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Old 02-02-2008, 13:57   #211
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Steve Callahan in the article, Two Hulls for all Seasons, Cruising World, September 2004 listed measured bridgedeck clearance on 14 different production multihulls. The Manta 42 Mark II was shown as 1'10" - tied with the Broadblue 38 as the lowest of all boats except the much smaller Gemini 105 at 1'6". Interestingly, even the Maine Cat 30 had 2'2" and the FP Lavezzi 40, PDQ 44 and and Island Spirit 40 all had 2'6", while the Voyage 440 had 2'8". So while I agree the Manta is capable of making offshore passages, one can expect more pounding than in most comparable cats. This not insignificant shortcoming is further exacerbated by the fact that the Manta is also relatively heavy for its size.

And I wasn't suggesting that the camber-spar jib doesn't have some advantages (in fact I referred to it as being ideal for short-handed sailing); as I said, however, it cannot be reefed. Yes you can carry multiple headsails ( although a question here -is the standard track adequate for the necessary range of sheeting angles ?).

Nevertheless, I suspect that it would not be the first choice for most sailors who are venturing offshore. As you say, you will want/need a larger jib in typical light to moderate trade-wind sailing, and a storm jib for higher winds. This is not merely a matter of convenience (although that is part of what multihull sailing is all about): it forces you to go forward to change headsails in precisely those conditions where most would rather remain in the cockpit. In fact, the spray through the netting on the 'foredeck' of a cat (made worse by the weight of a typical sailor at the very forward extremity of the boat) makes it in some ways less comfortable and safe than the foredeck of a mono in comparable condtions. Of course, as I recall Manta had a furling jib available as a factory option, and the majority of boats that are not so equipped could be upgraded.

My apologies, however, in reference to the anchoring arrangement - I was not aware that Manta had gone to standard twin rollers on its later boats.

Brad
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Old 02-02-2008, 15:03   #212
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Couldn't agree more but I would also add that the sole of the hulls be above the outer hull forming a series of water tight compartments. If some are breached during a grounding or somesuch there is still a sealed sole to prevent further ingress of water. This was a major factor in me choosing a Schionning design over others. The Wilderness has 20 compartments in each hull as well as every other feature you list except for the watertight doors.

Mike
it's interesting that you should raise this now, because it's something that I am having difficulty with deciding on. While my build doesn't require soles in the hulls, you can of course fit them if you wish. I am fitting a floor in the galley area of my boat for a couple of reasons - so the cook will be higher relative to the bridgedeck and thus less isolated, and also so that I can fit the galley benches higher in the hulls, where there is more width, and more space available under them for cubpoards.

Trouble is, I'm not sure whether to permanently build the floor in and seal it, thus providing some watertight compartments, but also denying any access to the inner hull skin, or whether to screw it down, which would probably not be watertight, but would allow access if needed.

The way I see it, in the event of a large hole being made in the hull, having a sealed sole could be an advantage. But in the far more likely event of small "bruises" or knocks to that part of the hull, it would make it a major job to check for any damage internally.

At the moment I'm just not sure which way to go, the floor is sitting in place waiting for me to decide....
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Old 02-02-2008, 15:58   #213
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I would think that in the area of which we are thinking that it would not be subject to knocks from docks etc only from running onto something. if it was only a minor scrape externally the inner skin would be unlikely to sustain a lot of damage epecially with the grid of support bearers, the floor can alwys be cut out and resealed. The Schionning has a centerline rib and athwartsip bearers roughly every 600 mm. Also I am going to put 2 more layers of glass in the forward area back to about 40% of LOA, I also put an extra layer of 300 g kevlar externally to 40% LOA. I am putting the water tanks, sub floor, in part of the area beside the forward berths. If an incidence is severe enough to open a hole I would definitly prefer to have the sealed floor.
Do you have the headroom to install the floor?

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Old 02-02-2008, 18:13   #214
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That area won't be subject to knocks from docks but what about rocks? (Am I channelling the cat in the hat? )

ie.When beaching the boat, you might run onto a rock, or the boat might actually end up sitting on a piece of rock or coral, which wasn't seen before beaching.

The 44C "Outahia" ran onto the reef at Great Keppel at night at about 6 knots and sustianed some minor dents to one of the chines. Because the owners could see the internal hull in that area they knew the damage was only minor, that the hull hadn't been penetrated, and that repairing the dents could wait until they slipped the boat for other reasons. If there had been a sealed floor they would have either had to cut it open to inspect the inside of the hull, or slip the boat more urgently.

So I can see your point, but I can also see there is another side to it. Which leaves my dilemma.

And yes I have a little spare headroom in the deepest part of the hull. It's also the area where the hull is open to the salon, so the side deck doesn't impinge on it so much.
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Old 02-02-2008, 22:01   #215
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Originally Posted by Southern Star View Post
Steve Callahan in the article, Two Hulls for all Seasons, Cruising World, September 2004 listed measured bridgedeck clearance on 14 different production multihulls. The Manta 42 Mark II was shown as 1'10" - tied with the Broadblue 38 as the lowest of all boats except the much smaller Gemini 105 at 1'6". Interestingly, even the Maine Cat 30 had 2'2" and the FP Lavezzi 40, PDQ 44 and and Island Spirit 40 all had 2'6", while the Voyage 440 had 2'8".
Brad
I measured the bridgedeck clearance on our Manta 40 today. It was 24" at the lowest point, but differences in loading could account for the 2" missing from Callahan's measurements. I have spent 4 weeks sailing an Island Spirit and there is no way that boat has 30" of clearance. It certainly pounded almost continuously - much more than I have experienced in four years with the Manta. I have also spent time on a Voyage 440 and question Callahan's number on that. I can get my dingy under our bridgedeck and I could not get it under a Voyage 440 moored next to me. In addition, the Voyage has vertical facing components to its bridgedeck that must catch water in a bad way regardless of its height.

My point on the headsail was muddled - sorry. What I was trying to say was that the full camber spar jib area was equal to the area of a conventional roller furled jib furled to the minimal size that still makes it usable. Furling jibs simply aren't usable as infinitely reefable sails. You can reef them 10-20% and then they no longer function well unless being used simply as extra windage going downwind. I don't buy the argument that a roller furling sail is a better storm management system (unless it is very small to begin with).

I don't want to get into a defense of Manta or a tit for tat debate, but you do seem to be making judgements about some of these boats and their capabilities without direct experience with them.

Mark
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Old 02-02-2008, 22:44   #216
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This not insignificant shortcoming is further exacerbated by the fact that the Manta is also relatively heavy for its size.
Brad
Sorry, a second post must seem like I'm obsessing, but I seemed to have cut off the full quote I meant to address in my last message.

Regarding weights - don't believe anything published by the manufacturers. I would guess that even they don't know what their boats actually weigh. As for our Manta 40, we have had it on the scales at two different places and both times it weighed 18,000#. This was with full fuel and water tanks (1,800#), 300# of anchor gear, 400# dinghy and outboard on davits, 6KW generator, two 16,000 btu AC units, full Corian everywhere, etc.

Manta lists its weight as 16,500# with empty tanks (but much of the same equipment), so their published weights seem to be pretty close.

I listed the weight just to establish a data point. I don't know what weight is acceptable for its size. But if we except 18,000# for a Manta in real life and look at manufacturer published weights from other manufacturers:

Lagoon 380 15,697# unloaded
Lagoon 400 22,712# (doesn't mention load)
Lagoon 410 16,000# unloaded
Broadblue 385 15,432# (doesn't mention load)
Broadblue 415 20,061# (doesn't mention load)
Lavezzie 40 13,227# unloaded
Island Spirit 40 16,868# unloaded
PDQ 44 22,132# (doesn't mention load)

Again, I don't know when a boat is too heavy for its size, but the Manta seems to be right in with other production boats, even if you take the manufacturer data at face value.

(As an aside, the weights listed above must have our friends down under wetting their pants with laughter - so for their sake, I would like to assure them that these boats DO NOT have lead keels)

Mark
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Old 02-02-2008, 22:47   #217
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I think one must flip a coin on this one. I know balsa transfers more shock to the inner skin but I think in running onto some thing it is more likely to be a scaping action rather than an impact, unless one is bouncing up and down on rocks, so inner skin damage is less likely but I am beefing it up just in case. On rocks or if I hit something hard enough to damage the inner skin I would think it will be obvious and then the sealed floor will be worth the possible extra work in repairs. At this level of damage it would most likely be an insurance job anyway.

Mike
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Old 02-02-2008, 23:06   #218
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Originally Posted by colemj View Post
(As an aside, the weights listed above must have our friends down under wetting their pants with laughter - so for their sake, I would like to assure them that these boats DO NOT have lead keels)

Mark
Glad you put that bit in as it was very tempting to make a facetious comment.
Schionning Wilderness 40' 13,900# including 4,000# payload. 110 square meters of rags. Reasonable alowances for anchor and chain, 100 kg, batts, 120 kg, and other normal stuff does not form part of the payload. I think Schionning is quite realistic and honest.
During the long 420 thread it became obvious that some production builders get very creative with wieghts, such as no sails and other basic equipment in the empty wieght. Seems like a nightmare to get to the truth. Maybe we should have a thread where people could list the wiegh of their boats with a guess as to how much stuff they have on board.

Mike
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Old 03-02-2008, 03:31   #219
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Originally Posted by colemj View Post
Lagoon 380 15,697# unloaded
Lagoon 400 22,712# (doesn't mention load)
Lagoon 410 16,000# unloaded
Broadblue 385 15,432# (doesn't mention load)
Broadblue 415 20,061# (doesn't mention load)
Lavezzie 40 13,227# unloaded
Island Spirit 40 16,868# unloaded
PDQ 44 22,132# (doesn't mention load)

(As an aside, the weights listed above must have our friends down under wetting their pants with laughter - so for their sake, I would like to assure them that these boats DO NOT have lead keels)

Mark
Those weights are incredible. Down here we build cruising monohulls no heavier than that. M.C.Y 46 Specifiacations

Bob Oram's approach is fairly simple - he gives a figure for displacement at the design waterline. If you build light, you have more payload capacity. If you build heavy you have less. If you build a little sneaky like I have, and extend the waterline length a little, maybe You can exceed the design displacement a tiny bit and still float on the lines.
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Old 03-02-2008, 04:25   #220
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Just for interest - Lightwave have done a recent build of a 38 with a single board, and a bit of attention to detail in terms of lightness. Did a test sail for an upcoming article in the Australian Multihull World the other day, and in light breezes it pointed higher and sailed faster than some very good monos (eg Farr 1020) - any breeze at all and it dispachted the rest very easily
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Old 03-02-2008, 06:38   #221
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Mark, I wasn't trying to insult your boat. Frankly, I think Manta has developed an excellent reputation because they are well designed, built and priced for their intended primary purpose: coastal, caribbean and bahamas cruising with the occasional offshore passage. I am confident that even Manta would not suggest that they designed or built the boat with a view to circumnavigating.

As to criticizing me for commenting on boats that I don't have personal experience with, sorry but I repectfully disagree with your efforts at playing censor. Furthermore, in this case I was largely a conduit. I quoted a well-known author with respect to bridgedeck clearance measurements - he DID have personal experience and this is what he reported. As you know, cats are extremely load sensitive: the 2" difference between your measurements and his could easily reflect that (as with differences on some of the other boats you have mentioned).

Furthermore, I was not/would not recommend a Lagoon or Island Spirit for offshore use - I was merely reporting what was written and, based upon that and other observations, expressed an opinion. In that connection I said that I believed that the bridgedeck clearance issue was compounded by relatively high displacement. In my opinion, the displacement is relatively high in comparison to Foutain Pajot's (which I had made a comparison with), but lets face it, also in comparison to boats that are intended primarily for offshore use, such as Gunboats and Outremers.

I am sure you quite rightly love your boat; I have no doubt that it was the correct choice for you. But there is a tendancy for all of us to turn the occasional blind eye to certain features that may make our boats less than ideal for someone else. The original posting concerned a boat intended for circumnavigating: while, as I also said, it could no doubt do it, I believe that the bridgedeck clearance and camber-spar jib are two things that he should at least direct his mind to in considering the Manta for a circumnavigation. You have the right to disagree.

Brad
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Old 03-02-2008, 07:18   #222
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PS Mark - The 10-20 % max for reefing a furling jib is simply incorrect with current technology. In fact, the 10% figure would be incredibly low for even a coastal sail without a foam luff. What was your source for that statement, as the LOWEST number I have ever seen published was 20%? Beyond that the concern was inadequate material weight /stitching for stronger winds and the increased belly in the sail from furling without a foam luff, or equivalent.

A furling jib made to offshore specifications and with a foam luff can be reefed effecitvely to at least twice those numbers (many would say more than that). Here I speak from personal knowledge based upon years of experience. In addition, I am in currently in the process of ordering a new offshore, furling 120% genoa for my boat and have been assured of the same by both North and UK/Halsey, my lofts of choice.

I agree that for truly extreme conditions you may want to carry a 'galerider' storm - jib: I say 'may' because in the case of a cat, there are many who suggest that when the going gets that rough, you are better off running before the storm with bare poles. Storm jibs are great for heaving-to, or for efforts at clawing your way to windward in extreme conditions. Cats, however, are hardly at their best going to windward in extreme conditions and the issue generally becomes one of slowing the forward speed of the boat, even under bare poles. Storm tactics are, however, better left for another thread.

You may prefer an inventory of hank-on sails, but as I said, most people who are going cruising would prefer the numerous advantages of roller-reefing. Ask the delivery skippers of the literally thousands of French and South African cats that have crossed the Atlantic to the Caribbean with only the standard, manufacturer's roller-furling jibs in their inventory.

Brad
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Old 03-02-2008, 07:35   #223
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Mark, I wasn't trying to insult your boat. Frankly, I think Manta has developed an excellent reputation because they are well designed, built and priced for their intended primary purpose: coastal, caribbean and bahamas cruising with the occasional offshore passage. I am confident that even Manta would not suggest that they designed or built the boat with a view to circumnavigating.
Brad,

I think it's you who is totally off the mark here. Manta describes their Mk IV as an offshore cruising cat and describe some of their features that (in their opinions) make that the case: MANTA Catamarans - What is a Cruising Catamaran?

You originally mentioned shape in your comments on bridgedeck clearance - the Manta has a unique under-bridgedeck shape, that is very smooth; there are no protrusions or hard edges. Of the Manta owners I've spoken with, none have expressed a desire for more bridgedeck clearance. Reputation aside, one only has to look around a Manta to realize they are very solidly built. I'm not an owner, but the Manta is definitely is on my short-list to circumnavigate with my family.

Kevin
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Old 03-02-2008, 09:05   #224
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It's generally accepted that in a circumnavigation around 85% of the time is spent either at anchor or alongside (depending on budget, of course) so in my book crew comfort is a major consideration rather than out and out speed or being totally 'bullet proof' (or as near as you can make it). Some will claim that speed is all and can get you out of weather trouble..... well, I'm not an experienced cat sailor but I have my doubts about that one, frankly.
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That is sort of what I understand.
I can see needing a well constructd boat (more expensive) but for me there will have to be a compromise. Oh yea, it's a boat......yea that's right, it will be a boat
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Old 03-02-2008, 09:57   #225
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My apologies Kevin - I haven't kept up with Manta's advertising literature. Of course, at some points even Gemini have advertised their boats as suitable for crossing oceans. I have, however, never suggested that Mantas are not solidly constructed - in fact if you read my posts, you will see that I have stated the exact opposite.

I also agree that under-bridgedeck shape is important in reducing pounding (although I take issue with your suggestion that the design employed here is 'unique' - look at virtually every cat designed by Eric Lerouge, for example). Perhaps that is something else from their sales brochures.

On the other hand, despite your disagreement, bridgedeck clearance is still a critical factor in the design of a cat for offshore sailing. Ask any self-respecting naval architect - within reason, more is better than less. Or am I missing something? Admittedly, I haven't read the brochures for Manta but I thought this was something that was now generally accepted. In fact, as I recall Manta utilizes an upward curving frp front cross-member in order to raise the height of the same from the water. I wonder why if the actual clearance is not important?

Frankly, I did not say that the Manta could not be used for crossing oceans. I only suggested that the relatively low bridgedeck clearance and the standard camber-spar jib were potential shortcomings that the prospective purchaser should consider. I could have gone on to criticize the standard water tankage (although I must assume that if Manta is now producing these as circumnavigators, they have increased their standard tankage from the original 100 gallons).

Honest people can honestly disagree. I am not calling you, nor anyone else "totally off the mark." Really, all boats are compromises. It may be that the Manta would be the perfect compromise of cost, accomodation and performance for you. It would not be for me, and it may not be for the person who started this thread. For a circumnavigation I personally would want more bridgedeck clearance, a roller-reefing jib, more tankage and a galley down arrangement. For that matter, I would also prefer a cat with less displacement, boards and and higher speed potential.

My current cat, although a boat that was built to Lloyd's 100 A-1 unlimited offshore standards, is not one that I would choose for circumnavigating. Why? Despite having (very) solid construction, twin furling headsails (yes, a dedicated inner stay for staysail/storm jib), good bouyancy and twin 'knuckles' forward to reduce the risk of burying the bows, terrific tankage, a large galley down which is open to the main saloon, a full size chart table by the companionway, a bridgedeck shape which also has no protusions and which is completely curved from the leading edge aft, it is has two failings in my view.

Firstly, it has too little bridgedeck clearance aft when loaded with solar panels, wind generators, large house battery bank, watermaker, twin regrigeration units and davits. The resulting 17" is still right around the oft-cited 10% of maximum beam -and the boat does not pound in anything except when sailing to windward in a bad chop. Even then the motion is really not 'pounding' because of the 4 foot clearance at the leading edge of the bridgedeck and the gentle curve aft. Still, I personally would want much more clearance - likely 24" with my beam, and about 28" with the beam of the Manta.

For a circumnavigator I would also want boards, rather than keels because of the significant advantages when sailing to windward (and the reduced drag when sailing downwind). Finally, I would be looking for less in the way of creature comforts and weight, and more in the way of performance if I were intending anything more than short passages offshore and the Caribbean.

Again, your priorities and the perfect compromise for you may well be different. But surely these issues are legitimately subject to debate, rather than a suggestion that a contrary opinion is 'totally off the mark.'

Brad

As to the camber-spar jib, again let us just say that we agree to disagree. You obviously believe that bridedeck clearance is unimportant and that
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