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Old 25-02-2008, 11:54   #1
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Slamming?


First hand expense with Hull slamming?

After the boat show">Miami boat show we sort of narrowed our search down to three boats:

Voyage 44 plus or lightly used 50 owner’s version
Broad Blue maybe a 415 or 435 a lightly used 48ish would be ok as well
Manta

I know there is couple of price ranges here and that may be what shakes out what boat we choose in the end. But we are interested in now is general sailing feedback things like average passage speed, comfort at anchor, general safety, and Slamming and under what conditions. The Voyage is a nice design very clean and functional, but it sounds like some of the early boats in this line had issues with slamming 400 and 430. the Broad Blue has a different approach to hull shape and bridge deck clearance and it just looks like it would cause slamming, the Manta is sort of a different beast but it has a very clean underbody if a little low towards the aft.
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Old 25-02-2008, 12:01   #2
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Quote:
Originally Posted by Brandywine View Post
First hand expense with Hull slamming?

After the Miami boat show we sort of narrowed our search down to three boats:

Voyage 44 plus or lightly used 50 owner’s version
Broad Blue maybe a 415 or 435 a lightly used 48ish would be ok as well
Manta

I know there is couple of price ranges here and that may be what shakes out what boat we choose in the end. But we are interested in now is general sailing feedback things like average passage speed, comfort at anchor, general safety, and Slamming and under what conditions. The Voyage is a nice design very clean and functional, but it sounds like some of the early boats in this line had issues with slamming 400 and 430. the Broad Blue has a different approach to hull shape and bridge deck clearance and it just looks like it would cause slamming, the Manta is sort of a different beast but it has a very clean underbody if a little low towards the aft.
It is simple

Hull and bridgedeck slamming happens most with low bridgedeck clearance and heavy boats , the more weight the less the boat will follow the waves and the lower the bridgedeck so much closer the waves will be that hit.
In the cats that you describe , between 42 and 50 feet a minimum bridgedeck clearance of 2 foot 6 inches is necessary to get minimal slamming.
Hull shape has to do with hull slamming the flatter the undersides of the hull the more slamming will occur, a Catana for instance has got minimal hull slamming and bridgedeck slamming because of hull shape and high bridgedeck clearance , A Voyage is on the other side, reasonable flat hulls and minimal bridgedeck clearance and heavy on top of that.
They are good cats but you have to take that into account

Greetings
Gideon
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Old 25-02-2008, 12:38   #3
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Gideon,

At the Miami show of the three 50ft boats the St Francis, the Catana and the Voyage.

the voyage had the highest bridge deck clearance as measured at the aft and I believe it was also the only boat that had people and stuff on it... not having a dinghy handy I was unable to make any other measurements. The nacelle on the Catana also looked to make a more complicated form. But on a practice stand point the Catana is way out of line from a cost stand point the Euro being what it is to the dollar and it being some what of a premium brand.
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Old 25-02-2008, 12:41   #4
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Gideon,

At the Miami show of the three 50ft boats the St Francis, the Catana and the Voyage.

the voyage had the highest bridge deck clearance as measured at the aft and I believe it was also the only boat that had people and stuff on it... not having a dinghy handy I was unable to make any other measurements. The nacelle on the Catana also looked to make a more complicated form. But on a practice stand point the Catana is way out of line from a cost stand point the Euro being what it is to the dollar and it being some what of a premium brand.
Hallo Brandywine

What is the amount you intend to spend on a Catamaran and what size is your preference\

Greetings
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Old 25-02-2008, 12:55   #5
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Originally Posted by Brandywine View Post
After the Miami boat show we sort of narrowed our search down to three boats:

Voyage 44 plus or lightly used 50 owner’s version
Broad Blue maybe a 415 or 435 a lightly used 48ish would be ok as well
Manta
Besides a large price span, there is a large size span here also. The Manta is really a 38' boat. It is difficult to compare 38'-50' with regard to passage speeds (1-2kt difference in hull length alone), comfort at anchor (they will all be much more comfortable in a rolly anchor, but the larger ones will have more living space, amenities and larger wine lockers and humidors, safety will be more dependent on build and outfitting quality of the boat and the skill level and risk mitigation of the crew, and less dependent on the size of the boat (safety arguments can go both ways regarding vessel size).

As for slamming, I can only speak for our Manta in the conditions that we have sailed it in. We rarely slam in our boat. We do have times when the boat speed, direction and wave conditions are such that water is rushing through the bridgedeck area and flowing high on the hull sides and bridgedeck. This isn't slamming per se, it's just a constant movement of attached water flow. I think this trait is a result of the smooth, constant curve surface of the Manta bridgedeck, which has almost no horizontally flat area to it and starts 15' aft of the bows. I'm sure it slows us down, but it doesn't make noise.

Most of the hard noise and vibration comes when in a steep waves just forward of the quarter bow or just aft of the quarter stern. Then the waves miss one bow (or stern) and slam into the other. this happens outside the bridgedeck area, so I don't think height comes into play. It is worse than the same conditions on most monohulls because the hull shape on cats are rather slab sided in these areas.

Motoring directly into a steep chop produces slamming on the bridgedeck when the boat falls onto the waves. In these conditions, I have a difficult time believing any bridgedeck lower than 4-5' would help.

I have sailed other cats in similar conditions that had long horizontal bridgedecks at the same or higher height than our boat that slammed so much your feet hurt.

Mark
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Old 25-02-2008, 13:17   #6
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its a long story but my final budget will not be set for some two months, it will fall in the range of 400K to 700K but at this point I can not make any predictions on were it is going to land.

That is why we have been looking into boats at several price points.
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Old 25-02-2008, 13:35   #7
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Slamming

We chartered an almost brand new Voyage 440+ in the BVI in November last year. The bridgedeck clearance was 350mm (14") below the escape hatch in the saloon. It was easy to measure as the escape hatch is 450mm (18") and when open 100mm (4") of it was in the water. The boat had full tanks, fuel and water, generator, aircon and with 6 adults aboard. I think if you added another 500 kilo's (1000lbs) of crusing gear the 350mm clearance would have been reduced probably by another 25mm or so. Saying that, the boat performed quite well and tacked easily even in lighter winds.
To return to your concern the bridgedeck slamming in mildly choppy water was terrible and on occasions would jar your whole body, on one rough day it was unbearable. Personally I couldn't travel any large distances with the amount of slamming we encountered at all points of sail.
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