malahini hull fairing difficulties

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obd
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Joined: Sun Dec 30, 2012 3:39 pm
Location: Mount Pleasant, SC

malahini hull fairing difficulties

Post by obd » Tue Mar 19, 2019 8:37 am

I am trying to get my hull adequately faired prior to veneering with 1/8 inch sapele. Unfortunately, I have already epoxied on my first row of veneer. I am starting at the sheer line and plan on working up (technically down, but the hull is upside down of course). I noticed my fairing issues after the first row of veneer went on. It actually looks pretty good and my one flat area can be corrected with some minor demolition, and repair. However, I now see bigger fairing issues looming.
I am looking for advice on adequate length and dimensions for a good batten and technique. When I use pieces of my veneer as a batten, my shallow areas seem to vary depending on whether I run the batten from one frame to the next versus longer stretches, say the span of 3 frames. I guess it is no surprise that the flat areas are mainly where the hull plywood is joined. I used the plywood butt-block method but would use scarf joints if I had to do it over again.
I am also interested in batten material other than wood, something that won't stick to the epoxy fairing material. I read about one technique on the West epoxy website where a batten is gently pushed into longitudinal strips of uncured fairing material to establish approximate fair lines. Obviously, this kind of batten would need to be made of something that doesn't bond to the epoxy. Any advice is welcome. Thanks. Bob

footer
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Re: malahini hull fairing difficulties

Post by footer » Tue Mar 19, 2019 9:33 am

I am way confused. Do you have any pictures of what you are referring to?

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Jimbob
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Re: malahini hull fairing difficulties

Post by Jimbob » Tue Mar 19, 2019 11:08 am

You could still use wood for the battens. If you cover them with strapping tape or wax paper, then they won't stick to the fairing epoxy.
I would use battens at least as wide as the planks you are planning on using and long enough to touch the high points at each end (3 frames?). Squish down the fairing material in the low areas using your battens. Use a long board sander on the fairing material when you are done. Probably lots of checking and re-checking along the way, but the final results should result in a nice non-wavy hull.
Jim
Jim Neeley
Building a Barrelback in Sacramento, CA
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Tony Hain
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Joined: Fri Aug 26, 2011 3:01 pm
Location: Queensland Australia

Re: malahini hull fairing difficulties

Post by Tony Hain » Tue Mar 19, 2019 11:11 am

obd
Three comments on fairing:
1. Better to fix it now than trying to fix it after the final planking.
2. The longer the batten the better (I used a piece 3/8"x5/8")
3. As far as the use of a fairing compound it is hard to tell without seeing it but ideally it is better if you don't have to use any.
Tony Hain
"Never under-estimate the bounds of human stupidity" (Robert Heinlein)
and on a more optimistic note "nor the capacity for human brilliance"

TomB
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Location: Holland, MI

Re: malahini hull fairing difficulties

Post by TomB » Tue Mar 19, 2019 12:19 pm

Get the longest piece trim stock you can get home from the home center. I use a 1/2"x 2" x16' poplar for a batten. I used a 3' piece with a very slight curve wrapped in packing tape as a screed. Use the batten layed on the hull to find and then mark the high/low areas. Practice crossing the area with the screed, load the low area with fairing compound and pull the screed a cross to get it close, sand for perfection.

Take your time, it will be fantastic.

Tom

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Re: malahini hull fairing difficulties

Post by footer » Wed Mar 20, 2019 3:26 am

I didn't do my sides, but on the bottom, I used Quickfair and a 4' aluminum level as a screed, tilted it, and from frame to frame, pulled from the keel to the sides. Sanded smooth, then I took an 8' long 1.5" x 1.5" aluminum square tubing and did the same tilted pull from keel to side. The Aluminum gave me a real straight rigid screed which was easy to clean.

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