Attaching Swim Platform

[rozicrc]

I've got a 20' Imperial cuddy cabin that I just got done building a mahogany swim platform for (60X24). I am planning to use 6 two inch angle brackets to support this to the transom of the boat, and use 4 1" stainless bars at a 45 degree angle to attach the outer support to the boat. For the two inner ones, no issues - I have a composite transom and can through bolt (as well as all the upper angle supports to hold the platform to the transom). The issue I have is with the lower supports - they will be under the deck and I don't want to cut it. Can I get away with 5/16-18 lags here, or will they pull out over time? There is no wood here to help hold the lag - just 1/2" of fiberglass to form the hull. Option B is to run a long 1" bar at a 45 to the center of the transom where I can through bolt, but this is going to be a real strange look for the boat as they will need to be 4' long. I'd really prefer to use lags on only the outer bottoms, but I am afraid of the upforce from a wave hitting the platform pulling the lag out. Anyone have experience with this?

 

[Grub54891]

Re: Attaching Swim Platform

How about adding deck plates to access the lower bolts? Nice clean look and easy to install.

 

[chriscraft254]

Re: Attaching Swim Platform

A lot of people don't take the time to mount swim platforms correctly and they regret it later. The deck plates as already said are quick and easy to install. The swim platform brackets imo should be a bolt through application. You want it to be just as strong as the boat and not have to question anything.

Don't forget to use 5200 below the waterline either. I bought these but at half the price, used 4 of them and bolted through. There rock solid and easy to install. I truly think there the best platform brackets out there. Platform Bracket Swim Platforms Ladders Boat Marine Fishing Sailing Lake Ocean | eBay

 

[fishrdan]

Re: Attaching Swim Platform

a mahogany swim platform for (60X24)...... and use 4 1" stainless bars at a 45 degree angle to attach the outer support to the boat. For the two inner ones, no issues... The issue I have is with the lower supports - they will be under the deck and I don't want to cut it.

Would running the outer supports at 22.5* (instead of 45*) solve the problem if them entering through the transom, above deck?

That 60x24 swim platform isn't all that huge and 4 - 45* supports may be overkill, not that overkill is a bad thing with pounding waves.

I built a 64x22 swim platform and only used 2 custom aluminum brackets, and it's friggin strong. The brackets are angled at something like 22*.

 

[rozicrc]

Re: Attaching Swim Platform

thanks guys, this is helpful. I can bolt through at a less aggressive angle if perpendicular with the transom, but I am concerned about the additional loading (will be 2.5 times more horizontal force if I angle at 22.5 degrees). I can still get the 45 degree angle by swinging the bottom mount in at 45 degrees, which will put more shear force on the bolt but they will handle it and then some. What I am struggling with is can I get away with it. I need to remove a significant amount of wiring and hydraulics to put deck plates in to access the location where the bolts will come through.

Unfortunately I think I know what the right, clean solution is. I was hoping to have someone tell me they did it and had no issues for 20 years.:facepalm: