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  1. #1
    Join Date
    Mar 2009
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    Default Hollow wooden surfboard

    Hi all
    At school I am taking part in a surfboard making club, now I am making a hollow surfboard (basic ply frame/skeleton then veneer over top and around edge). I have made the basic frame and am up to the stage of placing the veneer on top. I just wanted to know would it be smart to put marine foam inside the surfboard, for accoustical reasons (to reduce the noise of splashing water under neath and if in the event of a break would provide some support) ?
    Thanks for any advice
    David
    Just another 17 year old who can work the remote

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  3. #2
    Join Date
    Jun 2008
    Location
    Perth. WA
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    377

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    I think solid foam inside would make the structure stronger. Also, if by chance you get a leak, your board won't sink!
    Pugwash.

    Never criticise Australia Post. One day they might find out where you live.
    www.clivequinn.com

  4. #3
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    Mar 2009
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    Sydney
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    Hi
    Thanks Pugwash for your speedy reply, I found a place in Australia that has marine suited foam, would I just get the liquid/expanding type and spray it in and have a bit of scrap ply on top and bottom to keep it flush and then remove excess once it has set?
    Thanks again for your advice
    David
    Just another 17 year old who can work the remote

  5. #4
    Join Date
    Apr 2007
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    Arundel Qld 4214
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    701

    Default Hollow surfboard

    Cub,
    I sell a lot of Paulownia to hollow surfboard builders and have talked to most of them about their boards. I have never heard of any of them putting foam inside the board. Some attach the strips for the skin to a sheet of glass/epoxy to make a single section and the 'glue this to the frame. The outside is then glass/epoxy and this provides the strength and waterproofing needed. The big thing is to have a drain plug to control air expansion and contraction within the board. Some guys even have the drain plug as a release valve to maintain an even pressure within the board.

    Having said that I can see no reason for not putting foam inside the board if that is what you want to do. It will add some weight but the final decision is yours.

    Whitewood

  6. #5
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    Mar 2009
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    Quote Originally Posted by whitewood View Post
    Cub,
    I sell a lot of Paulownia to hollow surfboard builders and have talked to most of them about their boards. I have never heard of any of them putting foam inside the board. Some attach the strips for the skin to a sheet of glass/epoxy to make a single section and the 'glue this to the frame. The outside is then glass/epoxy and this provides the strength and waterproofing needed. The big thing is to have a drain plug to control air expansion and contraction within the board. Some guys even have the drain plug as a release valve to maintain an even pressure within the board.

    Having said that I can see no reason for not putting foam inside the board if that is what you want to do. It will add some weight but the final decision is yours.

    Whitewood

    Hi
    I really like the idea of a drain plug hope you don't mind me borrowing that.
    We will be fibreglassing it in the end but I just thought the foam being dense would provide support for the veneer on top which is about 6-7mm thick. Should I bother? I'm perfectly fine going the extra mile if it gives me a stronger board.
    Thanks again all for the ideas.
    David
    Just another 17 year old who can work the remote

  7. #6
    Join Date
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    Arundel Qld 4214
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    Default Hollow surfboards

    Hi
    I really like the idea of a drain plug hope you don't mind me borrowing that.
    We will be fibreglassing it in the end but I just thought the foam being dense would provide support for the veneer on top which is about 6-7mm thick. Should I bother? I'm perfectly fine going the extra mile if it gives me a stronger board.
    Thanks again all for the ideas.
    David
    __________________
    If I can do it, you can do it

    David
    I believe it is absolutely essential you put a drain plug in the board. If not to drain water but allow you to stabilise air pressure within the board. As the board goes from hot sun to cold water the air pressure changes a lot. If the board is sealed completely at construction time in a cool shed then as soon as it is in the hot sun the air inside expands and can open up seams thus causing leaks.

    Most of the Paulownia I sell for hollow boards is 6 mm thick. This thickness is my recommendation. Some guys have used 4.5 mm and extra epoxy which i believe defeats the weight saving as epoxy weighs more than Paulownia. The part I can't advise you about is the spacing of the internal frames to support the skin. In my mind the strength of a board comes from within and depends on the method used by the designer to build the frame. This is way outside my expertise so I won't comment other than to say I don't believe any 2 hollow surfboards are built exactly the same. There are some basic concepts but each builder appears to put his own ideas into the finished board.

    Whitewood

  8. #7
    Join Date
    Jun 1999
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    Westleigh, Sydney
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    While the foam would certainly add strength, it probably isn't necessary if you use 6mm ply or paulownia. However, it could cause problems by retaining water. IMHO, you'd be better off leaving it hollow and including the drain plug.
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  9. #8
    Join Date
    Oct 2007
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    Alexandra Vic
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    I agree with AlexS about foam. To be totally waterproof, it is fairly heavy, anything less than than totally waterproof will absorb and retain water, becoming increasingly heavier as it absorbs more water.

    Also make sure that every rib and stringer in the frame has moderate sized half moon notches so that water can run to the drain plug when the board is stood near vertically for drainage. You definitely need the drain plug to allow air pressure inside to equalise with that outside. The board will be subject to fairly extreme temp changes in use, causing expansion/contraction of the internal air. (on car roof on a 40deg day into water at about 15 deg). Leave the bung in the drain but loosened about a turn or so to release the seal, close just before enterining water, and remove to drain when leaving water and return to one turn loose position.

  10. #9
    Join Date
    Mar 2009
    Location
    Sydney
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    Default

    Hi all
    Thanks everyone for your advice, after thinking about what you all had to say I won't be filling the board with foam (phew decision made), but I will be incorporating a drain plug and a small passageway for water to migrate back to the drain plug. Thanks again everyone for your helpful input. If someone has anymore tips they would like to share go for it and share it.
    Thanks again
    David
    Just another 17 year old who can work the remote

  11. #10
    Join Date
    Oct 2007
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    Alexandra Vic
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    How is the internal frame configured? You will need multiple drainage channels to ensure that every cell in the framing is able to drain. A single drainage channel suggests no internal longitudinal framing between the rails, which I suspect means a broken board fairly early in it's life.

  12. #11
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    Apr 2007
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    Arundel Qld 4214
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    Default hollow surfboards

    Quote Originally Posted by malb View Post
    How is the internal frame configured? You will need multiple drainage channels to ensure that every cell in the framing is able to drain. A single drainage channel suggests no internal longitudinal framing between the rails, which I suspect means a broken board fairly early in it's life.
    I still don't hold the opinion that I have expertise in designing or building hollow surfboards. Malb is right about the drainage holes. Depending on the types of wood you have used in the construction it will be important to absolutely essential to get all moisture drained out of the board. Even moisture from the air can condense inside the board. You should not have to hold the board in 1 position for a lengthy time to allow any moisture/water to collect into 1 drain passage. Most builders remove excess timber from the frames with a keyhole saw so drainage is quick and dry air can circulate inside the board to complete the drying process.

    On the question of a board breaking because it doesn't have a longitudinal framing may not be so black and white. Depending on the designer longitudinal strength can be built in through the rails, as done by Roy Stewart. I assume you have a design so you should follow it and you should not get into trouble.

    I'm not too smart with computers so can't work out how to attach a copy of an email showing photos of a board constructed by a 15 year old with advice from his father. If your interested to see it send me an email and I'll forward it to you.

    Whitewood

  13. #12
    Join Date
    Mar 2009
    Location
    Sydney
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    Default

    Hi
    Well below is a drawing of my frame, I will take a photo when school gets back to show my frame clearly. (you may ned to click on it to make it bigger)

    BTW whitewood to attach a photo the easiest way would be when your are in the section to write a message up the top where it says font etc theres a little paperclip click on that and there will be a popup and you just click on browse find your file or picture then lick upload, now once you have done that click anywhere in your text where you want your picture to be then go back to the paperclip and click on it, it should say manage attachments click on the image name and some words like ATTACH will apear in your text now your done, you can check in preview its where you want it to be.

    Would it be best to just drill some holes in the centre of the frame pieces or should I notch a bit on the edge(bottm side) so there is a clear path for the water to escape?
    Also does anyone know of some good drain plugs to use or would just someones off ebay be suitable?

    Thanks for the help
    David

    Attachment 167501
    Just another 17 year old who can work the remote

  14. #13
    Join Date
    Oct 2007
    Location
    Alexandra Vic
    Age
    69
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    Default

    Hi Cub,

    From your sketch you are building a hollow swallowtail with a single stringer (longitudinal structural member).

    Re info about a drain plug, we used to use an early version of this. You want to place it as far into the nose as you can get it,near the junction of a rail and the central stringer. You would need a drainage notch in the stringer to allow drainage to flow to the off centre plug.

    I have cobbled a sketch as a PDF file for a suggested layout for the drainage notches in the ribs (see link below). This shows a couple of notches near the centreline but clear of the stringer. These want to be in the order of 12mm wide by 6 mm deep, and placed on the ribs so that they fall behind the centreline of the plank, i.e well clear of the planking seams. The sketch also shows a couple of breather holes (10mm dia would be adequate) to allow air to enter cells while draining to prevent a vacuum developing. To minimise reduction of rib strength these should be placed accross the rib at about the horizontal centreline. There should also be similar hole in the stringer in the front bay near the drain plug.

    It would pay to seal the end grain of the notches and breather holes to ensure that moisture cannot get into the timber. Epoxy would be suitable.

    Hope this makes sense to you.

    Mal

  15. #14
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    Oct 2007
    Location
    Yarram
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    63
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    Default

    Just clarifying malb, you say to put the drain plug in the nose (of the board)? Like sunk into the deck or the bottom of the board? So it'd be best to rest/store the board nose to the ground?

  16. #15
    Join Date
    Oct 2007
    Location
    Alexandra Vic
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    I am going back about 50 years when my dad built my sister an 11ft ply plank. This beast had laminated softwood rails, nose and tailpiece, with 3/16 ply skins rebated into the softwood surround, two 1/2 in stringers and ribs about every 8 inches. Drain was in the nose on the deck. After use, pop the plug pick up the tail and walk forward, raising the tail till vertical. any seepage runs out as you the tail. Once flow stops, walk backwards to lower the tail, and loosely refit the plug, but don't seal the O ring. This allows the interrnal air pressure to vary with exernal pressure.

    I took this board over about 2 years after it was built and used it daily for 12 years before replacing it with foam/glass board. In that time it developed one crack due to cousins running along it on dry ground. Till then it was watertight.

    Drain needs to be on deck in nose as this is where it has least immersion and causes least drag when on a wave. Keep it as flush as possible.

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