GT23

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fallguy1000
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GT23

Post by fallguy1000 »

Planning to build the GT-23. I built the FS-14 from a kit. And then the Phillip Bolger OldShoe, from plans of course, but using materials (plywood, epoxy, paint, etc) from BoatBuilderCentral. I built a small Glen-L sailboat 50 years ago at age 13. Have also built a coupla self-designed experimental boats of dubious quality.

I have some questions about the plans/methods. I see that Naylene built a GT-23 in 2020, using a strongback. And the GT-23 plans do call for using "a jig"....But then the plans
go on to describe a seemingly jigless stitch-and-glue process, where the initial hull construction is done with hull right-side-up, using the panel shapes and bow and aft transoms to provide the curves and shape of the hull. After adding the stringers and cross frames and sole and foredeck, the plans only then call for the boat to be rolled over, bottom up, and the bottom glassed....and still no mention of frames/molds/strongback. Dimensions of the stations are given, but no direct instruction to set the hull upon any molds... Is this supposed to be simply "understood"? That one of course always uses molds to shape the hull? But if this is so, then in this particular case the shapes/curves will already be largely fixed, because the plans call for the inside keel, chine, and transom seams to be built (epoxied) before the boat is rolled over upside down for the bottom work....
I am confused...
bobby


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viewtopic.php?f=12&t=62495

fallguy1000
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Re: GT23

Post by fallguy1000 »

Jaysen-I took the liberty of creating a new thread for the OP. Maybe you can do it better.

But he wants to know about whether to build the gt23 upside down or rightside up.

I can't personally imagine any other way than on a strongback and jig.
My boat build is here -------->

viewtopic.php?f=12&t=62495

jacquesmm
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Re: GT23

Post by jacquesmm »

The GT23 can be built either way, right side up or upside down on a jig. The jig is made from strongbacks and molds, molds can be named frames, it is always the same method, same dimensions.
The other method, building right side up, does not guarantee perfect symmetry. It's fine for displacement speeds and looks easier but it is not. Building on jig is easier.

To build on a jig means with molds on strongbacks.
I dont' show dimensions for the strongbacks, that is up to the builder but I would use a minimum of 2x6's, two layers in order to get sufficient length.
The molds should be located at the frames, use the frames dimensions and spacing as on the plans.
Put the whole thing at the proper height using the DWL shown on the plans. Not too low in order to clear the floor with the transoms but not to high so that you can reach the bottom while fiberglassing. It is a big boat, even with the jig as low as possible, the middle of the bottom will be hard to reach. To set up the jig, I would have the BL at minimum 37" from the floor: the bow transom tip is 36" above the BL.
All dimensions are given from that baseline marked BL.
I recommend temporary molds made from cheap MDF.
When you build that way, the sequence is as follow:
- assemble the jig made from temporary molds except for the transom where you use the plywood transoms.
- plank the bottom then the sides using stitches
- build all outside seams, chien and transoms
- fiberglass the hull skin
- flip the hull with molds inside
- remove the molds, now you have an empty shell
- fiberglass the inside
- etc. etc: install inside framing, floor frames, sole, bulkheads etc.

I hope all that is clear.
I am camping on an island right now and have limited internet access, please be patient.
I can sketch a jig on my laptop but prefer not.
Check youtube with GT23 and GT27. There are several channels that show those boats built on a jig in detail.
I have links somewhere at home and will be back in my office around Jan 18.
Jacques Mertens - Designer
http://boatbuildercentral.com

drbobopp@gmail.com
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Re: GT23

Post by drbobopp@gmail.com »

OK thanks... I can build a jig, strongback and molds/frames using the drawings you provided.....No need to draw one up...

Thanks...

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