First go at a composite hull

Discussion in 'Fiberglass and Composite Boat Building' started by Mattskii89, Sep 2, 2019.

  1. Mattskii89
    Joined: Sep 2019
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    Mattskii89 Junior Member

    So I am a commercial fishermen in Bristol bay Alaska. Traditionally the higher end boats in my fishery are made of aluminum which is what I currently have. We regularly beat the snot out of our boats, some days i’ll Be playing around with 20 thousand pounds in 8 foot breakers right on the beach. My boat plus weight gets up to around 50 thousand pounds., there are time delivering where we have large waves bash us into steel crabbing boats while we off kid our fish. It’s an extreme environment sometimes for the most part.
    Anyway I’m considering building a composite hull, there are a lot of old non planning hills that are S glass from the 70’s that have held up well and some Kevlar boats made in the 90’s still moving around.
    Anyway my idea is to take lines off my current boat and make a mold in a smilies shape, 32(we have a 32 foot limit enforced so it’s become a high tech battle) by 16 and a half. Vacuumed infuse the mold using Kevlar to about 3mm and then use carbon fiber, S glass, Kevlar and honeycomb to finish out everything inside the hull.
    My idea would be to make everything in all the same thicknesses as my aluminum boat, just using composites, if I need quarter inch plate here, make it out of carbon fiber and add it ect. My goal of this project is to shave off several thousand pounds while maintaining durability. Weight saved is worth a lot of money, the fish like to hang out in the mud and it’s extremely competitive. It’s turned into a constant stream of boats making sets on a plane trying to get those last few inches of shallowness.
    My questions would be if it would be wise using my current boat as an effective mild and just copying the engineering? At a certain point it’s is probably better to go to a naval architect and have them look over the project. But on the other side of the coin for my industry and most commercial boats in general no one has made the leap in a big way into these lighter composites so there won’t be a lot of experience with what I’m hopping to achieve. Also work boats have some added difficultly in that we have massive sand inconstant changes in our weight distribution throughout the work day which makes things near impossible to plan around unless and even if you’ve been designing boats for this fishery.
    My next question would be if carbon fiber would even hold up in such a rough environment, and what do repairs look like if you do have an issue, can you repair it just like glass? my aluminum hull holds up pretty well, but it can bend a lot more then carbon can but also it takes a lot more force then aluminum. I’m most worried about slamming my hull on the sand bar in choppy conditions, a lot of times you’ll just slam your bow hard over and over and over again, I have cracked welds on stringers before, not on hull welds thankfully.
    How much would a vacuum infusion set up cost for a larger project like this, and what are good brands to look at? I probably wouldn’t want to spend over 200 grand. I can make my mold out of aluminum so that’s not super hard.

    Thanks for the help!
     
    Last edited: Sep 3, 2019
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Probably best to talk to someone who has designed boats for that fishery, and understands the requirements. Generally speaking, it won't be easy to save weight using single skin laminates, regardless of what the make-up, compared to aluminium. Sandwich construction you might, but the service requirements of the boats might find the method not really suited, as it is vulnerable to point loading. But you can mix that up a bit, with solid laminate when needed, but a lot of the boat would need to be sandwich, to save weight.
     
  3. Mattskii89
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    Mattskii89 Junior Member

    I know about 4 different builders to a pretty high degree, there all pretty married to aluminum, there is one guy I’ve talked to on our fisheries Facebook group that builds glass boats up in homer Alaska, but I think he just hand lays S glass and makes it thick. My one buddy who built a Kevlar boat in the 90’s never did any engineering work, he just used one of his glass boat molds and made everything thinner. It worked pretty well for him, this is a much more ambitious project though ‍♂️
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    hard knocks and scrapes suit alloy, and low maintenance under those conditions, I think you will find it hard to match that in any other material. GRP comes into its own with complex or difficult to arrive at shapes, but even then, only economical with series production. Do you have a picture of the boats ?
     
  5. Mattskii89
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    Mattskii89 Junior Member

    on my phone, finding it kind of hard to upload a picture of my boat, YouTubed Bristol bay and this boat is very similar to mine, I’m about a foot wider though. Pretty neat you can get the cut file and have the aluminum show up like that
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

  7. TANSL
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    TANSL Senior Member

    Although infusion lamination and the use of sandwhich panels, undoubtedly save weight (although in such small boats there may be little savings), lack of experience working with these methods can pose serious problems. Low temperatures and humidity can also be problems for reinforced plastic in general. Repair is not simple either.
    If you have a body lines plan and a general layout of your boat, I could make a quick calculation of the weight of the hull structure and the superstructure, built with GRP by the traditional, hand-rolled system, without sandwhich panels. A well projected structure can also save weight.
     
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  8. fallguy
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    fallguy Senior Member

    I am a casual lover of boats with no credential building a 32' powercat using wet bagging and corecell.

    I recommend you realize the points made by tansl. They are sound.

    The methods building foam composites are a bit artsy; learning curves high, build complex.

    The weight savings for composite are real, but do you need them?

    Why kevlar? Kevlar's best property is outside the layup for wear resistance or in a place of potential wearthrough.
     
  9. Mattskii89
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    Mattskii89 Junior Member

    Kevlar would be for abrasion and impacts on the outer shell which there are many, this is a commercial operation. it’s also lighter then S glass at the same volume while also not shattering like carbon fiber.
    And I absolutely need light weight if it doesn’t sacrifice the durability of the boat. Inch of displacement can mean huge sums of money, it’s a complete battle. It’s not uncommon for guys to put themselves on a 30 knot step and beach themselves while setting there gear just to get in 6 inches of water.
    I’m not terribly scared jumping on a project like this, I understand there is an art to all of this but that’s what trial and error is for. It can’t be that hard, to vacuum infuse a hull, and if it is, I’m sure I could find some expertise to guide me a bit, but it seems strait forward enough. My main concern is if the materials could survive the application, would be a sad day building a boat only for it to get wrecked on the sandbar you intentionally put it up on, in a storm.
    And TANSL i’m Shipping my boat down for some jet modifications I could probably get lines done off it within a month. I could probably get the cut file off that bot in the video though, and how much it weighs I would wager. I’m a foot wider but probably in the ball park.
     
  10. fallguy
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    fallguy Senior Member

    It is hard to infuse to avoid dry areas.

    If you get a pickup for the weight gain, then a sturdy composite hull could work.

    But what is wrong with your boat now if you like the hull so much?
     
  11. Mattskii89
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    Mattskii89 Junior Member

    It’s an arms race, I’m in about 22 inches of water now, the newer generation is getting in about 18(not on step) in the boat I showed it’s a top house design which is lighter then my flying bridge design. I’m tired of being outside all day every day while fishing. I’m still extremely competitive but the age of my operation is showing more with time.

    The way there achieving such lightness is getting real thing on aluminum, also my boat was built in 96 and the industry really didn’t know where it was headed so I was built a bit heavy.
     
  12. TANSL
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    TANSL Senior Member

    Well, my offer is still standing. If you need something, you just have to say it.
    I don't want to belittle anyone, of course, but you could also study whether a better design and calculation of the aluminum structure could save weight and how much.
     
  13. fallguy
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    fallguy Senior Member

    I would advise you consider all aspects of design. Your boat 4" less draft might disappoint.
     
  14. Mr Efficiency
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    Mr Efficiency Senior Member

    The idea of moulding a single skin reinforced plastic hull to save weight, over alloy, regardless of the reinforcement, is pretty well impossible. The only seemingly practical way would be fabrication using pre-fab infused panels
     
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  15. ondarvr
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    ondarvr Senior Member

    I was just in Homer visiting with some of my customers that build composite Bristol Bay boats. We sport fished off one while in Homer.

    Check with an existing builder, it will be far more cost effective and save a year or two of work.

    Just by talking to them you’ll be able compare the weight and draft to see if there are any improvements to be found.

    Ivan’s new hull mold is 32’x15’, the new mold was designed with infusion in mind.

    He will also sell you a hull and deck kit for you to finish as you wish, possibly even rent you the space to do it in his new shop.
     
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