On a full size yacht the skipper has a virtual unlimited length of sheet material to hand and multiple pulley blocks to help. On a model this isn’t the case, and in general you are restricted to the length of sheet allowed by the sail servo arm length. O.K., you can have a double purchace system to increase the available sheet length, but then you are reducing the pulling force available as well.
So, what is normally done is to set up the sheet attachment points to be about 60 to 90 mm from the main boom or jib pivot positions and as close to the relevant booms as possible to avoid innefficient pull angles. On Bob About Brett has chosen to exit the sheet from the transom so he then takes the sheet through a wire loop on the mainsheet post in order to get it close to the main boom. A ring on the deck would have been possible but would have been a bit far away from the boom.
The Forespar is a way of locating the jib boom swivel forward of the main deck. The jib boom is attached to the Forespar by a short length of looped sheet material which allows for a very flexible and adjustable swivel. The locating pin probably refers to a means of restraining the Forespar to the deck to resist the upward pull of the Forestay. The jib boom itself is able to rotate freely through far more than the 90 degrees each way you need. Set up the Forespar to jib boom loop to be about 25% of the length of the jib boom length when measured from the front. This will ensure that when you tension the Forestay bowsie at the mast head the boom will pivot about the attachment point and pull down on the rear of the boom thereby tensioning the Jib leech. You my well then have to attach a Topping Lift, which is a bowsie adjusted line between the mast head and the rear of the jib boom to be able to adjust this tension.
When locating the sheet attachment points it is worth ensuring that the distance from the jib attachment to its swivel is about 10% greater than the main boom attachment to its swivel - the Gooseneck - in order to get both booms to to end up equally far out when running down wind. This requirement arises because you will have, when close hauled, set the main boom to be about 5 degrees to the hull centre line and the jib boom to be about 10/12 degrees in order to achieve the correct slot.
I don’t know why Brett has his sheet exiting on one side, probably because he thought it would make a better angle with the servo arm. I have always put mine in the centre in order to be as far away from the water as possible on either tack.
Firstfooty, your reply was really informative and I’m very grateful that you took the time to write. Now, I’ve read and re-read the bit quoted above. They are words and sentences but I for one just cannot understand what it means!
Once I thought about your notes I had no problem with rigging and it did make sense (perhaps the full size sailing helped).
The “BobAbout” is in the water and floats which is a good start!!!
Rigging seems to be working OK but have a problem with sail material. Used drafting film which is a bit heavy … cannot buy ripstop nylon in Thailand so will have to put my lateral thinking cap on to come up with suitable alternative. Could try sneaking around one of the camp sites and cutting a square out of some drunks tent I suppose!*#.
Mike, ripstop nylon is pretty heavy, too. Try dry cleaner bags, florist wrapping, or similar. In the UK, Roger Stollery uses a lightweight bin bag that is great…but I haven’t been able to find them in the states. If you are willing to spend some money, the light weight TriSpi is very nice.
Bob About is a traditional Bermuda type rig, and many of the terms in my post #2 would apply to many other rig types. Perhaps if you could resubmit your reply #4 and highlight in some way the bits you need explaining then I could be of more help.
If, as your name suggests, you have come directly from aircraft, then perhaps you do need explanations of Transom, sheet and leech as well.