PVC pipe idea I haven't seen yet

Discussion in 'Boatbuilding' started by HonkyTonk, Nov 12, 2012.

  1. HonkyTonk
    Joined: Nov 2012
    Posts: 5
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Estonia

    HonkyTonk Junior Member

    I'm just thinking out loud about the following design:

    Usually, when people talk about PVC pipes, an easy boat to make is a catamaran like RebelCat.

    Now, picture an inflatable dinghy, but instead of inflatable chambers you would have PVC pipes. It would have a rigid flat plywood/plastic floor and a small keel underneath it, which is also a PVC pipe, to help with stability, and for a slightly V-shaped bottom. Ideally, this boat would look like and work as up to 16' dinghy.

    Of course, there's the problem of making this airtight, since in an inflatable dinghy it's the fabric that makes the bottom and stern airtight. Connecting the floor and stern to the pipes and sealing it is where I picture most of the problems would be.
     
  2. troy2000
    Joined: Nov 2009
    Posts: 1,743
    Likes: 170, Points: 63, Legacy Rep: 2078
    Location: California

    troy2000 Senior Member

    Isn't there a thread on here somewhere about Chinese boats made of pvc piping, that were traditionally built of bamboo?
     
  3. rwatson
    Joined: Aug 2007
    Posts: 5,839
    Likes: 276, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    The other problem is that PVC is rather brittle without re-inforcing.

    Generally, its cheaper and more effective to build shapes out of polyester resin and fiberglass, if you have to buy PVC tube.
     
  4. gonzo
    Joined: Aug 2002
    Posts: 13,607
    Likes: 382, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    There was a company building them about 12-15 years ago. The boats where too heavy to compete with more traditional methods of construction.
     
  5. Petros
    Joined: Oct 2007
    Posts: 2,936
    Likes: 139, Points: 63, Legacy Rep: 1593
    Location: Arlington, WA-USA

    Petros Senior Member

    The size and amount of pipe you need is way too costly and heavy for a boat, unless you get it surplus somewhere. far cheaper, better shape, and lighter out of wood or fiberglass.

    there is really no benefit to pvc pipe, it is not even that strong. It was not designed to be used as the a load bearing member in a structure.
     
  6. masalai
    Joined: Oct 2007
    Posts: 6,823
    Likes: 120, Points: 0, Legacy Rep: 1882
    Location: cruising, Australia

    masalai masalai

    been done using 3 ft dia pipes - - Not elegant and may have been junked to end its life as a pontoon jetty... even then seemed to lack "integrity"
     
  7. penguin78
    Joined: Jan 2010
    Posts: 14
    Likes: 1, Points: 3, Legacy Rep: 22
    Location: aus

    penguin78 Junior Member

  8. liki
    Joined: Nov 2008
    Posts: 220
    Likes: 12, Points: 18, Legacy Rep: 114
    Location: Finland

    liki Senior Member

    There are companies specializing in manufacturing RIB-alike boats from rigid PE-tubing for more and less special uses.
     
  9. HonkyTonk
    Joined: Nov 2012
    Posts: 5
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Estonia

    HonkyTonk Junior Member

    Oh, I see. So the problem is with the material. But what about alternatives to PVC? Are there any pipes made out of a stronger, less brittle material?

    I'm picturing an approximately 16' dinghy alternative, a boat which you can take a couple of miles offshore, also maneouverable in relatively shallow waters, but which doesn't go 'puff' if it goes against a sharp corner. Also cheap, otherwise certain types of RIBs or even a hovercraft would match the requirements quite well.
     
  10. rwatson
    Joined: Aug 2007
    Posts: 5,839
    Likes: 276, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    Penguin28 is covering his with epoxy, but unless he also includes fibreglass cloth, it will not be a big improvement. Actually, Polyester resin and fibreglass would be cheaper than epoxy, and contribute really useful strength. It also bonds to the PVC really well.

    When you say cheaper, have you actually gone and priced the equivalent amount of materials in fiberglass and polyester resin in your area ?

    For a small dinghy, you can actually build a framework, pull tight nylon material across it, and lay the glass over it like a skin. You will get a better quality result if you use light, cheap rigid material like mdf, that can be pulled off later.

    I think you are making a lot of extra work for yourself running around looking like 'cheap alternatives', when the actual project is quite a simple, straightforward little job.
     
  11. rwatson
    Joined: Aug 2007
    Posts: 5,839
    Likes: 276, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    You are making a big job out of a small outcome. PVC pipe with epoxy is not all that much stronger without fibreglass. You will get a better result if you use ordinary, cheaper polyester resin with 6oz fibreglass cloth.

    That design of yours will be a terrible performer, costing far more than its 'normal' equivalent. A waste of time and money - but, its your time and money, do what you want.
     
  12. hoytedow
    Joined: Sep 2009
    Posts: 5,402
    Likes: 194, Points: 73, Legacy Rep: 2489
    Location: North of Cuba

    hoytedow Wood Butcher

  13. penguin78
    Joined: Jan 2010
    Posts: 14
    Likes: 1, Points: 3, Legacy Rep: 22
    Location: aus

    penguin78 Junior Member

    Regarding the 'design', what part will perform terribly ?
    I have made a 4mm ply version of the concave punt and it planes beautifully at low speed.
    Try the slight concave, you will find it much faster than the bathtub-shaped hull invented 5 thousand years ago. Instead, look at modern shapes with low-speed thrust (surf board).

    My main requirement is to not use messy itchy fiber glass cloth.

    The point is that the epoxy brushes on and glues the pipe.
    The cost of the pipe is 2.75 per metre.
    I have test glued some 15mm glued to 90mm pipe, and it can't be pulled apart with a hammer.

    Polyester resin is from the seventies. It is at least half as strong as Epoxy.

    But, the PVC is heavy.

    If this is not the cheapest simplest way. Then I would like to build a hull template shaped with COREFLUTE and glass over that (coreflute is polyethylene and so can be removed easily)

    Or.

    Ribbing based on 32mm pipe, and the spaces filled with with epoxy and EPS foam, or just EPS foam and glassed.

    Strong skeleton:
    If you wrap fiber glass tape around PVC pipe paint with resin (epoxy or polyester) then tape it up with electrical tape.

    The tape comes off later and you end up with a very strong pipe similar to a pole-vault or sailing mast.

    So has anyone got any knowledge on these methods...
     
  14. Wynand N
    Joined: Oct 2004
    Posts: 1,257
    Likes: 144, Points: 73, Legacy Rep: 1806
    Location: South Africa

    Wynand N Retired Steelboatbuilder

    Why not use Sikaflex 292i (structural marine bonding compound) instead of epoxy? It will also allow for some bending and twisting epoxy cannot handles and probably stick better as well.

    I use this all the time and once had to removed a large skin fitting from steel hull fitted with this 292. Had to destroy by chiseling off the skin fitting and still the Sika stuck to the hull and plastic. Grinder just slips over it and cutting torch did not helped either. Magic stuff if you plan to glue and joint permanently. :)
     

  15. rwatson
    Joined: Aug 2007
    Posts: 5,839
    Likes: 276, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    With very little rocker, its rowing ability is compromised, but if you are only motoring in it, the flat nose will prevent you doing much speed in waves.

    There are heaps of designs that will do both much, much better.

    Question - if you have already made a 4mm ply version, why on earth would you convert to PVC or any kind of glass ? Plywood will give you all the strength and lightness you need, and even longevity with a coat of epoxy and glass over it.


    Glass cloth is not itchy, its the glass matt that is problematic. In any event, have you ever heard of gloves ?? You put the stuff on the boat, not on your skin !

    Polyester is half the price of epoxy, and works out cheaper than $3 per metre for 50mm PVC pipe. With Poly you still wont be able to pull it apart. Epoxy sticks better to most things, but on PVC, Poly is as strong as you will ever need.

    In any event, plain epoxy wont cure your brittle PVC problem. It will help, but the impact strength wont be that impressive. Try coating a small section of PVC with Poly and 6oz cloth, then using a hammer, compare the strength of PVC with just a coating of epoxy.


    Wood is from 2000BC - but it still makes great boats. Why dont you try carbon fibre nano-tubes, they are from the 90's if you want to be modern ? Poly is only 20% less strong than Epoxy - but in both cases, the strength is dramatically increased with quite lite f'glass cloth.

    ... and brittle,

    yes, I have tried all of them and more. they are all possible, but I am trying to advise on the best value solution for the best possible performance. Coreflute isnt that cheap either. Flat panel glass boats are not very strong, you need compound hull curves if you want to do it in glass.

    If you wonder why you have never seen a boat like the one you designed, its because there are a lot better ways. Plywood and epoxy is hard to beat in price/performance combination, with lots of cheap designs that work great.
     
Loading...
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.