Davit system for Tomcat

B

Beflyguy

New member
Been thinking about a davit system for the top of a Tomcat. I want to be able to easily put a hard shell like a Water Tender 9.4 upside down on the top. I may start with a Yakima rack or build from scratch with 1" stainless. The davit will essentially hold a rope or small cable out from the top and side, the dinghy will be lifted out of the water and up until it contacts the davit arm, then the Dinghy will flip onto the top of the cat. I think if I install the lifting points correctly in the dinghy, it will be possible to tilt it and wash the inside of sand etc, before flipping it onto the roof.

Davit_system4.jpg


Davit_system3.jpg

Specs on the Water Tender 9.4 are:

112"X55"X15.5" 115lbs Capacity 480lbs Max 5hp $549 at WM

2_G.jpg
 
I thought of a similar setup for the 25, but don't have access to any fabricators I trust, nor do I have my own facilities. I assume that the boom standing Horizontal in the first sketch will follow the dinghy up until it contacts the vertical mast. The dinghy will be "on it's gunwales" then it will lay upside down on the cabin top...
 
toyman":2zdrgl7g said:
I thought of a similar setup for the 25, but don't have access to any fabricators I trust, nor do I have my own facilities. I assume that the boom standing Horizontal in the first sketch will follow the dinghy up until it contacts the vertical mast. The dinghy will be "on it's gunwales" then it will lay upside down on the cabin top...
Click to expand...

Exactly. The whole thing could be supported by the existing rails although the idea of supports and crossbars from a cartop rack would allow for more carrying capacity as well as options for carrying kayaks and other items.
I think it could be built almost entirely with cartop tubes and some parts from Mcmaster Carr.

Would love to put one of these up there.

 
Could it be done--yes. Is it going to be practicle? Not so sure of that. Generally this type of lift with a hard dinghy uses two lifting points. What you show seems to use a gin pole type of device to transfer the load on the horizontal arm as you lift the dinghy. Lifting 115 lb dinghies is a bit more difficult than you may think. A winch system will probably work best. Block and tackle are do-able, but get complex. You also have to stabalize the gin pole, and then pull it down to flat over the cabin top (actually it will have to be a bit above the cabin top crown) You have to hoist the boat to the horizontal arm, then tip that arm up, slide the whole rig over and tip the boat back up side down. The process is reversed to launch the boat. As you have found out; the side decks are narrow and not easy to balance on. The other question is are the hand rails you are using as a basis, adequately supported for the weight of the dinghy. The side parts of the tops (at least on my boat) is not cored--the center part is. It is possible that you may end up increasing the bearing surface of the SS railing on the cabin top.

I would work out all of the details with models first. I have carried hard dinghies and RIB's on larger boats. They are not easy to hoist aboard, unless you have a crane davit, or mupltiple davit system.--even with just over 100 lbs.


On another but related subject: You were going to go with a 1 1/2" greater pitch prop--based on a very lightly loaded boat. It appears as if you are going to be substantially increasing the loaded weight of the boat.
 
Beflyguy,

Les at EQ Marine makes a nice davit. Doryman and SeaPal have them installed. No need to reinvent the wheel/davit.
LoriAnn_davit.jpg

 
Roger - that davit won't tip the boat over which is what he's trying to accomplish. However, that davit plus a more typical inflatable might be a better solution. My guess is that he wants the hard shell dinghy for it's longevity and the hard shell is what is driving him to want to turn it over. An alternative is to have a cover for the dinghy and leave it upright. That would require some racks on the roof to keep the dinghy from rocking but would be the simpler solution.
 
Not having an album nor knowing how to put pictures in post, ve put 2 in the Library of a diavit on our 25 ft. (cockpit & accessories then detail pictures, then back page.) Theres no reason this would not work on tom cat too. Ve like the cleaness of it and use it to load dingy(sometimes, not that old yet) and to pull shrimps pot.
Martin
 
For those that had trouble finding Martin's pictures, here they are:

Davit_in_dingy_lift_position.jpg


Davit_stored.jpg


Very nice Martin! I am sure that folks will want to know brand, etc, etc.!

Charlie
 
They looked fine when I previewed them. Will try again.

Warren, can't help you. Someone took them out of the album. When I went back to get the properties again, they were gone.

Sorry

Charlie
 
Sorry for the confusion people. When I saw Charlie put them on the post I deleted them from the other location to elimenate redundancy. I will replace them.

And they are back now, sorry again. :roll: As penance for my problem, I put one showing the hauler too. (in the library)
Martin
 
Martin's set up is what is done in most crane davits on trawlers and sport fishers etc. It is a good engineering solution to the problem. The cabin aft bulkhead takes the lateral load and the cabin side takes the fore and aft loads. Downward load is transimtted to the floor. It is a clean and elegant solution to a problem--now with a winch on the davit arm, it would lift a dinghy easily.

But there is also the effect of an extra 100 to 130 lbs on the top of the boat. Does it make a difference? Yes, especially in beam seas at slower speeds.
 
Total weight of this davit including the cylinder full of oil that the thrust bearing runs in is under 60 lbs! And with a small (3/4) block set up DOES lift the dingy easily.
Martin
 
Martin, it was not just the 60 lbs of the davit system, but the 100 to 120 lbs of dinghy and racks etc. (some up to 150 lbs) which is being added to the top of the C Dory which may be of concern. Is it unsafe--most likely not. But as you add more and more weight, it will affect handling.
 
Brent,
I find that putting the davit on the port side, all of the way aft in the cockpit (just enough to clear the lazarette door, and then the brace on the railing. This allows me to pick up outboards, the generator and even an inflatable (rolled up) and put them on the swim step or an outboard onto a dinghy.

The second position is on the aft side of the cabin house--outboard of the head--with a removable foot and support bolted through the lip of the cabin house.

I thought about putting another position in the cockpit by the starboard boarding area, but the position which lifts items to the top of the boat, will put items from the dock to the cockpit.

The reason I have the Garhauer davit is because of a bad back. I am not putting any more than about 60 lbs of dinghy on the cabin roof. I can slide it up there if there are two of use. If just one person, the davit works for me to work as the second person and lift a majority of the weight of the boat.
 
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