Inexpensive hull construction materials

Discussion in 'Boat Design' started by fpjeepy05, Dec 9, 2019.

  1. Rumars
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    Rumars Senior Member

    You want some non rotting cheap stringer formers just laminate a single layer of light CSM over some waxed cardboard positive. You could even make a rebate at the end so the sections fit better.

    Wood stringers will eventually rot, so what? They will still take 20-30 years to do it, as evidenced by countless boats buildt that way. And if labor is to be ignored at that time you simply cut it open and put in new wood.

    Cheap is a matter of definition. How long do you want the boat to last and with how much regular maintenance?
     
  2. fpjeepy05
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    fpjeepy05 Senior Member

    I've never seen "Cut it open and put in new wood" be simple. And wood can rot away a lot faster than 20-30 years...

    Things break and need repairs on their own, why build one with a built in expiration date?
     
  3. Rumars
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    Rumars Senior Member

    Because you want to cheap out on materials and the only way to do that is by compromising somewhere else. There is no magic bullet. And you clearly stated that labour costs be ignored, so how often it needs repair or how complicated that repair is does not matter.
    If you want less material in the skin and stringers to stiffen it, then wood is the cheapest option. Next is a hollow stringer, next a foam stringer.
    If you want sandwich construction then balsa or plywood is going to be cheaper then foam.

    Now if you want to build the best boat for the least amount of money in materials then other factors like boat size become paramount. A big boat might be cheaper in ferro or steel or even aluminium while a small boat might be cheaper in wood or plywood. It all depends on how you choose to define "best".
     
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  4. fpjeepy05
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    fpjeepy05 Senior Member

    I am not criticizing your response. I'm trying to encourage discussion for outside the box solutions. I know there is at least one customer in the world (me) that would like an inexpensive alternative to wood. Exterior grade plywood works out to ~$1.30/bdf. Composite decking is as low as $3/ bdft. Polypropelene honeycomb comes in $3.00-$3.50. Recycled plastic pellets in a hopper gun I can't put a number on that. I wonder if one could end grain butcher block a piece of EPS foam with Epoxy or Styrene free resin to make a grid to make it strong enough to be used structurally.
     
  5. gonzo
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    gonzo Senior Member

    There is not inexpensive alternative to wood. That is the reason it keeps on being used. Wood stringers will last for decades if properly enclosed in mat and polyester resin. You want a cheaper material than the cheapest available. That would the unobtanium sulfate.
     
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  6. fpjeepy05
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    fpjeepy05 Senior Member

    You may be right. From now till the end of time wood stringers enclosed with polyester resin may be the only inexpensive method to construct a hull.

    I can, however, guarantee who will never discover an alternative method.
     
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  7. Rumars
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    Rumars Senior Member

    Of course it's not. Right now somewhere in the US someone is sending carbon windmill or helicopter blades to the landfill. Those could be made into stringers if you like.
    Or you could melt down and compress waste plastics by hand and build a boat out of it like this guys: The Flipflopi Dhow — The Flipflopi http://www.theflipflopi.com/the-flipflopi-dhow
    The only problem is that none of this methods are going to be cheaper in the CONUS than poly/CSM with wood stringers if you have to pay for it. Not at todays oil prices and with wood as cheap as it is. The only way to be cheaper is if you can get materials for free.
     
  8. waikikin
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    waikikin Senior Member

    Close enough to the same thing, just bulks the laminate quick & easy... typically 4mm bulker gets laid on 300gsm chop & another layer of same over the top so close to 5mm in one hit- thickness equals stiffness if that's what you need, you can always put in another tomorrow.. It will use less resin than using choppy in building thickness but obviously wont be as "strong". There's strong enough and stiff enough & if you have woven or stitched fabrics inside & out the job can be done. Not sure on pricing at present but 1k used to buy 50 metres.. kind of depends what your goals and labour cost/skills is.
    Jeff.
     
  9. ondarvr
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    ondarvr Senior Member

    Split PVC pipe works, and is cheap, but the shape isn’t optimal for stiffness. Also, it doesn’t add any real strength, so all it is is a Shape.

    Composite boards are similar, only much more expensive and heavy.

    And again, EPS foam is just a shape, although there is a bit of flotation provided too.

    Since all of these are just a shape to glass over, with the glass laminate providing all the strength, it brings cardboard and wood back into play. It makes no difference if they rot or go away, they are just providing the shape.

    One advantage is that wood and cardboard can be made into any shape easily, so you can optimize the shape for strength.

    The comment about cardboard floating around in your bilge is inaccurate, it’s totally sealed off within the stringer, you would never know if it dissolved, nor should you care.

    The one advantage of wood is that while it’s there, it does supply some strength.

    I would rather use hollow stringers pre-made to the exact shape needed. This allows you to put in as many limber holes as needed with no concerns, and requires no additional materials. It also cuts down tremendously on labor costs when more than one hull is built.

    I work with just about every segment of the composites industry, and every one of them wants to build their product for less money, if there was a miracle product out there to cut down on cost and increase the strength it would already be in play.
     
    Last edited: Dec 16, 2019
  10. fpjeepy05
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    fpjeepy05 Senior Member

    The "goal" is a laminate cheaper than polyester resin. No labor concern.

    Doing more calculations than anyone should do for fun... Coremat says it uses about 600 grams of resin per 1mm per sq meter. That translates to 3.1 lbs/ft^2 Pure resin would be 6.9 lb/ft^2 so put another way coremat laminates are 45% resin, about half.

    $1000 50m roll of 4mm coremat is ~ 108 bdft Which is roughly $9.25/bdft Adding 45% resin comes to $12.05/ bdft

    In short, it makes the laminate more expensive not cheaper.
    I would call the false sense of security a disadvantage.

    I completely agree, but expensive.

    The guy that is going to invent the next "miracle product" would not agree with you.

    A high-value production builder is not going to try a new product on their production line because they have too much at stake. I don't see many industries being a penny pinching about composites as cheap boats maybe cheap surfboards.

    Recycled plastics are less than 20% the price of polyester resin. Floated in a Polyester resin at 50/50 ratio it would have plenty of compressive and shear strength. I think the reason it is not being done is because it only saves a small amount of money that would be consumed by extra labor and equipment. And it's not sexy enough to add any value to the boat. So to make it a "miracle product" you have to make it cheaper, stronger, easier and sexier. Which would be a miracle.
     
  11. ondarvr
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    ondarvr Senior Member

    There are products that combine cheap recycled plastics, they have little to no strength and have a very low HTD, the compressive and shear strength sucks too. Plus the cost can be higher, sometimes significantly.

    Many companies have tried to recycle composites, it’s very difficult and expensive to process, then using it in production costs even more.



    I work with some extremely creative companies, many don’t take the more traveled road. It still comes down to using what’s actually out there at a reasonable price.

    The recycled plastic thing doesn’t pay off, it rarely does in any application. The recycling industry is seeing very hard times because it’s frequently cheaper to use new material.

    This goes for most recycled products.

    If labor isn’t an issue, and all you’re looking at is cost of materials, maybe reed boats should be considered. Or there’s birch bark canoes, seal skin kayaks, hollowed out logs, etc.
     
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  12. Rumars
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    Rumars Senior Member

    The only thing that maybe has the potential, for what you want is textile (meaning fiberglass or carbon) reinforced cement. I can not offer you any data on price, you have to extract that from the few people knowing it.
     
  13. rxcomposite
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    rxcomposite Senior Member

    The "modern way" and still in practice is to wrap the reeds in styrofoam blocks and tie the ends. shasha.jpg
     
  14. portacruise
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    portacruise Senior Member

    Reed boats would be very low-cost materials, but the OP original post wants to use a mould and presumably plastic materials? That leaves the search restricted to reinforcing materials and cheapest amount of resin? Maybe heat welded and formed plastic laminate if such a thing is possible, or something like cheap moulded kayaks. Otherwise go to a free used junk boat to be fixed up, some kind of inflatable, or one time use things like cardboard?
     
    Last edited: Dec 17, 2019

  15. fpjeepy05
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    fpjeepy05 Senior Member

    I hear what you are saying, but your generality is not true all the time.

    Lets do a mental exercise.... Lets make a control sandwich panel. 1 gallon or polyester resin and enough cabosil (or thickening agent of your choice) to make a peanut butter consistency. Then lay out on a laminate table a layer of mat and some 24oz woven. Then 1/4" of putty. Then another layer of woven and mat. Set that aside and let it cure.

    Now lets make another panel. Start by running 2 liter bottles through your blender till you have some plastic sawdust. If you drink a lot of soda these are free, but if not you can buy scrap plastic for $0.18/lb Now lets make a putty with 1 gallon of polyester, 1 gallon of soda bottle dust, and enough cabosil to make peanut butter. Again mat and woven down on the laminate table. This time 1/2" of putty (because you have twice as much) Then another layer of mat and woven.

    Which panel do you think is stiffer? I'm going to guess the 2 liter panel is at least 4 times stiffer. Would you say that the 2 liter panel has "little to no strength" or that the "compression and shear strengths sucks too" Would you say that the 2 liter panel cost "higher, sometimes significantly"?

    I'm not trying to pick a fight, but just because the "extremely creative companies" you work for haven't chosen a method doesn't mean it is not worth consideration.

    I don't want to include labor cost in my discussion prompt. When you make yours you can include it. The purpose for this is two fold. One, labor cost isn't constant. Cuban workers make $20/month; Americans make $20/hr. Where you build boats will play a part in the construction method. Secondly it breaks the problem into smaller more manageable pieces. First identify all possible construction methods that use materials that are the same price or cheaper than the current preferred method. Second go through all of those methods and try to find a way to minimize the labor associated with that method.

    If throwing recycled plastic popcorn out of a hopper gun into a boat mold will cost more material wise than a standard chopper gun it is not worth investigating. If the materials can be done cheaper, then it is worth investigating.

    I have always thought cement was heavy and brittle, but I guess I need to do a little more research.
     
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