Transferring plans to plywood

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Lachlan1
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Transferring plans to plywood

Post by Lachlan1 »

Hi guys

I’ve been tracing my Zip frame templates to a sheet of plywood(using Pins and carbon paper) and noticed that the center line and set up level are not at 90° for most of the frames. 89° at the transom and a little over 90° on frames 2 and 4. Doesn’t seem like much but say on the transom, working off the centreline, the chines/sheer end up +1/4in (higher) and at frame 2 they would be -1/4in (lower). Which one of these if more important to the overall shape of the hull? Can I trust the measurements on the building form plan sheet to help transfer these? Little worried that if I get the frames a little off shape, that the sheer line won’t look smooth.

Thanks
Lachlan
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FL-John
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Re: Transferring plans to plywood

Post by FL-John »

Just a guess but... The plans aren't laying completely flat. It looks like the fold and curve at the top of your picture could account for the majority of that 1/4".

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Roberta
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Re: Transferring plans to plywood

Post by Roberta »

Use the top of the bottom frame members as the datum plane for frame layout. Use called out measurements when given. Shrinkage and folds can make minor discrepancies. Fairing will correct any minor errors and smooth things out. Wood boats are like snowflakes. No two are alike.

Another thing to consider is the motor you will be using. The plans are showing a transom designed for a short shaft motor (15"). If you are using a long shaft motor (20-22") you will want to modify the transom.

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

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Bill Edmundson
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Re: Transferring plans to plywood

Post by Bill Edmundson »

The transom height is the distance from the cavitation plate (the plate just above the prop.) to the engine mount bracket. There aren't many modern engines that are 15" anymore. It's best to identify the engine you think you want and get a diagram. If you make it too high, you can cut it later. Too low can be fixed. But, it's more difficult.

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

Hercdrvr
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Re: Transferring plans to plywood

Post by Hercdrvr »

“Wood boats are like snowflakes. No two are alike.” Well said Roberta.

Thank goodness ! I’d still be working on my Squirt if it had to perfect.
Matt B

TAB
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Re: Transferring plans to plywood

Post by TAB »

also don;t trust framing square. they are normally off by a degree or two. you can fix them by taking a punch and dimpling them to "shrink" the metal to square them up. there are a few vids on youtube that explain the process.

you can check them by using a fine point of a pencil and a true edge ( a machined side of a quality level works pretty good.) use that edge, draw a line, then reverse the square and draw another line a short distance away( like a 1/16-1/8"). compare the gap between them. also never let them sit in the sun. they have away of "growing" out of square.

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Roberta
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Re: Transferring plans to plywood

Post by Roberta »

Good point on checking the accuracy of a square. This also brings up the reason levels are flipped over to verify they register the same on both edges.

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

TAB
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Re: Transferring plans to plywood

Post by TAB »

Levels are the only self testing tool.

I have yet to find a framing square that was square out of the box. I have had good luck with starretts being close. They are not much more than the stardard squares you buy at the box stores( 25 instead of 20.) They were never ment to be that accurate in the 1st place. A degree is not really a big deal when you are building a house. More so for what they are used for. No one sets corners with them. You always 3 4 5. For things like sqauaring rough openings, cutting rafters angled sheeting and stair stringers, they work great.

Lachlan1
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Re: Transferring plans to plywood

Post by Lachlan1 »

Thanks guys for all the responses,
FL-John wrote:
Wed Sep 09, 2020 4:47 am
Just a guess but... The plans aren't laying completely flat. It looks like the fold and curve at the top of your picture could account for the majority of that 1/4".
TAB wrote:
Wed Sep 09, 2020 11:22 am
also don;t trust framing square. they are normally off by a degree or two. you can fix them by taking a punch and dimpling them to "shrink" the metal to square them up. there are a few vids on youtube that explain the process.

you can check them by using a fine point of a pencil and a true edge ( a machined side of a quality level works pretty good.) use that edge, draw a line, then reverse the square and draw another line a short distance away( like a 1/16-1/8"). compare the gap between them. also never let them sit in the sun. they have away of "growing" out of square.
I did think that at first but I used good old Pythagoras and still had discrepancies +/- 90°.
Roberta wrote:
Wed Sep 09, 2020 6:51 am
Use the top of the bottom frame members as the datum plane for frame layout. Use called out measurements when given. Shrinkage and folds can make minor discrepancies. Fairing will correct any minor errors and smooth things out. Wood boats are like snowflakes. No two are alike.

Another thing to consider is the motor you will be using. The plans are showing a transom designed for a short shaft motor (15"). If you are using a long shaft motor (20-22") you will want to modify the transom.

Roberta :D
I will get another piece of plywood and re-trace the frames using the horizontal reference line. I figured I would be able to fair some discrepancies, just got me a bit worried when I was having issue on the first step of the build :?

Planning on a short shaft motor but I will probably start building the transom to suit a 20” and cut down after the flip, just in case I change my mind.
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Lachlan1
Posts: 12
Joined: Sun Sep 24, 2017 3:13 am
Location: Macedon Ranges, Vic, Australia
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Re: Transferring plans to plywood

Post by Lachlan1 »

Roberta wrote:
Wed Sep 09, 2020 6:51 am
Use the top of the bottom frame members as the datum plane for frame layout. Use called out measurements when given. Shrinkage and folds can make minor discrepancies. Fairing will correct any minor errors and smooth things out. Wood boats are like snowflakes. No two are alike.

Another thing to consider is the motor you will be using. The plans are showing a transom designed for a short shaft motor (15"). If you are using a long shaft motor (20-22") you will want to modify the transom.

Roberta :D
Transferred to a new board using set up levels and it’s looking a lot better. Thanks again.
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