Mistakes made in building boats

Discussion in 'Boatbuilding' started by mariobrothers88, Dec 3, 2020.

  1. mariobrothers88
    Joined: Sep 2020
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    mariobrothers88 Senior Member

    Hi guys, I thought it would be cool to share the mistakes we made while building boats so that we can learn from each other :) I've learned so much already so I thought I'd start it off with my own mistakes while building a 34' woods catamaran:

    I used construction grade Douglas Fir with too many knots as the frame piece timbers that are glued to the plywood bulkhead. Instead I should have used furniture grade (class C&better) Douglas firs with vertical grain pattern and with high grains/inch and absolutely NO knots. However, this mistake was a blessing in disguise because at the advice of members of the forum, I decided to replace the knots. When I removed the knotty sections, it exposed another mistake I made. Most of the area that I had glued (with epoxy and milled fiber) was actually dry and there was no glue in a lot of areas. . I had a made a mistake earlier- I hadn't precoated the wood surfaces prior to gluing! I've had to go back and remove all the timbers I had glue-ed, which was a lot of work. I ended up using a circular saw to cut long cuts into the timber and a hammer/chisel to clean up. I ended up needing to use a router jig to do the final clean up. You can also use a table saw, but I found this difficult to do personally because I had one of those small jobsite compact table saws and it was hard to balance the bulkhead pieces on it. I found the router useful to clean up.

    Please share, I look forward to learning from you all!!
     
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  2. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    The biggest error you can make is mismixing epoxy and sheathing vast expanses of hull. Or burning the boat down with smoking resin pots.

    So far, only about 6 square feet of unstirred resin got me. Took me 8 hours to peel the glass off .
     
  3. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    My suggestion would be to follow the directions from the designer to every material and tool that is used in the build.

    After you've built five successful boats, then possibly try some changes. But master and understand the basics first.

    Almost every day I get calls from customers that never even read the labels on the cans, let alone the application guides available for the products.
     
  4. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    The second day of working with a new company. They changed brands of epoxy. But didn't relabel all of the old containers.

    All day I mixed resin "brand A" with hardener "brand B". Fortunately it was the first layer of glass. Only took a week to reprep the mold.
     
  5. cracked_ribs
    Joined: Nov 2018
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    cracked_ribs Senior Member

    Ouch.

    My biggest mistake so far was doing a really clean job on some joins in a stitch and glue dinghy. I planed them to much less than a sheet of paper. People warned me I'd need gaps. I didn't listen.

    It caused absolutely no structural problems but after I slapped epoxy on everything and saw the rich wood tones and tight joinery I loved the look so much I decided to finish the entire boat bright.

    I am NEVER doing that again. That stupid art project got hauled up and down the beach twice a day for six months. Every single scratch and ding was a dagger in my heart.

    Never again.
     
    Will Gilmore likes this.
  6. fallguy
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    fallguy Senior Member

    some designers are pretty high level and details like pre-coating the wood and mixing epoxy ratios are simply not in building plans

    I find ending the day thinking is my best approach. I ask myself how am I going to do that. In the case of the carbon overlay, I got advice to try the petG method after asking how and getting a less the ideal answer. Fortunately, you came along and helped me more. But I spend a LOT of time thinking. And I believe it helps.
     
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  7. mariobrothers88
    Joined: Sep 2020
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    mariobrothers88 Senior Member

    Thanks Fallguy, I agree with the thinking aspect. For the fumed silica, is it a 50:50 ratio mixture with the epoxy to get a peanut butter consistency for glueing? Just wanted to double check with the master :)
     
  8. fallguy
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    fallguy Senior Member

    No.

    try 6 oz by volume mixed resin
    12-14 ounces by volume of fumed silica



    The test is the mixture should not sag when piled up in the middle. This way you can apply to vertical surfaces like bulkheads for taping without the mix running downhill.

    I have a different mix for fairing compound that used microballoons or sil32. Ask later about it.

    Again, avoid milled fiber. Way too heavy. Cats are meant to be light and fast. There will be a few times you will want strength.
     
    Last edited: Dec 4, 2020
  9. ondarvr
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    ondarvr Senior Member

    All epoxies are different, it depends on the exact epoxy blend you're working with as to how much silica to add.

    Keep track of the first batch and write down the amount of each that gives you the desired result.
     
  10. mariobrothers88
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    mariobrothers88 Senior Member

    Wow thanks for all the great tips and advice guys!! Keep them coming!
     
  11. fallguy
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    fallguy Senior Member

    What epoxy Ron?
     
  12. mariobrothers88
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    mariobrothers88 Senior Member

    fallguy likes this.
  13. keith66
    Joined: Sep 2007
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    keith66 Senior Member

    Back in 82 i bought a bare grp hull, a Wing 25 yacht. I put a wooden deck & cabin on it. First yacht i built.
    Well me & dad got the beamshelves bolted & glued in & i laminated all the beams. Measured from the breasthook back to the main beam position marked it & set the main beam in. From that i marked all the others. On went the deck then the cabin. All looked lovely, then i went to fit the forehatch in the forward part of the cabin, It didnt fit as the hole wasnt square.
    Much head scratching ensued until i realised to my horror that at the very first main deck beam position I had put the front side of the beam on the line to port & the aft side to starboard. All the beams followed that one.
    Because the cabin front was so curved it didnt really show otherwise.
    And so the nice square hatch was thrown away & a nice new Elliptical one was made, Over the years many people commented on the lovely varnished mahogany hatch with its ash inlay stripe round the edge.
    But i never let on until now!
     
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  14. wet feet
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    wet feet Senior Member

    I know of another similar mishap-nothing to do with me.A galley worktop was needed and it was specified as Corian,A fellow went to make a pattern and was a bit baffled by the corners not being square in places where they should have been.Further investigation indicated that the bulkhead at the forward end wasn't square to the centreline of the boat.For exactly the reasons in the example in the previous post.Then there was the glass boat that had teak decks as an option and very few people ever counted the number of planks on each sidedeck-or they would have noticed that the numbers differed.Again,nothing to do with me.Nor was the cruiser racer that had an aluminium extrusion toerail which revealed half a slot on one side if they were both cut to the same length.I admit to being a witness when a laminate floor was laid that reduced the number of visible hatches in a cabin floor,but it was done in a hurry.
     
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  15. Milehog
    Joined: Aug 2006
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    Milehog Clever Quip

    My biggest cockup was using free plans. The clear Douglas Fir that I wasted was criminal. The fasteners and glue? Gone. My hours of planning and labor, pissed away.
    This disaster was before Algore invented the interwebs. Now free plans may have a slim hope but make sure the designer is alive or at least luke warm.
     
    fallguy likes this.
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