Fitting Davits.

[pandos]

I am considering fitting davits.

Due to their shape and size they will be capable of exerting huge force on their mounting point.

They will be bolted through the deck. I intended to put a teak pad between the deck and base and also a teak pad underneath the deck.

Does this sound like enough?

Has anybody seen a deck damaged by a davit being pulled through?

(It is possible that they will take some support from the pushpit but this will only be established when work actually commences)

 

[Hoolie]

I've never fitted davits but I'm thinking about it. I would personally never rely on bolts through a GRP deck as sufficient. I would take the fitting through to the hull, a sound bulkhead or something robust. Having said that Plastimo and other suppliers seem to just offer a set of bolts /forums/images/graemlins/frown.gif

 

[oldsaltoz]

G'day Tony,

We have repaired a few failed davits over the years, most failures are due to a combination of:
Footprint too small.
Overloading.
Deck too weak.
Backing too small.
Not enough through bolts.

Footprint size is very important, the larger the better as this helps spread the loadings.
Overloading davits is another common failure, this is stressing an area not designed to be loaded.
Decks need to be strong, so does the backing, stainless steel or thick aluminium under the footprint and even extending down the inside of the transom.
Backing plates must be large enough and bedded to ensure the load is spread evenly.
Through deck fittings must be located to ensure the loads are properly distributed.

All this means a lot more weight on the stern of a vessel that was most likely never designed for it. Keeping the ends light improves handling and performance in all ships and particularly sailing vessels.

The lightweight alternative is the step or bracket at the transom and haul the tender pointy end up with it's stern on the step or bracket.

FWIW we fitted a targa across the stern of our cat some time ago, made of foam and fibreglass, all very light but strong. This spans the 18 feet between the inside edge of each hull and the top supports the cockpit canopy that extends right over the steps on the stern. The only weight on this is the last 4 feet of canopy and a few antennas for 3 radios and GPS plus a stern and fishing light.

We stow the tender on the foredeck for extended trips or the duck board on short runs if not towing.

Hope this helps.

Avagoodweekend......

 

[colvic]

I used steel plates beneath the deck, about 6mm thick and made to cover as large an area as possible just to spread the load. I used ordinary steel well painted after drilling etc.

After several years mooring in bays and coves we found the biggest risk with the davits was for another boat drifting on its anchor and getting its rigging caught. It seemed to apply more pressure than even the grandchildren swinging off them!!

 

[mocruising]

I have fitted two sets of Simpson (Now another company) davits, one on my last boat and old wood miller fifer and one on my present boat a HR 46. Both installations involved fixing the davit brackets onto curved surfaces. The first job was done in Plymouth and the company got it wrong. We had to retrofit a couple of ss brackets/supports as there was too much bounce in the original design. Anyway that boats sold now. On the HR 46 I purchased the davits and had them fitted in Portugal in Lagos. The ss mounting brackets they fabricated were never right from day one (Angle slightly out so davilts not parallel.). I lived with them for three years but had them remade in Greece last year and some additional stiffening in side the stern lockers as the hull was flexing and there are now some very minor gel coat cracks radiating out from the bolt holes. These will be ground out next season. I am waiting to see if they creep having installed the additional ss stiffening and support inside the stern locker. Both sets of davits are 100 kg per pair and I had an avon on the last boat but not a rib and an Avon rib lite with 8 hp at present all up weight with tank and oars is about 95 kg. Make sure you do your home work I thought I did in both cases. You can purchase everything from HR thats what I should have done 2nd time round.