WIZ is another IOM design which follows on and hopefully improves in performance from my three previous design experiments! I say experiments as I have never used computer modelling or naval architectural software to help in the design process, in fact I only use maths, besides geometry to divide the Loaded Water Line (LWL) into 19 spaces which gives me my shadow spacings. The only tools I use in my designs are 3 sheets of A3 paper, sticky tape to hold them together, a sharp pencil (usually borrowed from the Kids pencil case so anything from H-B will do!) a tape measure and something over a metre long which is fairly flexible. Oh, some weights and not forgetting a rubber eraser.
This post is purely how I go about drawing my designs up to forming the 20 foam board shadows. I'll leave the reasons and thoughts about the design for future topics a long with the building log (glog). So here we go, step one.
1) Selotape the three A3 pieces of paper together in landscape format, 12-20mm overlap is fine
2) Lightly divide the paper in half along the horizontal axis
3) Draw a horizontal line 70-75mm up from the bottom of the page. This will be the proposed Loaded Water Line (LWL). The bottom half of the page will show the longitudinal section through the hull and the top half will show the plan view. From these two drawings the body plan (shadow) drawings can be developed.
4) Roughly measuring equal margins I then measure and mark the LWL length = 998mm (just under one metre) and from the bow I measure back another 15mm for the thickness of the bow bumper and then another 3mm back for the bow bulkhead. I then measure from the transom to the bow bulkhead and divide this figure by 19 to give me my stations (shadow) spacings of approx 51.5mm which I mark on the LWL line.
5) On the top half of the page I draw a horizontal line approx 30mm up from the page centre. This line is the Centre line of the hull in plan view. I transpose the transom, shadow, bumper and bow bulkhead marks onto this line and then join them drawing lines vertically across the page.
6) Then I mark the draft of the cross section and beam on the section and plan views, using a flexible straight edge (contradiction) I draw the desired curves of the hull rocker, deck and chine. I actually use a 25mm wide piece of plastic trunking cover to form the desired shape!
7) I then measure and mark the centre line position of the mast from the transom onto the inside of the hull (mast foot) and draw a vertical line at 88 deg (mast rake) from which the mast dia is added and then the leading edge (LE) of the fin is positioned. I then lay my number 1 rig and fin on top of the section drawing to get accurate measurements of the rigging points, kicker well, mast ram etc.
NB all hull station (shadow) measurements are excluding the hull shell planking, in this case 3mm
There you go in less than an hour you can design the hull of an IOM!
Now the interesting bit
Producing the shadow templates also described as the body plans.
1) Using an A4 sheet of coloured paper measure and mark the vertical centre line in portriat orientation and mark another horizontal line approx 40mm from the top of the page. This line is the deck line, using the section drawing I measure down from the deck line to the chine and rocker line and transfer these measurements on to the shadow centre line. Then I measure and mark the chine width.
2) I place a scrap piece of paper or thin card onto the horizontal chine line and mark the width from the centre line to the beam. I then move the card on to the vertical line and using the beam mark on the rocker mark I make another mark where the vertical centre line intersects with the horizontal chine line.
Now the interesting bit
Producing the shadow templates also described as the body plans.
1) Using an A4 sheet of coloured paper measure and mark the vertical centre line in portriat orientation and mark another horizontal line approx 40mm from the top of the page. This line is the deck line, using the section drawing I measure down from the deck line to the chine and rocker line and transfer these measurements on to the shadow centre line. Then I measure and mark the chine width.
At the transom & bow the waterline is the draft
2) I place a scrap piece of paper or thin card onto the horizontal chine line and mark the width from the centre line to the beam. I then move the card on to the vertical line and using the beam mark on the rocker mark I make another mark where the vertical centre line intersects with the horizontal chine line.
Then arcing the card across keeping corresponding marks on the vertical and horizontal lines I spot a pencil mark at similar intervals.
This method produces the most uniformed curve possible from the rocker keel to the beam chine.
4) I then repeat this process for the 20 shadows. I then fold the shadow templates in half and then carefully cut them out. Important, from the deck line I leave a space of approx 30mm at the top to allow easy fixing to a wood batten which in turn is fixed to the building board.
Transom and shadow 11 area of roughly max draft and beam
no need for too much detail
Only another 17 to go but this does give an indication of the shape and size
The foredeck can drawn in the exact same manner as both the height and width are provided on the section and plan drawings. This produces a good rounded gunwhale which should help reduce drag.