Securing dinghy on davits - Page 3

Minnewaska · #21 09-25-2012

Chef,

My ratchets have a short piece of webbing sewn onto the rear bar. It is about a foot long and loop is sewn in the other end. This loop is used to wrap the short ratchet strap around a pushpit stanchion and the ratchet goes back through the loop, so it is essentially in a fixed spot. The straps that attach to the dinghy have a stainless hook sewn to the other end. Hoping that makes sense.

Gene T · #22 10-01-2012

Thought I would post a picture using the advise here. I had some SnapOn straps from Costco. I tied on some stainless carabiners for easier attachment. Still a work in progress but this worked great.

Gene T · #23 10-01-2012

When I was thinking about these davits I saw them on a Beneteau at Catalina Island. He had a larger RIB with a 20hp 4stroke and had been using it for 6 years, sold me. They are rated at 175 per arm but are easily removable. The owner mentioned using the topping lift to help support the load. I though it was a great idea and as I don't use the topping lift anyway why not. This shot shows it connected to the bridal, it pulls the dinghy in and shares the load.

Gene

Minnewaska · #24 10-01-2012

Way to go!

Using the topping lift, particularly while underway, is a pretty good idea. Assuming your boom isn't at risk of coming downing your head. Do you have a rigid vang?

I thought I would add that I slip an anti-chafe sleeve over the strap that wraps around the tube.

Unfortunately, if those ratchets aren't stainless steal, they will corrode quickly.

Gene T · #25 10-01-2012

I have a ridged vang and use the main halyard as a topping lift when the main is down. I'll replace the ratchets as needed. I'll also add chafe gear as needed. Thanks for the tips.

Gene

chef2sail · #26 10-01-2012

I am not sold or convinced using a toppping lift is an ideal solution. Our topping lift is in use and supports the boom. Are your saying your topping lift is useless on your boat? Not sure I would want that strain on my mast on the angle from the top, or the added force transferred up high as the weight of the dinghy was held by a point 50 ft above the deck. . If you were going to use a topping lift, why not use a secondary halyard instead.

On thing I noticed is that you dont have a cross piece beween the two arms. What keeps them from rotation and moving . What keeps the center of gravity equally between the two arms? Instead of the weight of the dinghy directly under each arm it looks like it is hung like a pendulum under the davits. That would increase the swing potential. I know on some of those huge transom boats like Benes, Hunter and Cats That may interfer with the swim platform. Thats why usually the have their davits imbedded in their hull and not the transoms.

I looked at the removable ones and that plus the lack of lower support pushed me to fixed davits. This may also help prevent " flexing" and movement. To me most of the forces should be applied lower than higher on davits and the removable ones all had the pressure poisnts up high and depended on the rear rails for support to much. The Garhauer davits we have came in two styles. either they go through the hull and are bedded on a plate on the hull. Or they are bedded on the trasome with a huge backing plate. This way the forces are spread out.

Also what are your attachment points. Do you have web starpping which comes to a stainless O ring or are using "line". It appears its line and does the line have a stretch component.

I looked at the forces not just the weight I was asking the davits to carry. As you boat pitches and swats in the wave action the forces of the dinghy/ motor will be many times more than just the weight of both and they are transferred to wherever you have attached them to you boat. It is important to spread those forces out a wide as possible and as low as possible on the boat.

The 11/4" stainless Garhauer davits we have are rated at 250 lbs per arm. Thats dead hanging weight.

Dave

Gene T · #27 10-01-2012

Dave, you have some good concerns.

The topping lift on my boat is just a spare main halyard. Never have needed it as a topping lift. In this use it just takes a little load off the backstay and is less than 3 feet off center. Negligible really.

No cross piece - No trapezoidal load either. There are braces mounted outboard and back to the rail, but I'm thinking of moving them inboard, but that will mean I will not be able to pull in the bow of the dink as far. There is no swing as they are lashed in tight to the pushpit. It is important to remember these are light duty davits. I would not use them for a long passage, I also have the option to remove the outboard and hang the dink the other way if I want. But the dink will go on deck for long passages.

Bridal is line - but stretch over such a short length is irrelevant. I have shortened them about 2 inches from what you see in the pictures. I would like to raise the engine end a bit as it was touching the water coming home with a large following sea and some 20kt winds.

I will still make some improvements but impressed with how well they worked and how solid the dinghy was. But I had things ratched in tight.

Gene

chef2sail · #28 10-01-2012

Gene I saw the braces on your rear rails. My concern was the forces seem to be in three pinpoint place ( 2 on the rear rails and one where the davit goes in the removable shoe) as opposed to being spread out low or wide with a backing plate buried behind your stern somewhere. This would even be more accentuated oif it swings even a small amount so its good you are racheting these down. So where are the pressure points of the ratchets...the rear rails again? What point takes the load?

Gene T · #29 10-01-2012

Not sure what you mean. The davits each sit in a bracket mounted lower on the transum, as low as I could go. But this design depends on tje rear rail. They are mounted outboard as far as practical and the pushpit is very strong there. When ratcheted in the weight is largely transfered to the center stantion because it pulls in on the davit arms. I plan to watch this point very carefully for any movement. If needed I can add some support brackets to beef up the pushpit.

Gene

chef2sail · #30 10-01-2012

Gene,

Good it is that secure.

The removable davits I have seen in the past slid into a "shoe" which was a plate mounted on the deck or sugar scoop transom. It looked like a suspect installation.
It has made me skeptical about the long term strength of the connection under any stress. You are confident yours are secure and the stress is spread out enough.

Let us know how this works out in the long run. I noticed you are in Long Beach area where the wind really blows and mostly off shore sailing. Great place to sail. We chartered a boa there last year and visited Catalina and Channel islands. Also got to sail on Stars and Stripes in San Diego

Dave