Jet Ski on Corniche 31

N

neiloakley

Member
Joined
27 Jun 2011
Messages
37
Visit site
Hi

Been looking around a while. Does anyone know if its technically possible to carry a jet ski on the back of a Corniche 31? Twin 200hp on shafts so weight is more central that the sterndrive versions. The boat already has davits installed for a small dinghy but obviously dont think they would take the weight of a 200kgs jet ski without some work - if atall!

Any thoughts, pictures, links all greatly received.

If it turns out not to be possible (or atleast without spending tens of thousands of pounds) then I will just have to enjoy the boat and ski seperately.

Cheers

Neil
 
No wouldn't expect it to hang on the davits but obviously need them to lift the thing out of the water. Just checked, the book says it weighs 948lb :eek:

It seems a lot of weight for the bathing platform to take as a static load and would obviously increase once the boat is pitching and rolling.

So if anyone knows if a) the mounts for the davits will take the strain and b) the bathing platform could take 948lb static load (more dynamic).

I'm prepared to do some upgrades and strengthening if it needs it.
 
Need to know what the rating on the davitts is, but I wouldn't be happy carrying a jet ski of over 400 kilos on the bathing platform of a 31ft boat (is that the length?). The sheer weight of that ski if added to a full fuel tank and passengers might well take you over the safety limit of the boat, it sure will have an effect on trim
 
neiloakley said:
No wouldn't expect it to hang on the davits but obviously need them to lift the thing out of the water. Just checked, the book says it weighs 948lb :eek:

It seems a lot of weight for the bathing platform to take as a static load and would obviously increase once the boat is pitching and rolling.

So if anyone knows if a) the mounts for the davits will take the strain and b) the bathing platform could take 948lb static load (more dynamic).

I'm prepared to do some upgrades and strengthening if it needs it.
Click to expand...

Wow. That's 430 kilos. I wouldn't be happy with that much weight on the swim platform. It's the equivalent of having approx. 5 average sized people standing on the platform as you're tackling the waves.
 
5 average sized people standing on the platform as you're tackling the waves.
Click to expand...

:rolleyes:

if that beyond my expectation !

g.php
 
You may be able to carry a Yamaha Superjet or a Seadoo 3D.

Proper chocks on the platform would be the only way, no way on the davits. Possibly use the davits to help lift it on.

If you go out with a full crew on board just leave the ski behind.
 
Going slightly off topic but we have found the bic kayaks to be as much fun as the Jetski we carried. Plenty of sizes to fit most places on a boat. Strapped to the bow or bathing platform. Even carried one as a tender on my rib this year.
 
I suspect that's just too heavy. You'd need 600kg davit pairs (ie 1200kg) total and motorised for that weight. I've never seen such large Davits on a 30-40ft boat, and anchoring them would require major reinforcement across the entire transom/stern area with blocks, steel and extra grp. Other factor to think of is how it will all fair out in rough weather, strain on platform, restraining straps if boat pounds and slams in heavy seas.
 
oceanfroggie said:
. I've never seen such large Davits on a 30-40ft boat, and anchoring them would require major reinforcement across the entire transom/stern area with blocks, steel and extra grp.
Click to expand...

Thats the major issue. Even if you could find a set of davits or a crane with 600kg lifting capacity, the transom is unlikely to be suitable to mount them and the amount of reinforcement needed to strengthen the transom would be extensive. IMHO its a non starter unless the OP wants to spend £'000's modifying the transom and/or bathing platform.
Then it's likely that having 0.5t on the back of the boat will seriously affect it's trim so the OP might have to spend even more money on bigger tabs plus save a bit more money for the increased fuel consumption
 
neiloakley said:
Hi

Been looking around a while. Does anyone know if its technically possible to carry a jet ski on the back of a Corniche 31? Twin 200hp on shafts so weight is more central that the sterndrive versions. The boat already has davits installed for a small dinghy but obviously dont think they would take the weight of a 200kgs jet ski without some work - if atall!

Any thoughts, pictures, links all greatly received.

If it turns out not to be possible (or atleast without spending tens of thousands of pounds) then I will just have to enjoy the boat and ski seperately.

Cheers

Neil
Click to expand...

I remember seeing a similar set up many years ago davits and a 2 seater Seadoo it had chocks, and extra supports under the platform.did look a bit stern down
 
Ive owned 2 corniches both with shaft drive 200hp, id say the boats already stern down when the water tanks full, also I doubt very much the platform would take that kind of weight without some more fabrication to attach it to the transom, from memory its just a moulding and single skin at that say 6mm thick, so I doubt it would hold that kind of load without ripping it out the transom.
 
volvopaul said:
Ive owned 2 corniches both with shaft drive 200hp, id say the boats already stern down when the water tanks full, also I doubt very much the platform would take that kind of weight without some more fabrication to attach it to the transom, from memory its just a moulding and single skin at that say 6mm thick, so I doubt it would hold that kind of load without ripping it out the transom.
Click to expand...

wise words/....


but I think you have to look state side if you want to ignore this advice..

wellcraft.jpg


http://www.powerdavits.com/wellcraft.php
 
Thanks everybody. As i though it's just asking too much of the boat. I wouldn't have the ski on their all the time, just on nice sunny calm days when I didn't need full tanks or have the whole family on board.

I was hoping that someone on here would come back and say 'Yup - Ive done it by doing this this and this and it's all fine' but i did realise that was wishful thinking.
 
neiloakley said:
Thanks everybody. As i though it's just asking too much of the boat. I wouldn't have the ski on their all the time, just on nice sunny calm days when I didn't need full tanks or have the whole family on board.

I was hoping that someone on here would come back and say 'Yup - Ive done it by doing this this and this and it's all fine' but i did realise that was wishful thinking.
Click to expand...

I think you are going to need a bigger boat :D
 
yes we have a jet ski on our bathing platform and the same questions you are asking was our big worry as well.
it worked very well on our pearl 43ft, the ski was just over 300kg and i wouldnt want to do any ruff sea stuff with it on the back, it made the back sit low and a fair bit of wash went over the platform.
the platform was made to take a big rib and has a crane, dont think davits would lift the ski with fuel, oil and a bit of bildge water.
if its just river use i would give it a go but i think the biggest problem will be launching and recovery, it was scarry having 300+kg swinging around when at anchor trying to recover it.
they look soooo much bigger out the water....
good luck
steve
 
Last edited:
Unfortunately your platform is an integral part of the boat, the Corniche one less so. it is just bolted (to be blunt) onto the transom. I have accepted now that I cant put 500kg on a Corniche bathing platform unless I am prepared for the boat to sink!
 
Does anybody else think that this Fairline is going to have trouble getting up on the plane and staying there with this hanging off the back.Trims tabs or no,the fuel consumption on a boat with its nose stuck up in the air cannot be good and what about effects on steering in straight line ?
Only practical test would be load up boat with enought weight to represent jet ski/davits and any stuff that may also be required such as fuel and put it all well aft.
 
oldgit said:
Does anybody else think that this Fairline is going to have trouble getting up on the plane and staying there with this hanging off the back...........
Click to expand...

With only 400 hp on tap, on the 3.6Litre lumps ..... I'll bet a virtual pint that there is no-way she'll get up on the plane with 400Kg suspended behind the stern.

My guess is that the engines will struggle to get enough RPM to push the hull into speeds that will resemble semi-displacement.... Run like that (much above displacement speed at about 7 knots) for a while and you'll have overloaded the engines and it is bye-bye Volvo's after a short while.... (unless the 41's re-buildable ??).

If it is to be done, then take off existing swim platform and build a new one, which includes extending the hull to get additional bearing for the weight and waterline lenght... but then you are talking ££££ and no idea what it will do with the seakeeping etc of the boat ....

Got a friend which built a 1.5M Teak/SS swim platform on a Laguna 11.5M (much beamier boat), and his strengtheners goes through stern and down through hull... but would "only" take a 200 Kg RIB ...

All IMHO of course...
 
Last edited:
You must log in or register to reply here.

Share this page

Top