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Thread: cabin construction advice needed

  1. #1
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    Default cabin construction advice needed

    Im at the stage of fitting the cabin beams in.

    I would like some advice trying to determine what amount of headroom I can expect in the boat given she has a draft of 4-6" and I have already laid the cabin sole flooring (as low as reasonable).

    Andrew is 5-10" so I would like to give him some head height in the the cabin. The cabin beams will be 2" x 2" laminated.

    Im thinking Im going to have to give the cabin beams a bit of curvature to get the head height central but obviously lose a bit of height outboard.

    I dont want the cabin looking like she has a 'turtle back' but feel a though some 'shape' is necessary to achieve a liveable space below decks.

    Im sure I already posted about the cabin beams etc but Im not going to use the ones I have already laminated as the curve is too flat which means the cabin sides are way too high and the cabin looks way too darn boxy.
    Last edited by Bernadette; 03-29-2020 at 12:38 AM.

  2. #2
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    Default Re: cabin construction advice needed

    Sounds like you've mocked it up? Some battens and scrap ply are probably more helpful than we can be.

    A trick to lower the apparent height of the cabin trunk is a moulding along the top edge.

    Another trick is to heavily curve the cabin top to side joint and add a trim piece lower. Kind of like this.


  3. #3
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    Default Re: cabin construction advice needed

    Something Sparkman and Stephens (Aage Nielsen at the Boston office?) did was make the cabin top beams more of an ellipse than an arc of a circle. So flatter in the middle and more curve at the ends. This makes the cabin look less boxy.

  4. #4
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    Default Re: cabin construction advice needed

    thanks Steven. I think thats been part of my problem: making the beams an arc of a circle.

  5. #5
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    Default Re: cabin construction advice needed

    You know the two stick method for scribing the camber? I'm sure there is a good pic around here somewhere. Two stick, two nails, a bit of ply gusset, and a pencil. It gives you the ideal arc- which is not a section of a circle.

    Use it to scribe right on your beam pattern. I'll post a pic if I can find one.

  6. #6
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    Default Re: cabin construction advice needed

    the one thing I do want to get some idea of is, what sort of usable space under the cabin I can expect to get given the dimensions I have.
    without having other 30 footers about to give me some idea, Ive taken a look at yachts on the internet but the images just aren't as good as the real thing.

    Im also giving some thought to sweeping the cabin sides parallel with the deck line. I would normally run this through on a horizontal line.

  7. #7
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    Default Re: cabin construction advice needed

    just curious...what size is this yacht, and her beam?

  8. #8
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    Default

    That's confusing.

    Sent from my CPH1851 using Tapatalk

  9. #9
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    Default Re: cabin construction advice needed

    Here is a standard method of creating a camber:

    Screenshot 2020-03-29 at 05.29.38.png

    Depending on the style of the boat – traditional – modern – etc., "A" as a percentage of the total width "L" can be between 4% and 10%.

    "A" used to be expressed as x" in 1', and still is often referred to that way, specially in the US. So a common camber would be " in the foot which is just over 4%.

    While 10% seems a lot, I regularly use 8% or 9% cambers on coachroofs. In practice it doesn't look excessive and it enables you to keep the coachroof coamings a bit lower and not look so boxy. The camber doesn't really contribute so much visually to the height of the superstructure because it's not like a hard edge or line - but a 3-dimensional curve spread over an area that has a lot of other bits on it – hatches, ventilators, mast, handrails etc etc.

    Also, when heeled at sea, a larger camber can be easier to work on (to windward at least) than a flatter one because it tends to feel nearer to level.

    The camber formula given above will produce a different shape for each beam, unless the cabin coamings are parallel. It will however produce a surface that ply can be laid on relatively easily – i.e. it produces a developable or near-developable surface. This will be true with curved coamings with either a straight top edge or a curved top edge (looked at in profile)

    If you are thinking of sweeping the coamings with the deck, a common setup is to make the sidedeck width narrower aft, gradually getting wider as you go forward. This usually looks right and is practical as it gives you better sidedeck width as you move forward. You could, say on a 7m sailboat, start at 150mm to 200mm aft by the cockpit, widening to about 400mm forward.

    Cheers -- George
    Last edited by debenriver; 03-29-2020 at 04:56 AM.
    To be truly free to live, one must be free to think and speak.

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  10. #10
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    Default Re: cabin construction advice needed

    On my smaller project (20.5') I plan on eliminating the cabin beams by laminating the top, squeezing in a couple more inches of sitting room. Also it will have a rolling, or changing, camber. This is the mold that I used when building a much smaller cabin for a sharpie:
    Steve B
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  11. #11
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    Default Re: cabin construction advice needed

    As Steve B says - you can also laminate the coachroof top. This works best with a reasonably heavy camber - say 7% to 10%.

    Our 30' Naja class sailboats had a laminated beamless coachroof construction – 3 layers of 4mm ply laminated on a jig. The camber was about 8% as far as I remember. So did/does our Sapphire 27' class.

    We used extended hatch runners to make external coachroof runners that ran fore-and-aft the whole length of the coachroof. These were about 70mm high, 45mm at base and tapering to 35mm at top. They work very well - they stiffen the cabin top and make great footholds when working on the top at sea.

    I use this system on most of my current designs so that the cabin beams are just those that occur on ring frames - no intermediate beams.

    It is all a question of breaking up the panel areas of the roof – and this can be done internally or externally, or a mix of both.

    George
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    A C Grayling

  12. #12
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    Default Re: cabin construction advice needed

    Quote Originally Posted by debenriver View Post
    Here is a standard method of creating a camber:

    Screenshot 2020-03-29 at 05.29.38.png

    Depending on the style of the boat – traditional – modern – etc., "A" as a percentage of the total width "L" can be between 4% and 10%.

    "A" used to be expressed as x" in 1', and still is often referred to that way, specially in the US. So a common camber would be " in the foot which is just over 4%.

    While 10% seems a lot, I regularly use 8% or 9% cambers on coachroofs. In practice it doesn't look excessive and it enables you to keep the coachroof coamings a bit lower and not look so boxy. The camber doesn't really contribute so much visually to the height of the superstructure because it's not like a hard edge or line - but a 3-dimensional curve spread over an area that has a lot of other bits on it – hatches, ventilators, mast, handrails etc etc.

    Also, when heeled at sea, a larger camber can be easier to work on (to windward at least) than a flatter one because it tends to feel nearer to level.

    The camber formula given above will produce a different shape for each beam, unless the cabin coamings are parallel. It will however produce a surface that ply can be laid on relatively easily – i.e. it produces a developable or near-developable surface. This will be true with curved coamings with either a straight top edge or a curved top edge (looked at in profile)

    If you are thinking of sweeping the coamings with the deck, a common setup is to make the sidedeck width narrower aft, gradually getting wider as you go forward. This usually looks right and is practical as it gives you better sidedeck width as you move forward. You could, say on a 7m sailboat, start at 150mm to 200mm aft by the cockpit, widening to about 400mm forward.

    Cheers -- George
    Hello George
    thanks for your reply. and yes,I know how to do this. its what Ive used. I just probably need to increase the camber height thats all.
    interesting comment about side deck width though, getting wider moving forward. it would be a nice design touch. however, ive set my side decks parallel to the sheer. they are good and wide so im happy with what ive got there. I think you are spot on when you describe the camber not contributing so much visually to the height. On my build I figured that even with the skylight, mast, handrails and port lights, the cabin height and relative low camber profile, it just looked too boxy. Im back in the shed again tomorrow and will experiment with some camber battens before proceeding. I do plan on building in my beams rather than laminating the cabin top.
    Last edited by Bernadette; 03-29-2020 at 05:31 AM.

  13. #13
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    Default Re: cabin construction advice needed

    Quote Originally Posted by J.Madison View Post
    You know the two stick method for scribing the camber? I'm sure there is a good pic around here somewhere. Two stick, two nails, a bit of ply gusset, and a pencil. It gives you the ideal arc- which is not a section of a circle.

    Use it to scribe right on your beam pattern. I'll post a pic if I can find one.
    This is a great method. I think bud's book has a good diagram.

  14. #14
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    Default Re: cabin construction advice needed

    I had similar questions about a boat I've been thinking about building. Since I have the plans I used masking tape on a wall to roughly draw out one of the midship stations. Use the floor (or ground if outside) as the cabin sole height. Quick and easy you have a full-sized line drawing of the interior, at least at that point, which should give you a pretty good sense of what might need adjustment.
    Dashed line is my current boat for comparison
    Last edited by stromborg; 03-29-2020 at 01:56 PM.
    Steve

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  15. #15
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    Default Re: cabin construction advice needed

    Historically not all boats are designed with full standing head room! With the galley under the sliding scuttle hatch there is usually full headroom with the hatch slid open. Forward of that should be a pair of settees or bunks that provide sitting heard room which are sat on or laid down on.
    From a personal point of view, none of the boats I have ever owned have had full head room. Our H28 has what is desribed above and I have never needed more as my wife Annie is 5'2" and as long as she is happy, I am too! Some Tuesday next week, I might add a tan canvas dodger like this to our H28 so I can cook in the rain without getting wet.
    Jay

  16. #16
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    Default Re: cabin construction advice needed

    thanks Jay I appreciate the calming influence of your words! I think im just used to standing head room throughout the entire cabin on my two previous yachts and was trying and thinking I ought to build this new one to achieve the same. anyhow, with some thought overnight im pretty much settled on a course action to achieve a compromise.
    nice boat ^ by the way!!!

  17. #17
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    Default Re: cabin construction advice needed

    hey steve, your idea is a good one! I probably could have done as much myself!

  18. #18
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    Default Re: cabin construction advice needed

    Here’s an Aage Nielsen coach roof.


    If you need another couple of inches, a cold-molded coach roof might make the difference.
    You might even consider going high-tech with structural foam core and glass. It’s a very good place to reduce weight.
    Last edited by JimConlin; 03-29-2020 at 05:38 PM.

  19. #19
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    Default Re: cabin construction advice needed

    Brookman offers one solution that many builders use to get a couple inches more at the same height but they often run fewer beans parallel to centerline and larger beams aren't much of a problem run fore and aft. If its a smallish boat, I get along fine with less than full headroom as most getting about on a small boat is done in a partially bent over fashion anyway. 5 1/2 feet plus a decent hatch and cooking area placed well together is also a big help.
    Tom L

  20. #20
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    Default Re: cabin construction advice needed

    I remember reading somewhere that that you should either go tall, as in 6'-2" or more or keep it under 5'-6" the range in between is where people are likely to forget and bang their heads.
    Steve

    If you would have a good boat, be a good guy when you build her - honest, careful, patient, strong.
    H.A. Calahan

  21. #21
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    Default Re: cabin construction advice needed

    Quote Originally Posted by stromborg View Post
    I remember reading somewhere that that you should either go tall, as in 6'-2" or more or keep it under 5'-6" the range in between is where people are likely to forget and bang their heads.
    I think this is the best advice. Either have standing headroom or not. I have been on far too many production boats with around 6 ft of headroom and I invariably hit my head on a beam or something. I do not ever recall banging my head on a boat that one has only sitting headroom.

  22. #22
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    Default Re: cabin construction advice needed

    I served in the submarine service. We had all manner of things that would jump out and bite you aboard. We just got used to navigating through the boat and never gave it a thought once we did!
    Jay

  23. #23
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    Default Re: cabin construction advice needed

    Quote Originally Posted by Jay Greer View Post
    I served in the submarine service. We had all manner of things that would jump out and bite you aboard. We just got used to navigating through the boat and never gave it a thought once we did!
    Jay
    2 1/2 years on a destroyer taught me how to avoid steel stuff that could lay an unsuspecting guy low as well. A fleet sub was much tighter than even a destroyer but neither are clearly not built to provide promenades for a crew. Running to GQ can be as dangerous as the action.
    Tom L

  24. #24
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    Default Re: cabin construction advice needed

    Nice to know you were once on a "Tin Can" Tom! During fleet maneuvers we raised our scope under a Destroyer and bent the hell out of our #2 periscope! The skipper said that all he saw was rivets!
    Jay

  25. #25
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    Default Re: cabin construction advice needed

    building the cabin is kind on hold again as I leave to head back to work on Friday (via a 14 day mandatory isolation period)...
    Im not sure what I will do about the cabin and really the time isn't right just now with so many other things happening.
    im going to have to decide to perhaps just lower only the forward end of the cabin and keep with my original beams. I did in fact raise it to its current height so going back to my original marks on the height might be prudent.
    Or I will lower the entire length of the cabin and rebuild new beams with a deeper camber.

    thanks all for your input.

  26. #26
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    Default Re: cabin construction advice needed

    How to build the cabin is very much a matter of personal taste. In my view the percent rise in many cabin tops (and decks for that matter) is too small. I've never seen too much curve, but have definitely seen plenty which look way too flat. Go with 10% as a minimum, more might be ok. Mock it up and see what you think. Also go for a proportionally greater rise in the cabin roof than what was used for the deck. If standing headroom is not achievable within the limits of what is aesthetically pleasing, consider alternative options such as taking Jay's suggestion a bit further with an extra long sliding hatch over your companion way, or perhaps a two part hatch such that the opening is small for use at sea, but can be opened further for use at anchor. A boom tent at anchor will keep the weather out if you want a really big hatch.

  27. #27
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    Default Re: cabin construction advice needed

    Small boats rock, offers some good advice that I very much agree with as to making a mock up of the deck house and setting it in place! That is something we normally do for a new design or modification. A mock up will save all manner of grief and regret later on down the line! I do like your decision to retain the deck beams in the house as they will serve the needed purpose of transferring loads and moments of torque from one side of the boat to the other thereby keeping the form of the boat in better configuation as the hull attempts to twist or distort when underway! Plus they will offer great aid in keeping the coach roof from oil caning when weight is placed on it. One other thing is that traditional tongue and groove box car siding staves are easy to lay on a crowned surface, can be pre-painted and just look darn nice, when viewed from the underside.
    Jay

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    Default Re: cabin construction advice needed

    Not sure exactly where you are in this but I would use battens to give you a basic visual and take measurements down to the cabin sole with. I actually prefer the "turtle back" look myself. I am partial to sea turtles and have always felt that the shape of their backs isn't out of place in a cabin top personally. Both my Tartan and the Malabar Jr. have a nice arc to the cabin top and I think it suits the designs perfectly. Although "there is no accounting for taste" as my Scottish Gram always used to say. Also I second Jay's advice about the beadboard (I think we are talking about the same thing) I am planning on using it to trim out the interior of my Malabar hull.
    Last edited by MalabarJr; 03-31-2020 at 11:53 PM.

  29. #29
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    Default Re: cabin construction advice needed

    ^Thanks for the comments everyone. I appreciate the input.

    Essentially I've got the fore and aft laminated beams in situ and the 4 cabin sides in place. I've laminated up the rest of the beams (all are 2" x 2") in preparation to build in but have obviously stopped short of proceeding due to my query about what amount of head room a boat of this size will afford her crew. The beams in way of the mast, skylight and companion way hatch will remain full size whilst the intermediate beams will likely get dressed down to a smaller width.

    I plan to line the underside of the cabin top with a nice lightweight (featured timber: probably use up some Huon Pine I have left over) panelled veneer which will be bright worked. I am constructing the cabin using marine ply on the sides and overhead and these get 'dressed' up in the interior. Boards measuring say 4 or 5" in height for the cabin sides and smaller boards (maybe approx up to 1 5/8" wide) for the overhead between the beams. I will run the router over the top edge so the boards will fit in nicely. The exterior of the cabin will be glassed over and painted with a 2 pack polyurethane. Tough and durable.

    Dad is of the opinion the cabin is just right how I've built it thus far but Im not convinced: hence the angst with aesthetics. In any case I'll have a number of months to mull over my decision and will be doing a mock up with battens when I get back from my time away at work in the Northern Territory. I leave on Friday.

    I personally don't mind a bit of camber but would tend to to steer away form too much "turtle back".

    Im not inclined to be relying on the hatch opening or boom tents etc to keep weather out. I do understand and appreciate the advice though. However, I like to be able to close all hatches to keep weather out and still carry on down below with whatever needs doing especially when under way.
    Last edited by Bernadette; 04-01-2020 at 09:17 PM.

  30. #30
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    Default Re: cabin construction advice needed

    Since you are on a bit of a haidas you have a bit more time to think about your cabin, a cabin that will tell you what it wants when you are quiet and not brain storming! I also agree with you thoughts on the turtle back concept.
    Jay

  31. #31
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    Default Re: cabin construction advice needed

    Quote Originally Posted by J.Madison View Post
    Sounds like you've mocked it up? Some battens and scrap ply are probably more helpful than we can be.

    A trick to lower the apparent height of the cabin trunk is a moulding along the top edge.

    Another trick is to heavily curve the cabin top to side joint and add a trim piece lower. Kind of like this.

    Nice boat and, you are absolutely right about the coach roof moulding!
    Jay

  32. #32
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    Default Re: cabin construction advice needed

    we always put on a white beech (unpainted) trim just past the turn of the cabin top. it looks very "shipy".

  33. #33
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    Default Re: cabin construction advice needed

    Quote Originally Posted by Jay Greer View Post
    Since you are on a bit of a haidas you have a bit more time to think about your cabin, a cabin that will tell you what it wants when you are quiet and not brain storming! I also agree with you thoughts on the turtle back concept.
    Jay
    yes, I expect so!

  34. #34
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    Default Re: cabin construction advice needed

    Personally I like headroom on a boat! And hopefully you spend more time on the boat than you do looking at it. So it's better to be comfortable. For me the aesthetics, though obviously important, are somewhat secondary to function and comfort. If good headroom makes the boat more enjoyable for you – and it does for me – then go for it because you'll probably regret it otherwise. And a few extra inches height will get lost in the general 'clutter' of hatches, handrails and so on. Running the roof colour down the coamings a couple of inches and finishing on a moulding works well.

    Cheers -- George
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    A C Grayling

  35. #35
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    Default Re: cabin construction advice needed

    thanks George. I understand what you are saying...its always going to be a compromise...!

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