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-   -   ?Supporting boat to work on bottom?? (http://www.sailnet.com/forums/gear-maintenance/31326-supporting-boat-work-bottom.html)

rbaroni 04-12-2007 11:13 AM

?Supporting boat to work on bottom??
 
:rolleyes: I just bought an Ericson 23 which is on a trailer. The bottom needs some work, but what are some methods of supporting the boat while working on the bottom. It would be very difficult to work with it on the trailer, espescially to paint, etc. I have a shop with horrizontal rafters that I could possibly attach to, or if I need to construct something, I can do that too. Thanks in advance for any suggestions.

TrueBlue 04-12-2007 11:35 AM

If you have the height to raise the keel off the slab and are considering hanging the boat from existing overhead structure, like garage ceiling joists, chances are the members will be insufficient for the loads.

Consider hiring a structural engineer to size two beams at points strategic to sling locations on the hull. Otherwise, purchase a set of boat stands which can be repositioned as required when doing bottom work. - Brownell Boat Stands

Problem with stands though is the convolutions required to remove the trailer.

rbaroni 04-12-2007 12:00 PM

Thanks for the suggestions. The ceiling supports in my shed are not ceiling joists, but reasonably large member trusses spaced at approximately 9 feet apart. These were engineered for 70 pound snow load per s.f. of roof, so I think they would support the boat. The stands you mentioned looked good also, I wasn't able to figure out what exactly I would need. Thanks again.

sailingdog 04-12-2007 12:04 PM

If you can use the trusses, then I would recommend you do that... but do get a couple of boat stands, as you'll probably find them useful for when you have to reposition the straps coming down from the trusses.

TrueBlue 04-12-2007 12:13 PM

Roof trusses are engineered to carry loads over the top chords. The diagonal web members are in compression and bottom chords are actually in tension - resisting lateral forces.

Your trusses could very well work and I could do a quick calc to qualify the loads for you - but not knowing the Ericson 23 weight, existing live and dead loads on the structure and assuming the truss design, is risky business at best.

Perhaps others will chime in with creative alternatives to support the boat from below.

kennya 04-12-2007 12:39 PM

If your trailer is one with adjustable pads, as I would suspect, for an Ericson 23, I believe they have a fixed keel and centerboard arrangement. You can fashion a brace and relieve one pad at a time to make your repairs. If your trailer has the full runners , purchase a couple of boat stands and do one side at a time.

christyleigh 04-12-2007 12:39 PM

I did a smaller scale but similar project on my Siren 17 at only around 800 lbs way back when. I made my own plywood boxed boat stands/cradles, used a come-along from a rafter to lift the stern, pulled the trailor out some, slid in the rear stand/cradle, let the boat rest now on the trailor AND cradle, and then did a similar thing up front. Not very elegant, a bit tricky, but not supporting the whole boat weight at any one time from the ceiling rafter of my garage may be the key in my example.

rbaroni 04-12-2007 09:43 PM

Thanks for the suggestions. I am comfortable with using the trusses for support, since I can add temporary posts at approximtely 10 foot to make that the span. Let's move on. Are two straps enough to support the boat, not concerned about the straps, but the boat? Regarding the boat stands, how do you figure out how tall to purchase? Thanks again.

sailingdog 04-12-2007 10:11 PM

Most boat stands are somewhat height adjustable. Figure out how high you'll be hanging the boat from the trusses, and then base the height on that.

sailaway21 04-12-2007 11:27 PM

I had the same issue with my boat. I got four stands, two that are more often seen supporting power boats. I was able to position those two stands under the hull aft, where the hull form is fairly flat. I then screwed the pads up to raise the stern a bit. Then I took a ten foot 3x5 timber and placed it thwartships under the bow. Inside the forward end of the trailer I used an over-sized bottle jack with a 'V' block cut out of wood. I got the bottle jack, 20 ton, for $30 at the local discount tool store. I bought it oversize just for stability purposes. I used the bottle jack to raise the bow. After I'd raised it about a foot, I placed concrete blocks on either side of the trailer, with the 3x5 resting on them. I then lowered the boat down on to the 3x5 and blocked up my jack for the next lift up. I think I ended up with the cement blocks four high on each side. I adjusted the rear jacks as I raised the boat. Once I got the bow up to the fourth block height, that was sufficient for my trailer's fenders to clear the 3x5, and I pulled the trailer out. I continued jacking until I got to the height where I could get my forward boat stands under the bows. I then raised it further with all four boat stands.
The 3x5 was handy because sometimes I needed the 3" height, and sometimes the 5" height, while jacking up the bow.

I was seconds away from getting the final paint stripped from the hull, and the new bottom paint on, when winter returned with a vengence. With my luck, someone will make an offer on my 'for-sale' house and I'll have to lower it back on to the trailer, transport it, and repeat the procedure before i get it painted.(g)

I hope you have an older barn. I could envision some fun if you have pre-fab joists.


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