Forums: The Deben 5-Tonner: WLA? New Topic Post Reply
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Posted: Oct 13th, 2011 at 19:13   |   Subject: WLA?
I was looking at the table of offsets pdf for the 4 tonner and I don't know what "W.L.A." stands for. I understand all the other anacronyms. I assume there will be something similar listed for the 5 tonner hence me asking here.

Can you explain?

Posted: Oct 16th, 2011 at 11:57   |   Subject: WLA and 5-tonner offsets
Sorry to be so long coming back to you Greg.

The Deben 4-tonner offsets are a little oddly set out. WLA is however simply the waterline 12" above the DWL. There is an explanation on the website – Boat Plans:Deben Class Yachts:Deben 4-Tonner – and in the Offsets paragraph you will see that you can click through to these notes.

When I first started out boatbuilding, Offset tables were usually set out in Feet:Inches:Eights – 2:3:2 would mean 2' 3 1/4" (2 eights equalling a quarter). To get a little more accurate some designers would add a + or - sign after the eights, to indicate a 1/16th – so 2:3:2+ would mean 2' 3 5/16". And so on. W. M. Blake's Table of Offsets is a little idosyncratic to say the least!

The Deben 5-Tonner Table of Offsets is on the site now – not too idiosyncratic I hope. I will post some notes to go with it and the Lines Plans, which I will also post in the next day or so. So that they can be printed on 12" wide paper, the lines plans will probably be in three drawings (Plan View, Profile View and Body Plan).

Best regards

Posted: Oct 16th, 2011 at 20:27   |   Subject: WLA
Thanks George for the info.

I was aware of the basics from reading things here, other websites and books; but that did not mean I knew all! LOL .. after going through the 4-tonner offsets I thought that maybe the WLA was just another form of describing the waterline -like "A" for above the waterline, "B" for below.

I will go have a look right now at the 5-tonner offsets! I was thinking of practicing laying them out at maybe ~1/8 scale - on 36" long paper. DO you think that is a good idea before doing it full scale?

Posted: Oct 17th, 2011 at 12:26   |   Subject: WLA
There is a new Table of Offsets for the 5-Tonner – the only difference is the it notes that the Offsets are to Outside of Planking. The offsets themselves haven't altered.

The Plan View of the Lines Plan is also on site now.

There is no harm in doing a scale layoff – but for myself, I wouldn't bother. At that size (1/8th) you can't be accurate and it really isn't the same as doing it full size.

When we got yachts that were bigger than our lofting floor (which was 50' x 20') we used to lay them off in two overlapping sections, but not at half scale. It did get a bit confusing, two sets of lines on the floor ...

So I would simply go for it at full scale. It is not actually a difficult process. And I will write a set of notes to lead you through it.

Specifically you are going to be laying off full size in order to obtain the shapes and bevels of the temporary moulds to Inside of Planking.

I can of course produce the shapes and bevels of the temporary moulds directly from the 3D CAD program – though it is a bit of a pain to do it to Inside of Planking. Nowadays I design to Inside of Skin and then make the necessary allowances for skin thickness in the hydrostatics. But for this design, I stayed with the traditional format and designed to Outside of Planking

I really used to enjoy laying off (or lofting) and it is the only way you can get sizes and shapes of anything in the boat without reference back to me and the computer! So you need to be able to keep the lines on the floor during the build so you can reference back to them whenever you need.


Posted: Nov 1st, 2011 at 23:36   |   Subject: Laying Off
Thanks for the info George. I was planning to use the 1/8 scale lofting just as practice for reading the table of offsets and such (and yes for a bit of play time as well!). Then when the time comes, using the gym floor at my church to do a proper laying off of the lines.

Since I would not be able to nail into the gym floor, I was thinking of using 1/2" sheets of 4x8 ply laid edge to edge. Would this work? I can stick tacks and small finishing nails in that for battens.

cheers and Happy November!
Greg H