I have noticed that the swing rigs on the RG65 have the main boom pointing up slightly. Is there a reason for that? I think I will try a swing rig for my boat.
when boat is heeled going to weather it reduces the tendency of the end of the boom to drag in the water and slow the boat down if the main must be sheeted “out”.
It is also worth making sure the jib boom is up and out of the way as well. Usually this is not an issue as the jib yard is much shorter than the main boom. This is not as much of an issue as the main boom dragging, but it makes for interesting sailing when the jib digs in.
What would you suggest for the T-fitting to hold the yards? It seems almost anything but soldered, butted tubes would have significant weight, or is this one place you expect or allow to be ‘heavy?’
I was just going to build it like for the Footy, with a rod going through the mast and glued into plugs on each yard.
I made my rigs by butting the jib yard and main boom to the mast. Then CA’d in place. I then reinforced the joint with a small triangle of 1/16 ply which had holes to allow lashing to the mast and boom/yard. that way I did not compromise the mast strength. The rigs were quite strong and ended up fairly light.
Mine is pretty much the same - carbon tubes tacked in place with CA, then balsa built up via triangular sections under each and a final coat of 4 oz. glass and epoxy to seal. All outside the mast - no holes thru the mast. Weight was pretty minimal when I was done.
Google and download the building info on the Dutch XL25 class - as they offer some good ideas on a swing rig and sail build. I have link at home, but not here at work.
BTW - I use carbon arrow shafts ($4.00 @ Wal-Mart) with the screw in insert for arrow heads. As I recall it is # 8-32 thread so you can clip off the head of a 2 inch long machine screw, and epoxy into the base portion of the mast insert. Leave the other end as screw in/out and you can easily and quickly change the height of the mast for different sail sets.
Look up Bauanleitung Jolle Swing Rig on http://groups.yahoo.com/group/RG65SailboatsUS/files/ for a good translation (by Angus of footie fame) of the original German article The basic Jolle is similar to the Dutch XL25 class.
There is also the “balanced rig” from Roger Stollery. He outlines the design of the rig on the last page of the Bug3 Footy plans and uses variations of it on bottle boats and other larger-than-Footy classes. Basically the idea is that the swing rig yard and sails rotate around the mast rather than having the whole rig rotate in a mast tube. The fitting that connects the jib section to the main section is a twist of wire and there is a delrin or teflon stop ring on the mast that keeps the boom assembly from riding up the mast. It is simpler to build than the ones described above and self regulates jib stay and main leech tensions so you don’t have to worry about it. Overall tension on the rig is adjusted for the wind conditions to keep the boom assembly from binding on the stop ring but otherwise it is evidently an easy rig to sail. A bunch of the Brits swear by it.
Tom, if you want a CF fitting I have mold for one with upswept booms. The mast and boom for this fitting are spec’ed at .188". I imagine that for RG’s the boom spec may be a bit large but I have a method to get a 5/32 tube to fit. Send me a note and we can go over it.
Roger’s design gave me an idea.
You can get bronze flanged bushings in 1/4" and using that you might wrap a double-wire around it to use as attachments for the boom & yard. You shouldn’t need the bushing at all if you get enough wraps of the wire, to keep it all snug, but I was thinking of soldering the whole thing together, maybe, so it wound turn like Roger’s design does.
How important is it to have both boom & yard at the exact same height? If it isn’t, you could just skip the whole bushing and just wrap one wire more turns and use the two ends to hold the tubes.
Picture A is the first idea, and B is the second. The trick it this is to build the wrapping jig right, and I think ‘A’ may even have to be wrapped upside-down!
Maybe it’s the little screen on my notebook PC, or the photos in Roger’s document are difficult to understand. Is there a better drawing or other photos of the Bug3 swing rig that I can look at?
It may be of any interest ? This is what I did for my CD65. The flat plate on top of the main boom was made with the purpose to avoid air to flush from one side of the sail to the other, and therefore increasing theoretically the main efficiency.
Greetings and happy New YEAR
Beautiful work, Claudio,
You should enter the boat into an art competition instead of a regatta.
Please tell us how you joined the tubes in photo 3?
simply with epoxy resin
In picture number 8 your pond looks a little small:)
Well Tomo, to make a Stollery style balanced swing rig in the way you are planning you defeat the “balance” aspect of the design. The jib stay tension/main leech tension balance out only if the “gooseneck” is a loose fitting single or double loop of wire around the mast. The loose fit allows the rig to self adapt to wind speed changes, to lift and fall as it reacts to the wind, and keep the rig fitting from binding.
Other important features to keep in mind, the jib/main ratio should be between 25/75 and 28/72, and the pivot point for the jib be at a point 20 percent of the jib foot length aft of the leading edge of the sail.
And Claudio, you’ve made what was once called a “Broadway Boom” ala '80’s Americas Cup. I used one for a while on my M’s 25 years ago and it was used on some A boats over here back then. Its main advantage in big boats was to form an endplate effect but you don’t get that with a loose footed main, like the those that are standard in model yachts. In fact it may even cause more drag than a round boom because of it’s sharp edges.
I tried to implement the double-wire yard ‘arms’ idea and I got something promising. It needs to be a little tighter and you’d need to solder it together, but I was able to get both wires to wrap in the right way. I used copper wire this time, but I’d use 2 or 3mm wire for the rig.
And Claudio, you’ve made what was once called a “Broadway Boom” ala '80’s Americas Cup. I used one for a while on my M’s 25 years ago and it was used on some A boats over here back then. Its main advantage in big boats was to form an endplate effect but you don’t get that with a loose footed main, like the those that are standard in model yachts. In fact it may even cause more drag than a round boom because of it’s sharp edges.[/QUOTE]
you may be right, it was the Park Avenue already used on the first J Class Enterprise in 1930, but this was suggesting a lot of questions among “which motor are you using ?” !!! heheheh
Happy New Year
Hi Claudio and Happy New Year to you too.
Let us know if your broad boom makes any decerneble difference. Just because I abandoned the concept doesn’t mean it isn’t viable on model yachts.
On broad booms on big boats the foot of the sail runs on tracks to maximize the endplate effect. Such an arrangement on our size sails would hinder the sail’s reaction in light air tacking just as full battens have proven a liability in such conditions.
An experiment you might try, and I know how you like to experiment, is to place thin mylar ribbons along the top centerline of your wide boom and do the same thing to the round main boom of another rig. If there is a different airflow pattern for each rig then you may be on to something worth investigating further.
Tom, I guess that you skipped my earlier post about the Balanced Swing Rig needing a loose fitting main fitting connecting the main boom and the jib yard.
I don’t think one should skip ahead and try to improve on Roger Stollery’s designs until you’ve actually put one of his together and learned exactly how it works. Just my two bits.