cutting out plywood decks

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miracle
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cutting out plywood decks

Post by miracle » Sun Apr 13, 2014 1:48 am

cutting out the plywood deck shapes ready for fitting on a miracle

which tool , jigsaw, dremel type tool , or other ?

its more tricky than i thought , has to be spot on first time

Graham T
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Re: cutting out plywood decks

Post by Graham T » Sun Apr 13, 2014 9:25 am

It's easier than you think - providing you are renewing the outer gunwhales you only need the centre foredeck join and the small join on the side decks to be precise. Try and use the factory edge of the ply sheet for the foredeck join. Plane a slight undercut angle down its length so with the curve on the foredeck the top edges butt up nicely. Roughly cut out the shape with a jigsaw oversize on the outer edges. Plane the side deck joint straight and slightly undercut as this needs to butt up with the side decks nicely. Glue the whole thing on. Plane the edges down to size afterwards making sure you follow the angle of the inner gunwhale piece - don't plane at 90 degrees to the deck or there will be gaps when you put the outer gunwhale on. A sharp block plane will make short work of this. The trickiest bit is the shape of the cockpit side of the foredeck. I use a combination of bearing guided router, curved surform, spoke shave and abrasive paper on a flexible block to get this right....

Hope this helps
Graham
Graham T
Osprey 1340, Osprey 1245, Osprey 55, Miracle 1358, Laser heap, ancient Mirror kit half assembled, Project Miracle in need of decks........
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miracle
Posts: 54
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Re: cutting out plywood decks

Post by miracle » Sun Apr 13, 2014 11:46 am

Graham T wrote:It's easier than you think - providing you are renewing the outer gunwhales you only need the centre foredeck join and the small join on the side decks to be precise. Try and use the factory edge of the ply sheet for the foredeck join. Plane a slight undercut angle down its length so with the curve on the foredeck the top edges butt up nicely. Roughly cut out the shape with a jigsaw oversize on the outer edges. Plane the side deck joint straight and slightly undercut as this needs to butt up with the side decks nicely. Glue the whole thing on. Plane the edges down to size afterwards making sure you follow the angle of the inner gunwhale piece - don't plane at 90 degrees to the deck or there will be gaps when you put the outer gunwhale on. A sharp block plane will make short work of this. The trickiest bit is the shape of the cockpit side of the foredeck. I use a combination of bearing guided router, curved surform, spoke shave and abrasive paper on a flexible block to get this right....

Hope this helps
Graham
Thanks Graham , i hadnt even thought of an undercut to help with the slight curve when joining, shows how much i know about working with wood, i have one outer gunwale already off, well it literally fell off actually , the other outer gunwale is fine and in place , i have a feeling that using filler scratching my head and saying bugger ! will be the order of the days ahead. :mrgreen:

miracle
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Re: cutting out plywood decks

Post by miracle » Sun Apr 13, 2014 1:42 pm

P.S which poses another question ive still been pondering ,seat and secure the decks with wood glue or epoxy , im 60/40 in favour of epoxy . However taking a deck off if a repair is needed id imagine could be troublesome if it is done with epoxy.

chris
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Re: cutting out plywood decks

Post by chris » Sun Apr 13, 2014 5:24 pm

I think most people will say epoxy. Ok it will be a lot of chiselling if you do have to replace later but it will be a reliable bond. I'm sure other adhesive will be good too though and may be easier to undo later.

Cutting plywood: if using a jig saw beware of it splintering and chipping out. It's best to mark out the sheet on the underside and cut with the underside up to keep the good surface good. The saw cuts upwards. In fact that is an easy way to mark the shape out from the hull and you will be marking out the under side. Certainly if the gunwales off leave a bit to trim after gluing.
I like using the Japanese hand saws for plywood. They are not very expensive, have replaceable blades and leave a wonderful finish. You can safely cut on the top side of the sheet now.

JimC
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Re: cutting out plywood decks

Post by JimC » Sun Apr 13, 2014 5:32 pm

If one gunwhale is off anyway rip the other off.
- Far easier to get the decks on
- job will be incomparably more satisfying when you've finished
- Not that much extra work really, indeed if you work out the hassle in fitting decks with gunwhale on place its probably less time.

miracle
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Re: cutting out plywood decks

Post by miracle » Mon Apr 14, 2014 11:28 pm

first deck cut out and ready to go on , not the best fit , took ages to mark it out and still got it slightly wrong , getting a good line with a jigsaw is not easy considering ive never used one before, anyway , up close its not great , but at a distance on a rainy day will pass.

miracle
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Re: cutting out plywood decks

Post by miracle » Wed Apr 16, 2014 8:42 pm

one word trying to fit the decks , FRUSTRATING

Michael4
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Re: cutting out plywood decks

Post by Michael4 » Wed Apr 16, 2014 10:35 pm

Try using a jigsaw with a hacksaw blade in it. Slower and much more controllable. Tidy finish on ply

Alternatively you can get downward cutting blades for those of us who are so spatially inept that we don't understand upside down shapes.
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miracle
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Re: cutting out plywood decks

Post by miracle » Wed Apr 16, 2014 10:50 pm

Michael4 wrote:Try using a jigsaw with a hacksaw blade in it. Slower and much more controllable. Tidy finish on ply

Alternatively you can get downward cutting blades for those of us who are so spatially inept that we don't understand upside down shapes.
the cutting is fine ,im using a jigsaw with a hacksaw blade , it cuts well , it is my terrible marking out and mathematical ineptitude thats the problem :lol:

JimC
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Re: cutting out plywood decks

Post by JimC » Wed Apr 16, 2014 10:53 pm

miracle wrote:one word trying to fit the decks , FRUSTRATING
It really shouldn't be. I always find it a quick and easy job. Cut it oversize, staple it down, plane down almost to the inner gunwhale then finish with a belt sander.

If you're having enormous trouble with marking out and sizing what I do with bulkheads and other such things which do have to be accurate is to blag some large sheets of corrugated cardboard box and cut those to exact size with scissors and taping bits back on if I cut it too small, and when I've achieved perfection then cutting the carbon or ply or whatever with a guaranteed accurate template.

Image

miracle
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Re: cutting out plywood decks

Post by miracle » Thu Apr 17, 2014 3:41 pm

just been rechecking the ply deck thickness and it seems i have got it totally wrong, ive been trying to fit 6mm ply ,which is not that flexible, when actually the ply decks on the miracle are thinner and very light and flexible, any idea folks as to the exact thickness of ply decks on the miracle surely it cant be 6mm .

just rang a few places and its 4mm , bugger , another homer simpson moment

2 8x4 ply sheets should if i reckoned right , supply the 4 deck panels.

miracle
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Re: cutting out plywood decks

Post by miracle » Fri Apr 18, 2014 6:11 pm

found another hole 3 x 3 , here we go again :mrgreen:

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