength. I am debating whether I need struts at all. I could probably do away with the center strut, since it has to be located so far inward to avoid interference with the outdrives.

 

[Scott Danforth]

Ted, looking at the pics, the factory one looks to have a heavy reinforced edge bolted to the sides of the hull sponsons. the height of that edge and the fact that the fasteners are in shear helps alot. not sure on your transom if you can have that same mounting feature