help

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carlos miranda
Posts: 4
Joined: 10 Mar 2010, 22:55
Sail number: POR 11
Club: Grupo Naval de Olhão
Design: TS2- britpop

help

Post by carlos miranda » 02 Oct 2015, 11:07

Someone has design piece with measures to pre-bend the mast

Thanks

Hiljoball
Posts: 270
Joined: 06 Jan 2006, 00:47
Sail number: CAN 307
Design: V8
Location: CAN

Re: help

Post by Hiljoball » 03 Oct 2015, 22:19

I use a home made three wheel bender.

https://www.flickr.com/photos/136579380 ... 7091890774

I bend the tubes before I cut them to length. I start by measuring from the mast heel to the lower band, and then from the lower to the top band and mark it with tape. Then I measure back down to the extent of the desired bend and tape that. Now I set the top tape at the centre wheel and push through the bender until the bend limit tape is at the centre wheel. After bending and drilling, I cut off the excess at the top. That way the bend extends all the way to the top.

Different alloys and different mast tubes (dia and wall thickness) require different pressures.

The French 11mm tube is hard to bend. It has an amazing ability to ‘spring back’. So when I use the bender, I try to creep up on the setting by running the tube, once in and out, then remove a nd look down it – no change, add half a turn and go again.

The way I do it is
1. Sight the tube for any existing bend, and then put the prebend in the same direction. I do not cut the tube until finished.
2. I measure from the bottom of the mast to the lower band, and then from the lower band to the mast tip. Tape the tip with masking tape. Then measure down from the tip to the length for the bend and tape again. That way the extension of the tube is at the top and you can apply the bend over the entire length (just trim off the top once finished).
3. Mark the centre line of the mast on both sides at top middle and bottom for reference.
4. Place the tip in the bender at the middle wheel and run forward until the bend limit is at the middle wheel, and then run out – hold the mast tight on vertical as it will try to twist. Pop out of the bender and sight down the tube – adjust the screw and repeat as necessary until the bend is achieved.


John
John Ball
CRYA #895
IOM CAN 307 V8
In my private capacity

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