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Mal Smith

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  1. I think what is interesting about the crab claw sail is that with only a flat piece of material and two light spars, you get a pretty good twisted airfoil, assuming the sail bellies out to an approximately conical shape. I'm not sure the same could be said of the lug sail, which would probably require some shape to be cut into it for best results. Side view: Plan view:
  2. Here's a closer photo my wife took of About Face at a wooden boat show in Sydney, late 80's or early 90's, I'm not sure. The name on the side is 'Bosna', so I guess it was still with the original owner. The interesting thing about this boat is that it has the proportions of a Pacific proa, so it's very conservative for an Atlantic type.
  3. I vaguely recall that it's a soft sail. It looks that way in the photo. The AYRS rig has full length battens.
  4. Prior to designing the Mi6 I'd had a lot of experience with swing rigs on model yachts. As long as the main/jib proportions are right, the rig won't overbalance. Essentially the rig behaves as a una rig. In model yacht circles it is generally accepted that swing rigs are twitchier than conventional sloop rigs i.e. the power is either on or off. With a conventional sloop rig you tend to sheet the jib home and then play just the main, which is a bit smoother for controlling the power of the rig. In fact on model yachts they will tend to use swing rigs in light air and sloop rigs in heavy air. As
  5. I managed to find a few drawings. Not much detail, but one of then shows how the existing rudder system is supposed to work. See the attached PDFs. Mi6-RudderSystem.pdf Mi6_GA.pdf Mi6_mast.pdf Mi6_spreaders.pdf
  6. Another shot which sort of shows one of the rudders.
  7. A shot showing the vaka profile and the mast.
  8. Here's a photo of the mast insertion process prior to the mast breaking (on the day this photo was taken).
  9. Hi Russel, there's an animation here of a modified version of the rudder system. It's basically as is, but with the addition of a bar on top of the steering yoke and a double tiller arrangement to simplify shunting the rudders - There are a few more photos of the boat, but no videos (it was pre-digital age). Somewhere I've got drawings of the rig, which I'm happy to share if I can find them. The rig was aluminium construction. I describe it as a stayed ballestron rig. The lower section of the mast is large diameter and tapers sharply up to the spreaders at wishbone level
  10. Yes, the transverse location of the rig is very important and can be used as a tuning tool. With the Mi6, the main hull displacement is maybe 80% or 90% of the total displacement when loaded, so the 'centre of transverse resistance' (CTR) is quite close to the centreline of the main hull. The true centre of resistance (CR) is the combination of the CTR and the CLR. For transversely symmetrical boats the CTR is usually ignored, but on a proa it's important. The helm turning moment is a function of the distance between the thrust line of the rig and the CR. I have often considered that it would
  11. If anything, the Mi6 had more weather helm than I would have liked. The rig could have done with being a little further to windward, which is one of the points for further development work. We did capsize the boat once. We were launching off the beach in 25 knots of wind and due to inexperience with the boat, got the rudder lowering/sheeting on sequence wrong, which did lead to a backward capsize. The teething issues were more around detailed design. One of our goals was quick set-up and launch time and we needed to do more work on that. The boom had been under-designed and we've sorted t
  12. On the half a dozen occasions that we sailed it, it was pretty quick. It was particularly quick in light airs, and it was a pleasure to sail. As with all development work though, there were teething problems that needed to be sorted. We had gone into it with the foolish idea that we could make business out of it. Unsurprisingly, we weren't able to attract any investors for the further development work we needed to do and we moved on to other things. Rob, The boat is currently languishing in Ian's mums backyard. I'm not sure what state it is in, I haven't seen it for over 20 years.
  13. There are a lot of variables, so it's difficult to compare one configuration to another. I suggested using weight, by which I mean total displacement, because it roughly corresponds o both cost and utility. For instance, if you utilise the available volume in the catamaran for extra accommodation, you are adding extra weight, so you have to scale down the catamaran to bring the displacement back into line. Getting back to the issue of the Atlantic proa hull length, the advantage of the Atlantic proa compared to a catamaran is the increased righting moment. If the overall beam of the cat a
  14. I would argue that it also applies to Atlantic proas, perhaps to a lesser degree than for Pacific proas. An Atlantic proa is more easily compared to a trimaran with one ama removed. The material from the missing ama can be added to the remaining hulls for extra length. I'm also working on the assumption that equal weight means equal accommodation (payload).
  15. No, but it can potentially outmatch the the load carrying ability of a catamaran of equal weight while maintaining similar performance. The advantage of proas is that the optimised weight distribution allows a greater hull length for the load carrying hull. Proas and other multihulls should be compared based on equal weight.
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