Ceiling attachment on an electric hoist to lift a trailer/boat combination.

Builder's Forum
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Hello fellow boatbuilders who might also be knowledgeable about stick construction of houses:

 

My question: how do I attach hoist and pulley support wood boards to a garage ceiling made out of I-Joists (I-Beam Joists also known as TJI construction) and covered with painted sheetrock?

 

Thank you in advance for your thoughts and suggestions! Project background info follows:

 

My garage is 20 X 24' with the rear section behind a transverse I-Beam truss and a load bearing wall. The boat will go between said I-Beam and wall. Not sure at this point whether the I-Beam is steel or actually a wood I-Beam (enclosed with sheetrock).

 

I plan on installing a hoist to lift my Chester Yawl and its aluminum Trailex SUT-250 trailer, together up to the 9’ ceiling and out of the way. The garage ceiling is also the floor of my office so I cannot install the hoist and cables directly above the garage ceiling.

 

Thus, I was planning on using 10 inch lag screws and washers through 2X4’s (hoist and pulley supports), through the sheetrock and through the joists, until I discovered they were not solid joists! It is apparently a TJI construction (OSB board sandwiched between two 2X4’s) using I-Beam Joists that are allegedly more rigid, subject to less twisting, less flex, with a higher load bearing capacity and good up to 26’ span when spaced 16” on center.

 

Initially the 10 each lags minus the 1 1/2” of the 2X4 and the thickness of the sheetrock would leave 8 inches of lag thread through solid wood. I was planing on screwing the 2X4 supports over three joists using 6 lags (2 in each joist) for load distribution.

 

BUT, with I-Joists, there would barely be “1 1/2” into solid wood and the rest might or might not even hit the thin OSB board part of the “I” in I-joist, possibly even damaging it. All of a sudden it no longer seem wise or safe to install a boat hoist that way!

 

The hoist I selected is a ARKSEN 1100 Ibs (dual line floating pulley) and 550 Ibs (single line) / 2HP electric motor with 5/32” cable. Unit weighs 37 Ibs.

 

I planned on attaching the hoist line to 4 cables running around fixed re-directing pulleys, each cable going through a fixed downward pulley to an attachment point on the trailer.

 

The aluminum trailer is only 169 Ibs and the boat 150 Ibs so call it 319 Ibs. Pulleys are rated at 420 Ibs each.

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   Paint a 9' 2x6 to match your ceiling, then lag it into the bottom chord of 5 of your tji's. Use 2- 1/2" X 4" lags per lap (10 total), and pre drill the tji's w/ 3/8" holes to prevent splitting. You can also use Timberlok or SDS screws instead. TJI's are limited to about  500# downward load to any given bottom chord- distributing your small load across several is an easy way to ensure things are never overloaded.

Next, mount your turning blocks and hoist to this plank.

3

You gotta love this forum! 20 minutes after posting a question comes an answer ... Thank you, Nemochad! 

Some of us thicker than others appreciate the sometimes obvious (in hindsight) answers. Given the spread of the attachment points and therefore pulleys, an even longer board might work best. I located a 16' section of 2X12" ... Two 1/2" X 4" lags per TJI over 12 of them ought to do the job with more than enough safety margin. That certainly gives me plenty of room for setting up my hoist/cables/blocks contraption! 

Thank you, again for the advice. If anyone else has a different idea that perhaps is even more elegant ... I am certainly open to alternatives. 

Cheers,

Eric