Bouyancy!

05/08/2007 09:18:48
Andy3324
Have had very little chance to sail 3324 since I got her due to crew issues however yesterday I lent her out to a friend and his Sailing Instructor daughter as their Fireball is currently under repair. It was quite windy and in the end they went for a swim - what concernns me is the total lack of bouyancy in the boat. The front tank was Ok (thank god or the boat would have been lost and the rear tanks had a little water in them - however not enough to cause the boat to be so low in the water as to be unrecoverable by the occupants. In the end crew was taken aboard the rescue boat and boat ws towed in.

Did they do something wrong here or is this a common problem with rear tanked boats. I'll be a little bit annoyed if it is as I specifically went after a boat with rear tank as I've never liked bouyancy bags.

Cheers

Andy

05/08/2007 09:42:13
Jez3550
Andy it depends on the tank as there are several shapes of tank. My experiance of a rear tank in my last boat was that it floated higher than bags and was empty rather quicker.In fact one of Phil Kings old boats 'Bananarama' had a very shallow rear tank at floor level with almost no transom so as to sail the water straight out and that floated well too. I would suggest your mates where either too far aft when full or there was rather more than a bit of water in the tank.

05/08/2007 09:48:22
CHAIRS
I had a rear tank on one of my boats.  We even put a drain plug through it.  Never drained well on the water and susceptible to clumsy foot stomp damage. Not my favourite Merlin.

However, my new boat,3379, the same NSM4 design, is a delight and qualifies as a mature boat at the nationals! Whay not come and join us, not too late!

05/08/2007 09:55:16
Chris M
It's a Rowsell boat so it should be OK, and it must have passed it's initial buoyancy test on measurement.

I suspect you are too far back in the boat when you right it. The crew needs to be forward as does the helm until the boat is moving. Then you can both move back behind the thwart and the boat will empty. All Merlins float low, especially compared to sailing buoyancy tanks like fireballs!

In some ways rear tanks are better. They get the lift low down where you want it, they add a great deal of stiffness to the back of the boat and they don't pop out due to stress. The major disadvantage is that if you go over in marginal condidions the transom flaps are not as effective for as long as a bagged boat as they are higher so it can take a lot longer to drain the boat. Also they are quite heavy, right at the back and that i suspect is why there aren't that many of them and none since about 1987.

05/08/2007 21:46:14
Andy3324
Thanks for the input guys. My boat doesn't have flaps - it's an open transom job and the rear tank is split in two internally. One tank was dry - the other quite full and the boat was really sufferring. Having said that - i don't really know where the guys were in the boat so that may have some bearing...will just have to wait until I stuff it in myself and see what happens!

06/08/2007 09:36:31
Kev
Andy. I had the same experiences earlier this year with my nsm4 with rear tank (3389). If the boat filled up, it would take forever to empty as the tank at the rear would prevent efficient discharge from the higher positioned transome flaps. The boat was very very low on the water and I too had to be recued because the boat wouldn't empty at all as no speed could be gained, hence chicken and egg!
As this was a problem, the tanks were removed and a new transome with lower flaps and bungs were fitted with crewsaver bags.
From my experiences last week, I can say that it works very well!!!!!!!!!!!!!!!!!!

29/10/2012 17:59:36
Alan3463
Intersting old thread.  I have recently been swimming with 3463, Bagley NSM2 with rear tank... can't get the water out the back even if we sit on the transom and get her moving well on a reach as the tank is so high.  Has anyone ever fitted tunnels through the rear tanks?

29/10/2012 19:42:17
Stuart Bates (MR3615)
There are quite a few of the Bagley boats that have tubes through to the Transom, just need to remember the rules on Openings on the Transom and flaps.

30/10/2012 09:02:33
Andrew M
The counter to the problems with the amount of water aboard after capsize in a Merlin was brought home to me when race officer at Hampton and one of the modern GP14's with double bottom etc. went over.  It was floating so high on it's side that it was not possible for the (admittedly not agile) crew to get on to the board from the water and they needed to be rescued.  Far better to have a boat that comes up easily and is then nice & stable.  Have been reading the thread on aft tanks with interest, Andy Hay's conversion looked really good & it does stiffen up the aft structure significantly.

01/11/2012 19:26:18
Andy Hay - Business as Usual
Interestingly enough, we have significant opportunity to check the buoyancy arrangements at botht eh Champs and later at Weymouth. Maybe increased the tendancy to invert, but I had ample opportunity to climb over with the boat on her side. Much better with the hoop as a step!!

02/11/2012 10:30:30
Andrew M
Andy I tested the buoyancy more at Lyme than I ever remember doing before, (8 including 3 in one race) and one other issue with the bags for wooden boats is that there's not much meat for the screws to hold into for the bag straps & I had to repostion some of the fittings during the week.  Just wondering what sort of outlay is required for a rear tank conversion?

02/11/2012 10:55:17
Chris M
It'd be easier, lighter and cheaper to adapt the boat to take the covers fitted to most new placcy boats.

The extra screws would spread the load out and the bag physically cannot escape out of the end.

02/11/2012 15:36:59
broz
I took the rear tank out of 3316. The boat floated with back of the boat under water. Also made life difficult when you were on the c/board, ie. leaning backwards.

03/11/2012 18:43:55
confused
Andy please don't remove the tank as you know it really makes the boat very pretty and stiff.
How do I know - well I rescued this boat from the frost at stonehaven - gave her lots of hours in refurbishment and as you can see the result was very worthwhile. Then sold her to the chap on NI 2 years ago.

I sailed her for two years at East lothian YC winning many handicap races off an unadjusted handicap against all the modern designs including the usual Phantom ansd Solo bandits so my conclusion is that she is very fast.

The conditions here tend to be 20 Knots+ and big seas- so we capsised many times. Although the boat comes up with alot of water in it we always managed to sail her dry very quickly, the trick was to sail her quite free on a fetch to get up speed and momentum then as she emptied progress towards a broad reach to finish the job. I found this second nature but then I used to sail 14s 12s and Fireflies 30 yrs ago and that is what we used to do.
Maybe your freinds are so used to the modern boats that they expect her to come up dry and start planing again straightaway - this will not happen. Should also add that the boat floated perfectly on her side with the board close to the water and that made righting much easier - im reckon we recovered and were back up to speed faster than the RS 200, RS400 and Laser 2k at our club.
Hope you get on with her as I am sure you will
Stewart

03/11/2012 18:46:42
stewart G
sorry dont know why my recent post went under the heading confused - I am not.
Stewart

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