Raising Cabin Height on this Bertram

Discussion in 'Boatbuilding' started by crankit, Jun 30, 2023.

  1. crankit
    Joined: Oct 2007
    Posts: 30
    Likes: 0, Points: 6, Legacy Rep: 10
    Location: Aus

    crankit Junior Member

    Hi All,
    I'd like to raise the cabin height including vbirth roof on this Bertram 23 (Australian).

    I'm considering cutting the cap along the red line in the picture from midships to the bow and then raising the area 2 inches with jack bolts along the side and beveling in a layup consisting of 16 layers of 17oz double bias and epoxy.
    The thickness of the laminate along that area is 1/3 inch.

    How would you go about doing this??

  2. Darkzillicon
    Joined: Jan 2023
    Posts: 137
    Likes: 44, Points: 28
    Location: Palm Beach

    Darkzillicon Senior Member

    I have some concerns regarding the potential modifications you're planning. While the thickness of the laminate and the effectiveness of epoxy shouldn't pose significant issues, I believe the primary concern lies in the stability of the boat. It would be advisable to seek advice from a naval architect to assess whether the increased windage and cabin height might compromise the stability of the vessel. They can determine if adding some weight lower down would be necessary to maintain stability.

    To illustrate the importance of stability, let me share an anecdote about a friend who owned a 60-foot Bertram yacht. Despite its size, the yacht experienced severe rolling and snapping in rough seas, indicating poor performance. If you raise the cabin roof higher and increase leverage, similar stability issues may arise. Additionally, the increased windage could negatively affect maneuverability when docking. While it is certainly possible to proceed with the modifications, I strongly recommend seeking the approval of someone knowledgeable about your boat's stability. It's an investment worth making to ensure a safe and enjoyable experience.
    rwatson likes this.
  3. comfisherman
    Joined: Apr 2009
    Posts: 539
    Likes: 266, Points: 63, Legacy Rep: 10
    Location: Alaska

    comfisherman Senior Member

    I've cut up several boats to stretch and raise bulwarks, some solo and a few as a helper. Lesson learned is more jigs the better. I'd build some kind of internal frame with some diagonal support going from the centerline out on the cabin side. Also brace the remaining section. I'm always amazed at how far stuff can move with floors and bulkheads removed when separated.

    I'm not familiar enough with epoxy to comment, all the boats up here are vinyleater or poly and most get fixed with like kind.

    I'll say this 16 layers of 17 oz cloth seems... excessive. But it's a narrow section so probably a moot point.

    I'm not terribly worried about weight up top, 2 feet... yeah 2 inches... nah. Old Radars up high vs modern is probably the equivalence.
  4. bajansailor
    Joined: Oct 2007
    Posts: 3,465
    Likes: 1,432, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    Is it really worth your while to do all this work to gain an extra 2 inches of headroom in the cabin?
    Or would this mean the difference between being able to stand up inside, or not being able to?
    wet feet likes this.
  5. fallguy
    Joined: Dec 2016
    Posts: 7,469
    Likes: 1,619, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    A 2" lift like you are explaining would not be done with 16 layers of biaxial.

    You'd use wood and sheath it with a layer or two of db1200. The amount of work to do a quality laminate 16 layers thick is not justifiable for 2" of lift.

    I don't know how the cabintop is attached, but you ought to determine that first.
    ondarvr, wet feet and bajansailor like this.
  6. comfisherman
    Joined: Apr 2009
    Posts: 539
    Likes: 266, Points: 63, Legacy Rep: 10
    Location: Alaska

    comfisherman Senior Member

    I dunno my last build was a 32 foot workboat that in lieu of a house had a flybridge venturi. My proportions aren't quite right so at the base we made a cut all the way around after jigging it for support. Built an external mold from waxed hard board with wood reinforcement. ground back the glass and did overlap with what became 5 layers of 24 oz combi mat. In hindsight I'd of done a core instead of vertical ribs glassed in, but its been plenty stout so far. My lift was 8-9 inches in an application where a fair bit of green water lands on it, so far so good.

    Totally understand lifting a cab. My first boat had a ceiling height that was 7 inches shorter than I was barefoot. Decade in it was spend a bazillion lifting both levels or sell it to a normal person. Still see it from time to time, but don't miss the ache in the back and neck.

    Keep in mind even a few inches can throw off the look. My grandfather had one of the iconic small seine boats built to fit him. It's very easy to pick out in pictures... and not because 4 inched of cabin and 4 inches of flybride made it prettier.
  7. crankit
    Joined: Oct 2007
    Posts: 30
    Likes: 0, Points: 6, Legacy Rep: 10
    Location: Aus

    crankit Junior Member

    2 inches is pretty much the difference with being able to stand or slouch. I realise it's alot of work, but I've just replaced the transom, Stringers, floor, currently rebuilding the vbirth. I figured now is the time if I'm going to have a got at it.
  8. wet feet
    Joined: Nov 2004
    Posts: 1,295
    Likes: 368, Points: 83, Legacy Rep: 124
    Location: East Anglia,England

    wet feet Senior Member

    Have you considered simply increasing the camber of the wheelhouse roof?More headroom would result in the area and the amount of work is a great deal less.As it the amount of material and hence cost,Not to mention the retention of existing bulkheads and structure below.
    bajansailor likes this.

  9. kapnD
    Joined: Jan 2003
    Posts: 1,259
    Likes: 385, Points: 83, Legacy Rep: 40
    Location: hawaii, usa

    kapnD Senior Member

    I’d add the 2 inches at the base of the windows.
    Much simpler than cutting off the whole cap.
    Cut wood or make a simple mold to layup a C channel of appropriate dimensions and strength, and bolt it together.
    I’m thinking that standing room in the forward cabin is not worth the effort.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.