Fixing Whittall Davits to stern of Pearson 424 ketch

[Lewisboy366]

Dear Esteemed Pearson 424 experts,

I had this great idea a few weeks back to whip off the monitor self steering system which although makes me look like a hard going ocean sailing nut does little for me bar provide self shelter for spiders. Once it was “whipped off” I was going to replace it with some davits so the kids can go crazy with the tender (kids also being reason for never being able to use a self steer system in the big blue……….they prevent other stuff too but that’s not for this forum for fear of putting my therapist out of work)

So whipping off was quite straight forward, still have to get the fixings off but I am hopeful that will not be too hard. I have now acquired a set of 100kg Whittall davits which look the bomb fair play and quite straight forward – 6 big drill holes, bish bosh bash tighten some nuts and Bob’s your uncle…..

BUT – I am sure it cannot be that easy and so I am asking the experts-

1) will the transom area at the back of a 424 be strong enough to just have these things bolted to it and then lift and hold a tender? The davits bases are flat with 6 big bolts sticking out the bottom so I suspect the amount of force being applied to that davit footprint is pretty substantial, I am not questioning the Pearson build quality as fair play I have bounced the bow off the pontoon plenty of times with no ill effects…… to the boat anyway, but that leverage force acting on that transom is pretty fruity surely??

2) will it be simply a case of drilling through, fitting some tidy washers and then doing up the nuts and happy days?

3) will I need to make up some sort of supporting back plate arrangement, encase the rear in armour plating and embark on other such crazy engineering madness?

I have attached pictures of the davits and the target area to this post…. along with my hopes and dreams of success and keeping the Lew-nies entertained for at least ten minutes.

I hope someone can help shed some guidance and advice for this mission, ideally the kind of advice that goes something like “yeah, no worries, just stick em on and they will be just fine and dandy” – if not that, I had better brace myself for something more substantial and hard work. I am hoping it so over engineered and its such a key structural area of the boat that I should be ok, even if a few contingencies are required….. ideally I would like to avoid peeling the stern off!

Many thanks for any guidance or reassurance you can provide in advance

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[RichCarter]

I installed Edson davits on my 424 when I first bought her 30 years ago. The davits bolted to the aft combing deck. From the photos, what you have appears similar. The deck area around the combing is quite strong, being cored with an inch or more of marine plywood. The lever arm presented by the davits is enormous however. While the davits could support 250lbs each, there is no way that the deck would support that kind of load. My dinghy weighed about 400 lbs empty, with about 250lbs on the end with the motor. The motor was a 30hp 2-stroke weighing about 135lbs. Though this was within the rated load for the davits, this proved unworkable. My dinghy was a 12’ 4” inflatable, so even if I took the motor off, really impractical, the thing only worked under motor. Any angle of heel would drag the bow or stern of the dinghy in the water. The arrangement would probably support a short dinghy with no motor.

I came up with a method of towing that worked. I pulled the lid off the motor and used a bridle to lift the engine and stern of the dinghy, leaving the bow dragging in the water. This reduced the load on the davits and distributed the load evenly between them. There was no longer an issue with the width of the dinghy either. The load on each davit was now about 75lbs. Though this worked, it still had issues because of shock loads transferred to the davits when running into a chop. I replaced the davits with custom made welded stainless. These have two legs on each davit to spread the load. They aren’t the prettiest things but they are functional and provide a great place for solar panels.

http://www.richardcarter.net/boat/davitSwimPlatform/

I’ve since replaced the dinghy and now have a 4-stroke motor. These new engines are much heavier than their predecessors, weighing in at almost 200 lbs. I still tow the thing by lifting only the motor end and leaving the bow in the water. I’d never take a chance transporting it this way in a severe chop such as Buzzard’s bay, but this works for me.

Rich

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[Lewisboy366]

Dear Rich,

Many thanks for your insight and experience on this matter… also for the super quick response fair play!

My tender is pretty tiny (2.6m) with just a 3.5hp engine so I am hopeful the weight will be far less than a 30hp beast (though you have me thinking now….mmmmm… more power!!)

Just hearing about your experience and confidence in the strength of the deck area of the combing is reassuring but as you say that “lever” effect is substantial…… so maybe my wishes are not answered just yet and simply bolting them on will not be sufficient and more reinforcement will be required.

Thanks, I await any further advice or experience

[rdugger]

I have Kato Island Model Davits. Our dinghy is a 10′ RIB and we keep a 8hp 2 stroke on it. Our davits are attached to the coming area and then supported to the back rail and with supports bolted to the rear deck. See attached photo of davits without dinghy. Agree that the davits present significant lever forces.
Suggest you reinforce and use substantial backing plates.
Rick
Eclipse #73

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[Author]

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