Selway Fisher Designed Wood Epoxy Narrowboat

Discussion in 'Boat Design' started by rossgiles, Feb 29, 2008.

  1. rossgiles
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    rossgiles New Member

    Hi to all,

    As a newbie to construction of boats I'd appreciate any 'two pence' that any you have on the construction of a wood, epoxy f/glass narrowboats or barges.

    I notice that a few people have been on the forums on the same subject in the past, from ideas similar to mine, to one chap that wanted to chop up a sea container and make it into a two storey house boat??
    It's all interesting to read, if nothing else!

    So, I have ordered the study plans from Selway Fisher Design for the 36ft hull they have on their site, with intention of costing it up when the plans arrive and possibly moving on to plan the project from there.

    I'd also like to hear from anyone that can take a design like Selway's and add to it, by possibly lengthening it, for which, I could pay a modest fee.

    I am thinking that I would like to use a sandwich foam approach if I dont follow Selway's plans to the letter.
    This is due to finding a load of cheap 8mm and 6mm ply and other miscellaneous wood planks and beams.

    8mm ply outer - foam center - 6mm ply inner , glass,epoxied for the hull

    However, as I may have the materials for the skin work, I am no naval architect and have no idea on sizes and types of beams to use for the frame work, to achieve rigid and robust set of sides and floor.

    Links to other narrowboat or barge plans (wood epoxy glass) would be greatly appreciated also.

    If anyone else is currently building a barge or narrowboat using this or similar methods, I'd love to see some progress pictures and share information etc....

    fair winds and calm waters to you all
     
  2. erik818
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    erik818 Senior Member

    Rossgiles,
    I've had some thoughts on using plywood/foam sandwich for a boat, with the surfaces protected with epoxy/glass. Plywood/foam sandwich will result in a very stiff structure for the weight so it's tempting. Enclosing something between two moisture-tight surfaces is however risky.

    In my experience, moisture always gets in wherever there is a sealed volume. The problem is to get it out. On a small boat I'm working on right now I will use plywood/foam sandwich but arrange the sandwich with air channels so it is possible to dry it out if needed. The air inlets and outlets will normally be sealed with airtight caps, and I will use humidity indicators to see when drying-out is needed.

    I think this method will work for me, with a boat I'm building for myself, but maybe not for a consumer market. On the other hand, checking humidity indicators is not more complicated than checking motor oil level. You have to decide if it might work for you.

    I would be reluctant to use a plywood/foam sandwich without the possibility to dry it out. I'm sure there are more experienced thoughts than mine on this problem.

    Erik
     
  3. rwatson
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    rwatson Senior Member

    If you need re-design and recalculation - Selway Fisher should be happy to do revised designs for you - thats how half the designs on their catalogue got there. They responded quickly to my email last year.
    Surely the original designer would be the best, cheapest and easiest way to get a mod done.
    Erik has made the assumption that the foam center is able to absorb water, but you dont actually state what kind of foam you want to use. If it is a closed cell foam, it might not be a problem. But then you need to make sure it can survive epoxy coating.
    My interest is in why you feel foam would be an improvement. Is it for thermal value, structural value or what ?
    If you are keen to use foam, you might do better using just foam core and fibreglass with VynylEster, and ignore the Ply. Check out the cost variation between Epoxy and VynylEster goo to see if there would be an advantage.
    The other unknown is your reference to "cheap" plywood. Are we talking marine grade here?
    There is a bit of detail missing before you can solve the final equation I think.
     
  4. Pericles
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    Pericles Senior Member

    rossgiles,

    The narrowboat hull can be considered as a "U" shaped beam and hence a structure that resists hogging or sagging. Building this shape with marine ply and epoxy and reinforcing the chine and sheer with longitudinal timbers, will strengthen the resistance of the hull to the turbulent life on the canals. With that in mind the Hawfinch is a very practical boat for selfbuild. Paul Selway is a well respected designer.

    http://www.selway-fisher.com/Mcover30.htm

    The £10 study plans are unlikely to have enough detail for you to see how to alter the type of construction from layers of epoxy/ply on pine frames to what is essentially a ply/foam/ply composite panel construction. The full plans are indispensable and are only £160.

    If you have slabs of 2 part, closed cell, polyurethane foam, (also known as buoyancy foam, http://www.spray-insulation.co.uk/buoyancy foam.htm) and BS 1088 marine ply, then you have the correct raw materials. If the foam is EPS, it's too friable over the long term, even bonded between the marine ply. The working loads within the large structure will cause the EPS to crumble. http://www.boatdesign.net/articles/foam-core/index.htm

    Small boats have been made with EPS, but that's because the epoxy/glass cloth skins take most of the loads. For the Hawfinch, it must be buoyancy foam!

    Both rwatson and erik818 have pointed out the pitfalls and have given you very good advice. That said, I know the type of construction you mentioned will work, because I have used it myself. In my case I used neither buoyancy foam nor EPS, but Foamglas. It was an experiment to see if it were possible to replace Divinycell at £100 per square metre with a foam at £10 per square metre. It was not successful for curves!!

    http://www.foamglas.co.uk/literature-page.htm

    Using what is in effect, a black foamed glass insulation panel bonded with thickened epoxy between two layers of ply becomes a SIPS.

    http://www.buildit-green.co.uk/

    The panel I made was almost indestructible. A 6 lbs sledge hammer wielded with fury just cracked the uppermost layer of ply and left a dent through to the foam, but very easy to repair with thickened epoxy. Such a hull would not be compromised.

    A foam core and double ply construction panel built narrowboat hull would go together like Lego. But, I'm going to be building a cruising catamaran. :D :D

    Regards,

    Pericles
     
  5. tom28571
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    tom28571 Senior Member

    You do not say where you intend to use this narrowboat. If you intend to cruise the canals of England, construction of the boat will need to satisfy the requirements of the locks, bridges and tunnels of these canals. This includes beam, height, shape of above water structure and ability to hit and be hit by other 20 to 30 ton steel barges and stone structures with no more than dings and scratches.
     
  6. Pericles
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    Pericles Senior Member

    Tom, that's very strange!

    You did not mention these collisions that you were having up and down our canals, when you were on holiday over here last year. Your PM to me was that it was all cool, calm and collected. :D :D

    A correctly outfitted narrow boat has bumpers and fenders and black, black paint, plus a megaphone to voice your opinion and throwing axes to hole the offenders below the waterline. :p

    So, apart from the sinking Mrs Lathrop, how did you enjoy the voyage? :p

    All the best,

    Perry
     
  7. tom28571
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    tom28571 Senior Member

    Ah yes, Perry,

    I did not dwell on such trivia then because our steel boat DID weigh over 20 ton with rugged steel belting all round. Hitting stuff was most likely the other guys problem.:D :D

    We did meet five other narrowboats in one tunnel that is over one mile long. Only hit one and don't know which of us was one inch out of his lane. If he wasn't steel, he is probably still sunk in there.

    Great cruise but, would I do it in my homebuilt lightweight plywood boat? No way:( :(
     
  8. Meanz Beanz
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    Meanz Beanz Boom Doom Gloom Boom

  9. Pericles
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    Pericles Senior Member

    MB,

    The 39' Chaffinch is steel construction and lengthening the Hawfinch is easy.

    Pericles
     
  10. Meanz Beanz
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    Meanz Beanz Boom Doom Gloom Boom

    Oh I didn't fink of that. Do you think it would make a massive difference if she was lighter given the hull form?
     
  11. Pericles
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    Pericles Senior Member

    MB

    Chaffinch 39'-Displacement to WL 19845 lbs (9000 kg).
    Hawfinch 36'-Displacement to WL 17200 lbs (7800 kg).

    Hawfinch can carry more coal. :D :D

    Mike Storer has plans for a riverboat that suits the Murray River.

    http://www.storerboatplans.com/TC35/TC35.html

    Pericles
     
  12. Meanz Beanz
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    Meanz Beanz Boom Doom Gloom Boom

    Has it got wheels? Stuff all water left in the Murray :D
     
  13. Pericles
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    Pericles Senior Member

    Last edited: Mar 3, 2008
  14. Meanz Beanz
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    Meanz Beanz Boom Doom Gloom Boom

    Too many farms, too many governments, too cheap water, it ain't dry but its not that healthy. Been a dry country for the past eight years, looks like light at the end of the tunnel but we are not there yet.
     

  15. rossgiles
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    rossgiles New Member

    Cheers to all who posted a reply - some very good tips, for which I still have to research all of the links.

    A few answers to the questions:

    I was thinking of English canal use for the boat, at this stage.
    With anticipation of keeping the boat a few years before looking at another project of greater skill and reward - such as a cruising cat

    This is hopefully going to be a training run for a novice to aquire skills and confidence to build better things.

    Maybe, it will put me off for life!!

    The valid points about concrete, steel and fibreglass - who wins in a collision.
    Hopefully no collision: or I lose.
    Same as every other GRP boat on the canals, of which there are many.

    About bridges: and getting under them;

    As the Hawfinch is a Narrowboat design:
    I hope that Selway's have designed a hull that wont require so much ballast to achieve stability, at a reasonable watermark. Such that I can make a floor on top of the concrete slabs or whatever..... and still have room inside to live, with a normal cabin fitted.

    I'd like some advice on how much ballast would be required if any one can throw a ball park figure on it.
    I had thought of using concrete slabs as they are easily moved etc....

    Presuming all the normal kit, tanks, small diesel engine and a bit of furniture etc...


    I have non marine grade ply in 6 and 8mm available and lots of pine beams and planks.
    However, that does not mean I cannot buy marine ply and other wood as required, I am doing the costing, against the materials I have, and will need. Obviously I'd rather use normal grade ply that I have, rather than buy marine ply.... If that is an acceptable use of the material. If not - it's on the to buy list.

    I have read that normal grade ply - Epoxy and Glassed would be ok.

    Has anyone some first hand experience with the success or failure of this?

    I had not thought of moisture problems as Erik points out, however, I am sure that the issue could be addressed in a similar fashion to Erik's suggestion.
    I will give that some more though and pass on any ideas, if I have them.

    I have so far only looked at EFS foam.

    So now, I know the consequences of EFS foam - Thanks Pericles

    I have received the study plan.

    There is not enough detail to carry out full calculations by any means.

    Can someone give me a rough estimate of what glass weight and how many layers would be required. The study plan is for the wood hull only.

    I have thought that 3 layers of 450g/sqm on each side of the sandwich would be ok?
    Is this too much or too little?
    Or should I do more layers on the water bearing side such as :

    4 glass - ply - foam - ply - 2 glass


    Thanks for the advice once again and I look forward to more replies

    Ross

    PS, I am also on the look out for storage space (soon) and building space/workshop (in the summer), should this project go ahead.
    Most likely between North London and Hertfordshire.
    I'd appreciate good leads.
     
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