Lines to outside or inside of planking?

[dmede]

I have the plans for the Atkins Maud & Emeline, a lapstreak flatbottom skiff.

No where in the plans or accompanying article does he mention if the lines are drawn to the inside or outside of the planking. I know its usual to draw the line to the outside of planking for larger boats or boats designed for carvel or strip planking, but what about for a small lap sided boat? How can I check for this?

[BrianY]

This may be a stupid idea - if so just ignore me - but I would get out an architect's scale, measure the max beam on the scaled drawing/plan and compare it to the stated max beam in the plan specifications - which, according to the web site is 4'6". If the drawing measures less than 4'6" by the specified thickness of the planking - allowing for a bit of a fudge factor if the actual beam is not exactly 4'6" - you'll know that the lines are drawn to the inside.

[Bob Cleek]

If you purchase the plans, the complete plans and offsets table should tell you whether lines are to the inside or outside of the planking. If, on the other hand, you decide not to buy plans, you would have to scale up the study lines and develop your own offsets. In doing so, you will note that the text gives the beam measurement. Once you develop and fair your offsets, you will know by measuring your lofting whether you are spot on or shy by the width of the planking.

[paladin]

and most sets of prints will say "do not scale from this print"......look at the table of offsets..

[dmede]

I have the full plans, and looking over them again I see that Atkin has used the drawing itslef to rely this info by including small sections of the plank thickness at the ends of the lines drawing where it intersects the stem and transom. So it's to the outside of plank.

It's interesting how Atkins drew lines. There is no table of offsets, all the measurments are on the lines themsleves and for a simple boat like this it works great, much easier to read than from a table.

I have another question though. Since the line is to the outside of the plank but the planks are lapstreak, and so not in a straight line, I assume the drawn line represents the outter edge of each plank at the laps. So when I loft for the molds do I deduct jsut one plank thickness or the combined thickness of two planks at the laps?

[dmede]

Here's a scan of the stem area of the plans. You can see portions of the planks drawn in near the stem.

[Don Kurylko]

Dmede, this boat is a perfect candidate for the construction method described in “Ultra-Light Boat Building”, by Tom Hill. A great little book that will answer a lot of your questions - very simple and easy to follow.

[dmede]

Ok, so I have superimposed the lines drawing from the above scan over the corresponding detail drawing of the same section (shows the frames and planks). The line from the section (green line) runs from the outside corner of the bottom to the inside croner of the sheer plank. That doesn't seem right but its the same for all the stations. I probably should'nt be trying to figrue this out before the lofting.

[dmede]

nevermind, the drawings are simply inaccurate. The section lines connect the upper outside corner of each plank so I deduct one plank thickness to get the mold dimensions. Just needed to visiualize it a bit.

[Bob Cleek]

You got it! It will be a lot clearer when you loft the boat full size. Atkin and others often simply dimensioned their drawings of simple boats right on the lines drawing, omitting offset tables. The offsets come into play when the lines are more complicated and writing in the dimensions and dimension lines would render the drawing nearly indecipherable.

[RonW]

I have a sey of Atkin plans, the pennant, and just ordered another set of plans. I think the plans are excellent, unlike others I have from other architects, I do have the offsets. I think the more you study them, the more you will find all the answers, the measurements just are not always where you might expect them to be.

As a sidenote, I see Atkin has the oarlocks set at 9inches, just below is a thread on this with the opinions running from 11 to 14 inches.
This is of the old school, which means that you reach further forward and your oars go further back toward the stem, thus allowing more of the power stroke to be toward the stem or on the pulling motion behind you. Putting the oarlocks furthr forward moves more of the power stroke towards the transom, in front of you.Try the oarlocks at 9 inches as Atkin shows.Think you will be pleasantly surprised.