Forums: Whisstock Designs: help design 123 New Topic Post Reply
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vinci666
Posted: Sep 4th, 2013 at 01:48   |   Subject: help design 123
just got some plans for the first time. i could use some guidance on reading these plans. seems like the study plans tell u what to do but no examples to see if I'm doing the right thing.

Michael
debenriver
Posted: Sep 4th, 2013 at 15:04   |   Subject: help design 123
I just wrote you an email – copy below:


Hi Michael

I am happy to help.

You can make a grid on paper if you want to practice a bit first as you are doing, but in reality making the real grid is pretty straightforward. It is just a set of lines at 90º to each other at known intervals.

On paper, to practice and to get a grip of what is happening, if you use a sheet of millimetre graph paper it will make life much easier. At a scale of 1:10, each millimetre on the graph paper represents 10mm – so you can mark out most of the frames (or one side of them at least) on a single A4 sheet at 1:10 scale. Make one of the verticals near the left hand side of the page the centreline and one of the horizontals about 60mm up from the bottom the dwl. Then the waterlines wl 200, wl 400, wl 600 and wl 800 are 20mm, 40mm, 60mm and 80mm above the dwl. And the buttock lines b 100, b 200 ……. b 800 are at 10mm intervals to the right of the centreline. You might want to try a bigger frame than frame -450, as there is more curvature in the larger frames, so at scale it is more obvious.

However, honestly, I think I would go straight into marking out the real full-size grid as it is much easier to work full size and you have to do that in the end. You really will find it much easier to mark out the shape of a frame full size than it is to do it at scale size.


Setting-out floor and grid

Make a nice flat "setting-out floor" as noted in the instructions. The floor can be made from sheets of 18mm (¾") chipboard (particle board) or similar. Two sheets will make a floor 2440mm x 2440mm (8' x 8'), which is big enough. Fasten these firmly together on bearers – something like 75 x 50 or 50 x 50 (3" x 2" or 2" x 2") timbers, spaced at about 400mm (16") intervals. You can make the setting-out floor down at ground level, or, higher off the ground like a big table. Of course if you have a real timber or particle board floor that you can nail into (like a workshop floor), then you can use that as long as it is flat. Usually the floor is painted white so that you can see pencil marks easily – but you don'y have to do that.

Orient the grid so that the join in the setting out floor is the horizontal, so the join in the boards doesn't come right where you want to draw the centreline – see below. Then follow the detailed instructions for marking out the grid – or as outlined below:

Draw the Datum Waterline (dwl) as a straight horizontal line about 600mm (24") up from the bottom of the floor. The dwl is the vertical zero for waterlines and heights. Heights above the dwl are positive. Heights below the dwl are negative.

Then draw the centreline (c/line) as a straight vertical line. Draw the c/line in the middle of the floor so that you have equal space each side of it. The c/line is horizontal zero for buttocks and offsets (widths out from the c/line). Normally, because the boat is symmetrical about the centreline, buttocks and offsets are all positive – there isn't a positive or negative side. If we do need to distinguish, we use Port – left side standing aft, looking forward (fwd), or Starboard (Stbd) – right side standing aft looking fwd.

Take great care with these two lines that they are truly square to each other (at 90º to each other). You can check for square by using the 3:4:5 system as described in the instructions. So to check that the dwl and c/line are at 90º to each other:

Measure and mark 1200mm along the dwl out from the c/line (this is the "3" component); measure and mark 1600mm up the c/line from the dwl (this is the "4" component); then measure from the first mark to the second mark – this should be exactly 2000mm (the "5" component) if the lines are square (at 90º to each other). In inches you could use something like 45": 60": 75".

Once you are certain the the dwl and c/line are square to each other, mark out the other lines on the grid. Draw horizontal waterlines (wl) at 200mm, 400mm, 600mm and 800mm above the dwl and parallel to it. These are called wl 200, wl 400, wl 600 and wl 800. Draw wl -100 at 100mm below the dwl and parallel to it.

Draw out the vertical buttock (b) lines at 100mm intervals out from the c/line and parallel to it – draw 8 of them each side of the c/line. They will be b 100, b 200 ….. b 800. As mentioned above it isn't necessary to designate them "+" or "-" because the boat is symmetrical about the centreline.

Because the dwl and c/line are square to each other, the wl's and b's will also be square to each other.

It is worth taking time and care with the setting-out floor and the grid because this is where you will mark out and make the frames.


Marking out the frames

We use the grid as a convenient means of marking out the outline of a frame. The grid just saves us making two measurements every time we want a point on the frame outline. So for horizontal measurements we only need to measure out from the c/line on the appropriate wl. And equally for vertical measurements we only need to measure up or down from the dwl on a buttock.

On each frame drawing there is a "Table of Offsets" giving dimensional data of the aft face and the fwd face of the frame. Because a boat is not a rectangular box, one face of the frame is most always larger than the other. For frames fwd of the widest part of the boat, the fwd face will be smaller than the aft face. For frames aft of the widest part, the aft face will be smaller than the fwd face.

The above statement is not always true for all parts of the frame. For example the Sheer (the top edge of the hull, where it joins the deck) rises as it goes fwd. So, taking a frame fwd of the widest point, it would appear that the sheer height is bigger on the fwd face of a frame than on the aft face, whereas for the hull the aft face is the bigger. This is true in absolute terms but it is also true that the sheer "climbs up" the camber (the curve) of the deck, so as the frame gets smaller on the fwd face, the sheer has climbed a bit higher on the deck camber, so the actual bevel on the frame edge is not necessarily as it seems at first glance.

And other areas also don't follow the rule – the centreline of the coachroof gets lower as it goes forward, so on the c/line the fwd face is always smaller. The height of the coachroof edge is always 1200mm on this design, so at the edge, both faces of the frame will be the same height – but the coachroof is also getting narrower as it goes fwd, so the 1200 height is further inboard on the fwd face than it is on the aft face.

All this sounds very complicated and it is a bit complicated. But you don't need to worry about that too much – all you need to do is mark out the frame outline to the larger dimension, whatever face of the frame it is on. Then when you have laminated the frame up and cleaned it up to the right thickness (siding) you bevel the edge off to the smaller dimension. If the larger dimension is on the aft face, you bevel off to the smaller dimension on the fwd face. Conversely, if the larger dimension is on the fwd face, then you bevel off to the smaller dimension on the aft face.

Setting out, marking, making, finishing and beveling the frames is covered in detail, frame-by-frame in the instructions, including telling you which side is the larger and on which components of the frame.

Once you have made your grid, if you are having difficulty setting out the first frame (or any of the frames), or indeed if the grid is still giving you trouble, I would be more than happy to help.

Best regards

George

vinci666
Posted: Sep 4th, 2013 at 20:40   |   Subject: one more
Thanks George for the quick response!

I got the grid all figured out and understand it in full I believe.

The one thing I'm unsure of is in drawing and cutting the frames.(futtock part)

Are we drawing one side of the frame lets say the left of the center line side and laminating

2 /9mm plys aft and fwd face and then inverting that side to complete the right of center line of frame
(futtocks)

i believe once i understand this I will be able to proceed in making frames in full

thanks again
Michael