Topic: MAST CONSTRUCTION (Read 7626 times)

Neil · « **on:** February 13, 2013, 09:03:19 am »

I need wooden masts for my lifeboats, and they carry quite a bit of sail, so want them to take some strain........but how to construct them.

It would just be my luck to chose some dowel with a hidden "shake" and the first time out.....crack, bang, wallop and have to start again.

I am going to shape them from the square section in either lime or cherry which I have..............but when thinking about it last night I thought what would be better.three laminations of wood glued together, or the same, with hollow for a carbon fibre rod sandwiched in the middle.....the carbon fibre can be either solid or tube, as I have both....and these would be epoxied into the center and set solid...........

What do you guys think.
the exterior of the mast would be the same in either case and look wooden in build.

rmaddock · « **Reply #1 on:** February 13, 2013, 09:29:59 am »

Have you thought about hollow hexagonal masts Neil? Try googling images of "hollow wooden mast".

They're supposed to be strong and you could still put your carbon rod down the middle...which is quite a cunning plan, by the way.

tigertiger · « **Reply #2 on:** February 13, 2013, 09:47:32 am »

Yes agree with last poster.
If the mast is big enough you could try a birds mouth construction.

I would be inclined to steer away from hardwoods, as they are generally brittle and more likely to snap. By contrast softwoods will spring more and take the flexing much better.

Neil · « **Reply #3 on:** February 13, 2013, 09:50:36 am »

I'll have a look at that one Rob, and cheers for the input guys .
neil.

Martin (Admin) · « **Reply #4 on:** February 13, 2013, 09:57:37 am »

Quote from: tigertiger on February 13, 2013, 09:47:32 am

If the mast is big enough you could try a birds mouth construction.

Oh, it's a real thing! I thought I was being 'had on'..... again!
http://planingaround.blogspot.co.uk/2009/09/birds-mouth-mast.html

Neil · « **Reply #5 on:** February 13, 2013, 10:01:50 am »

think of the mess and the swear words I could utter, making those, lol

derekwarner · « **Reply #6 on:** February 13, 2013, 10:05:31 am »

Neil........
successive lamination of the same timber in the same plane will not produce any greater strength
cross laminations in opposing planes will produce greater strength...eg., building a mast in hexagional segments as rmaddocks s note sis a good idea
carbon fiber reinforced cored material has great strength in both tension or compression and in shear ...but this must be harnessed to achieve it's strength qualities
the same material will bend like a banana if unrestrained

....Derek
Derek

rmaddock · « **Reply #7 on:** February 13, 2013, 10:08:50 am »

Quote from: Neil on February 13, 2013, 10:01:50 am

think of the mess and the swear words I could utter, making those, lol

And imagine how often you'd have to tell people, in detail, just how complicated and sanity threatening they were since you wont be able to see from the outside!

dreadnought72 · « **Reply #8 on:** February 13, 2013, 11:15:36 am »

Quote from: derekwarner_decoy on February 13, 2013, 10:05:31 am

successive lamination of the same timber in the same plane will not produce any greater strength

Derek, you may gain strength depending on the glue used for the laminations.

Martin, the photo of the birds' mouth mast shows a central plug: these are used at the ends to keep water out. The mast is invariably hollow: making them easy to run wires up, but a difficult job when assembling, due to (slippy) epoxy.

Andy

Jonty · « **Reply #9 on:** February 13, 2013, 11:26:33 am »

How about trawling the junk shops for old split cane fishing rods? They used to be dirt cheap if not a well-known brand. Just need sanding to a round section.

Neil · « **Reply #10 on:** February 13, 2013, 12:24:42 pm »

the only reason I don't use split cane, Jonty ( and I have a couple of old split cane rods in the workshop, is I need a square section end piece on each to fit into a tabernackle, and I don't think there'd be any strength in the base of the mast if I had to laminate an extra piece onto the rod to gain that square.........it would be easier to use a single piece of timber run and plane it down to round.................
I have to disagree with derek though on laminating strips for strength, as all Ercol laminated chairs have great strength in their shaped frames which are all laminated.
Mind you, been looking for my carbon fibre rod this morning whilst casting........and can't find it

boatmadman · « **Reply #11 on:** February 13, 2013, 01:01:06 pm »

Neil,

If you can find a length of knot free straight grained spruce or douglas fir it will do your job perfectly.

These are used in full size boat building, I used spruce in my dinghy with great results.

Robbins timber might be worth looking at:

http://www.robbins.co.uk/marine/index.asp

Ian

rmaddock · « **Reply #12 on:** February 13, 2013, 01:56:54 pm »

Following from what Ian says, I made my Nobby masts from solid square stock. I spoke to Mr Nixon at www.twigfolly.com. You can see the posts HERE.

JayDee · « **Reply #13 on:** February 13, 2013, 02:55:08 pm »

Hello,
The mast on my J Class yacht was made from two fishing rods.
The rods must fit snugly inside each other.
Decide which has to be the inside one and rasp a really rough finish onto its outside.
Smooth it out a bit so it will fit into the other rod and mark how far it fits in.
Coat the "inside" rod with ordinary Silicon Sealant.
Wait about 9 or 10 minutes for the sealant to start to "go off" and slide and twist the rod into the outer one.
Get it as near to the mark put on earlier and tap it in as far as possible.
The sealant will glue the two rods together, making a very strong, stiff mast !!.
It will still be able to bend, but my Mast is over 6 feet long.
John.

boatmadman · « **Reply #14 on:** February 13, 2013, 06:54:00 pm »

Neil,

Having had a root around I have found a length of douglas fir, rough cut to nominal size 25mm square which will yield 2 lengths, 1x19", 1x24" after a knot has been cut out.

You are welcome to it if it is of any use to you.

Ian

Neil · « **Reply #15 on:** February 13, 2013, 07:14:52 pm »

Thanks for all your replies and suggestions guys.........have read your posts about the mast construction with great interest rob...........and think rather than use fishing rods this time( although used them many times on other vessels Jaydee with good results, and thanks for the suggestions) there will be a lot of natural timber on these lifeboats, so am going to go with Ian and Robs suggestions and make them from square stock douglas fir.......last time I used it was 35 years ago when making a canoe in canberra, Australia......lovely to work with.
I'll have a look at the lengths that I need Ian, and let you know, but I think I might need a good length because I have 4 masts and 4 lug spars to make, so might have to find a source ...Will look at Twigfolly.

Now, next thing is....and please don't shout at me folks.......anyone know what the maximum thickness you can brass etch and anyone who will do a single A4 size sheet..........I need 4 x tabernackles, and don't fancy cutting them all out. lol

Many thanks for all your help and suggestions.

neil

mk1 · « **Reply #16 on:** February 14, 2013, 01:25:23 am »

Hi Neal I used these people when I had 1 x A4 sheet of small washers done

PPD Ltd.
Unit 3 Highbank Park Ind. Est.
Lochgilphead
Argyll
PA31 8NN
T: 01546 602 963
www.ppdltd.com

John

irishcarguy · « **Reply #17 on:** February 14, 2013, 06:55:15 am »

I feel with all the help you are getting here Neil you had better get it right or you will have to hide the fact that it broke first time out, but I KNOW you can do a lot better than that, LOL. Mick B.

rickles23 · « **Reply #18 on:** February 14, 2013, 07:44:30 am »

Hi,

I sail Marblehead yachts and they have a sail area of 800 square inches. (I don't do metric).

I changed to a carbon fibre mast twelve (12) years ago and it is still going well.

Recently I was given an older model marblehead to restore so I thought I would have a go at making a wooden one.

Living next door to me is a professional yacht builder so I called him round for a coffee.

He gave me a plank of spruce and together we cut out strips to laminate the booms but the main mast is sawn from a single piece and we managed to saw a groove into it to take the sail.

I have sailed this this man and his work is top class and he has all the certificates as well. So I follow his directions and the only work to do is the actual shaping of the mast.

It will be roughly sanded on the electric sander and then by hand with finer grades of sandpaper and finish with fourteen (14) coats of varnish lightly sanded between each coat except the last.

Regards

Howard · « **Reply #19 on:** February 14, 2013, 01:33:05 pm »

For small scale mast on boats I use food grade plastic (chop sticks) very strong and free.
Regards Howard.

Martin (Admin) · « **Reply #20 on:** February 14, 2013, 01:35:03 pm »

Quote from: JayDee on February 13, 2013, 02:55:08 pm

Hello,
The mast on my J Class yacht was made from two fishing rods.
It will still be able to bend, but my Mast is over 6 feet long.
John.

'Very clever Mr. Bond!'

JayDee · « **Reply #21 on:** February 14, 2013, 03:25:40 pm »

Hello,
The "accident" that Martin is referring to was at Wicksteed.
I was sailing past a post which is in the middle of the lake.
A gust of wind blew the top of the mast towards the post, which went inbetween the mast and the rigging.
Stopped the boat dead!, it swung around the post, bending the mast a lot!.
It was rescued by my saviour, Stavros, who untangled it all.
Thank you once again, Stavros!.
John.

Tug-Kenny RIP · « **Reply #22 on:** February 14, 2013, 04:36:10 pm »

Now that would make a 'Caption competition'.

Stand by for comments.

Ken

Neil · « **Reply #23 on:** February 14, 2013, 05:10:04 pm »

went and took the plunge today and took a trip down to my local timber merchant where I buy my mahogany, and obeche.......boaught a nice piece of Douglas fir, 60" x 6" x1.5" lovely straight grain for the masts.............£12 45p...........not bad at all....get a few masts out o' that lump.

News:

Author Topic: MAST CONSTRUCTION (Read 7626 times)