swim platform rebuild

[boatman37]

So very early in the process here (just thinking out loud now) but my swim platform needs a rebuild. It is a bolt on with a soft spot just behind the transom door. There are 2 vents and the soft spot is right near the one so my guess is it wasn't sealed very well. Had the boat surveyed last year when we bought it and that was the only spot that we found to need attention so I figured no big deal.

No pics right now as the boat is still in the water but the platform is about 8' wide by about 20" deep with a built in fold out ladder that has a hinged door over it. The boat is a 2006 Crownline 250CR if you would like to search for images. I will be pulling the boat in about 2-3 weeks and plan to remove the platform and leave it in my garage all winter so I can do the work.

Plan in to cut the bottom out and remove all rotten wood (soft spot is about 18" round). Planning to remove all wood and replace as 1 piece unless you guys think it's ok to only replace 1/2? How about using Coosa board instead? I plan to reinstall the vents and don't want this to happen again. There are 2 other boats at our marina identical to ours and theirs are fine so don't think it was a design issue as much as it was an anomaly or something.

So when I cut the bottom out should I plan to save it to replace it or just rebuild a new bottom from scratch? Not so much worried about aesthetics but want it to look as good as I can due to my OCD...lol.

Next question...there are tiny cracks on the top side around the soft spot likely from it flexing with no support. Should those be ground down from the topside and filled and smoothed? Or can I patch them from underneath (inside) and leave the topside alone? There is brown 'goop' oozing out of the cracks from what I assume is wet wood mash?

I'll get pics and will post a thread on the rebuild and will be asking tons of questions.

 

[boatman37]

No responses yet? Geeeesh. Well here area a few pics I took today to give you an idea of what I am talking about.

You can see the brown ring. There is a hairline crack where these stains are. I'm guessing it is the rotted sopping wood oozing out? There are a couple of spots near the ladder too but they are small and no soft spots there but obviously it must be wet.

 

[AShipShow]

Should be a pretty simple job... keep us posted on your progress... worst part is gonna be the itching... other than that it's basically a transom replacement but on a workbench...

Looking forward to watching.

 

[kcassells]

Yea it'll be a blast. :joyous:
Once you are able to remove it..... Like you said work on the bottom side to expose all the mush. Looking forward to demo pics.
I think the biggest issue you will have is that there will be a bunch of compartments that need expose and rebuild.

 

[boatman37]

Yeah. Hoping it won't be tht bad. Just hoping it looks good when I'm done. I think the hardest part will be patching/sealing the cracks in the topside. They are hairline so I think if I get it all solid and seal it from the bottom side the top may take care of itself? Or will I still need to fare out the cracks and fill them?

 

[kcassells]

We'll see what it looks like when you get there.

 

[boatman37]

Got it off today. Wasn't as heavy as I thought. Maybe 100-150lbs. Came off pretty easy. Go a few pics but havedn't really looked at it much but you can see where the vents are the wood is soaked.

 

[Grub54891]

I think you will have to fix the cracks on the topside also. With the brown oozing out, water will get in there again.

 

[emoney]

I dunno that’s gotta be a sandwich. I bet when you get the bottom skin off and replace the structure, you’ll be able to using faring on the top and do gel coat touch up. At least that’s my hope. Good luck and keep us posted

 

[boatman37]

Yeah. I'll get better pics another day. I was pretty beat by the time I took these. And as you can see I need to clean my garage up. Step-son has a 15' tri-hull he did an engine swap on and used that garage for everything then when I got the boat home I threw everything out so have some cleaning and organizing to do.
And I'm sure I'll find more once I get into it. For now the plan is to cut the bottom and get all the old wood out then patch the upper side cracks from the underneath inside then re-core and re-glass the bottom. Then probably grind out the cracks son the topside and fill with gelcoat. Hopefully it matches good. I can put Sea Deck over the topside but these cracks are on edges and seams that probably wouldn't be covered.

Gonna look into Coosa board too

 

[boatman37]

Took the boat to storage tonight so now have to get through sons wedding next week then finish cleaning garage then start on platform. Gonna get better pics then draw out where I think I should be cutting and post those pics here for expert advice to see if my thinking is right.Figuring on cutting about 1/4" from the 'angle' the whole way around.

Would it be best to re-glass the whole bottom or try to get the bottom out in 1 piece then glass that piece back in? I ask cause if I am making a new bottom then I will make a few cuts across the bottom to make it easier to remove,

 

[kcassells]

I would try to separate it first off then see where you have to go as you make the attempt.

 

[Scott Danforth]

looks like core material. cut the inner skins out, then look. may be Balsa. probably 1/2" thick core

 

[boatman37]

Contacted Swimplatforms.com and asked about a new one. They do have the template and have made these before. They sent pics and they look identical to my factory one other than their sticker on it. So I would have to send them my ladder and they do everything else. Price was about $1770 for the platform plus about $350 shipped to my zip code. Not bad but I'm thinking I can repair mine for about $400? That extra $1700 saved would pay for my windlass in the spring...lol. But at least I know their is another option if I really screw it up.

 

[boatman37]

So hope to get started on this rebuild in the next couple of weeks. Plan is to cut the bottom out then chip out the old core. Wife works at a vo-tech school and the auto body teacher said they could do it and I just buy the materials and supplies. I haven't talked to him yet but from what my wife said he told her it sounds like he has an idea of what he is doing. He mentioned to her about waterproofing the new wood. I'm just concerned that he won't be as meticulous as I would with it.

Next question...port side is sturdy but I haven't gone over it thoroughly yet. Is it a bad idea to only replace the bad 1/2? The good 1/2 is where the recessed ladder is and I'm a little worried about trying to cut around that. If I did that I would likely cut it as close to the center as possible then butt the new piece to the existing one then lay another piece over the center that would overlap both by roughly 8" on each side (a 16" wide piece). You can see in the pics where the reinforcing ribs are. I would lay that piece to fit right between those 2 ribs. I'm sure this isn't as good as doing the whole thing in 1 piece with all new wood but really don't want to screw up that recess for the ladder. Aside from that recess it doesn't look too bad of a job. If I let the school do it I would probably try to take a day off work to go up when they coat the wood to waterproof it.

Not too worried about the cracks in the topside. I will grind those out with a Dremel and fill with Spectrum Gelcoat and smooth.

Thoughts?

Shopping list? What would I need and how much? If I go with Coosa Board I found a 4'x8'x1/2" for about $325 plus shipping. Wouldn't have to worry about waterproofing then.

Swim platform is about 8' wide at the widest and the center not including the wraparound ends is about 24" or so deep.

.

 

[boatman37]

Stopped at the local marine shop this morning and they gave me a ballpark of about $1500 to re-core it. He agreed with my 'guess' of about $500 to do it myself. He said he would try to just replace 1/2 like I mentioned earlier providing he finds good solid wood. My problem there is a brand new one is only $2300 shipped to my door so $1500 isn't reasonable for me. Not to mention if he gets in there and finds more bad wood and has to re-core the whole thing now we are probably closer to $3000. Doesn't make sense to me. He added his concern with a new one is the color not quite matching.

 

[boatman37]

So drilled some test holes yesterday. One hole was good clean wood. A few had nothing but air between the fiberglass layers..lol. A few had wood but it was dark and mushy and it was spread out in various spots the whole way across so only re-coring 1/2 of it isn't an option. My biggest concern with doing a re-core is cutting and working around the swim platform recess.

Oh, and tried drilling a hole right next to the support standoff under the platform and it's aluminum? Apparently there is an aluminum plate or block encased in the fiberglass for the support to bolt into.

 

[Scott Danforth]

unless you start cutting, you wont know

Aluminum backer plates are common. my boat has them in the swim step for the ladder and each gunwale for cleats, etc.