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Technical Manual

Controls, Side Decks, Toe Straps An' All

More thoughts on the renovation theme
by Nigel McKrill and Trevor Gore

After my article and illustration in the last Newsletter, Trevor Gore asked me to produce some gen on re-equipping an old OK, so here goes.

To me one of the advantages of the OK is that you can design your own control layout for everything from the toe-straps up. Unfortunately this advantage all too often becomes a disadvantage when not approached correctly. Therefore this article is intended to help not only newcomers to the Class, but also those people who haven't yet got the controls working effectively on all points of sailing.

I have based this first series of illustrations on my own boat, so can vouch for the control systems shown. The overdeck control system may look something of an anachronism in the days of underdeck controls but that is because my boat started life with a wooden rig. When I installed the metal rig I adapted what was already there to get on the water as quickly as possible, and gradually refined the systems and added the curved traveller and built up side decks. Hopefully the illustrations will be self explanatory but the side decks require some description.

When I bought my boat I immediately modified the side decks on the inside faces and planed the sheerline as far as I could, but this outer edge was still uncomfortable. So how to modify it without increasing weight, and in the shortest possible time? The final job took me one evening and doesn't weigh 1lb in total! This was achieved by using Polystyrene blocks of high density on the top of the deck and thin low density (ceiling tiles) on the inner faces. The adhesive is Copydex (carpet glue), although local Hobby Shops can supply an even better adhesive used for making foam core model aeroplane wings. A tip when using the white coloured adhesives on white coloured foam is to mix some food colouring as a dye so that one can see where it's being spread. Most adhesives will dissolve Polystyrene foam, particularly Evo-Stick, although Epoxy resins won't. I wouldn't advise Epoxy though, because it isn't flexible enough and it is heavier, and not instant. The surfaces of the deck to be covered in foam should be dry, and the existing varnish abraded with a medium. sandpaper. When you have glued the blocks on, cut to shape with a padsaw and finish off with a surform and sandpaper. Seal any vulnerable areas with a mastick sealant and then cover the side decks with lightweight sailcloth or spinnaker cloth using Evo-Stick as the adhesive around the edges of the Polystyrene on the deck only and not the foam, and Evo-Stick around the sailcloth edges only.

Toe-straps should be considered as part of the side deck assembly in that it is the combination of side deck shape and toe-strap geometry that dictates the degree of sailing comfort. The diagrams show methods of producing secure attachments at both ends of the cockpit. If you are experimenting with side deck shapes it would pay to make the toe- strap adjustable for position and length. The latest thinking in sitting out is the straight leg position. The toe-straps are set very long such that when sat out with the knees just outboard and the legs perfectly straight, they are parallel to the water when the boat is level. It's a strenuous position, but projects weight well outboard and keeps your backside out of the waves. The arch exponents are the Westergaard brothers.

The track used to attach the straps is Holt Allen anodised track; the same material being used to attach the blocks by the mast.

It should be noted that the control-line splits (port and starboard) are accomplished on the boom rather than over the foredeck. Although this makes for lots of string on the boom it leads to better adjustability. It also reduces the stress on the deck blocks by the mast. These are held to the track using short rope strops to allow sufficient movement.

The kicker system is the well known strut and strop arrangement, lately discarded by many. However, it does have two significant advantages, the longest range of useable adjustment and the most effective use of the tensions applied. The wire should be checked for fraying periodically (see last Newsletter).

The clew outhaul system is simple but effective. The use of the double load block in the boom helps reduce friction such that on this boat the tension in the foot shock cord is all that is required to pull the clew in. The tack is fixed.

The Cunningham system is self-explanatory on examining the drawings.

It is very important to have a good traveller system in an OK as it is essential to good sail control. Curved travellers are to be preferred as they allow full travel of the slider, and increase the useable length of side deck. The position of the final take-off point for the mainsheet and the cleating position are always the subject of many arguments

If the take-off point is the bottom of the cockpit, there is a greater chance of the slider reaching the end of its travel under its own steam. Cam cleats on the side decks have traditionally been the most popular arrangement, especially with open water sailors.

Small diameter (8mm) mainsheet and ball bearing small diameter blocks reduce rolling friction and allow the J/C straps (John Christian - a Finn sailor) to do their job on light weather runs. Small diameter blocks also help to windward in that with the upward curved traveller the boom can be sheeted lower before the chock-a-block position is reached..



Nigel and Trevor are very enthusiastic about the strut and winch type of vang, rarely seen these days, as they acknowledge.

Underdeck controls were popular in Britain in the 1980's, but no longer. Nigel's lay-out would be quite commonly found today, but with the turning blocks on the deck forward of the mast, and the mainsheet block usually mounted on the cockpit floor, not on the centreboard case.

Another article on this topic by another contributor appears in this selection.