Lofting / Determining hull panel shapes

**TK1** · 18th January 2008, 04:31 PM

Hi,

I soon to start building one of David Payne's kayaks, the Marathon TK1. Currently I'm drafting the mold station and bulkhead templates.

Unlike stitch & glue or strip kayaks, it's built on longitudinal chines, etc like his larger boats, with the panels epoxied to these.

So, having not done this before...how do I get the hull side and bottom panel shapes easily?

My thoughts so far are:
(a) use a cardboard or thin MDF/ply template tacked to the hul, traced and then cut out and transferred to ply panels
(b) run a stringline along the sheer and then measure points from this to create a lofting plan, transfer to ply panels and cut out
(c) rip ply into strips - e.g. 10-15cm wide - and apply like planking to the hull and then trim the excess.

I'd prefer not to do (c) as the panles may not sit together properly and extra epoxy will add weight. So I need some way to transfer the curved hull shape to ply panels and then cut out.

Any thoughts from those who've got more idea than me (that's all of you

)?

Thanks,
Darren

**Dry Water** · 18th January 2008, 05:53 PM

If it was me I would be using cardboard or the MDF/ply template and transfer to the ply, cut oversize and fit to the hull and trim where necessary. This should provide you with the best option from those above.

**bitingmidge** · 18th January 2008, 10:45 PM

Darren,

Do the plans have any directions as to method?

The normal practice would be to set up the moulds and stems and run longitudinals (chines, deck clamps and keel) between them, bevel the longitudinals to their final shape, then hold the ply against them while pushing it against the frame (if you are working by yourself you can use a few gyprock screws to hold them in place).

Trace the actual shape, then remove the ply and cut!

Note that while this may sound cumbersome, you are only working with a full sheet of ply some of the time!

Remember to cut the sheets oversize and plane them down after they are glued in place for a perfect fit.

cheers,

P

**boatchippy** · 18th January 2008, 10:59 PM

On larger boats we used to make stick templates from strips of ply or steel flat bar.
On a little boat you could use sheets of thin cardboard or make small stick templates.
Or if you want to get real technical you could exspand the shapes of the hull plating from isometric drawings, if you have these.

**Boatmik** · 20th January 2008, 03:03 PM

Midges reply is the normal method for external hull panels.

Boatchippy's is right for working out bulkheads and furniture inside the boat - though I think David's plans have these things worked out already.

I don't know why you are thinking about stringlines etc.

If it is the plywood chine version the ply is not cut up into 100mm strips etc but will bend into a shape to match the longitudinals. If it is 17ft long like the racing class kayak then each panel of the hull will be made up of only 2 and a bit pieces of ply.

Two will be full sheet lengths (or close to that) and one will be only around a foot long.

2 x 8 plus 1 = 17

**TK1** · 20th January 2008, 09:54 PM

Hi,

Thanks for the replies.

There's no instructions on the plans but I agree with the suggestions of just holding the ply panels up and cutting them a a bit oversize. This sounded logical to me, just wasn't sure if it was "the way things are done"

.

I'm starting to trace the bulkheads and molds, and will shortly order some paulownia for the stringers, and set up the strongback.

No need to wait for the Chesapeake 17 to be finished, I worked out I can fit both in the workshop

Promise to have some pics soon...

Regards,
Darren

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