Bending and Twisting Battens Question

Outboard designs up to 14'

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bjfrater
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Bending and Twisting Battens Question

Postby bjfrater » Sat Feb 21, 2015 3:07 pm

Hi there,

Im attaching the battens and trying to figure out how they will bend and twist at the forward most frame.
The problem is that when I pull the batten down to follow the curve of the boat at the front, a hump appears further back between the aft frames.

I have attached some pictures to hopefully show the problem. Im sure others have seen this. Im just not sure how to correct the problem. Would this be resolved with Kerfing? I was hoping to avoid kerfing if possible.

One other point is that the batten will take on a bit of a twist at the front, It seems quite aggressive and i was wondering if others had issues getting the batten to hold the twist when attaching at the forward most frame. Any tips with this?

Carl? I know you recently went through this on your boat.

thanks
Brendon.
Attachments
20150222_104521.jpg
Before pulling down on the batten it is nice and flat.
20150222_104600.jpg
When pulling down on the batten a hump appears between the frames further aft, after the clamp.

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Roberta
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Re: Bending and Twisting Battens Question

Postby Roberta » Sat Feb 21, 2015 4:33 pm

I planed mine down a bit in front to get them the bend easier. You could put some kerf cuts in the forward part to reduce some of the bending stress, then fill in the gaps with epoxy after the flip. Steaming is another option using sleeves made from plastic sheeting and a wall paper steamer.

Roberta :D
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

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chugalug
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Re: Bending and Twisting Battens Question

Postby chugalug » Sat Feb 21, 2015 7:33 pm

:D On my Bo-Jest,I cut curf(split the batton with table saw) a little ways back from front end almost to frame then drilled small hole in end and inserted a wire(unbent coat hanger works) and twisted and bent batton down past where the ply would go.Glued battons and screwed back on frames.you could taper the front ends to fit a little better.then after planking and after flip,(or crawl under)release battons after applying glue.Kerf can be glued at same time too. :Doops forgot.fasten wire down to build form.Maybe that would work with steam bent too.
Working on regular-sized Bo-Jest


"If it's not crooked,It's not mine

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mrintense
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Re: Bending and Twisting Battens Question

Postby mrintense » Sat Feb 21, 2015 8:50 pm

Brendon,

I have a slight hump on both of my battens near the keel. However, initial fitting with scrap plywood seems to indicate that the hump won't be much of a problem. I have my battens completely glued in place now so if it is a problem, I will have to correct it after the fact. On my boat at least, I think that if necessary, I can wrap the hump in plastic, apply some steam using my steamer (similar to the wall steamer Roberta mentioned), and apply some downward pressure using ratchet straps.

I am going to start fitting bottom skins tomorrow, so I should know fairly soon if I have to make a correction.

As for getting the twist and the bend to happen, I used ratchet straps to pull down on the end and when I got ready to add the screws, I took a long clamp and two boards and made a lever to apply a slight twist. I used another ratchet strap on the lever so that I could free up my hands for drilling and inserting the screws. I left all of this in place for nearly a week after gluing in order to give the epoxy plenty of time to cure.
Carl
a.k.a. Clipper

Crafting a classically styled Vera Cruise named "Some Other Time"

Clipper's Vera Cruise Build

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ian bell
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Re: Bending and Twisting Battens Question

Postby ian bell » Sat Feb 21, 2015 10:24 pm

When I did mine on the Renegade I used 3/4" and bent one then laminated another two pieces over that for the thickness required with epoxy glue in between.
Ian

bjfrater
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Re: Bending and Twisting Battens Question

Postby bjfrater » Sat Feb 21, 2015 11:29 pm

Thanks for the tips guys.
Based on your suggestions I think i will try a combination of things to get them into place.
I will heat/steam them with some hot water and towels and plane the ends down a bit to assist as well. I am hoping that by making the battens bend easier at the front it will take the pressure out and reduce the hump that forms further down. I am avoiding Kerfing as I dont have a table saw so as a last resort I may have to try doing it using my other tools.
I already have an eye bolt in my building form ready to tie them back while I fit the bottom panels.

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vupilot
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Re: Bending and Twisting Battens Question

Postby vupilot » Sun Feb 22, 2015 12:22 pm

I cut them and secured them in place then carefully faired them so that there was just a bit of pressure against the plywood when in place. I didn't have any humps further back because they were faired more than they were bent. https://plus.google.com/photos/11285674 ... 9575019574

I could have made them just a couple inches longer I think though.

-CA

gdcarpenter
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Re: Bending and Twisting Battens Question

Postby gdcarpenter » Sun Feb 22, 2015 2:19 pm

My Two Cents:

I essentially faired and thinned the forward ends of the battens as in the photo. I then used long gutter screws (since I had then on hand) to pull them down and out of the way prior to attaching the hull ply, and, as soon as the hull ply was secured, released the screws to let the battens spring up to contact the ply and be epoxied there.

On my build I added strongbacks or stiffeners on the top of all my battens for extra rigiditity:)
I also went with 3 battens per side in case you are scratching your head.

You do not want the aft sections of the battens 'popping up' - they must be flat as a pancake!
Attachments
DSC02913.JPG
This is my first, last and only boat build.

http://www.gdzipbuild.blogspot.com


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