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-   -   DIY davit or lift? (http://www.sailnet.com/forums/gear-maintenance/56425-diy-davit-lift.html)

corny 07-22-2009 12:42 PM

DIY davit or lift?
 
I know there's some very nice davits available in the $500 to $1500 range. I could just buy one...but I enjoy the satisfaction of making things and saving some money in the process.

Has anyone ever built their own davit or lifting device (using a block and tackle sort of arrangement) to raise/lower things in and out of a dinghy? My need is fairly simple...raise and lower about 75 lbs. safely and with relative ease.

corny 07-22-2009 02:36 PM

I'm kind of cooking up something in my head using Schedule 120 PVC pipe, some nice sanded and varnished plywood gussets, possibly slipping over a lifeline stanchion with a guy wire running thru the top of the stanchion and attaching at two angling points behind the stanchion for support, having the pipe pivot on the stanchion (with lifelines removed for use) and probably a stainless plate mounted below the stanchion on the underside of the gunwhale for additional support.

The whole thing would assemble with stainless bolts, washers and wing nuts so it could easily be broken down and stowed, yet simply assembled in a few minutes.

WanderingStar 07-22-2009 10:06 PM

I'm thinking of simple straight oak peices with blocks. Mounted to the mizzen gallows with jaws or lashing at the base. Supported by a line at the top. Angled 45 degrees. One line, run through blocks on the fwd and aft thwarts of the dinghy. About 2-1 advantage (less friction). Haul away til she's at the rail. Maybe incorporate the support lines too, so it comes inboard at the end.

corny 07-23-2009 09:01 AM

Well, first attempt with PVC was a failure, but not ruling out PVC as the construction material...yet.

The problem was trying to build all of it with PVC joints, bends, etc. Since the pipe only fits into fittings 3/4", the cement and bond is not strong enough to handle the stresses. Next attempt will be with solid pieces, drilled and bolted together with stainless hardware.

Bene505 07-23-2009 10:02 AM

Quote:

Originally Posted by corny (Post 507778)
Well, first attempt with PVC was a failure, but not ruling out PVC as the construction material...yet.

The problem was trying to build all of it with PVC joints, bends, etc. Since the pipe only fits into fittings 3/4", the cement and bond is not strong enough to handle the stresses. Next attempt will be with solid pieces, drilled and bolted together with stainless hardware.

PVC snaps cracks and fails, expecially at the joints, which are not made to be load bearing at all. I build a $1000 frame for a tarp last winter. The wind destroyed it. The 2" pipes' fittings snapped. I ended up messing up my gel coat big time in one place and also over an extended area to a lesser degree. That experiment is over. Suggest you stay away from PVC as a construction material. There's a reason no one else in the world uses it for anything load bearing!

EDIT: I like the oak idea. Pine is not a very strong material.

Go with something that was made to take a load. Stainless steel pipe is used for radar posts, for instance. In retrospect, I wish I had used 2x4s. At least I'd have something that I could re-use next winter. For what you are talking about 4x4s might work. You could take them and carve them into something rounder or engraved/beautiful if you know anyone who can sculpt, and you could stain them any color you like.

corny 07-23-2009 10:49 AM

Yeah, I'm more and more thinking *not* on PVC.

We have a 28 Ranger, so it's not like we have the room for anything permanently mounted, unless it was a commercial offering in stainless. Ideally, it should come apart or fold up for easy stowage and be as light as possible (which is why I looked away from wood).

Here's a question, how much weight would the boom be able to safely handle? I could just hook the block and tackle up to the end of the boom and swing it over the side of the gunwhale. The heaviest thing we'll be raising and lowering is a deep cycle battery for an electric motor.

ctl411 07-23-2009 11:42 AM

I think Good Old Boat had a article on homemade wooden davits they looked nice.

TractorJohn 07-23-2009 01:02 PM

support boom with halyard
 
Quote:

Originally Posted by corny (Post 507799)
Yeah, I'm more and more thinking *not* on PVC.

We have a 28 Ranger, so it's not like we have the room for anything permanently mounted, unless it was a commercial offering in stainless. Ideally, it should come apart or fold up for easy stowage and be as light as possible (which is why I looked away from wood).

Here's a question, how much weight would the boom be able to safely handle? I could just hook the block and tackle up to the end of the boom and swing it over the side of the gunwhale. The heaviest thing we'll be raising and lowering is a deep cycle battery for an electric motor.

If the boom lift is connected near where you connect your load (block and tackle) you should be able to handle a lot but as you swing over the side the force directions change and your boom to mast conection is stressed. Also the lifting halyard may not like being pulled sideways, that being said we used to swing our boom over the side and hang a rope swing for swimming with no problems. I would think a battery lift is no problem either.
TJ

imagine2frolic 07-23-2009 01:41 PM

We have a guy in the marina building with 1"SS tubing, and using a conduit tubing bender. Except for some small scratches it's working out for him.......i2f

CaptainForce 07-24-2009 08:50 AM

My DIY dinghy davits are SS pipe with added shrouds from their ends to the top of the mizzen.
http://i305.photobucket.com/albums/n...e/IMG_0141.jpg
This photo shows a bording ladder laying on top of the davits so it's difficult to distinguish the davit pipes, A solar panel is fitted above. 'take care and joy, Aythya crew


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