Help with layup design

Discussion in 'Fiberglass and Composite Boat Building' started by DogCavalry, Mar 26, 2020.

  1. DogCavalry
    Joined: Sep 2019
    Posts: 489
    Likes: 194, Points: 43
    Location: Vancouver bc

    DogCavalry Senior Member

    So, I'll start glassing my sea sled in the next few weeks.

    Since there isn't much in the way of available designs, I was obliged to do that myself. So far, so good.

    For scantlings I used Gerr's Elements of Boat strength. Calculations based on his formulas gave me ⅝" strip planking on 5 bulkheads. I went with 6, because that worked well with interior layout. Formulas also provided 39oz glass outside, and 26oz inside. Per square yard, of course. That seemed fine when glass and epoxy were months in the future. Now its weeks.

    Of course you're laughing by now. I don't know composition or number of layers.

    The boat will be driven hard while heavily loaded, landed on pebble beaches and generally work for a living.

    Thoughts?
     
  2. Steve Clark
    Joined: Jul 2004
    Posts: 194
    Likes: 14, Points: 18, Legacy Rep: 163
    Location: Narragansett Bay RI

    Steve Clark Charged Particle

    Sea sleds were all structural nightmares. Pounded themselves to death.
    How big?
    Vectorply is a good tool for laminate comparison.
    sHC
     
  3. Rumars
    Joined: Mar 2013
    Posts: 653
    Likes: 245, Points: 43, Legacy Rep: 39
    Location: Germany

    Rumars Senior Member

    I would go biaxial (no matt), 450g/sqm (13oz/sqyd), two layers, one +/-45° one 0/90° for the inside. Outside same fabric, 3 layers, just add a +/-45 on top.
     
    BlueBell and DogCavalry like this.
  4. DogCavalry
    Joined: Sep 2019
    Posts: 489
    Likes: 194, Points: 43
    Location: Vancouver bc

    DogCavalry Senior Member

    Thanks Rumars. That's what I was thinking. Can't really go wrong with that. I was getting myself distracted with heavy woven roving and the like.
     
    Last edited: Mar 26, 2020
  5. DogCavalry
    Joined: Sep 2019
    Posts: 489
    Likes: 194, Points: 43
    Location: Vancouver bc

    DogCavalry Senior Member

    Is there any issues with going with lighter biax outside, and using a layer of woven roving between?
     
  6. TANSL
    Joined: Sep 2011
    Posts: 6,115
    Likes: 268, Points: 93, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    I would put what you like best. The strips of wood should have sufficient strength, that is, they do not need to increase their strength with the fiber. Therefore, put fiber to make the strips watertight and do not complicate your life with biaxial, triaxial or things like that.
     
    DogCavalry likes this.
  7. DogCavalry
    Joined: Sep 2019
    Posts: 489
    Likes: 194, Points: 43
    Location: Vancouver bc

    DogCavalry Senior Member

    ⅝" or 15mm planking does seem like enough in a 26' or 790cm boat. I had a Dragon Olympic class sailboat when I was very young, and its planking, without any glass at all, was well under ½".
     
  8. Rumars
    Joined: Mar 2013
    Posts: 653
    Likes: 245, Points: 43, Legacy Rep: 39
    Location: Germany

    Rumars Senior Member

    Woven rowing is a pain for what you want, since it leaves a big textured surface. Lighter glass goes down better, needs less epoxy mixing and in the end less fairing.

    How much glass you need depends on how the boat is buildt. You need transverse strenght for your strips, so either you have appropiate frames on the inside and any outside glass is only for abrasion resistance, or you don't have frames and all the glass is structural, sandwich construction style. How did you calculate the boat initially? Strip plank composite or strip buildt on frames?
     
  9. DogCavalry
    Joined: Sep 2019
    Posts: 489
    Likes: 194, Points: 43
    Location: Vancouver bc

    DogCavalry Senior Member

    Strip plank composite, per Dave Gerr's relevant chapter.
     

  10. Rumars
    Joined: Mar 2013
    Posts: 653
    Likes: 245, Points: 43, Legacy Rep: 39
    Location: Germany

    Rumars Senior Member

    Then you need the glass, inside out. You need support at 90°to the fibers and at 45° for torsional loads. Some say either one of the angles is enough. Work with what glass you like, 13oz biax is just a convenience, but hand laminating anything over 17oz with epoxy by hand is not fun anymore. It can of course be done, and there are triax fabrics of nearly the right weight.
     
Loading...
Similar Threads
  1. fallguy
    Replies:
    19
    Views:
    445
  2. Spyder
    Replies:
    2
    Views:
    559
  3. s2dm
    Replies:
    5
    Views:
    1,584
  4. Scuff
    Replies:
    146
    Views:
    12,018
  5. Husk
    Replies:
    5
    Views:
    2,264
  6. Jmooredesigns
    Replies:
    9
    Views:
    3,058
  7. mbam
    Replies:
    4
    Views:
    1,975
  8. Reefdog
    Replies:
    25
    Views:
    1,316
  9. RSD1
    Replies:
    31
    Views:
    1,263
  10. SamC
    Replies:
    28
    Views:
    1,179
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.