swim platform

I took a look at your diary and I see what you mean. First, it's hard to tell from the pictures because there are no close ups of the platform area, but it looks like the platform brackets are not correct for the boat, that's why it's shimmed. Watch the parts board and maybe you can find the correct set of brackets there. It is mounted high, normally it is mounted between the exhaust and the speedometer pitot with the stainless steel lag bolts going into the rear of the stringers so that the transom doesn't flex if a lot of weight is on the platform-thus causing hairline cracks in the gel coat. Has there been any fiberglass repair in that area? Maybe the platform was raised up to that position to take advantage of making new holes.

I agree, the platform is too high and too narrow...all wrong. I believe you need zero degree brackets (Marine Alloy) for that vintage boat. The platform should be full width of the transom and mounted just above the water level when the boat is normally weighted. This will place the brackets close to the bottom of the transom. From first hand experience, I can tell you that it is acceptable to thru bolt the brackets. If you thru bolt, you should use 1/4" aluminum backing plates of at least 2"x2" (bigger is better). Two brackets are sufficient and even better is a support angle "L" at mid span.

I think you will find that it will be cheaper to construct the platform using IPE. It will be several pounds heavier that teak, but will last just as long, if not longer. IPE has a very attractive reddish brown color that can be maintained by oiling. If left untreated, it will weather to a drift wood grey.

I have plans I drew up for a reproduction platform. I bought my brackets from marine alloy. When they are here I will take pics of the install. The bracket measurements I used are 90 degree rise, 15 degree swing (from 90) and 14 1/2" long. I measured with a protracter from the back of my boat so I'm pretty sure that's right. I'd measure myself if I were you to be sure you're getting the right angle of swing. There is a post that shows a pic I took of my unfinished platform. I will take more of the mounting when I get my brackets.

I also took pictures of the transom while it was in the water to find the waterline, also to make sure I get the placement right

I got my brackets from Alloy yesterday. I hope to be putting the platform on this weekend. I'll take pics of the process.

MArk, That is sweet. Awesome color that ipe finished up to. is that stained or natural with oil?

Love those brackets.

nice job

It's finished with teak oil wich is pretty clear. But that is the color of ipe with an oil on it.

Marine Alloy is www.alloymarine.com

My measurements for the brackets turned out to be a 15 degree swing angle with a zero degree rise. I know that's works for a 78 not sure for others.

Thanks, I thought that if I noticed any change to the wake for the worse I would put a little weight upfront. (I only slalom) I skied off of it with the platform and the wake hasn't changed for the worse. Maybe a litte to the better but that could just be wishful thinking.

It might last forever, but if it ever comes off in the water I'll lose it. Ipe doesn't float. lol

Now I just need to get an Acme prop.

Teak and Ipe are dimensionally more stable than Mahogany, I believe. I think you will see a lot of swelling and shrinking as the mahogany gets wet and dries that could cause the joints of the platform to loosen over time. You can find Ipe at your local/regional wood deck supplier.

Yes, old wooden boats were mostly built from Mahogany, but precisely because the swelling of the wood was a desirable factor in helping to seal the joints against leaks. And given the relative rot resistance (not as good as Ipe), color, grain, weight, etc. was the best choice of wood for many boats.

It is strange mahagony gets such a bad rep considering it was a top choice for boat building. I'll check IPE availability and prices here.

Alloy. Aluminum 6061 T6 anodized