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CalmSkipper

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I downloaded a fascinating article on the lessons learnt from Fastnet and as part of the article it a series of formula's to help estimate the boats vanishing angle when the manufacturer doesn't supply the curves. There are 4 formulii

1. Ballast Ratio = Ballast (Kg)/Discplacement (Kg)

2. Disp Vol Seawater = Disp (Kg) / 1025

Disp Vol (freshwater) = Disp (Kg) / 1000

3. Stability Value = Beam squared/ (BR x DCB x Disp Vol)

4. Est Range = 100 + (400/(SV - 10))

Unfortunately it didn't define 'DCB' - I expect I'm being dumb as I'm new to all of this. Can anyone help please??? /forums/images/graemlins/confused.gif
 
A quickie google shows it stands for "Draft of canoe body".

I'm sure it won't be too long before someone sensible explains what that means! /forums/images/graemlins/laugh.gif


<edit> see what I mean? /forums/images/graemlins/wink.gif
 
I meant to add, being new i'm looking at all options and at one stage, attracted by the versitiliy was looking at a MacGregor 26. I emailed them requesting the stability curve but they wouldn't release it. Now I don't want top get on the McG knocking bandwagon - I haven't entirely ruled it out until I know more about what I really want from sailing and it really does come down to 'horses for courses', but them not releasing the info was slightly worrying. So if anyone can tell me what DCB is I'll have a stab at the estimation for a MacGregor
 
stablty2.gif

from

http://www.radford-yacht.com/stablty1.html
 
[ QUOTE ]
I doubt I can get this data or the MacGregor

[/ QUOTE ]

The latter might not be such a bad thing in the longer term /forums/images/graemlins/smirk.gif
 
In fairness (he says, not wanting to become the Salman Rushdie of the MacGregor world) it does depend on what you want to do. If you're after flexibility, low cost of ownership and you're happy to accept that you only go out in mild seas it certainly has a place - you can then do lakes and inland waterways as well etc etc.

I tried, in an earlier thread, to hear from MacGregor owners who sailed the channel but got no responses. Thats either because a) they don't sail th channel or b) they don't partake in ybm.forum any more as they are always under attack!. A bit of both maybe, and also in part an unfair quastion from a newcomer...Even the owner of the company suggestes limiting the sailing area. It's a shame they won't publish the curves and be done with it. Ah well!
 
Well I (unqualified, using a formula (above (please not that in SV you have to divide 'beam squared' by the cube root of the displacement, not the Displacement value)) quoted as being from the marine safety agencies code of practice for small (.15m) boats) calculated a range of 125 degree's based on a DCB guestimate of 0.25m. So, big health warning on the calculation (a novice with an estimated bit of data using a formula which only gives an estmate in the first place) but if 125 degree's is anywhere near true its probably not at all a bad figure for a water ballasted trailor sailor. Either way the big lesson from the Fastnet report I read was that

1. its breaking waves that do the damage
2. A breaking wave the height of your beam could capsize you
3. a breaking wave 60% LOA WILL capsize you

I suppose the worry for the channel (says he who's only as yet crossed in a ferry!!) is that its relatively small and prone to smaller choppier waves??

Anyone crossed the channel in a MacGregor, if so, what was your experience?
 
Does your formula take account of where the ballast is mounted, as well as the ballast ratio? For example 1/2 ton of water just under the floor boards may give the same ballast ratio as 1/2 ton bulb at the end of a 5 foot keel. But the latter would give much more stability.
 
Absolutely. No it doesn't, and I recognise that's an important point. There's a second formula to help estimate how much we reduce stability by adding things to the boat (particularly anything to do with the mast of course as the turning moment increases with distance from the fulcrum).

I guess knock downs are an occupational hazard for racers but as they know this they are more likely to use lines when needed. Also as they want to keep the weight down they will have minimised most things that reduce stability anyway.

For cruisers I guess its a question of being aware of how stability has been reduced by the things that have been added to the boat and not being seduced into optimistic interpretations of forecasts when setting out.

This sailing malarky is fascinating isn't it!
 
[ QUOTE ]
1. its breaking waves that do the damage
2. A breaking wave the height of your beam could capsize you
3. a breaking wave 60% LOA WILL capsize you

I suppose the worry for the channel (says he who's only as yet crossed in a ferry!!) is that its relatively small and prone to smaller choppier waves??

[/ QUOTE ]

I find some of the worst waves are in the channel, mainly because of the short period between them they seem to be particularly steep. I came up the French Coast one year on a spring tide into a F7 NE which had been blowing for about 5 days. We had a wave break as we neared the crest and I felt the boat going. We hit the bottom of the wave at a heel of close to 70 degrees and wet the mast in the next wave. But she righted herself as we climbed the next crest.

My understanding, and I could be wrong, is that in theory only, a breaking wave needs to be 3 times your beam to roll you if you are lying-a-hull. I have a 10 foot beam and have been in a rather nasty Atlantic full storm where the waves seemed enormous, but I have no way of measuring them, laying a hull and while I spent most of my time at 50 to 60 degrees heel with waves breaking over me, the boat never rolled through 360 as I was expecting it to.

I have seen two Macgregors 26X in Boulogne who had crossed the channel. So it has been done.
 
Was there not an article in one of the mags about a McGregor that went to the Scillies?

Is that a silly question?
Donald
 
All sounds pretty scary to me I must say!. My plan is to try and avoid that but at least to find out as much as possible to help when avoidance almost innevitably fails!
 
[/ QUOTE ] I have seen two Macgregors 26X in Boulogne who had crossed the channel. So it has been done.

[/ QUOTE ]

On a trailer, via the ferry. /forums/images/graemlins/grin.gif
 
There was also an article about one crossing Biscay coupled with a french canals cruise. I seem to recall the centerplate fell off ....but they did get there. I would imagine they have a high AVS because there is a lot of coachroof/ freeboard that calculations of AVS consider to be buoyant.

There was a lot of stuff around in the aftermarth of the Fastnet about spade rudders and modern fin/skeg vs long keel designs etc. For me the biggest lesson was active tactics rather than passive. From memory, it was the guys that lay ahull or suffered gear failures (mainly early, lightly built, spade rudders) that suffered the most. Those who carried on sailing or at least staying in control of their boats did ok. For an example take the then new Sigma 33 which finished the course despite (I believe) only having an AVS of 117 degrees. Now this boat would have enountered breaking waves far bigger than those that the wolfson unit report said would capsize it.....and yet it didn't.

Having said all the above, in all honesty, I wouldn't cross the channel in a McGregor and having previously crossed the Atlantic I am really quite disturbed about the young lad that is about to contemplate a transat in one. As we all know, the weather can change very quickly!
 
I sure thats not in a MacGregor. I not 100% certain but think (so someone please put me right if this is wrong) its a Tide 28 (PBO Nov p127), a trailorable RCD B with leaded keel. whether I have the right boat or not the issue was in the october monthlies because the authorities are also very concerned. The boy will be accompanied by his father sailing (I think) a second identical craft both for safety/backup and because his son not yet being 18 is not licensed to use R/T

I overheard the father talking to someone about it at the southampton boat show - I think the father is the designer/company owner also. I'm on a steep learning curve regards sailing but I do know a bit about people. He came across as someone very knowledgable and very passionate about his sailing. I'm sure others are also concerned but I'm sure also he will have assessed the risks so all anyone can do now is wish them the best of luck
 
Apologies if I'm wrong about it being a Mcgregor.

I'm afraid I disagree about "all we can do is wish them luck". I went across when I was 20, more yrs ago than I would care to admit :-) in a 43' beneteau with a VERY experienced delivery skipper. I know similar boats were delivered without rigs, having been rolled (with equally talented and experienced skippers) - Don't get me wrong, I'm not against adventure or taking risks. If they did it in a Contessa 26 /32 or even a 21' coribbe etc I would be fine with what they are doing, it's just the choice of boat.
 
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