How many screws for a Zip?

What kind, options, etc.

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Roberta
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Re: How many screws for a Zip?

Postby Roberta » Mon Mar 05, 2012 10:16 am

Using epoxy on more solid wood and framing with a joint designed for adhesives makes sense to me. The area and configuration must lends itself to good adhesion and structural integrity. Some of the plywoods like DF and meranti that I have used (BS1088 and marine grade) have had issues with the plies chipping out at the edges and delaminating because of poor gluing at the manufacturer or poor grain configuration. I personally prefer to use and leave the screws in place, wherever possible, as additional holding power for plywood planking attached to framing to prevent stressed plywood from delaminating and tearing loose from the framing leaving behind one well glued ply. While the new epoxies have great strength, some of the glues in marine grade plywood do not seem to hold so tenaciously. JMHO

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

sawford11
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Location: Pittsburgh, PA

Re: How many screws for a Zip?

Postby sawford11 » Mon Mar 05, 2012 6:25 pm

Roberta - I agree with your last post. Epoxy is very strong, no doubt. But just using epoxy to hold a plywood panel to a frame member doesn't seem like the best idea to me. When I first got started, and as an epoxy test, I epoxied two plywood panels together with a simple overlap. Once the epoxy cures and you try to break the joint, the epoxy holds tight. However, if you continue to stress the panel joint, the plywood simply delaminates. The epoxy is simply holding the two outer layers of the panels to one another and as such, the joint is only as good as the weakest layer of plywood glue/lamination. I like having the screws driven through the plywood and into the solid wood members to ensure that the full section of plywood (i.e. all layers) are 'connected' to the longitudinal members. Also, JMHO.

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Bill Edmundson
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Re: How many screws for a Zip?

Postby Bill Edmundson » Mon Mar 05, 2012 7:54 pm

Ah Grasshopper, You have graspped the pebble.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

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Andy Garrett
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Re: How many screws for a Zip?

Postby Andy Garrett » Tue Mar 06, 2012 4:51 am

Well, this conversation went further than I expected... :o

For the record, I would not be comfortable trusting adhesives alone to hold my hull together unless I employed heavy fiberglass on the exterior.

Just as fabric provides the lion's share of strength in carbon fiber, kevlar, G-10, and Micarta, I believe it would become the primary source of strength in a screwless hull with stressed panels bent over a frame.

I'll keep my screws--that's why I spent the money for bronze. :wink:
Andy Garrett

Perhaps the slowest Zip build in Glen-L history...

Oyster
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Re: How many screws for a Zip?

Postby Oyster » Tue Mar 06, 2012 5:01 am

I would not be comfortable trusting adhesives alone to hold my hull together unless I employed heavy fiberglass on the exterior.


I am not sure if anyone has suggested this at all. I know I didn't. Choosing the right fiberglass is key if you are considering incorporating glass as part if not the sole component of the structure, especially in the joints. There are also different components and even additional components required and configured in a different manner too in some cases that we do not see in most of these type builds either. Of course canoes and kayak type builds are exempt in most cases from using the same type fiberglass in construction methods thats an exception from most of these conventional plywood on frame construction hulls in the site.


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