Mast Buoyancy (Capsize vs Turtle)

[James V]

Frank C - interesting question.

Let's first assume that everything stays in place and the boat does not have anything in it. The starboard side with the galley and head is heaver on an X or 04 M. If the boat was on the starboard it should self right at 90 degrees or a little more. Port side, it should go over.

Now enter the problem of all the stuff that we carry, including people, and it becomes quite a different problem.

I only loose about 1/2 mile per hour with a fully loaded ballest tank with my 50 hp BF 14 x 10 SS prop and the ride is MUCH easier. In all but the most ideal conditions I will be sailing/motoring with the ballest tank full.
(from now on)

[TonyG]

I bought a 2005 M last year.The second time out, alone ,I fogot to put in the ballast.I was sailing with main only in light wind.Everything was fine for about 15 min. when a gust knocked me down.Mast in the water.Several seconds later she came back up and went on her way. What the heck???? Oh my what a dummy.Well, I just love this boat.
It seems to take good care of dopey sailors.

[James V]

I found this link

http://sailingusa.info/cal__hull_speed.htm

It gives capsize formulas as well as stability formula. The angle of stability unballested is 110 degrees and with ballest is 118 degrees.

Stability chages from unballested 2.22 (vulnerable to capsizing) to ballested 1.99 (stability predicted)

[Frank C]

Greg wrote: wire loop & spray foam ...
There's a double-duty solution - great for Macs!
I'll be upgrading my mast somehow this season. The beauty of Roger's solution - foamed air chambers - is that air provides both the cheapest & lightest-weighing buoyancy.

TonyG wrote: 26M took an unballasted knockdown and self-righted !~!
Yours is the first I've read of a 26M taking an unballasted knockdown!
Spectacular stunt, spectacular results ... Great feedback!
IIRC, same has been reported of the unballasted 26X, though it's not necessarily true.

James wrote: (Link to US Sailing Performance Ratios)
Great resource, James. Thanks!

[Frank C]

The NETS link of the Champlain tragedy reveals a heartbreaking capsize story in which two children, tangled in the rigging, might have induced a capsized 26X to remain mast down. Searching for lost victims 7 to 10 feet deep in cold, dark, nighttime waters is a daunting task. There's no design flaw there, just tragic happenstance.

Reading that story STILL brings a lump to my throat. I encourage everyone to read it again ...

I began this thread suspecting that the 26m's mast might be heavy enough to turtle the boat if the ballast tank is empty. My related, second premise was, " ... that M owners who defeat or impair mast buoyancy might risk a very costly (completely swamped) interior cabin - or worse."

TonyG's report shows that my first premise is false. Foamed air chambers would float the mast, but couldn't possibly contribute to his unballasted self-righting. (This ignores for simplicity, the stability factors that James has linked). Further, of course, if the mast was heavy enough to turtle the unballasted boat, then it should be heavy enough to prevent Tony's self-righting event. Since Tony self-righted, the mast is probably not so heavy to turtle the 26M. Obviously we see at least one case where the unballasted 26M can self-right, which is great news - looking forward to similar successes.

Perhaps Macgregor Yachts simply decided that a "flotation mast" might have kept those children closer to the surface? ... and closer to rescue! The former design wasn't faulty, but the 26M's flotation mast is simply better ... better for the kids, better for crew ... or, just better able to save a few BoatBucks of cabin restoration.

Isn't it completely understandable that Roger refuses to add a wiring channel up the mast? Just one error by an unaware owner could defeat two-thirds of the mast flotation. Yes, he could embed a couple of extra lengths of wiring thru the foam ... but should he also embed a coax and a 5-wire for my wind instrument? Since we've got to drill the mast to employ those extras - isn't there still the potential for an owner's error? Roger probably wants those errors on the owners' consciences, not his.

IMO, re-reading the Champlain story affirms my second premise, yet much more. Would a flotation mast help to hold tangled victims within 3 feet of the surface? ... and, is it worth ten bucks to even HOPE that it could?

It seems that all of us Mac owners (especially 26Xers) might add an important measure of boating safety with just a $10 can of foam. FWIW, your kids or your guests could be the winners ... owners too! ??

[Frank C]

Would anyone with knowledge or experience about the best formula of expanding foam for this purpose, please make such a suggestion of brand or style?
Very much appreciated.


FWIW, it's easy for an informed owner to add BOTH mast flotation AND a wiring chase. The simple solution is to be sure that the chase exits, both top and bottom, are in very small air chambers. This means foaming the mast just below the top exit, and just above the bottom exit. The best wiring chase might be a fully sealed 27-foot length of half-inch PVC (sch 125 if you can find it). Properly done, this leaves the X-mast with a sealed, central air chamber about 25-feet long.

[Scott]

Actually some are closed cell some are open cell. I read somewhere on the internet to be sure and use closed cell as open cell is absorbant.

I dont remember the Brand I used but the can did specify "closed cell expanding foam"

[James V]

I don't think that foam in the mast would have helped in the Champlian tragedy as the mast went down so hard that it was stuck in the mud. I also believe that the bow was still tied to the other boat eventhough it was not admitted.

I will have to check my books to find the foam. Some of the foam is only water tight on the surface and when cracked or holled it will let water in. You want foam with No expansion.

[baldbaby2000]

It's suprising how much floation is provided by a sealed mast. I had a C-scow that had a sealed mast and an E-scow that did not. I capsized the C countless times and never had it turtle. The boat laid on it's side and could then be righted. A capsize on the E-scow almost always resulted in the mast filling with water and a turtle. If someone could swim out to the end of the mast quickly and attach a couple life jackets that would help. I think the class rules eventually required that foam triangular floats be zippered into the top of the sail. The same deal with Hobie 16s and 18s. You want to right them before the mast fills with water or they want to turtle.

[Chip Hindes]

I don't think that foam in the mast would have helped in the Champlian tragedy as the mast went down so hard that it was stuck in the mud. I also believe that the bow was still tied to the other boat eventhough it was not admitted.

Is this anything more than pure conjecture?

Because I was on Champlain the day before this happened, and like that boat, my boat also lacked the warning stickers Roger Mac insists were on the boat, I've taken special interest in this story. I've read everything I could find on it and the fact that the mast was stuck in the mud was ever mentioned. The people on the other boats the Mac was rafted to insist all the lines hd been cast off when the Mac went over.

I believe it would be quite difficult for a boat that is stable enough to be self righting to get its mast stuck in the mud deep enough to keep it that way. Especially one which was at least partially afloat upside down and had been subjected to wave action and numerous wakes from other boats during and followng the incident.

On the other hand, on a boat which is inherently stable with the mast down, as I maintain, it wouldn't matter whether the mast was actually stuck.

[Lease]

I used to sail a 16' trailer sailer called the Hartley TS16. That boat weighed 360kgs and had a centreboard of 60kgs. So it was not self-righting.

We lost it in a viscious westerly during a race one day. Knockdowns on these things were plentiful, but as long as you stayed on the high side, you could bring it back up when the gust eased. On this particular day we went in at speed and both of us ended up in the water.

As we were untangling ourselves, I saw the leech of the main filling and moved around to the centreboard, but it was too late. Once that sail starts to fill, it's all over. Unless your boat is self-righting, it will stay down. Closed-cell foam in the mast, either as a plug, or better still, all the way down, will make all the difference to a knockdown v capsize. Others would be able to calculate it, but the righting moment of trapped air only has to exceed the weight of water that spills over the leech for it to be effective.

A note on that apalling tragedy, and whether the mast was stuck, or not. From the articles published it mentions one child being rescued from an air pocket inside the boat. If a Mac goes over whilst unballasted, then one would assume a pretty sizable air pocket inside the boat. Wouldn't that be another inhibitor to the boat coming back up and contribute to the inverted stability?

[Frank C]

... From the articles published it mentions one child being rescued from an air pocket inside the boat. If a Mac goes over whilst unballasted, then one would assume a pretty sizable air pocket inside the boat. Wouldn't that be another inhibitor to the boat coming back up and contribute to the inverted stability?

Excellent point, Lease. It is totally unremarkable, once inverted, that a 26X might remain mast-down, especially with a large bubble of air against the upturned cabin sole. But it's totally inconceivable with the buoyant leverage of 25 feet of mast-air, plus the existing bow and coamings flotation.

[James V]

Here is an online video of "Scoop Method of Capizing Recovery"
http://www.videos.sailingcourse.com/capsize_wmv1.htm

Other cool video's from the same site -

http://www.videos.sailingcourse.com/

[DLT]

I wonder if our daggerboards/centerboards could withstand that...