Fiberglass Repair Option

Discussion in 'Fiberglass and Composite Boat Building' started by bucketlist, Sep 1, 2021.

  1. rxcomposite
    Joined: Jan 2005
    Posts: 2,532
    Likes: 466, Points: 83, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    It can be done using the LR method. I fed it into my LR software program and it needs 7.1 mm thick of WR with 50% CSM, 1,000 x 500 mm panel, 33 kN/m2 of pressure, typical of a 8,000 kg, 15m boat running at displacement mode. No failure on laminate even with a safety factor of 3.

    For the same specs, ISO calculates lower bottom pressure at 16 kN/m2. Thus needing only 6.5 mm of laminate operating in "inshore" mode. Of course, if I override the pressure to 33 kN/m2, ISO will require 9,3 mm of laminate. But that is not what ISO is calculating given the parameters.

    It is not apples to apples. There is a lot of variables. Just trying to figure out what works.
     
    fallguy and bajansailor like this.
  2. fallguy
    Joined: Dec 2016
    Posts: 5,875
    Likes: 1,160, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    I remember where the thing fell apart was the use of an excess of coremat and not fabric is anticipated. The internet rumor from another burn is perhaps two layers of glass and the rest coremat. If a layer of heavier wr is a full millimeter, then you are saying 6 layers of fabric? Not 2 layers of fabric and a 4mm coremat? Does this boat meet ISO based on what we are seeing. Two layers of glass is say 65% csm? Yes, speculative, but the likely problem is a boat made of mainly mat does not appear to be strong enough.

    His statement of fact RT won't give him the layup is telling.
     
    Last edited: Sep 4, 2021
  3. rxcomposite
    Joined: Jan 2005
    Posts: 2,532
    Likes: 466, Points: 83, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    Coremat or "approved felt material" is allowed under Class Rule. It may not be strong as WR but if located in the center it works. You can use several layers of CSM in the center if you like. Coremat is a better substitute. Balsa is better. Foam core is the best. It is all dependent on how you calculate the stresses.

    Even if the manufacturer refuses to give the laminate schedule, it can be derived by a burn test. I don't know why the manufacturer refuses to divulge the lam schedule. Only when a litigation is imminent does the buyer seek the expertise of a surveyor familiar with or specializing on composite design to find out what went wrong. Note that even me, I refuse to say that the design is inadequate. I do not have the details. I implied that it is within range give or take a few.

    To prove that a laminate is failing, you have to define the parameters, the load conditions, the area of operation. Then you have to know under what guiding principle it was calculated. LR, DNV, ISO, ABS?

    Most laminates when subjected to the first principles passes. It is the guiding rule that varies and defines the operating conditions.
     
    fallguy and ondarvr like this.
  4. rxcomposite
    Joined: Jan 2005
    Posts: 2,532
    Likes: 466, Points: 83, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    I am not saying that.
     
    fallguy likes this.
  5. ondarvr
    Joined: Dec 2005
    Posts: 2,776
    Likes: 466, Points: 83, Legacy Rep: 506
    Location: Monroe WA

    ondarvr Senior Member

    The manufacturer probably felt threatened and stopped responding. Plus there is no way to determine what party was in possession of the boat when the damage was incurred. And, only the original purchaser has a warranty.

    This isn't a simple fix that a manufacturer would take on for good customer PR, it is a complicated repair with a good deal of liability associated with it.
     
  6. rxcomposite
    Joined: Jan 2005
    Posts: 2,532
    Likes: 466, Points: 83, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    Looks like it. Keel was damaged. That is supposed to be the strongest part of the boat.
     
    fallguy likes this.
  7. rxcomposite
    Joined: Jan 2005
    Posts: 2,532
    Likes: 466, Points: 83, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    FG- Here is a typical analysis of a plate with the core filled up with just CSM. Just look at the column "Stress fraction". As long as it does not exceed 0.333, it is not failing. 0.333 means a safety factor of 3 or derived stress/Ultimate Stress. Note that I am just using 2 layers of WR on the inner/outermost ply. The "center laminate" is the core which you can substitute with coremat. Not a direct substitution on a thickness basis but just to show you it works.

    I used 16 kN/m2 on a 1,000 mm x 500 mm pure plate, no stiffener.

    The laminate is just for proof of analysis. It will not pass the sub rule like having CSM on the outermost and innermost layer and that there must be a minimum of 50% WR, 50% CSM by weight.
     

    Attached Files:

    Last edited: Sep 4, 2021
    fallguy likes this.
  8. fallguy
    Joined: Dec 2016
    Posts: 5,875
    Likes: 1,160, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    @rxcomposite
    @ondarvr

    If the hull sheared at the stringer, can the boat be repaired from the bottom? I can't see it being done very well attempting to repair tabbing from below, but the other side is probably okay..and maybe the tabbing is mosty intact?

    @bucketlist

    Here is a picture of tabbing. It is simply tying the stringer to the hull. The shear line is probably on the edge of the tabbing. The concern is if you have broken or compromised the tabbing for 100"; it should be redone.

    Others ought to remark.
     

  9. ondarvr
    Joined: Dec 2005
    Posts: 2,776
    Likes: 466, Points: 83, Legacy Rep: 506
    Location: Monroe WA

    ondarvr Senior Member

    It depends on how it cracked.

    If it failed near the outside of the tabbing on the hull, then the stringer is probability still bonded securely in place. If the stringer broke loose from the hull it's a bit more involved.

    The thicker you make the hull the less it relies on the stringer for support. That is why I said you need to build up the hull over a large area, maybe the entire thing. This depends on further examination of the damage after it's opened up a bit.
     
Loading...
Similar Threads
  1. Duck
    Replies:
    15
    Views:
    3,541
  2. BC Chris
    Replies:
    2
    Views:
    2,361
  3. trailrunner
    Replies:
    29
    Views:
    11,994
  4. RandyRathmann
    Replies:
    3
    Views:
    2,133
  5. Nitro57
    Replies:
    6
    Views:
    7,263
  6. FieroFixer
    Replies:
    7
    Views:
    11,810
  7. highhopesgarden
    Replies:
    10
    Views:
    4,652
  8. redfish99
    Replies:
    2
    Views:
    4,060
  9. frog man
    Replies:
    21
    Views:
    5,808
  10. n421fn
    Replies:
    0
    Views:
    2,621
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.