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Old 04-05-2008, 00:29   #1
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pirate solid vs. trapoline decks on cats

i have always heard that a cat with a solid deck is going to slap the waves when at anchor and i have only sailed with trampoline decks which make it a pain in the but to change the anchors but i also understand that prout overcame this problem if anyone has info please post.
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Old 04-05-2008, 05:13   #2
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i have always heard that a cat with a solid deck is going to slap the waves when at anchor and i have only sailed with trampoline decks which make it a pain in the but to change the anchors but i also understand that prout overcame this problem if anyone has info please post.
Having just bought one with a solid foredeck, I haven't experienced any additional slamming due to the foredeck. The slamming (if any) tends to occur further aft, amidships or even sometimes below my feet in the aft cockpit.

Slamming is also a pretty harsh term for it... I would almost call it "splashing" since there is not real "BANG"... it's kind of a muffled whoosh sound.

The advantage is you get a lot more deck area and storage, good for anchoring and stuff as you said.

The disadvantages (theoretically) are having more weight forward (I currently don't have ENOUGH weight forward) and the possibility of the deck catching on the water if you are in a nearly pitch-pole position with the nose down, flying down the face of a wave.

So far, the disadvantages haven't been an issue for me at all. In fact, my bows rise up very quickly (too quickly) and the forward part of that bridgedeck doesn't even come close to hitting, even in very steep, choppy stuff running dangerous inlets in FL. The bows just went skyward when I ran into those dangerous standing waves, head on.
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Old 04-05-2008, 05:42   #3
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Our Prout has a solid foredeck.

First the upside. Easy to move around when anchoring, mooring or docking. Great "patio" for enjoying sunsets or guests aboard. Two nice lockers where fenders, propane, second anchor, spare dinghy gas, anchor bridle, trash for later disposal, etc. can be stored.

The down side. When going to weather in choppy conditions she bangs. If going to weather in moderate to heavy conditions, she SLAMS. There have been times it felt like someone picked her up and dropped her in a parking lot. The rigging vibrates like crazy. While the boat is rugged as h**l and can take it, it is not easy on the crew.

When going to weather, we "detune" or reduce sail so we are not sailing as hard (read as fast) so that we don't get such a jolt.

Recently while southbound in the Bahamas another cat took a photo of us under Genoa only in mild chop. You can see how the solid deck has captured the sea and is spraying it forward of the boat.


If the thumbnail doesn't take you to the picture try going to http://www.stateham.com/sunspotbaby/...NearELSP01.jpg

As a cat with a tramp runs into the sea they pick up buoyancy as they get deeper in the water. The bow will rise with the wave, usually before the bridge deck slaps the water. With the solid fore deck the bottom strikes the sea much earlier and, trapping the water spews in forward.

Now, having said all that, all boat features have pluses and minuses. We love our little Prout. She has taken us on some wonderful adventures and will do so for many years to come.

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Old 04-05-2008, 05:43   #4
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Little Otter, there are some advantages/disadvantages to both designs (and indeed, there is a third possibility found on my boat and some others: netting forward, with a solid frp walkway to the dolphin-catcher/furling gear). On the other hand, the pendulum has clearly swung and solid fordecks are now primarily used only in smaller cats (eg., Gemini).

Netting between the bows does reduce weight forward (an advantage in terms of performance/motion) and anchoring arrangements are available either at the forward end of the bridgedeck, or at the bows that eliminates the requirement of setting anchor from the net itself. On the other hand, solid foredecks can create a more solid structure - although with the advent of finite stress analysis and years of experience in the boating industry, they are unnecessary for that purpose.

Are solid foredecks unseaworthy in extreme condition (ie, do they substantially increase the risk of pitchpoling)? If the boat is properly designed, absolutely not - just witness the incredible number of Prouts that have and are still circumnavigating.
Especially if you are buying used and on a limited budget, then so long as the anchoring arrangement was appropriate, a solid foredeck would be neither a must-have, nor a deal-breaker.

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Old 04-05-2008, 06:10   #5
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George! Enighten me please!

Your picture shows *exactly* the motion that annoys me on my cat. The bows are leaving the water in a very calm sea state. Why?? Is that normal? Is this annoying motion something I need to get used to?

Also, looking at your boat in the water, I see it seems to rock fore and aft on the same axis as mine. Doesn't it feel as if when the bows go up like in your photo, the axis of rotation for the pitch is not centered on the boat, but too far aft?

The motion your cat has in the photo is *exactly* the bow motion I'm looking to correct, even though I haven't had any big splashes like that - don't know what our bridge deck clearances are for comparison.


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Originally Posted by Sunspot Baby View Post
Our Prout has a solid foredeck.

First the upside. Easy to move around when anchoring, mooring or docking. Great "patio" for enjoying sunsets or guests aboard. Two nice lockers where fenders, propane, second anchor, spare dinghy gas, anchor bridle, trash for later disposal, etc. can be stored.

The down side. When going to weather in choppy conditions she bangs. If going to weather in moderate to heavy conditions, she SLAMS. There have been times it felt like someone picked her up and dropped her in a parking lot. The rigging vibrates like crazy. While the boat is rugged as h**l and can take it, it is not easy on the crew.

When going to weather, we "detune" or reduce sail so we are not sailing as hard (read as fast) so that we don't get such a jolt.

Recently while southbound in the Bahamas another cat took a photo of us under Genoa only in mild chop. You can see how the solid deck has captured the sea and is spraying it forward of the boat.


If the thumbnail doesn't take you to the picture try going to http://www.stateham.com/sunspotbaby/...NearELSP01.jpg

As a cat with a tramp runs into the sea they pick up buoyancy as they get deeper in the water. The bow will rise with the wave, usually before the bridge deck slaps the water. With the solid fore deck the bottom strikes the sea much earlier and, trapping the water spews in forward.

Now, having said all that, all boat features have pluses and minuses. We love our little Prout. She has taken us on some wonderful adventures and will do so for many years to come.

George
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Old 04-05-2008, 08:06   #6
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Sully:

EVERY boat on the water was hobby horsing on this day. Cats and monos and the poor trawler drivers were going every which way. In the picture, it doesn't look bad, but the wave period must have been just right to irritate anything in the 35' to 45' range.

The Lagoon 38 that took the picture was actually up and down more than us, but not banging forward. When the solid foredeck hits the water she stops going pitching forward abruptly.

George
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Old 04-05-2008, 15:35   #7
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Thanks, George, for the input.

This is the kind of sea that was irritating me in my current cat and it was performing exaclty like yours.

My 45' Gulfstar would eat that sea up all day long without so much as a splash. It would sit like a rock, nice and level riding up and down the waves like you were in an elevator, not on a rollercoaster. It often would bridge the gaps and go almost "crest to crest."

Could some of my issue just be that I'm now on a boat with a smaller waterline?

Could it be I have much less displacement?

Could it also be that I'm waaaay out back now instead of located in a center cockpit rising and falling with the boat's center of well.. everything?

Lastly, I see your boat is pitching on an axis about where your mast, or your companionway door is located. This is *not* the center of the boat. Does this irritate you? Do you feel you don't have enough weight in the bows in that case?

AM I F'N CRAZY??? ha ha ha

If any cat people want to chime in with theory, it would be greatly appreciated!

This photo captured exactly what was bothering me about the motion of my cat into seas of the same type.
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Old 04-05-2008, 17:57   #8
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Well your new boat is what, 11 or 12 feet shorter than the old one? Realistically you have to expect it to move around a bit more - especially pitching, where waterline length makes a big difference.

Also your boat appears to have a fair amount of rocker below the waterline. To my knowledge, most modern designers have moved away from this, making the ends of the boat more bouyant by comparison.

If it is a real problem to you, I would be doing everything I could to centralise the weight. Try to resist the temptation to put a lot of weight in the bows - it's better that the bows rise to the waves, even if it seems too much, than if they dont rise.
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Old 04-05-2008, 19:45   #9
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The photo might appear that we are pitching on an axis at about the mast, but when she pitches it feels forward of the mast, more on the center-line of the boat.

Sunspot Baby is a very comfortable boat under most conditions. Don't try to draw too much from a single photo.

I am heavily loaded for a 6 month cruise in this photo and am heavier fore and aft than I would like to be. Everything is a compromise. You would not want to be more heavy in the bow than Sunspot Baby is in this photo.

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Old 04-05-2008, 20:49   #10
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Solid foredecks...

Because of weight, windage, and the general mindset of the designer who does this, cats with solid decks over the entire length of the boat will often have poor sailing performance. There may be an exception but I have not heard of it. However, I doubt it will cause any additional wave slap at anchor.
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Old 04-05-2008, 21:57   #11
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I would ask Dave of Maxing Out if he has had any problems with his Privilege 39 with the mostly solid foredeck.

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Old 05-05-2008, 03:01   #12
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The main reason not to have a solid foredeck is not slamming , how about getting a wave on top of the trampoline area with 3 or even 5 tons of water that can slowly get away. In my feeling having a solid foredeck is more dangerous, this offcourse only counts if you travel the worlds oceans in all conditions.
A Privilege 39 for instance is a very good Cat but it does have this problem.
The added ( up front where you do not want it ) weight of around 5 % extra also counts .

My 2 cents worth

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Old 05-05-2008, 05:15   #13
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Thanks for the info, guys. That's why I'm asking. Maybe I'm just used to the other type of motion on a larger LWL boat.

Gideon: I think the designers modify the boat's bow shape/entry and general balance to account for the theoretical 5% weight added by a solid foredeck. I would highly doubt they take a catamaran design such as yours, which does not have a solid foredeck, then add 5% weight up forward without any modification to the design. The entire boat is designed to have that weight there, as yours is designed to have trampolines there.
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Old 05-05-2008, 07:54   #14
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I would ask Dave of Maxing Out if he has had any problems with his Privilege 39 with the mostly solid foredeck.

David
Privilege cats do have a lot of deck up foreward but I wouldn't consider it a solid foredeck. Because it isn't. There are tramps! Good example though!

I think the Privilege is halfway between the two.
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Old 05-05-2008, 08:20   #15
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Privilege cats do have a lot of deck up foreward but I wouldn't consider it a solid foredeck. Because it isn't. There are tramps! Good example though!

I think the Privilege is halfway between the two.

The Dean 441 is also similar in that it has two very small tramps. The point made to me by Dean was that a solid foredeck offers more buoyancy to stop the bow digging in. I still prefer big tramps offering less weight and if ever swamped more chance to get rid of the water quickly.
I think a case can be argued for both sides.
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