wood for a traveller bar

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billytwiglet
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Re: wood for a traveller bar

Post by billytwiglet »

Proper way to do a preform is to make a male and a female former; router with a compass some thick chipboard or mdf multiples glued and screwed together will give you a deeper mould. Different outside cuve/inside curve, difference is the thickness of the bit you want to form plus an allowance for glue. Use thin strips of wood or constructional veneer and glue them up into a multi club sandwich (lettuce not adviseable, hold the mayo) Clamp them into the former and leave until the glue has fully set. The resulting preform curve will not move appreciably if at all. The more thinner layers you use the better for accuracy and strength; max thickness 3-4mm per layer x ten or twelve layers. Looks like a bent bit of thick ply when done. Use packing tape to line the mould or you will end up gluing the shape to that too! It will be uneven on the edges as the layers squirm a bit; electric planer will sort it our or if you are confident or don't mind losing some fingers, pass it over a table saw. Remember if you clamp the form in the mould again with a bit sticking out the side you can easily plane the edges smooth with the benefit of the mould as a clamp/clamped to the bench.

It really works!

Oh, did I say you had to make a bench first?
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solentgal
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Re: wood for a traveller bar

Post by solentgal »

Oh yes Nessa I feel your pain.........the layers are in compression on the upper surface, and in tension on the lower surface when moulded... therefore the joint between layers is being compressed AFTER it is released from the clamped position and the components try to spring back...., so it depends on the bond between layers I think..(do we get into coeficients of friction at this point?)...no matter what the layers are made of.........this is an interesting issue ..but at the end of the day a traveller on a Europe is not always curved anyway.......but a curved laminated one looks really cool I'll admit!

Ok........shoot me down guys! :D
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Re: wood for a traveller bar

Post by Nessa »

I think I have a nice mahogany thwart left over from a marauder lying around somewhere. Now, where's my hacksaw.....
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Re: wood for a traveller bar

Post by Obscured by clouds »

billytwiglet wrote:Proper way to do a preform is to make a male and a female former; router with a compass some thick chipboard or mdf multiples glued and screwed together will give you a deeper mould. Different outside cuve/inside curve, difference is the thickness of the bit you want to form plus an allowance for glue. Use thin strips of wood or constructional veneer and glue them up into a multi club sandwich (lettuce not adviseable, hold the mayo) Clamp them into the former and leave until the glue has fully set. The resulting preform curve will not move appreciably if at all. The more thinner layers you use the better for accuracy and strength; max thickness 3-4mm per layer x ten or twelve layers. Looks like a bent bit of thick ply when done. Use packing tape to line the mould or you will end up gluing the shape to that too! It will be uneven on the edges as the layers squirm a bit; electric planer will sort it our or if you are confident or don't mind losing some fingers, pass it over a table saw. Remember if you clamp the form in the mould again with a bit sticking out the side you can easily plane the edges smooth with the benefit of the mould as a clamp/clamped to the bench.

It really works!

Oh, did I say you had to make a bench first?
or you could pound a number of large nails along the inside curve of your intended laminating job and lay your veneers up against them. holding them in place with yet more large nails.

That really works too!
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Rupert
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Re: wood for a traveller bar

Post by Rupert »

A row of nails was how I was taught to do it, but the pressures on them are huge, so they can't be into a thin bit of wood.
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Re: wood for a traveller bar

Post by Obscured by clouds »

Rupert wrote:A row of nails was how I was taught to do it, but the pressures on them are huge, so they can't be into a thin bit of wood.


Use more nails :lol: and have the first piece be sacrificial - use some other wood, taped up to avoid sticking
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Re: wood for a traveller bar

Post by jpa_wfsc »

one approach for a one off, another for production of a batch.....
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Re: wood for a traveller bar

Post by Brookesy »

Do you really need to have a curved support for you mainsheet track?
When I refitted the FD Superdocious we used Harken HiBeam Track 2271 which can be bent to your requirements by them and is secured at either deck, backed up by one or two threaded bar pillars which can be secured to the floor.
This sytem works well and the loads on the FD are I am sure much greater than those on the Europe.
The Harken catalogue gives you info on the recommended span distances and also the options of vertical horizontal or compound bends which are available.
A nice laminated beam will look great but do you need all that extra weight on a Moth?
I will try to find a picture this evening if its of interest.
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Re: wood for a traveller bar

Post by Nessa »

it is of interest to me, because I would rather not have a large thwart adding unnecessary weight. The traveller in the phantom menace was simply a section of tract supported at either end and bolted through the side tanks. on this europe there is already enough transverse stiffening anyway.
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Re: wood for a traveller bar

Post by jpa_wfsc »

Nessa wrote: The traveller in the phantom menace was simply a section of tract supported at either end and bolted through the side tanks. on this europe there is already enough transverse stiffening anyway.
and often done like that on Finns (but always secured in the centre to the back of the CB case to stop it tipping over) and the application is almost identical in both boats - albeit the Finn probably higher loading.
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Re: wood for a traveller bar

Post by jpa_wfsc »

Brookesy wrote: The Harken catalogue gives you info on the recommended span distances and also the options of vertical horizontal or compound bends which are available.
I believe that Harken bend them before heat treating them - certainly they are very difficult to bend if supplied straight. I bought a straight one for the Finn and then found that my local fabrications firm could not bend it with a rolling machine without damaging the roller bearing surface profile.
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Re: wood for a traveller bar

Post by Brookesy »

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Re: wood for a traveller bar

Post by Graham T »

Helm hiking cushions! I want some of them..... 8)
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Re: wood for a traveller bar

Post by billytwiglet »

'pussy pads' I think is the correct technical term!
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Re: wood for a traveller bar

Post by JimC »

jpa_wfsc wrote:I believe that Harken bend them before heat treating them - certainly they are very difficult to bend if supplied straight.
The other thing you should avoid is bending a track that comes predrilled. I shouldn't need to tell this audience why!
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