Swim platform project

[ohmthis]

Hey all,
Some of you may remember me wanting to build a swim platform on my boat. Well the time has come to do some serious research on materials and tools needed to do this. First off, I am going to build this out of stainless steel. It will have a round pipe outer ring and square or rectangle tube floor. I am going to tig weld this. Now comes the questions. What type (alloy) SS should I use? Then which filler rod should be used with which type (alloy). I will not ever have this boat in saltwater and I'm still wanting to powder coat it to match my boat. Thanks guys and gals!

[partagas]

" I will not ever have this boat in saltwater and I'm still wanting to powder coat it to match my boat."

If this is true, why would you need to spend the extra money on SS. When you powder coat it, it should be waterproof. So need to worry about rust.

Just my two cents.

[fredo]

ohmthis,

316 is the marine grade SS. like partagas said if your going to powder coat why not us aluminium? it will be lighter.

what size platform are you building?


Fredo

[Zrexxer]

IMO powder coating any easily oxidizable surface like aluminum or mild steel in a marine environment is a mistake. Don't let them talk you out of stainless.

Despite the fact that it's applied and cured differently, powder coating is paint, pure and simple, and is not inherently any more or less "waterproof" than a catalyzed urethane or any other conventionally applied paint system. If you have one point of ingress for moisture, the substrate will start rusting or oxidizing and the next thing you know your powder coat will be coming off in sheets.

Build it out of stainless as suggested, and if you want to powder coat it for color match then that's fine. Also be aware that many powders are not designed for UV exposure, and you will need to make sure your coater uses one with UV inhibitors so it doesn't fade or chalk rapidly being out in the sun.

[Raven]

I'll throw my two cents in for stainless or aluminum in this application. These two materials will hold up well in a marine environment. Both are regularly used for swim platforms, towers, railings, t-tops, etc. that I regularly see here along the gulf coast. Most are anodized aluminum or bright polished stainless tube. However, there is a fairly extensive use of powder coated aluminum railings and outboard brackets I have seen that seem to hold up fine. As a matter of fact, I have a custom made aluminum boat with regular old everyday paint on it that I use exclusively in salt water and have not experienced any significant corrosion. Just be careful of bolting stainless to aluminum or vise versa. Dissimilar metals can cause galvanic corrosion to occur at the point the two metals meet. I like to use plastic washers as well as some special paste that I have forgotten the name of in order to separate the different metals whenever possible. Although this may not be as big of a problem in freshwater as it is in saltwater.

The problem with using mild steel tubing with a paint or powder coat finish is that unless the tubing is completely sealed, which is unlikely, you will get corrosion from the inside out wether you use the boat in salt or fresh water.

[Sundown]

I built a transum for my Porta-Bote using MS three years ago, just primed and painted with black auto spray from Pep Boys. Hav't had any problems yet, but if I needed to do another one I would use aluminum for the weight savings, or SS is I wasn't worried about the weight.

[drizler]

Having busted my rails up over the years I discovered a grand source for the stuff. Ask the boat yard if you can check out their scrap. Most of those big bow bow are 1 piece and 25 or so feet long you know and all one long piece. They are also quite heavy, especially the ones off bigger boats. Its good solid stuff and a bargain if you are able to find stuff thats not corroded. Don't mistake the thin stuff they use for top bows and the like. You will know this stuff when you feel it, it has to be about 1/16" thick and quite heavy.

[ohmthis]

Fredo,
It will be about 7 feet long and 2.5 feet wide. Al. is not totally out of the question. I'm going to do some research on cost first. I wrote before that I haven't welded but about 4 weld bead 4" long on Al. It looked ok, but am afraid cracking. The powder coat is to color match to the boat. Polished would look super cool, but I think that it would blind people.



Zrexxer,
thanks about the info on the UV coatings.

at filler should be used with the SS stated?

[precisionworks]

Aluminum is durable in the correct size/gauge. It's not difficult to weld, but you'll want quite a few hours practice on scrap & test parts before starting this project.

Stainless is the material of choice for most boat manufacturers - they know they are unlikely to have problems or warranty issues. As Fredo said, 316 (in particular 316L) is the type most often used - it is the least suceptible to carbide cracking in the weldment:

http://www.azom.com/details.asp?ArticleID=2382

http://www.suppliersonline.com/resea...etals/1874.asp

A brushed finish is often applied to marine stainless parts. This is easy to do - any number of processes will work. On a larger part like your platform, bead blasting is quick & not expensive. Maroon ScotchBrite pads also produce a pleasing finish when hand rubbed.

Just make sure your filler is the same as the parent material for best strength & corrosion properties.

[ohmthis]

Precisionworks,
Thanks, for the links. I am getting ready to start the project as soon as the boating season has ended. Here in the bluegrass state it's coming quickly. I'll start by taking measurements and making a drawing. Then when I get the design right I'll have something to order my materials. Thanks again all!