Which Davits should be the Direct Replacement of my old Whittal Davits

[miyagimoon]

We were involved in an incident which seriously damaged one of our Whittal Davits. As most will know Whittal Davits no longer exist and in general the only ones around are made by Cooney Marine under the name of Simpson Davits. We now have to replace both davits which is not a real problem. But unfortunately the insurers surveyor and I are in dispute as to which is the correct Simpson Davit.

Simpsons traditional davits are rated by pairs. In that the SWL is per pair. i.e. The D100 Davits are rated as 100kg per pair, the D150 Davits are rated as 150kg per pair etc all the way to the D250. Their sales brochure states "Traditional Davits have been designed to lift or lower weights up to 250kg".

Now Whittal Davits are rated as maximum load per davit. My davits have a lovely label on them which states "Maximum load this davit - 100kg".

My limited knowledge of mechanical forces etc etc. makes me believe that my pair of davits can lift or lower weights up to 200kg as long as the load on one davit does not exceed 100kg. Therefore the direct Simpson replacement would be the D200's which are rated at 200kg per pair.

Now I understand that when underway sea conditions can mean that one davit can take more load than the other. But I do not believe (unless one davit totally fails) that all the load will be imposed on one davit.

When I initially contacted Cooney Marine via their UK distributor they stated that the direct replacement would be their D200's. Now after the surveyor has contacted them they have changed their mind and appear to have sided with the surveyor.

Am I right or can anyone with sufficient mechanical knowledge advise where I am going wrong.

I do not want any upgrade in davits I just want the replacements to be the same capability as the old ones. What I certainly do not want are davits that are smaller and weaker than the originals.

 

[PCUK]

All davits are rated per pair. The rating for the pair is the maximum load on one davit as each davit of the pair must be able to take that weight on it's own. If you have a heavy outboard fitted on the back of the tender then it is quite possible that the total weight will be on the davit nearest the engine due to the balancing forces involved. So there is no difference if they are rated as per pair or each davit.

 

[Robin]

Ours, made in USA are rated at 600lbs/pair but the maker's stated advice says up to 70% of the total load could be taken on just one davit in practice, no problems for us as our RIB is around 100lbs and 9.9hp motor with tank full about the same or a tad more. However the other factor is the human effort needed to raise the load. We ( on a sailing boat) have 6:1 rope tackles led through davit mounted jammers but if needs be the heavy engine end lift line can be taken, via an extra lead block I purposely fitted, to a cockpit Lewmar 44 self tailing sheet winch which makes for very light work of the load.

 

[miyagimoon]

Ours, made in USA are rated at 600lbs/pair but the maker's stated advice says up to 70% of the total load could be taken on just one davit in practice, no problems for us as our RIB is around 100lbs and 9.9hp motor with tank full about the same or a tad more. However the other factor is the human effort needed to raise the load. We ( on a sailing boat) have 6:1 rope tackles led through davit mounted jammers but if needs be the heavy engine end lift line can be taken, via an extra lead block I purposely fitted, to a cockpit Lewmar 44 self tailing sheet winch which makes for very light work of the load.

As stated our original Whittals are rated at 100kg each. They have been on the boat since new. We have a tender, outboard, fuel tank and bits and pieces (anchor etc) which total to 123kg. It is steel wire rope driven from geared manual winches. No real effort required to lift and lower. Based on your makers statement only some 86kg could be taken by one davit which is well within the single davit rating. Despite PCUK advise and the fact that Cooney will not state the max load of one davit, (all they will say is that theirs is rated at XXkg per pair) I am doubtful if the Cooney ones are truly rated for 100kg load on one davit.

 

[Robin]

As stated our original Whittals are rated at 100kg each. They have been on the boat since new. We have a tender, outboard, fuel tank and bits and pieces (anchor etc) which total to 123kg. It is steel wire rope driven from geared manual winches. No real effort required to lift and lower. Based on your makers statement only some 86kg could be taken by one davit which is well within the single davit rating. Despite PCUK advise and the fact that Cooney will not state the max load of one davit, (all they will say is that theirs is rated at XXkg per pair) I am doubtful if the Cooney ones are truly rated for 100kg load on one davit.

These are ours. I see their website has been changed since we bought 3 years ago, but I guess the info is still all there pics are Martek's, not ours BTW

http://www.martekdavits.com/index.php?main_page=product_info&products_id=3

 

[Boo2]

All davits are rated per pair. The rating for the pair is the maximum load on one davit as each davit of the pair must be able to take that weight on it's own. If you have a heavy outboard fitted on the back of the tender then it is quite possible that the total weight will be on the davit nearest the engine due to the balancing forces involved. So there is no difference if they are rated as per pair or each davit.

Don't think this is true : I looked at some Plastimo davits a while ago and they specifically stated that the davits were 160kg the pair or 80kg each. The davits were described as 160 so I concur with the OP's first suggestion that you need to halve the rating to get the per davit figure. But of course different makers may specify it differently...

Boo2

 

[Robin]

Don't think this is true : I looked at some Plastimo davits a while ago and they specifically stated that the davits were 160kg the pair or 80kg each. The davits were described as 160 so I concur with the OP's first suggestion that you need to halve the rating to get the per davit figure. But of course different makers may specify it differently...

Boo2

Ours are Martek and rated at 600lbs the pair or 300lbs each with a caveat that 75% could fall on the heavy end of the pair.

These are similar to ours but from Kato marine, USA and also rated 600lbs/pr or300lb each

http://www.katomarine.com/saildavits-island.htm

In our case BTW we also have additional support struts from the swim platform and a cross brace between the arms, all to help best distribute the loads.

 

[miyagimoon]

The key thing to me is that the originals spell it out quite clearly "Maximum Load this davit 100kg". Whereas the Simpson Davits state "designed to lift or lower xxkg per pair" this does not give the max SWL of each davit.