Swim Platform Support Design

Marshall Mahoney · Post by **Marshall Mahoney** » Jan 9th, '11, 12:47

I want to construct and install a swim platform and was thinking it would be nice to NOT have knee brace supports bolted below the waterline. Does anyone have a design has all thru bolts above the waterline? I was thinking of making trianglar shaped brackets, only bolted above the waterline at the 90 deg angle. But -- I fear it may to be secure enough.
--Marshall

Brewster Minton · Post by **Brewster Minton** » Jan 9th, '11, 13:09

I do not have one. But in waves, stopped, there is alot of forces trying to rip it off the back of the boat.

luis · Post by **luis** » Jan 9th, '11, 15:23

Talk with Giff Plume cause he has a swimm platform that can be closed or open by 2 cables and that could avoid the bumping of waves like Brewster says. You can raise down when you need it or you can have it up.
All the best

randall · Post by **randall** » Jan 9th, '11, 15:58

marshall.....what was wrong with the old one? i thought it was one of the best ive seen.

if you support it from above the braces will always be in the way. also it just seems stronger, gravity and all, to support it from below. whats a few more holes? B31 hulls look like swiss cheese anyway. we should have a contest for the most thru hulls.

CaptPatrick · Post by **CaptPatrick** » Jan 9th, '11, 16:14

whats a few more holes? B31 hulls look like swiss cheese anyway. we should have a contest for the most thru hulls.

Exactly...

JohnCranston · Post by **JohnCranston** » Jan 10th, '11, 00:34

Marshall,
Once you figure out a good option, please, let me know, I've got a Cabrera platform that doesn't have brackets, and I'm trying to figure out the best way to mount it. I was thinking of 4 triangle braces underneath that were made out of ss or aluminum. Has anyone seen any after market brackets?
The other idea that I have would be to get my glass man to glass some encapsulated wood triangle braces to the platform and the back of the boat..seems like he might be able to do it without having to re-paint the Alwgrip, but, would have to re-apply the bottom paint on the back.
. Thanks.
John.

coolair · Post by **coolair** » Jan 10th, '11, 00:44

john .. seriously???
those really nice transom fish boxes arent gonna get too many fish in them with a swim platform in the way!
by the way i tryed to rinse off your deck with the hose

PeterPalmieri · Post by **PeterPalmieri** » Jan 10th, '11, 11:33

With all the mods guys do on b31s. I am surprised know one has tackled the tailgate like has been done on the shelter island runabouts. www.chmarineyachts.com

Is this structurally possible on a b31?

CaptPatrick · Post by **CaptPatrick** » Jan 10th, '11, 12:20

That would involve a lot of real serious re-engineering of the B31 hull and transom. I'd guess about $30-50K worth... Not to mention that resell value could take a dump.

mike ohlstein · Post by **mike ohlstein** » Jan 10th, '11, 12:41

Maybe just a drop down door........

Bruce · Post by **Bruce** » Jan 10th, '11, 12:46

Marshall,
Depending on your platform weight plus the occupacy weight the platform will carry, you could use above the water line brackets. But to get the verticle height needed for the load capacity, it would put the platform quite high off the water.

One it would look funny and two make ladders needed to get on the platform.

I did do one platform on a 31 long before the 31 site was up for a fisherman who wanted one that would fold up.

I designed the transom curve to straight across adapter out of (1/4 plate)stainless 2" high. Back, top and bottom and front all welded together with 8 holes drilled thru the back for 3/8 thru bolts with stainless backing plates inside the hull.

Then the owner bought a Teak straight across platform which I mounted to my transom bracket with heavy stainless hinge.

Then on each outside was a folding stainless bracket I designed copying a Deitz plotter pivot which folded in half to bring the platform up against the transom. The brackets had a pin for locking so the platform wouldn't bounce and a catch at the top of the transom for locking the thing in place.

Worked extremely well and with the stainless polished and pasivated looked good.

Bruce · Post by **Bruce** » Jan 10th, '11, 13:02

mike ohlstein wrote:Maybe just a drop down door........

Like an old union suit trap door?

PeterPalmieri · Post by **PeterPalmieri** » Jan 10th, '11, 14:00

CaptPatrick wrote:That would involve a lot of real serious re-engineering of the B31 hull and transom. I'd guess about $30-50K worth... Not to mention that resell value could take a dump.

Maybe not economically reasonable. Still a fairly unique and interesting design.

Hueso · Post by **Hueso** » Jan 10th, '11, 14:05

Mike & Bruce:

Something like this?

Tony Meola · Post by **Tony Meola** » Jan 10th, '11, 22:29

Something about dropping the transom open makes me nervous. I would always looking over my shoulder wondering if a Greek wave is rying to sneak up on me.

Huesso, those stairs are pretty cool. I bet that cost a pretty penny. Have reinforce everything back there to make that work and hold the weight.

gplume · Post by **gplume** » Jan 12th, '11, 05:49

Marshall-

Here is apicture of the platform on my boat. it folds up. No supports below the waterline.

underwayfolded up (or at your own slip if you want to pay for 2 feet less)

Let me know if you want some other angle shots.

Rawleigh · Post by **Rawleigh** » Jan 12th, '11, 11:59

Now that is cool! It has me thinking!!

Russ Pagels · Post by **Russ Pagels** » Jan 12th, '11, 12:47

You and me both, great idea. the best of both worlds...Russ

John F. · Post by **John F.** » Jan 12th, '11, 13:44

Giff- That is great.

Marshall Mahoney · Post by **Marshall Mahoney** » Jan 12th, '11, 21:39

Thanks for the ideas!
Giff -- I was worried about the look of supporting the platform with cable/brackets from the top. I think yours looks great! I think I'm going for a similar design.

Randall -- my platform, supports and all, got ripped off the trans. by Katrina. (Still working on the boat in the driveway -- gives real meaning to "Suzie's Pissed"). The missing platform left nine, 1/2" holes where the bolts pulled thru. This would have sunk her if the back of the boat wasn't BARELY supported by some marshy ground. Hence my hesitation with with below waterline brackets... Thanks for the comment on the old platform -- there is a fine line between "custom" and "home made"

Again -- thanks guys

--Marshall

randall · Post by **randall** » Jan 12th, '11, 21:53

that platform was "custom". all the way. how many platforms do you expect to get ripped off? that said...giff's is very cool.

SteveM · Post by **SteveM** » Jan 17th, '11, 18:46

Giff, do you varnish or oil the wood dive platform. I'm restoring the teak dive platform that was on the boat. It's sanded down and ready for refinish. I'm thinking that an oil finish will allow you to not slip. A varnish finish might be more slippery. Any advice from divers, or others?

CaptPatrick · Post by **CaptPatrick** » Jan 17th, '11, 19:01

I know that some may disagree, but I would never, ever, varnish a swim platform... Oil is way to go and allows the wood to breath.

In Memory Walter K · Post by **In Memory Walter K** » Jan 17th, '11, 19:29

Varnish teak that will sit in the water is a set-up for a horrible complete strip job and redo in a fairly short period of time. Oiling is the only way to go.

randall · Post by **randall** » Jan 17th, '11, 20:22

or not....10 years in refinished once...

In Memory Walter K · Post by **In Memory Walter K** » Jan 17th, '11, 22:04

Unless Randall does it for you...

Carl · Post by **Carl** » Jan 18th, '11, 08:37

Nothing says welcome aboard like a slick swim platform...or a waxed foredeck.

Ask me how I know....

Okay...I'll tell you. A Dock Acquaintances first boat...they want to go to beach with us so they tag along in their boat. Where we anchor up is a bit of a current and they can't anchor....I tell them more scope...but they let out all the line.... and I mean all the line. So I jump in, grab the line and anchor...put it on my float..tell them to go up current and kill the motor. I swim over with anchor climb on platform which they waxed the crap out of and I proceed to slide from side to side with each passing ripple. Go in boat garb anchor and make my way up front going thru the window opening...another stupid idea...precarious place and you can't hold onto flimsy window frame...anyway soon as my foot hits the front deck I slide right down to the bow rail...again they waxed the crap out of it and being wet it's like ice...let down the anchor...set it and got off that boat ASAP.

Lesson learned...stay off bubble boats especially with bubble head crews.

gplume · Post by **gplume** » Jan 19th, '11, 21:07

Warning...on this website I could get shot for this......

Hate to admit it, but I use Cetol. 1-2 coats of the "light" per year keeps it looking nice. I agree with Captain Patrick...oil looks the best. But, Cetol is easy....and for the hours I work, I just don't have time to pamper my teak, and it does not look bad (to the non purist...get compliments all the time in my Marina---Sea Ray ville)....wears prety well also.

bertram31.com

Swim Platform Support Design

Swim Platform Support Design

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