Measuring stringerless EPS

Hello, from an increasingly chilly UK! 

First time EPS/stringerless shaper. What do you use in place of a stringer as a point of reference? I have seen people use a thin strip of masking tape, how do you make sure it is straight (beyond incrementally marking points and joining the dots) any tricks or tips? 

Cheers! 

Measure for the center at the front and back then use a strip of doorskin or thin flexible plywood with the factory edge laid on the center marks as a guide to lay down your tape or use it to draw a line with a pencil. It would work up to an 8 foot board.

Better yet lay down your tape somewhere in the ballpark of center and use the ply to mark a thin center line on the tape. That would be more accurate and allow you to remove it later. 

Thanks for the reply Dave. That’s a good idea with the tape. It’s for a 10’ SUP, so just need to find a piece of ply long enough I guess! 

 

Snap a chalk line?

I tried the tape, string and wood and found if I did it twice I got different center lines. Best for me so far is laser level. I turn the blank on it’s side in the racks and use the laser to connect the two end points. I found with some practice it was pretty accurate. Otherwise you need a good full length template and make the center line off the outer marks afterwards. 

And then use the tape and draw a line tracing the laser beam? 

 

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Hello Whiskeyjack-

(A) chalk line with a midpoint mark to check for a true snap or

(B) overlapping straight edges (like an 8 foot straight edge + a 4 foot level) and a pencil.

No worries marking up to 14’ with chalk for me. Cutting things out straight is another story…

-J

Thanks guys, I’ll try the chalk line tomorrow! I

Forget the chaulk line.  It doesn’t lay straight over curved surface.  Don’t believe me?  Snap the  line three or four times, and get three or four lines.  The answer is really simple.  Make a two sided template. 

And then decide which side you like best.     Me, I’d make a full size half template.       You only need to get ‘‘in the ballpark’’ at either end of the blank, to have a symmetrical outline.

I use a 8’ long flexible straight edge and get my center line right away. Then I set my length, and get the center and wide point(s). Once I decide where I want the wide point (center, forward or back of center), I can draw out the outline with any type of template. I often mix up templates using a nose or tail from different templates, and maybe even having a middle curve from a third template.

Everything is based off that centerline.

My newest templates are halves, the nose side is on one side and the tail is on the other. You can make longer templates that way.

 

Whiskeyjack, were you going to loft on the blank or make a template? -J

   Can’t argue with your method.        Quite sound.    Lots of flexability.

I tried out the chalk line today, seemed to work alright, but i do have concerns about accuracy. I think using a 10’ full template to square up a centre line as a reference point as Sharky mentioned is the way to go, but finding ply long enough to make one is a mission! I should have mentioned that the blank was already cnced so not working from a template. Could print it out from the shape file, but again need the right sized ply! 

Cheers! 

Hi Whiskeyjack-

What is common to use in the UK for templates? Have you thought about making a joint instead of using full long material?

Enclosed pic is 2 templates out of 1/8" hardboard from the same project, one is a full half and other is a spin template. The joint is 4oz cloth and resin, lam both sides or it cracks.

-J

Edit: Re-read that blank is CNC’d. So this is just a center reference…could you measure side-to-side 1/3 down from nose and 1/3 up from tail, mark midpoints, connect those dots with a straight edge and extend them to nose and tail?

To make a “both sides” template, take the standard one side template, draw it onto 24" wide paper, flip the template, and draw the other side. Cut out both lines. There is your perfect, symmetrical template. Fold it in half to get a center located for fin placement.

   If you already have a one side template, draw it out on the blank, flip it over, and…there you have it, eh?

For future reference, I’ve use a flesible piece of 2" wide x 3/16" aluminum (approx.) that’s straight as an arrow and 10’ long. It’s trim commonly used in commercial storefront glazing. Find your center nose and tail, flex the straightedge point to point, clamp, pencil line, done.

Absolutely. The flat side of the template is the straight line that some are looking for. My comment is more for those who need a straight line to replace the stringer.

Spin templates won’t work without a center. But full length will.