Carefully Cutting Cambers

pauls_SPT

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Hello,

I never thought I'd see the day, but here I am fitting new deck-beams to my boat (instead of hacking out old rot)!

I've fitted one so far, just forward of the transom to mark the forward end what people have variously called the lazarette, aft-peak or aft-locker...

...anyway, be that as it may, I carefully marked out the camber I was going to cut on my new deck beam (a piece of timber 2" thick) using a compass and measuring tape and set about it with my jigsaw...the result is people asking me "how much had you drunk when you cut that?" My cut apathetically meanders along the line I drew with the vaguest of nods towards it, which isn't really what I was hoping for, to be honest /forums/images/graemlins/frown.gif

I don't have access to a bandsaw or anything large and fixed in position like that, all my tools have to travel around with me in the back of my van, so how can I cut a nice, accurate camber for the next beam? I think this lacklustre result was mostly down to the thickness of the wood deflecting the jigsaw blade...

Any thoughts will be very much appreciated,

Thanks,

Paul
 

Niander

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So long as the wood is wide enough to support the jigsaw i don't understand why there is difficulty in following the line...i don't have a band saw so a jigsaw would do it for me.
 

aitchw

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A lot depends on how much material needs to be removed but I have always found it easiest to rough the shape out, cutting the waste of with hand saw, jigsaw or whatever and then planing the rest down to the desired shape. With sharp tools and a steady workpiece it can be remarkably quick.

Good luck.
 

pauls_SPT

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Thanks for all of this /forums/images/graemlins/smile.gif

Planing...right...I suppose I should have thought of that...

The problem isn't so much following the line, Niander, it's that the jigsaw blade starts going off at an angle in thick wood and instead of a cut perpendicular to the base of the jigsaw, I end up with a cut that follows the line one side, but meanders about the other side...

Thanks,

Paul
 

old_salt

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If you have a 240v supply a cheep second hand B&Q electric plane will work wonders have a look on ebay or at car boots if a car boot try to test it someone will have a Genny if the seller agrees. A picky of my new beams, you can just see the single sided-ed duff tail's to the side deck pieces. Faint lines to the two nearest ones. I think the only way is to do them by line of sight too much scribing with and trying to measure them may well have in the end to be finally trimmed by sighting and then it is a case of what looks right is generally right. I found most components on my 1905 boat where quite makable with hand tools, for thats all what the guys had in those days. Now we can have the help on a modern electric tool making the job a lot easier.
I hope this helps.
I have added this I bought a Clarke's £110.00 Metalworker Band saw at a car boot for £60. changed all the 1/4 " bolts in the blade guide mech for HT ones lube the bearings often and invested in a quality Bi-metal 6 & 8 tpi blades they are a bit dear but will out last any HC blade by 12 months or more ( plenty of suppliers on the Net) and it has done all you see in the pic. O and by the way it will go in the back of a van.

Cheers David.
scan0010.jpg


Another bit if it will help is my coach roof beams not that all the forward beams can be seen in total but hopefully gives you the idea, these were steamed green welsh white oak 2" x 2" planed up and trimmed and then jigged as suggested on a board with blocks wedges and clamps.
scan0011.jpg


I hope our original poster does not object to this intrusion by me. I post the pics only in the hope it gives some help and ideas to others.
MerciaIII018.jpg

Cheers David.
 

jhughes

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Using a jigsaw on deep sections of wood is not as easy as it seems, the blade follows the line but underneath you can end up with a wiggly line. To avoid this:
Use a good quality sharp blade
Don't apply excess pressure
Leave a good margin outside your line to plane back to
If you have a pendulum setting on you jigsaw set it to maximum
Use a square to make sure the blade is 90 degrees to the base
And if you start to veer from your track try not to get back on track by applying sideways pressure as this deflects the tip of the blade sideways.
Good Luck
 

burgundyben

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Hi Paul, glad you making progress.

Have you considered laminating the beams?

Mark out the shape on a board, screw down some blocks, bottle of glue and a pile on clamps and you've got the bend you want. Might be cheaper and bring less waste too.
 

pauls_SPT

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Thanks again /forums/images/graemlins/smile.gif

Laminating sounds like a good idea, too - perhaps a combination of cutting a cambered beam and laminating would work better...

I'd always tried to use the minimum pendulum action on my jigsaw, as it tends to rip through the wood a bit on maximum and you get a cleaner cut without it...so there's one thing I've learnt /forums/images/graemlins/smile.gif

How useful would a bandsaw be, then?

Paul
 

cliffordpope

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Been there! I cut curved beams for the cabin roof out of planks of 2" teak I just happened to have. I did manage it with my Black & Decker jigsaw by:

1) fitting a new blade every 3 feet of cut
2) cutting just outside the line and planing afterwards
3) always cutting into the line of the grain, rather than out, so that it tended to understeer on the outside of the curve. Vice versa on the underside.
4) backing off frequently to release any trapped dust
5) not having too "aggressive" a line of attack. A backwards-angled blade cuts more easily, but tends to run away with itself.
6) don't use an old worn out machine with side-play.
 

old_salt

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[ QUOTE ]
You are making a fabulous job of that boat!! Well done, nice to see work of that calibre.

[/ QUOTE ]
Thank you.
We are getting there slowly hope to be back in the water soon then I will put more on about her.
 

sarabande

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Is it worth thinking about pinning a guide rail to the timber you are about to cut ?

A 2 cm by 1 cm lath will deflect to a curve suitable to the deck beam, and this gives a consistent curvature along whoich you can run the saw or plane.
 

pyrojames

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I cut beams from 2x6 oak with a jigsaw, but it did wander a lot. I left between 1/4 and 1/2 inch from the line and then planed witha power plane, finishing in situ with a hand plane. I used full pendulum no the jigsaw and let it drive itself, with minimanl hand pressure. The more hand pressure the more blade flex you tend to get. Avoid lateral pressure on the jigsaw as this increases wander!
 

pauls_SPT

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>I hope our original poster does not object to this intrusion by me

Your original poster is starting to see that his efforts are all rather second-rate to your level of workmanship!

My goodness me, if I get my boat to within a tenth as good as that, I'll be happy!

Out of interest (and excuse my ignorance) what's that black adhesive you're using?

Paul
 

old_salt

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Hi Paul.
Thank you for you kind comments.
The black adhesive is Sikaflex 291 not so much as an adhesive but as a bedding compound and to stop any moisture ingress we used it under the floors and any where we have wide mating surfaces always backed up with screws. I don't reckon it much as a glue. But as a bedding compound it is good stops water and squeaks. The joints were screwed as well. Just visible as round dots.
 

nmiller

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Do not forget that the old men would have put some extra set on their rip saw teeth to yield a wider kerf, and sawn round the gentle curve of a deck beam camber by hand. This would also avoid vibration white finger, which is a risk from a chattering and buzzing jig saw.
 
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