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Thread: Why a bridge deck

  1. #1
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    Default Why a bridge deck



    The photo shows that I had Meg made with no bridge deck and a companionway sill as high as the deck. My reasoning was that a bridge deck is no stronger against a boarding sea - I've seen units that would be actually weaker - and they introduce a more dangerous entryway.

    Thoughts?

  2. #2
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    Default Re: Why a bridge deck

    On a bigger boat such as Meg I totally see your reasoning. On smaller boats, I like them for a couple of reasons:

    1: They create very useful stowage space in the cabin for cooler or porta-potti.

    2: A person can lie athwartship in the cockpit when the boat is heeled and someone else is at the helm.
    -Dave

  3. #3
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    Default Re: Why a bridge deck

    They also make for a stronger hull.

  4. #4
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    Default Re: Why a bridge deck

    Bridge decks I've experience may have a deck beam at the companionway end but rarely another at the aft side, based on the assumption that the bridge deck itself is as good or better than a beam. Many bridge deck installations I have seen have no deck beam, based on the assumption that the deck provides the strength. This may or may not be true in a given boat, but a properly made sill landing on a deck beam is every bit as strong.

    My big beef against bridge decks is that you have to step up before you step down. In dire conditions this can be a challenge. Some bridge decks solve that problem by being too narrow to lie down on, but easy to step over. That was the case in all of my previous boats. Hardly an improvement.

    The strength of the hull in the way of the cockpit is mostly carried by the wash decks, just as it is over the cabin area. Hard for me to see how a deck over one frame bay makes much difference unless there is also a deck stepped mast piercing it.

    And that can be solved. The pic does not show the mizzen, which is stepped closely ahead of the binnacle. That hole between the hatches connects to a impressive structure.

    Woxbox has a point if the bridge deck is wide enough. Somewhere in Meg's planning I abandoned all lying down while the boat was heeled. Radically so as you will notice that there are no cockpit combings. Always had taken them for granted as necessary but increasingly found them simply something to trip over, leaving too narrow a space for intimate maneuvers, not really keeping water off the seats, and not providing real back support anyway. So . . . done.

    Cockpit combings for boats with seats below deck level can benefit from combings, especially if they have a cap rail large enough for comfortable sitting.

  5. #5
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    Default Re: Why a bridge deck

    Quote Originally Posted by ahp View Post
    They also make for a stronger hull.

    Agreed. Here are the two bridge deck beams in my catboat. They are the only continuous deck-level athwartship timbers between the foredeck and the after deck. In this case the centernoard trunk is well reinforced by the forward timber. In a situation such as the boat pounding on a bulkhead these timbers reinforce the hull where it counts.

    The bridge deck itself provides a good space for the engine and various tanks.

    As mentioned, it's a good lounging place.

    And in a catboat the bridge deck reduces the volume of the cockpit, as in only seven tons of water will fit instead of ten.

    They're a pain to build, though as there's just that many more corners to keep tight


    Jim



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    Default Re: Why a bridge deck

    The built-in bridgedeck cooler on Avenger could hold 100 cans of beer easily with room left over for ice if required. Much less disturbance below for the off-watch crew. Seemed to work great for that, imho. / Jim

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    Default Re: Why a bridge deck

    Woxbox caught it for me.
    Its also a nice setting area for dishing out food from the galley.

    As for combing, I think you're right in most respects, but it makes a great solid handhold. I'd keep it just for that.
    It also creates a clear border when needed - beyond which you must be clipped on!
    It's all fun and games until Darth Vader comes.

  8. #8
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    Default Re: Why a bridge deck

    Quote Originally Posted by Ian McColgin View Post


    The photo shows that I had Meg made with no bridge deck and a companionway sill as high as the deck. My reasoning was that a bridge deck is no stronger against a boarding sea - I've seen units that would be actually weaker - and they introduce a more dangerous entryway.

    Thoughts?
    I can see how this arrangement, with the high companionway sill, allows for a continuous deck beam across the hull at two spots.

    I'd be interested to know how the flush hatches work, drain-wise. I've decided against a flush hatch due to the difficulty of keeping them watertight against spray and rain.


    jim

  9. #9
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    Default Re: Why a bridge deck

    I added a bridge deck to have another bulkhead reinforce the bilge keel stringers. An added benefit is a nice place sit athwartships, and the space below provided a foot well and storage to the small cabin. Since this has shallow draft and firm bilges, step down is not an issue.
    In my older cruising boat the bridge deck reduced cockpit volume, but this boat should not get exposed to those type of seas.
    Steve B
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    "If a man must be obsessed by something, I suppose a boat is as good as anything, perhaps a bit better than most." E. B. White

  10. #10
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    Default Re: Why a bridge deck

    all the vessels pictured/mentioned are way larger than my little girl and they impose different issues needing kneading...

    the bridge deck in my current project a Michalak AF-3 will provide a perfect location for the battery

    thumbnail-4.jpg

    centered on the bottom side to side and fore n aft at the deepest point in the hull

    a full sized battery is needed to power the APAP machine as well as running lights

    though it does take up cockpit space the interior location doesn't consume "cabin space" which is most certainly at a premium

    the location of this bridge deck just happens to provide a seat for rowing if/when needed

    and if/when i lay the little girl on her side the battery weight should help me get her mast pointing back up to the sky

    bridge deck ?

    they have different meanings/uses for different folks

    sw
    "we are the people, our parents warned us about" (jb)

    steve

  11. #11
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    Default Re: Why a bridge deck

    Meg is not a deep water sea boat though Ian, is she ?
    So, bridge deck or not, I think it has more to do with convenience. Engine under? Ideal place for a built in cooler? Or a shortcut to a bad tumble down the companionway?
    bruce

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    Default Re: Why a bridge deck

    Quote Originally Posted by Ian McColgin View Post

    Woxbox has a point if the bridge deck is wide enough. Somewhere in Meg's planning I abandoned all lying down while the boat was heeled. Radically so as you will notice that there are no cockpit combings. Always had taken them for granted as necessary but increasingly found them simply something to trip over, leaving too narrow a space for intimate maneuvers, not really keeping water off the seats, and not providing real back support anyway. So . . . done.
    "intimate maneuvers"? And here I thought we were a family friendly forum...

    I've been thinking a lot about what my "next boat" will be (a project that is a few years off but thinking about it is a form of meditation for me) and realized one of the attributes I want to carry forward from Marianita is her deep cockpit and resulting seats. There is a little step up through the companionway but it has a hinged lid and acts as storage for the washboards and some safety equipment. I like the deep seat arrangement, it keeps me out of the weather. When it got too hot yesterday (close to 90) to keep hanging siding on the house I went sailing. The 5-10 knot northerly was pretty brisk after blowing across 55 degree water between Whidbey and Bainbridge.
    Steve

    If you would have a good boat, be a good guy when you build her - honest, careful, patient, strong.
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  13. #13
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    Default Re: Why a bridge deck

    A bridgedeck adds a lot of strength against torsional wracking of the hull, but only with a good beam at each end and even better with ply decking as it can take shear loads. Otherwise the house and cockpit make one big opening (break in the deck beams) nearly from one end of the hull to the other. A bridge deck is a good way to break that up with some full beams and get a lot more stiffness.

    It can be designed around, but that is generally the reason for them. Plus they provide clearance for the engine on many designs.

  14. #14
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    Default Re: Why a bridge deck

    Back in 'the day', with traditional building methods, strength was a big deal. Builders and designers worked hard to build a strong structure with the materials at hand. Heavy, 'half tide' boats that were low and narrow also frequently had to deal with solid water coming aboard. For boats built to go offshore, a bridge deck really was essential. It also reduced the size/volume of the foot well or cockpit so that less water had to be cleared down the scuppers before being swept again by the next wave.

    For boats, especially small ones, that are lighter and stiffer with the use of epoxies, plywood and modern grid type build, a bridge deck becomes a traditional feature which we sailors tend to let go of so slowly. When I sailed both my Herreshoff America catboat (yup, snot, but nice snot) and my Yankee One Design, I hugely valued the absence of the bridge deck. I will go a long way to avoid having to have another one on a small boat especially. Ian has been around long enough to recognize the downsides of one. In fact, those of us who've been 'around' a while, find that the physical requirements of negotiating them have begun to detract from our enjoyment of the boat.

    One final note, we often envision and re-tell ad nauseam, of the dangers of cockpits full of tons of water. My thoughts are that IF you can even remember an occasion where you were sailing and those 'tons' of water filled your cockpit, may I suggest that providing you still sail those same waters and weather/sea conditions, you should by all means have a bridge deck. Me? Never seen it. I don't sail in seas nor weather where I am likely to see it and would especially have not plans to do that in a center/dagger board small sailing craft (other bad things happen before the cockpit fills...) But I have greatly enjoyed the protection and comfort of a deep cockpit with easy access into a small cabin. YMMV. My 'next' boat, won't have one...

  15. #15
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    Default Re: Why a bridge deck

    Quote Originally Posted by Woxbox View Post
    On a bigger boat such as Meg I totally see your reasoning. On smaller boats, I like them for a couple of reasons:

    1: They create very useful stowage space in the cabin for cooler or porta-potti.

    2: A person can lie athwartship in the cockpit when the boat is heeled and someone else is at the helm.
    Both of these reasons are why I added a bridge deck to my catboat. I wanted to retain that big comfortable catboat cockpit. The extra space it provides inside the cabin means I have a full 7-foot berth on a 14-foot boat.

    Bridge deck.jpg

  16. #16
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    Default Re: Why a bridge deck

    Massive bridgedeck on Riada, a real pia for access.
    Suddenly it became extremely valuable on the 13th of October last year, 3 days after we arrived in from Fiji ,when the Essence was lost 20 miles off the coast after doing the same passage. Reading the accounts at the time and again recently it's pretty clear to me she was downflooded from the cockpit after a knockdown and that very probably caused her loss.
    Ours makes a quarter berth cabin below and a nav station, so it's important to our layout as well.
    I'm thinking our knees just have to keep liking the hurdle.

  17. #17
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    Default Re: Why a bridge deck

    Quote Originally Posted by Dryfeet View Post
    Back in 'the day', with traditional building methods, strength was a big deal. Builders and designers worked hard to build a strong structure with the materials at hand. Heavy, 'half tide' boats that were low and narrow also frequently had to deal with solid water coming aboard. For boats built to go offshore, a bridge deck really was essential. It also reduced the size/volume of the foot well or cockpit so that less water had to be cleared down the scuppers before being swept again by the next wave.

    For boats, especially small ones, that are lighter and stiffer with the use of epoxies, plywood and modern grid type build, a bridge deck becomes a traditional feature which we sailors tend to let go of so slowly. When I sailed both my Herreshoff America catboat (yup, snot, but nice snot) and my Yankee One Design, I hugely valued the absence of the bridge deck. I will go a long way to avoid having to have another one on a small boat especially. Ian has been around long enough to recognize the downsides of one. In fact, those of us who've been 'around' a while, find that the physical requirements of negotiating them have begun to detract from our enjoyment of the boat.

    One final note, we often envision and re-tell ad nauseam, of the dangers of cockpits full of tons of water. My thoughts are that IF you can even remember an occasion where you were sailing and those 'tons' of water filled your cockpit, may I suggest that providing you still sail those same waters and weather/sea conditions, you should by all means have a bridge deck. Me? Never seen it. I don't sail in seas nor weather where I am likely to see it and would especially have not plans to do that in a center/dagger board small sailing craft (other bad things happen before the cockpit fills...) But I have greatly enjoyed the protection and comfort of a deep cockpit with easy access into a small cabin. YMMV. My 'next' boat, won't have one...
    +1. Even in conditions that knock around one of the world's most decorated offshore classic racer/cruisers, these seas that fill a cockpit appear to be far rarer in reality than in tales.

    I'm one who agrees with Ian that coamings can be problematic (and neither of my yachts has them), but I demand a deck-height companionway for their value in extreme conditions, as John notes. It all seems like one of those issues that gets down to personal tastes and situations.

    Surely if one demands large coamings then one is dramatically increasing the amount of water that will be retained aboard, high up, and close to the companionway sill if the "cockpit filling wave" occurs. So if one is worried about the cockpit getting filled, shouldn't one consider reducing cockpit volume and coaming height? Personally, I love open transom cockpits which can't fill.
    Last edited by Chris249; 09-12-2020 at 04:16 AM.

  18. #18
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    Default Re: Why a bridge deck

    Quote Originally Posted by John B View Post
    Massive bridgedeck on Riada, a real pia for access.
    Suddenly it became extremely valuable on the 13th of October last year, 3 days after we arrived in from Fiji ,when the Essence was lost 20 miles off the coast after doing the same passage. Reading the accounts at the time and again recently it's pretty clear to me she was downflooded from the cockpit after a knockdown and that very probably caused her loss.
    Ours makes a quarter berth cabin below and a nav station, so it's important to our layout as well.
    I'm thinking our knees just have to keep liking the hurdle.
    I missed the bit about the height of her lower companionway sill. Was it lower than the sidedecks, and if not would a bridgedeck per se have added to her survivability?

  19. #19
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    Default Re: Why a bridge deck

    Quote Originally Posted by Chris249 View Post
    I missed the bit about the height of her lower companionway sill. Was it lower than the sidedecks, and if not would a bridgedeck per se have added to her survivability?
    I dont know if the lower washboard was in, it probably was. Survivabilty? Maybe not, or maybe. I think it may well have, buts that's just my opinion.

  20. #20
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    Default Re: Why a bridge deck

    I love the compass binnacle.!

  21. #21
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    Default Re: Why a bridge deck

    Course, I don't even have a cockpit footwell. All flush with a small cabin. One deckbeam on the whole boat cut.We sit on a "park bench" 18 inches above the deck. In the worst weather I'm not steering on deck, I'm in my bunk.

  22. #22
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    Default Re: Why a bridge deck

    Bruce, what is that pegboard arrangement - an adjustable stop for the tiller, or?

    Pete
    Like a miracle, all the trolls disappeared

  23. #23
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    Default Re: Why a bridge deck

    As Dave, Jim and Mike describe, for this 6 m dayboat/pocket cruiser, the bridgedeck provides storage from both the cockpit and cabin sides, structural support of the CB case, flotation chambers, and cockpit seating. I think for this design, benefits outweigh potential impediment to the cabin.

    4A7D5D24-ABA9-4E49-85D8-E533816CEB7D.jpg

  24. #24
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    Default Re: Why a bridge deck

    Quote Originally Posted by epoxyboy View Post
    Bruce, what is that pegboard arrangement - an adjustable stop for the tiller, or?

    Pete
    Yes, Tiller comb.
    She is underway here (above) with the monitor steering ,so they are pinned at the ends , out of the way.
    My 24'er (below) has one too. The 24'er also has a bridgedeck,but no decent photo

    oh look, back in the days when we flew an American flag....haven't done that since Trump.

  25. #25
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    Default Re: Why a bridge deck

    I agree that with a deep cockpit side benches that are 90 degrees seat to back and canted about 7 degrees out are wonderful. The Golden Ball design allows for cockpit combing that's too low for back support, which I rarely want when sailing anyway.

    One of Meg's strength features is her three water tight bulkheads, two of which are in frame for my pic - aft end of main cabin and forward end of after berth. (Had to call that cabin just that.) So the engines are separated from the rest of the boat.

    The hatches and seat hatches all have oversized gutters with big drains. No amount of heavy rain has gotten in and the amount of seep past in the 3 minutes it should take for the cockpit to drain from full will be acceptable. All hatches are locking so they won't float open.

    I've yet to do my home stability test to find the angle of diminishing resistance to heeling.

  26. #26
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    Default Re: Why a bridge deck

    More pictures of Meg please. And a video tour!

  27. #27
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    Default Re: Why a bridge deck

    Quote Originally Posted by Dave Hadfield View Post
    More pictures of Meg please. And a video tour!
    Yep, need more Meg.

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