Custom Fiberglass Extended Swim Platform

[tpenfield]

shipping any resin has a hazmat cost.

you could come down here, there are a few fiberglass suppliers in the sunshine state ;D

Yes, probably all kinds of FG suppliers in FL . . . but then I'd have to haul everything back home

 

[Scott Danforth]

So your planning a road trip? LOL

seriously, call around, I bet there is a fiberglass supply house local to you. maybe Falmouth

 

[tpenfield]

Quick Update:

I posted some pictures of my swim platform on the 'boat design net' forum for comment. Nothing earth shattering so far, but several comments/questions on how I plan to attach the platform to the boat. It seems like that is a concern :noidea: . . . It got me thinking more specifically on how I plan to do it, which I should share.

So, I plan on using some pretty beefy stainless steel 'L' brackets. 4 underneath and 2 on the sides. The slab portion that goes over the existing swim deck will be secured with adhesive. The outer edges will have the struts, along with the center strut.

Here are some drawings on the current plan . . .

Here is an overhead view showing the stern area in black, the extended platform in purple dotted lines, the adhesive areas in green, and the hardware in red. I left out the center strut in this diagram, but it will be trough-bolted at the platform and lag bolted at the transom.



Here is a cross-section side view, showing the details of the 'L' brackets and bolts. Probably 1/2" SS bolts. . .



What say the group? Sufficient? I'm not sure where else/how else I can secure things . . . Thoughts? Comments?

 

[kcassells]

I am unable to see what the rise is on the interior sides but some ply or other material on inside perimeter with glass should give added bond. I might skip 5200 and go pb on all areas. KC

 

[Scott Danforth]

I would use plexus adhesive (its what is used in yach and boat building). Make sure your brackets are 316L stainless

 

[tpenfield]

Thanks guys . . .

Here are a couple more pictures after having done some refinements on the underside of the platform.


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I'm thinking that I would not want to do any fiberglassing to the boat itself, purely hardware and adhesives. I am wondering about the Plexus adhesive. Formula uses it for the deck/hull joint . . . supposed to be stronger than the fiberglass. So, I'm wondering, if I ever had to remove the platform in the future, would Plexus be a problem in that regard vs. a '4200' or '5200' type of adhesive? 5200 is supposedly permanent as well.

Also, on the brackets, it looks like I would have to get 316 stainless bar stock (8"x2"x0.20") and make them myself. I don't seem to be able to find anything suitable pre-made.

 

[tpenfield]

Here is a bit more re-engineering on the underside . . .
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[froggy1150]

Here is a little trick for stainless. If you have a hard time drilling holes go get REAL lemons and use the juice for cutting fluid.

 

[tpenfield]

Here is a little trick for stainless. If you have a hard time drilling holes go get REAL lemons and use the juice for cutting fluid.

I did not know that . . . (using my best Johnny Carson voice)

I plan on using cobalt bits (1/2" holes). So, I'll add the lemon juice to the mix.

Wondering about bending the bar stock to a right angle :noidea: I am thinking about heating the bend area until it starts to glow . . . then making the bend. Thoughts ??? :noidea:

I'm just not sure how stainless acts vs. regular steel.

 

[froggy1150]

I work in amusement industry and we use a lot of stainless on water rides. Around 15 years ago one of those " old timers " was watching me struggle drilling holes and told me that trick. I told him he was flippin nuts and what next..... go fetch him a skyhook..... he said just try it. it worked. You still will go thru bits but not as bad. Now that I am that oldtimer:facepalm: .....
you can't really cut with a torch well but a plasma will cut it. So will a chop saw. It will leave a sharp edge. As far as bending I don't remember ever having an issue bending. And to weld either tig or they do make a stainless welding rod that lays in like butter. I think it's both a ac and dcep rod. They even make a rod that will bond ss to mild.
-all technical details fall under old timers memory issues-

 

[mickyryan]

think ya bracing will work great !

 

[tpenfield]

think ya bracing will work great !

I'm a wee bit concerned about the 2 outer struts that support the platform. I have not done an exact measurement, but they are looking like about 4' in length. I am thinking that I should go with 2" round SS tube stock and flatten the ends where they will fasten.

I'm not sure if anything less diameter will resist buckling under heavy loads. . . but it has been a while (decades) since my structural engineering classes :noidea:

There may be times when the platform has 4-5 people sitting on the edge . . . could be upwards of 1,000 lbs

 

[zool]

I would assume the water displacement would take alot of the weight strain off the brackets when at rest with alot of ppl sitting on it...backing down in a following sea may be an issue tho...

 

[Scott Danforth]

you should be fine with 1-1/4" diameter, 0.120 wall tube

2" would be over-kill

 

[tpenfield]

The platform at rest is 'supposed' to be about 4" above the static water line, so I'm not sure how much displacement will come into play, but maybe somewhat with 1,000 lbs. hanging off the end.

I've been trying to do some 'column buckling' calculations using 316 stainless and a 2" diameter 1/8" wall tube @ 48" in length. It seems like I'm getting buckling loads either ridiculously low (50 lbs) or ridiculously high (30,000 lbs)

1-1/4 - 1-1/2" as Scott mentioned may be the way to go, just not sure. I'll have to check the calc's and data to see if I can come up with something that makes sense. Probably want a safety factor of 4:1 .

 

[Scott Danforth]

Ted, on our 800# manual davit, the manual strut is about 3' long and only 1-1/4" thick with a bunch of holes in it for a pin.

a 1-1/4 to 1-1/2" strut will be more than adequate since you will have 3 on the back of the transom

your over-thinking it.

 

[tpenfield]

Thanks, Scott. Good reference point, You’re right, I’m probably over thinking it.

I’ll plan on 1-1/2” tubing to be on the safe side.

 

[52FordF2]

I'm wondering about your swim platform

If when you accelerate would the back edge of the platform dip into the water?
If it does then would the underside of the platform drag or scoop the water?
That would cause a slight drag decreasing the acceleration until you get on plane.

You may want to bevel or smooth out the underside bottom where it would drag.

Just my 02 cent worth

 

[tpenfield]

I'm wondering about your swim platform

If when you accelerate would the back edge of the platform dip into the water?
If it does then would the underside of the platform drag or scoop the water?
That would cause a slight drag decreasing the acceleration until you get on plane.

You may want to bevel or smooth out the underside bottom where it would drag.

Just my 02 cent worth

Yes, the swim platform may come in contact with turbulent water during acceleration/deceleration to/from a stop. Normally, at rest, the platform will be a few inches above the waterline. So, it is a fair assumption that it may 'catch' some water during times of starting/stopping.

I do plan on beveling the last 8-9" of the underside, so that the platform has the tendency to 'ride' over any water, rather than 'drag' it.

Here is a slightly modified picture from a few posts back, showing the platform profile vs. the static water line. also showing where the ladder supports would hang a bit closer to the water. I would imagine that the platform will catch some water, but a beveled underside should help in that regard.

 

[Scott Danforth]

Ted, you could simply under-skin