LumberJocks

what is 360 divided by 10, anyone, anyone...

  • Advertise with us
Blog entry by Mark Shymanski posted 412 days ago 1215 reads 2 times favorited 9 comments Add to Favorites Watch

If you don’t remember the teacher from ‘Ferris Beuhler’s Day Off’ the title is not at all funny, it’s barely funny if you do remember the movie:-) Anyway, I got a chance to work on the birdsmouth joints Paul ( Shipwright) recommended for making my hollow mast prototype. Once I’d fabricated a zero clearance dado blade insert I did a couple of test cuts and then ran my 10 boards through for my trial glue up.

I had cut a pronounced taper on the boards figuring that a large taper would be harder to glue up. Well it was a bit awkward, I had hoped to do a dry run but couldn’t quite manage that. Then I realized after looking at all my boards and seeing during the dry run that I would not be able to close the mast, that the angles of the birdsmouth joints had been cut wrong. So I took my shoes and socks off ;-)and divided 360 by 10 ( using the simple formula recommended by Paul to calculate the angles depending on the number of segments used) and somehow got it in my head that I had to set my saw at 30 degrees as the complimentary angle to the 36 degrees I needed. I still can’t figure why 30 got stuck in my head:-( So the prototype didn’t come out as intended. I didn’t take a picture of the open side but it was about one more board width too open.

I did learn a lot about the work flow and that I am going to need to figure out a process to actually do a glue up. My trick of using masking tape and the just rolling the segments up worked well on the mitred joints of my first attempt but doesn’t work with the birds mouth joint because of the material behind the cut joint. The use of the dado blade worked very well. I may still try the two cut method that Paul described just to see which method is better. When I realized I’d cut the boards wrong I figured I’d still glue the boards together just to see what I would get. Because I would not be able to bungie cord the segments together I used hot glue to stick em together. I’d made a sufficient number of mistakes and tried a bunch if new things so I think I learned a lot. Which I guess is the point of a trial run:-)

-- "Checking for square? What madness is this! The cabinet is square because I will it to be so!" Jeremy Greiner LJ Topic#20953 2011 Feb 2



9 comments so far

View shipwright's profile

shipwright

4901 posts in 1425 days


#1 posted 412 days ago

+1 on James. That’s how I do it.
You don’t need a dado blade. Once on edge, once on flat at your predetermined angle. Unfortunately you still need to be able to divide 360 by X. :-(
Unlike James’, my columns were a single taper so bungee cord worked really well. It’s like the way mono-filament fishing line gets vice-tight when wound under pressure…. the more you wrap … the tighter it gets.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

View Mark Shymanski's profile

Mark Shymanski

5078 posts in 2340 days


#2 posted 411 days ago

Thank you James for the pictures. I will try just working with the single blade and see if that gives me better results. Paul those are some impressive columns. I think the bungee cords will work well. It occurs to me that the mast I will be making for the Puddle Duck Racer will be less than 3 inches at the base tapering down to 2” or so and it will be on the order of 16 feet long so the duct tape tip should work well until I get a few wraps of coord around it. I may even try just plain old cord to see if I can get the more turns the tighter effect you describe Paul.

Now I am off to study my division flash cards :-)

-- "Checking for square? What madness is this! The cabinet is square because I will it to be so!" Jeremy Greiner LJ Topic#20953 2011 Feb 2

View shipwright's profile

shipwright

4901 posts in 1425 days


#3 posted 410 days ago

This is a great learning experience but make the mast solid. The only advantage of a hollow mast is weight and that’s not going to be much here. There are disadvantages that outweigh them like the propensity to rot from the inside where you can’t see it and the need to re-enforce in way of fittings. Personally I hate hollow masts and would only use one for serious weight issues. I’d laminate a couple of 1 1/2” pieces together and shape them down.

Just my opinion.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

View Mark Shymanski's profile

Mark Shymanski

5078 posts in 2340 days


#4 posted 409 days ago

You are right that the mast should be solid. I started the idea of making a hollow mast thinking I could save a lot of weight. But I read one article which identified only small savings in weight but at significantly reduced strength. I hadn’t even thought about unseen rot forming on the inside. I’m thinking I will probably laminate several pieces together to make a solid mast and then plane it so it is sort of round. I’ve been looking at the pine boards at HD and at some I got from a real lumber yard and I am concerned I may not find boards with a clear run of 16 feet or so. I was thinking that if I am laminating the mast any way could I splice in pieces to lengthen the mast longer (taller?) than I can actually buy wood for? I was thinking maybe the best part of a 10 ft board scarf joined to the best part of a 6 or 8 ft board to give me a full 16 ft of clear lumber. If necessary I’d not have two scarf joints within about 20 or so inches.

-- "Checking for square? What madness is this! The cabinet is square because I will it to be so!" Jeremy Greiner LJ Topic#20953 2011 Feb 2

View DS's profile

DS

2131 posts in 1047 days


#5 posted 409 days ago

Why not fill the hollow with expanding foam…no rot, not much weight, adds more strength.
Jus’ sayin’

DISCLOSURE: I’ve never ever even been near a sailboat, but, I did stay at a Holiday Inn Express once

-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251

View shipwright's profile

shipwright

4901 posts in 1425 days


#6 posted 408 days ago

I’m a big fan of solid masts and yes, you can scarf them. 8:1 will give you the same strength as solid but you should still stagger your joints well.
If you need 16 feet and you were laying up three pieces from 10 foot stock, you could use 10’ / 10’ for one piece and 3’ / 10’ / 7’ for the other two, one with the short at the bottom and the other with the short at the top. That would give you lots of stagger.
My mast is about 28 feet and it’s only about 5” max diameter. It’s three pieces. Get sitka spruce if you can. It’s pricey but it’s the best and you don’t need much.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

View Mark Shymanski's profile

Mark Shymanski

5078 posts in 2340 days


#7 posted 408 days ago

Thanks Paul,

Did you just round them off using a plane or did you somehow turn them on what would necessarily be a really long lathe. The mast do,t have to be dead round so it would probably okay just to hand shape them? You’re right about not needing much for the mast so I’ll see if I can find sitka here in Brandon. I think I’ll have to go into Winnipeg to get the epoxy and fibreglass cloth so maybe I could check out the wood sources there. As I only need just shy of 3 inches I could probably do with just two boards and keep the lamination down the center. It looks like you’ve just laid them flat on one another. Is there an advantage to making the 3 boards with cross sections pie shaped and then gluing them up like that…or is that just being overly complicated. I like the idea of just glueing them on the flat as that would definitely be the easiest.

I like those doors in the second picture!

-- "Checking for square? What madness is this! The cabinet is square because I will it to be so!" Jeremy Greiner LJ Topic#20953 2011 Feb 2

View shipwright's profile

shipwright

4901 posts in 1425 days


#8 posted 408 days ago

Flat stack is fine. I’ve done some biggish masts that way .
The process is:
1) Square to taper
2) Plane to octagon
3) Plane to 16 sided, 32, etc, etc and then sand

That’s my shop. I like the doors too, thanks.
I’m gone sailing until Tuesday in case you have questions and don’t get answers. I’ll check in then.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

View Mark Shymanski's profile

Mark Shymanski

5078 posts in 2340 days


#9 posted 408 days ago

Enjoy your sailing, it is to be hoped by Tuesday I will have something that resembles a boat!

Thank you for the process. That makes a lot of sense.

-- "Checking for square? What madness is this! The cabinet is square because I will it to be so!" Jeremy Greiner LJ Topic#20953 2011 Feb 2

Have your say...

You must be signed in to post the comments.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com

Latest Projects | Latest Blog Entries | Latest Forum Topics

GardenTenders.com :: gardening showcase