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Re: drywall tape
By:George Cushing
Date: 1/4/2001, 2:19 pm
In Response To: Re: drywall tape (Scotty)

: get some of that drywall tape.

: Thanks for the comment on drywall tape, I'VE BEEN TEMPTED! TNX, Scotty
: (I imagine it's for inside seam use only, does it go clear, or stay white?)
: Thanks for the comment on drywall tape, I'VE BEEN TEMPTED! TNX, Scotty
: (I imagine it's for inside seam use only, does it go clear, or stay white?)
Scotty,
I'm trying to remember how I started down this direputable path. I don't know if there's a DTA with a 12 step program to help me to recovery. If you start down this path you'll know who to blame.

A short answer is that it stays white. This is no problem for me because I HAVE recovered from the need to varnish everything. And yes, I use it on the outside. No criticism intended, but there are a lot of folks who contribute to this site who are producing great works of art that fulfill a need for something more than just getting out on the water. I build boats that function, require little maintenace and meet a need for excercise and to connect with the water.

As I said, I had a bad experience with FG tape while building a couple of Bolger "Cartopper" skiffs. Bolger's plan distribtor and collaborator, Herb Payson, developed a ply panel butt joint that used FG tape as a replacement for wood blocks. Payson advised grinding a recess at the joint so the tape wouldn't stand proud. Given my experience with the FG tape and the fact that the light ply I was using couldn't be ground, I looked around the shop for something thinner. I came up with a FG mesh used by masons to reinforce joints in foam plastic sheathing prior to applying stucco. It's like the drywall tape only wider (up to 3') and with heavier fibers. Destructive testing of this tape on test joints led me to adopt it on my first S&G yak for joining panels.

Happy with the way the mesh tape worked on the panel joints I desided to try the lighter drywall tape on the chines. As the tape has a light adhesive it will usually stick in place until resin is applied. On this first yak I ran one layer fore and aft. It tended to lift at the edges as the cross fibers resisted the bend across the joint. To overcome this, and add strength, I applied short pieces of tape on the bias (45 deg. to the joint). Then I applied a third layer of short pieces 90 deg. second. Each layer was cut to extend about 3/4" beyond the last to create a taper down to the hull panel. Then the whole thing was bonded together with epoxy thickened with microballoons. A 3" long section of this joint was jumped on by a 250# friend as a test of its strength. The wood failed first.

The tape's open mesh has to be filled. This is one reason it's lousy for drywall work. But it is easier to blend into the hull panels with less filler than FG tape.

For second drywall tape yak I got lazy and did away with the bias tape. Instead I ran one ply fore and aft over the joint, one length either side of the first centered on the edges of the first, and one final layer centered over the first. I got a little edge pick up on the last layer but was able to keep most of it tacked down while the epoxy cured.

This resistance of the tape to bend across its width can work to your advantage. Even if you don't want to disgrace yourself by using it on the exterior, it provides a nice armature for filleting in bulkheads and the like on the inside of the structure. The bending resistence produces a nice cove that can be filled with thickened epoxy applied with an acid brush. The open weave permits the epoxy to pass through the tape and fill the space between, say, the bulkhead and the hull panels. I find this a lot neater and controlled than trying to work with a squeegee it these tight areas. And of course the joint when cured has the added strength of the tape.

I've taken advantage of this characteristic to form the final stem profile on various craft. If the tape is applied from one side of the boat around the stem to the other where the panels come together at the bow or stern a nice rounded shape is formed. This shape can be filled with brushed in epoxy, as described above, producing a smooth entry to the water. If your stem has a lot of curve to it you may have to use several pieces to get the shape you want. I went to this method after trying to build up a stem with just thickened resin per someone's building instructions. I'm still tripping over the resin that ended up on the floor.

This is a long response to a simple question. I hope it's helpful.

Geo.

Messages In This Thread

fiberglass weave...help! :o
brett (the hitman hart)onnink -- 1/1/2001, 11:52 pm
Re: fiberglass weave...help! :o
George Cushing -- 1/2/2001, 3:07 pm
Re: drywall tape
Scotty -- 1/3/2001, 10:58 am
Re: drywall tape
George Cushing -- 1/4/2001, 2:19 pm
Re: drywall tape
brett the hitman hart -- 1/6/2001, 12:40 pm
Re: kayak heresy
George Cushing -- 1/8/2001, 11:30 am
Re: fiberglass weave...help! :o
Chris Casazza -- 1/2/2001, 12:27 pm
Re: fiberglass weave...help! :o
Jay Babina -- 1/2/2001, 11:05 am
Re: fiberglass weave...help! :o
Jon -- 1/2/2001, 2:27 am