4087, how much weight on the transom..-gctid360974

[Guest]

Hi all, I am looking at a 4087 to purchase and was wondering how heavy of a dinghy I can mount on the stern? Specifically, {with the correct davit} I want to lift a 13 Boston Whaler that is around 900 lbs. The 4087 I am considering does not have a gen set so there is 400 lbs less in the lazerette to start with. Any suggestions?

Thanks, Gary

[mmichellich]

900 pounds should be doable, BUT be careful, be careful, be very careful who does it and make sure they know what they are doing. I know of two motoryachts that have sunk in last few years due to improper davit installation on the transom-and both were with lighter inflatables not all fiberglass runabouts and both were installed by professionals making or selling the davits. With that amount of weight, the weight and load needs to be shifted from transom to stringers and other major support in the bilge. One of these accidents even tore holes in the hull of the boat. Overkill is the word here. Don't let anyone just tie the davit to the transom even if beefed up somehow on inside or next time you are in rough water and really stressing things, your transom could be ripped apart and very large holes created, letting a lot of sea water into the boat, then you have the added issue of maybe not being able to get the dingy free of the busted arrangement when boat starts sinking, resulting in a swim. The loads need to be spread over a wide area of stringers not just bolted to them in one spot, leaving little load on the transom. Be prepared for transom gel coat cracking or worse no matter how you do the installation. The weight should not be too bad since you do not have a gen set. from a stability issue. I personally do not like davits that are in the way of folks walking across my swim step. A for fun exercise is to look at the loads created in rough water for 900 pounds plus weight of davit hanging on a lever arm of several feet, with a few Gs of vertical and horizontal acceleration due to rough water.

[Machog]

Excellent advise from MM.

I have a Walker Bay with 18hp Tohatsu & central steering on a Ross Kelly davit, only 450 lbs total on my 4087. It can really bang about in rough weather so I use sturdy tie downs to stop the motion, in addition to the harness. Even with only 450, I have very heavy duty supports, large backing plates and big hardware. Talk to your davit manufacturer and take his advise.

One added bonus the 4087 is a bit bow heavy, 900 lbs should help that.

Send some pics of your installation.

Machog

[Guest]

Thanks for the advice! I would probably go with the Rosskelly type of swing arm davit, at least the load is in shear. They make a version rated for 1000 lbs, I wonder if this includes the g-loads from boat movement? { i know, call them..} Do you tie the Walker bay to the boat with standoffs?

On another note, is the transom of the 4087 cored with ply or foam?

Thanks, Gary

[Guest]

+1 on the excellent advice from MM. I have weaver davits on our inflatable, so weight hasn't been a factor.

[Uncle_Bob]

Cored with ply? My 39 has wood coring around the swim ladder but not throughout the grid.

[mmichellich]

islandmech wrote:
Thanks for the advice! I would probably go with the Rosskelly type of swing arm davit, at least the load is in shear. They make a version rated for 1000 lbs, I wonder if this includes the g-loads from boat movement? { i know, call them..} Do you tie the Walker bay to the boat with standoffs?

On another note, is the transom of the 4087 cored with ply or foam?

Thanks, Gary

I hope you are not looking at the RS-1 model. I believe that is the kind of davit that ripped up the two boats I mentioned. It is sure not a shear load when in rough water.

[Machog]

IM, no stand offs, dinghy squashes into the stanchions (obviously with a Whaler you couldn't do that). But say again it really needs tie downs, or the be very secure in the weather to stop it banging about and putting a strain on the davit.

If you already have dinghy, you don't have a choice other than towing.

But if you haven't bought it yet I would seriously look at a lighter option-Bullfrog, don't know much about them, but told they are very tough. My Walker Bay has been excellent, seems to take a lot of punishment.

Machog