Wood vs Fibreglass

Discussion in 'Materials' started by JordieS, Nov 11, 2011.

  1. JordieS
    Joined: Apr 2011
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    JordieS Junior Member

    What would you choose as a material of choice for a 6m runabout and why?
    What are advantages and disadvantages of each?

    Thanks
     
  2. Wynand N
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    Wynand N Retired Steelboatbuilder

    Marine ply - lighter than GRP (580 : 1500 kg/m3) and much easier to build a one off economical, and yes, it floats...
     
  3. PAR
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    PAR Yacht Designer/Builder

    Wooden structures in smaller sizes are difficult to beat in the all important strength/weight ratio. Plywood is handy if you have a developed design. Most traditionally shaped runabouts aren't developed shapes, but with some building skill a carefully planned relief cuts, you can make plywood work.

    There are other wooden building methods that will be lighter then plywood sheathing, such as molded and some forms of strip planking, to name a couple.

    In the end, the choice of hull material is based on several factors, as panel strength can be engineered into all the build materials available. I have a client facing this decision right now. He wants wood, but is more familiar with 'glass. Balancing an honest answer about maintenance, neglect duration, use, building skills, etc. can be a difficult decision for many.
     
  4. JordieS
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    JordieS Junior Member

    If you do build a wooden runabout, would it be necessary to fibreglass the wood in or could you just coat the whole thing in epoxy?

    I know my questions are probably silly but I'm enjoying the learning.

    Thanks everyone
     
  5. PAR
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    PAR Yacht Designer/Builder

    Amazingly enough, once, just after the dinosaurs died (shortly before I was born), there were nothing but wooden boats, including runabouts. No epoxy, no waterproof glues, no 'glass fabrics, no plywood, no metal fasteners, just solid wood and good joints.
     
  6. gonzo
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    gonzo Senior Member

    If you build a wooden runabout, alkyd enamel will do fine. I think I am of the boatasaurius species like PAR
     
  7. JordieS
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    JordieS Junior Member

    Hahahahahahah, If I ever did build a boat I would probably want it to be wood but I would like to get the paint as smooth as if it were a fibreglass hull. Would this mean I have to fibreglass over the wood once or twice or could I seal the whole hull in epoxy and paint over that?

    Would the epoxy base make it as smooth as a regular fibreglass hull?

    When I drive my boat around the marina and such I really don't like the look of some wooden boats with paint over the top, you can see the outline of the planks through the paint and it isn't smooth or anything.

    Thanks
     
  8. rwatson
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    rwatson Senior Member

    You will be pleased to know that you can prepare wood to a glossy, smooth surface, just like fibreglass, but it may not last as long.

    When you say wood, you need to decide between solid planks or marine plywood. With plywood without something substantial like epoxy, the finish wont last as long as fibreglass. With planks, you will always see a gap between them using traditional building methods. This can also be reduced by an epoxy/fibre surface - but 'print thru' is always a possible issue.

    Epoxy by itself will provide a tougher, lower maintenance surface, but you tend to get significantly longer lasting surfaces if you use even a very light fibreglass with it.

    The other thing you probably haven't experienced yet, is the drudgery of maintaining these 'dining table' surfaces. Experienced sailors generally go for a satin, low maintenance surface.

    Fibreglass usually has a gelcoat finish that gets more and more dilapidated and stained over the years, and is very 'hard' to paint.

    Epoxy on wood has to be painted periodically depending on usage - but like one guy said "Sure I have to paint the hull - but every year, I have a new boat - while the fibreglass boats just get more dilapidated every year"
     
  9. tunnels

    tunnels Previous Member

    Me being a glassing person would build totally from glass simular to stitch and tape ! just make all my panels 99% to shape and size on a smooth shiny bench for the outside including the tape recess built in every where and finish the inside laminate when its stuck togetherand the outside has been completely taped with triaxle tape 90/45/45 so all the three layers would be working across the join . solid glass for the bottom of the hull and a cored topside using 8 mm H 80 foam core sheet , Infuse all the panels on the bench then when all fitted infusing the last inside layers to finish it off completely !! Could be simple and easy to make a complete glass boat with no wood at all any where . Build over a collapsable timber frame that can be taken apart and set up anywhere for others to be able to use . Did this with my sons boat and made 3 off the same frame work .Really simple and gets easyer as you make each additional boat . once you purfect the system it all just falls into place , very little grinding ,filling and sanding !theres almost no fairing at all . if the frame is 100% and with the glass fame work attached it a piece of cake !! :D
     
  10. rwatson
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    rwatson Senior Member

    That's a good approach for someone who is expert in the material, and can get the materials cheaply - but there were a few 'hidden catches' for someone who is totally new to boatbuilding like this poster is.

    " Infuse all the panels on the bench" - what bench, what sort of materials (peelply, breather layer, airtight mastic, airtight outer layer) in the 'stack', what vacuum pump, what piping, what resin trap ? etc etc and one mistake and the whole mess gets thrown out .... . And you have to do it twice - once with the foam on top, and once for the inside glass layer. -- and all for the creation of what is essentially a flat panel like plywood.

    " Build over a collapsable timber frame" - with stitch and tape and plywood, you would probably need a lot less framing as the material is self fairing.

    "including the tape recess built in every where " - so the hull is a developable shape, no compound curves - and the chine surface with its raw glass outer surface has to be coated with the rest of the hull, so the strips on the chines don't show out, which sort of defeats the purpose of a high quality glass exterior.

    But for the extra effort and cost - you do get a rugged, non rottable, low maintenance hull . It would probably hold its resale value better as well.

    I am hanging out for one of those 'printers' that can carve the shape out of plastic powder -

    http://www.youtube.com/watch?v=xP-Gqi4YQhk&feature=related

    but for something 30 feet long.
     
  11. sabahcat
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    sabahcat Senior Member

    Composite
    whether that be simply ply with glass
    or strip plank or sheet core material with glass in and out.

    All painted in appropriate epoxy primers followed by a urethane or poly urethane coating.

    I use industrial primers and urethane topcoats, they are:
    easily repairable
    easily buffable
    More affordable (pictures of bulldozers and oil rigs on front means cheaper than the ones with pictures of luxury yachts, yet paint is probably similar quality)
    and they are certainly strong and long lasting.
    I have seen a cat that had a 20 year old bright yellow top coat that was chalky, given a quick buff and look fresh as a daisy.

    Solid glass and gelcoat in my opinion results in a boat that is far to heavy and requires too much HP.
     
  12. tunnels

    tunnels Previous Member

    I have a old power boat built 1975 its all glass and apart from the fact that the gel coat faded and discoloured its a solid as the day it was first made .There is no wook any where !!

    I am not and never have been one for mixing glass and wood where its possible . . glass is glass and wood is wood ,wood boats get glassed on the outside so they look good all the time so what does that tell you ?
    I like to use my boat not keep working on it for weeks each year just to keep it up to a acceptable level !!:D
     
  13. sabahcat
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    sabahcat Senior Member

    Fallacy

    In all the years of ownership of my previous vessel, (timber composite) the only maintenance it required to the structure was antifoul, same as any permanently moored boat.

    What I didn't get with an epoxy structure was osmotic blistering.
    Can a solid fiberglass, invariably polyester structure claim the same?
     
  14. PAR
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    PAR Yacht Designer/Builder

    Yes, depending on the polyester formulation. I've inspected polyester boats that have been continuously berthed for a couple of decades (zero haul outs), that still have dusty bilges. Naturally, this assumes someone has tended to thru hulls, etc. but yep, it's possible, even with polyester.
     

  15. rwatson
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    rwatson Senior Member

    These two conditions in the same 'sentence' convey the dilemma of boat owners. Gel coat does get very shabby over time - many people prefer an easily repaintable surface.

    Fibreglass isnt the perfect material, any more than wood is - both are fraught with traps ( Rot V Osmosis ? )

    You really have to set your priorities, like Tunnels - most people don't want to spend a lot of time and money on the perfect finish, while others cant love anything but perfection.
     
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