Rabl Method

Outboard designs up to 14'

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mdweber
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Rabl Method

Postby mdweber » Mon May 12, 2014 5:31 pm

Hey Folks,

I have searched through the forums and read Building with plywood, but I can't seem to find that answer I'm looking for. I am using the Rabl method in fairing my Squirt, and I have a question about where to stop measuring for the keel and chine.

On my boat, I started measuring at the intersection of the chine and the stem, and STOPPED measuring at the forward most frame (frame 2 on the squirt). After getting through about half of the fairing, I am now wondering whether I should have measured from the intersection all the way back to the transom.

Any insight?

Thanks,
Mike

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BarnacleMike
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Re: Rabl Method

Postby BarnacleMike » Tue May 13, 2014 6:18 am

Hi MIke,

You've got it. Aft of the forward frame, the fairing process is considerably more straightforward & easier to figure out than the stem. The Rabl method is a tremendous help in fairing that confusing stem-chine-sheer area.

Just take your time... It's easy to fair away too much material. (Of course, you can always add more if needed. I sure have!)

OH: Avoid a mistake that I made. When I was fairing the vertical parts of my forward frame, I wound up removing the slight curve that is shown in the plans. In other words, I made a straight line where I needed a curve. This left me a small gap between part of the frame and the planking. I did not add wood back to the frame in this case... I just added a shareholder's worth of GelMagic.
-Michael

Built Utility "Perseverance" — completed Aug 2016
Currently building a Zip
My Boatbuilding Blog: http://barnaclemikeboats.blogspot.com/
My Website of Boat Photos: https://michaelsmaddox.wordpress.com

mdweber
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Re: Rabl Method

Postby mdweber » Tue May 13, 2014 6:44 pm

Thanks Mike.

I just about finished fairing the bow to forward frame section. The Rabl method worked very well!

IMG_0518.JPG

IMG_0512.JPG


I moved to the transom to begin fairing as discussed in Building with Plywood. For the aft sections, do you continue with the Rabl method, or do you switch to more of a trial and error approach by placing plywood against the sheer/chine, and fairing until it will lay flush?

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BarnacleMike
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Re: Rabl Method

Postby BarnacleMike » Wed May 14, 2014 3:29 am

As for myself, I started by fairing the chine at the frame joints, then "connected" the areas in between.... basically the same theory as the Rabl method.

The section between frames 1 and 2 was a little tricky, as the chine begins to bend and twist. The bevel for the bottom planking kind of rolls outward right along there.

Just take your time, and check your progress frequently with your test piece of plywood. It looks like you're making great progress.
-Michael

Built Utility "Perseverance" — completed Aug 2016
Currently building a Zip
My Boatbuilding Blog: http://barnaclemikeboats.blogspot.com/
My Website of Boat Photos: https://michaelsmaddox.wordpress.com

brad1516
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Re: Rabl Method

Postby brad1516 » Sat Aug 30, 2014 8:38 am

hey guys I am having a problem fairing the front v of my squirt boat if you guys could help me and explain it in simple words would be a great help its from frame two to the bow of my boat. what angle is your stem, is it the same angle the whole length of stem? and I don't understand how to draw that line on my chine log I don't even know if it has the proper twist any advice as to where to start? thanks brad

lakeracer69
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Re: Rabl Method

Postby lakeracer69 » Sat Aug 30, 2014 11:05 am

brad1516 wrote:hey guys I am having a problem fairing the front v of my squirt boat if you guys could help me and explain it in simple words would be a great help its from frame two to the bow of my boat. what angle is your stem, is it the same angle the whole length of stem? and I don't understand how to draw that line on my chine log I don't even know if it has the proper twist any advice as to where to start? thanks brad



Is the angle the same, no

Starting from where the chine meets the stem make a line that starts half the width of the chine. take a flexible batten and draw a line from that point to where the chine is fair at the most forward frame. That is from the book. Worked for me.
As Conan the Barbarian says, " It's not how hard you can hit, it's how hard you can get hit and remain standing".

brad1516
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Re: Rabl Method

Postby brad1516 » Sat Aug 30, 2014 8:09 pm

I did that did you have to angle your chine log on the 1 1/4 side to make it line up with the sheer ? and does the whole with of the sheer need to be belved so plywood meets flush with the two angles and that line I drawn is straight but when you look on the chine it is not. does the whole serface up from the line need to be planed so the plywood touches the whole way and on half the stem? what I mean by this is from the line drawn on the chine does the btm plywood need to touch the whole surface above the line ?

brad1516
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Re: Rabl Method

Postby brad1516 » Sun Aug 31, 2014 9:31 am

okay so I figured out my stem chine problem I glued my chine in the wrong spot on the stem if you take a measurement from the top of stem to chine interection its suppose to be 9 inch mine is 10 1/2 is this a problem ? or does my fairing just need to be different and if so how can I fix it. I missed an important information on chine placement please help thanks

lakeracer69
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Re: Rabl Method

Postby lakeracer69 » Sun Aug 31, 2014 11:30 am

Now you need to devise a miracle recovery. Either cut out the chine and start over, or figure out if you can save it by adding material to it. Chine location can be determined in the table of offsets.
As Conan the Barbarian says, " It's not how hard you can hit, it's how hard you can get hit and remain standing".

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Bill Edmundson
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Re: Rabl Method

Postby Bill Edmundson » Sun Aug 31, 2014 1:14 pm

I hate :!: to cut out! I would build it back up and reshape. The only thing that I've cut out is when I realized that I had used some Red Oak.

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

brad1516
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Re: Rabl Method

Postby brad1516 » Sun Aug 31, 2014 1:29 pm

whats the table of offsets ? and I found out today if I add move to the height of the chine then shape it the btm planking will work perfect but this changes the v of the front a little bit is that a crucial part?

miyot
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Re: Rabl Method

Postby miyot » Sun Aug 31, 2014 2:21 pm

Bill Edmundson wrote:I hate :!: to cut out! I would build it back up and reshape. The only thing that I've cut out is when I realized that I had used some Red Oak.

Bill
Red oak gets a bad rap. It is good wood and although it has a reputation for sucking up water, it also sucks up epoxy and whatever type of goo we put on it. It also has much better gluing properties than white oak! I have no fears using Red oak, I just seal it good with epoxy.

miyot
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Re: Rabl Method

Postby miyot » Sun Aug 31, 2014 2:29 pm

brad1516 wrote:whats the table of offsets ? and I found out today if I add move to the height of the chine then shape it the btm planking will work perfect but this changes the v of the front a little bit is that a crucial part?
If your chine makes a fair curve and is going to work, use it. If it looks good it is good. The Flying saucer plans give measurements for chine placement. It would not go to that spot. I let it fall where it wanted to go. I had to add a shim to the chine for the topside planking. I still ended up with a little concavity just at the bow where the top sides and bottom planking meet.

I didn't worry over it for a second. I just fared the bow with some epoxy filler. Although I am just going to have a work boat finish, I think my bow looks good. Always keep in mind the boat builders quote. IF IT LOOKS RIGHT IT IS RIGHT.

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Bill Edmundson
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Re: Rabl Method

Postby Bill Edmundson » Sun Aug 31, 2014 3:26 pm

Red Oak has its use. But, I don't use it in a boat on anything that is difficult to repair and may be exposed to a lot of water. I've used RO in the cabin, for seats, etc.

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

brad1516
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Re: Rabl Method

Postby brad1516 » Sun Aug 31, 2014 3:28 pm

thanks I was never going to take my chine off because the side planking was already planed and fitted perfectly I just have a sharper v nose and I added onto my chine and shaped it so my btm plywood has a good fastening spot thanks for the advice and the direction to go in. does anyone have any ideas on the transom I am putting a short shaft 35hp 2 stroke on it was going to make it stronger


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