wood for a traveller bar

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Nessa
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wood for a traveller bar

Post by Nessa »

I have to make a traveller bar for the roland europe. I can't decide between using a single piece or trying to laminate something out of strips of ply. This isn't something I have done before so any suggestions very welcome, including the best way to fix it in place once made!

This is all for da yoof, who is quite small, so we are trying to fit the boat to allow for his size and get the traveller quite high across the boat if possible.
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Re: wood for a traveller bar

Post by jpa_wfsc »

The traveller bar will be _very stiff_ and so will carry the load so you do not need to make anything to support it. I bought one for the finn a year or so ago and my local fabrication engineers could not bend it with their kit.

People often do make a supporting thwart though - as its a convenient place to secure control line cleats etc.

But you do need to transfer the loads into the hull carefully. So laminate up some shaped pads that will take the outboard (flat) ends of the traveller bar to the curved topsides of the tanks. Also make some pads that fit well to the inside of the tanks. Epoxy those in place and then use bolts though to secure the traveller bar.

The traveller should also be fixed to the top of the C/b case - which will also stiffen that up.
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Re: wood for a traveller bar

Post by Rupert »

Laminating something from strips of alternate light and dark wood can look good in the right place, or just in mahogany for a more classic look. The problem with plywood for this kind of thing is the much of the grain is running across the bar, not along it.
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Re: wood for a traveller bar

Post by Ed »

may be missing something here.....

but we are talking about the wooden base for a traveller track....right?

Is it curved? fore and aft or up and down?

If it is flat, it is easy and I presume you wouldn't be asking...so a curve.

Rupert is right, avoid ply, make a laminate using thin strips from 3mm (bit thin but possible) up to about 8 or 9 mm (depending on how easy and how much you have to bend it) of hardwood.

You can alternate a nice mahogany with a light softer wood if you want. Looks good and is plenty strong enough. You can also if you wish drill holes in some of the inner layers to lighten it up a bit. I have made beams in the past by alternating mahogany (for outer layers, with a soft wood (drilled out) for alternate inner layers. Looked fine and plenty strong.

Finally if you want to beef them up a bit, run a layer of Uni-carbon between the laminates. Trip it up afterwards and it can look very nice.

If you must use ply, use a 2 or 3 layers of good plywood and laminate uni-carbon between. I made the top plate for Stu's IC like this from I think 2 layers of 3mm with uni between (may of been 3 layers?) and it looked fine and was plenty strong enough.

Which ever way.....you will (as always) need plenty of clamps!

cheers

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Re: wood for a traveller bar

Post by billytwiglet »

I considered a 'traveller bar' but opted for a cool box instead :wink:
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Re: wood for a traveller bar

Post by Nessa »

had it been for me I was going to forego the bar and opt for a sort of carbon rod thing with a slider.....
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Re: wood for a traveller bar

Post by RonnyDG »

Could this image encourage you before fitting a carbon rod?
Image
What you see is me messing with two strips of 4mm oak and a strip of 160grm2 glass in between bonding with Epoxy (9 clamps involved), not high tech at all.
Laminating strips is challenging in the sense that it involves some trial and error but it's not hard to do and the result is rewarding.
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Re: wood for a traveller bar

Post by JimC »

RonnyDG wrote:What you see is me messing with two strips of 4mm oak and a strip of 160grm2 glass in between bonding with Epoxy
I don't know that I'd bother with the glass in between: by the time its doing any work won't the wood have failed catastrophically? There's a lot to be said for a nice stripey pale/dark wood laminate:-)
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Re: wood for a traveller bar

Post by billytwiglet »

good example RonnyDG. Pre-forms are stiffened by the number of glue lines, like ply which is stiffer with more layers, so if you laminated 4 layers of 2mm it would be stiffer than 2 layers of 4mm. Would also be stiffer than the equivalent 1 layer of oak steamed to shape. The glass layer effectively adds another glue line = stiffer.

just like pre-formed laminated chairs.
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Re: wood for a traveller bar

Post by RonnyDG »

Thanks for coming to the rescue John, I was starting to doubt my own knowledge there.
There is a practical side effect as well. If you add a layer of glass, the curve of the lamination will be much the same after unclamping. Do the same without glass and the assembly will spring back a lot more. Meaning that the outcome is more of a guess.
Granted the piece will be heavier and maybe stronger as need to be, it will save the time of having to start all over again.
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Re: wood for a traveller bar

Post by JimC »

RonnyDG wrote: There is a practical side effect as well. If you add a layer of glass, the curve of the lamination will be much the same after unclamping. Do the same without glass and the assembly will spring back a lot more.
I'd need to see that demonstrated to believe it I fear. Consider two identical layers of wood with one layer of glass between them. Put a weight on the top. Roughly speaking the bottom layer of wood is in tension, with tension increasing as you reach the edge, and the top layer in compression with compression increasing as you reach the edge. The middle is in equilibrium so what's the glass doing? Think of I beams...
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Re: wood for a traveller bar

Post by Rupert »

Theoretically I agree with Jim, here - I can see a sandwich which went glass-wood-glass-wood-glass being far stiffer, but the layer of glass in the middle is neutral. However, theory and practice don't always match, so I'd like to see the finished article, too.
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Re: wood for a traveller bar

Post by jpa_wfsc »

I guessed that you would have to allow for some spring back when doing this - and searched for it. There is a formulae but I'm sure there will be many other opinions! And factors to make for different timbers. Maybe Chris has some data?

Image

and guidance on what thickness of laminate to use:

Image

Sadly I've never made a curved lamination - i'd love to - but I'd be worried if I thought that glass between the laminations was going to prevent the spring-back. You would be locking in a lot of tension which surely would cause problems eventually?
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Re: wood for a traveller bar

Post by Nessa »

aaaaaaaaaarrrrrrrrrggggggggghhhhhhhhh

:evil: :twisted: :evil: :twisted: :evil: :twisted:
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Re: wood for a traveller bar

Post by Ed »

This is starting to remind me of a conversation with an old mate: Wizz Dease at Matrix Mouldings:

"I know it works in practice.....now, I just need to see if it works in theory".

one of my favourite sayings, right up there with:

"If it is worth doing.....it is worth doing badly"

My experience is that an inner layer of glass or better still carbon, does stiffen the laminate and decrease 'spring-back'. On the other hand, I understand the theory of why this shouldn't be the case.

I can't really think of any advantage of 'spring-back'. I would much more rather introduce a 'stable' bit of laminated wood/carbon rather than a bit of laminated wood which needs to be bent back into shape to get it to fit and is therefore already 'stressed' before it even goes into the boat.

Any more evidence or thoughts?

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