15th Nov 2010, 02:30 PM #421
Here is Brian's prototype RAID41. So it is an option to explore. He does have a vang as well, but you just can't see it in this shot for some reason.
Couple more pics here - Flickr: Search keyhavenpotterer's photostream
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15th Nov 2010, 03:22 PM #422
Thanks, will try moving the vang and downhauls closer together then. Like this...
19th Nov 2010, 08:16 PM #423
21st Nov 2010, 08:59 AM #424
Yesterday's sailing on Grahamstown Dam was interesting. It's the first time I've encountered the local southerly breeze on that waterway. It certainly kept me on my toes, with occilations in direction up to 90deg and big variations in the power of the gusts. Putting ones bum over the side on the beats needed some courage and lots of tiller work to stay upright. We had 10 knots, gusting 15 which is right on my limit on the beats without a reef, but it did make for some nice reaches.
I had a race around a windward/leeward course with a guy in a Laser 3.8. I was a little late for the start so he had the jump on me by about 10 meters, but we rounded the weather mark the same distance apart. I gained about 5 metres on the broad reach to the wing mark. The next leg turned into a beat due to a big wind switch and he extended a bit. The next beat was really gusty, and I could have done with a traveller that holds the boom out further, but was nevertheless pointing really well and he took nothing away from the Goat on that leg. I was spilling a fair bit in the gusts, but he was able to keep sheeted and fully powered up. I gained a bit on the last run home as we split gybes and I was able to pick up a nice puff on the starboard side and almost pipped him to the line. We were only 5 seconds apart at the finish.
I used my new downhaul and kicker arrangement, but brought them closer together in a similar configuration to keyhavenpotter's scow in the pic above. This worked very well and I had the sail looking like a blade! Earlier in the day I tried it out and fiddled with all the settings so I had a fair idea of what was needed for reaching and running. For the beats, I slacken off the vang and pull the downhaul on hard so the boom moves back leaving only about 200mm of sail is in front of the mast. This has fixed my lee helm and now I have a very slight weather helm, which is just right. It has made a huge difference to the pointing too, which is now almost as good as the Laser, so I'm very happy with that. On the reaches, I slacken the downhaul off a fair bit and apply lots of vang. This pushes the boom forward so that the luff is about 600mm in front of the mast and the luff still stays nice and straight. This powers up the sail nicely, and it's like having a jib.
There are a few things from yesterday for me to think about. While I like the sheeting arrangement off the end of the boom, on three occasions in the race the rope hooked on my PFD and nearly caused me to capsize. They were spectacular recoveries with the gunwale nearly going under each time! In the end, these mishaps probaly cost me the race. Maybe I just have to learn to duck lower The other disadvantage of the arrangement is that you cannot grab the sheets and haul the boom across and gybe quickly as you can with a central system. With the end sheeting, you really have to wait until the sail comes over by itself, as a consequence of which gybes are more violent.
I need to mount my windicator on the bow, Laser style. Looking up at the mast is giving me a sore neck and more often than not the sun is always there too
A fixed traveller arrangement would be nice too, but I'm not sure if I want the complication of it. The problem with a rope traveller is that the boom tends to centre itself and the sheeting is too far inboard on the beats when the breeze is up.
Now that I'm happy with the function of the vang, I also have to bring the controls for it and the downhaul back to the mid seat where I can reach them easily. I also need to make a stiffer boom as the vang is stressing it much more than the downhaul alone. The boom was making all sorts of creaking noises, and it would not have surprised me if it had popped yesterday.
The really nice thing about freshwater sailing is that there is no washing down to do afterward. The boat just sparkles straight out of the water! I'm getting quite proficient at packing it up now. I can single-handedly recover the boat onto its road trailer and have it all packed up and lashed down ready for the road in 30 minutes. I couldn't do that with the old box trailer.
I'll have some pics next outing as I've bought a small waterproof camera that can be strapped to my hat.
Once again, lots of interest in the GIS. Lots of people coming up to have a look and saying how good it looks out on the water. Lots of questions too about the rig, because it seems to them to be performing better than they expect. It's amazing how many people are also commenting on the bow and how good it looks with 2" clear of the water. It really is different to other boats in a lot of ways.
21st Nov 2010, 06:03 PM #425
Nice to have you out there against other boat. Would be interesting to do a comparison with two up as overpowered upwind. Maybe one day.
No reason not to try centreboom apart from needing a bigger cross section boom. Which boom are you using now?
21st Nov 2010, 06:54 PM #426
It's a box boom utilising clear 40X10mm radiata pine for the sides and finger jointed stuff for the cappings. It has 19mm thick Paulownia infills.
Finished dims are 58X38mm with a 10mm taper along the bottom at each end.
Some time ago Ian H provided me with some calcs for the new one, which I'll make to a better material standard than the current one.
I found an Oregon painter's plank under the house and am eyeing it off, but I know that one day I'll probably come to regret any decision to cut it up.
22nd Nov 2010, 10:17 AM #427
Give the centreboom a shot.
With the sheet catching you - you can put a seat belt webbing loop hanging under the boom at the point where you are most likely to be under. It just attaches both sides of the boom and hangs down in a U shape with the sheet running through the middle.
That should keep it out of your hair Lifejacket neck.
Nothing to stop the traveller being moved forward as long as it doesn't interfere with the tiller so you can grab the sheet - but then again lots of boats with this sheet system manage by oversteering in a gybe, a big trim of sheet to start the gybe and when the boom starts coming over to bear away onto the right course.
I was taught one trick by my old crew (and excellent single handed sailor) - focus on the heel of the boat only during the gybe. Don't make any guesses about which way the forces are going to go and preempt them too much - that's when most capsize. If you just watch the heel and respond you are less likely to start heeling too much.
This means the sail handling part of gybing has to practiced enough to be mostly unconscious.
22nd Nov 2010, 07:31 PM #428
I think I'll give your webbing over the boom idea a shot first. My brother has also mentioned this solution as they use this on PTs and in the Starling class which my nephew sails. For a centreboom arrangement I'd need to buy more blocks, so the cheap solution comes first
For gybing, I'll try some new things, like pre-sheeting a bit before the gybe. The Goat handles the gybe manouvre very nicely actually, and of course the key is always to do it at full speed when the apparent wind is lower and the boat has a higher stability due to it's speed. It also has a very nice rudder that grips well, so its very controllable and predictive. It has no vices at all really, now that I come to think of it!
I agree 100% about concentrating on the heel of the boat during the gybe. One of the most difficult boats to gybe that I have sailed was the South African 14' Sprog because it has no inherent stability and requires an active and vigilent crew on downwind legs. The Finn is also a pig I've been told, and probably much worse than a Sprog because of its long boom and cat rig. But a good trick with such boats that want to round up violently after the gybe is to ensure the boat is flat, and the instant the boom crosses the centre, apply a hard rudder to bear away. This keeps the boat flat and counteracts the momentum of the boom crashing across.
When I was young and crewing for a future South African and European champion in the Sprog Nationals offshore in Durban, the first time he screamed "get ready to to GYBE" while we were surfing down a huge wave at full speed with near zero visibility due to stinging spray, I was incredulous. I thought he was a mad man and I was going to be killed. But when he yelled GO, the boom just came across so quietly and gently that I could not believe it. After that, I never feared gybing in heavy wind again. I'm not saying I always did it right and stayed upright, but I had the confidence to do it.
22nd Nov 2010, 08:09 PM #429
(After you reported your results from adding carbon tow to your wooden yard, I had a go at figuring out how much carbon tow you'd need to add to get a decent increase in stiffness, even on best assumptions of the tow and the wood working together, I think you'd need a carbon tow/epoxy laminate of at least 1 mm thick around a spar to make a difference)
Great information on the changes you are trying with tuning your rig!
22nd Nov 2010, 08:33 PM #430
Thanks Ian, I'll try that. I can get Tasmanian Oak very cheaply. I'm not sure if you know it? It's not really oak as it's a eucalypt, and fairly ubiquitous over here. Would this be OK?
General Species details
23rd Nov 2010, 07:16 AM #431
Yes, I thought Tassie Oak and Vic Ash were just different names for the same eucalypt species, or at least timber that is functionally the same. I'm using some in my GIS, I got a 150x50x5500mm plank, though it wasn't cheap down here. Seems very nice timber - clear and straight, the thin strips I ripped from the big plank have stayed straight, which is a relief. Stiffness about 16Gpa from what I read, so about twice finger jointed radiata pine. You wouldn't make a whole spar from it as it's too heavy, but a thin layer just where it can do the most good should do wonders for the stiffness and strength of your boom without adding much weight.
I'm about to start laminating up my boom. Sides of 4mm Gaboon ply, 8mm of Paulownia top and bottom with 7mm of Tassie Oak on the outside top and bottom. Overall dimensions 70x48 mm or so with some taper towards the rear.
23rd Nov 2010, 03:23 PM #432
Sounds good Ian. It will be interesting to see how it turns out. I have plenty of ply left over from my Goat that could be used for a boom. Are you scarfing the joints or using a butt joint?
The Tassie Oak we get has quite a large range of densities. It's a bit like Meranti, which as you know can vary from extremely hard and dense through to very light and soft like Paulownia. Well, maybe the lower density TO is not quite as soft and light as Paulownia, but it doesn't have to be heavy stuff for use in boats.
However, TO has a lot of uses and there is never any wastage from knots as there usually none. The great thing is that it's quite cheap. My sail maker in Tasmania made his yard from Tassie Oak from the light end of the spectrum as he too was having issues with spar bend. He was able to make a stiff spar without going to the larger diameter that would have been necessary with pine type timbers.
26th Nov 2010, 10:39 AM #433
Be good to add this boom construction to the Google document on Goat setups,
Did I give you the permissions for that Ian?
27th Nov 2010, 05:10 AM #434
27th Nov 2010, 09:46 PM #435
Today's sailing was simply exciting, and we went the fastest we've ever been on some screaming broad reaches. It was awesome. Sorry, no pics again as things just got too hairy for taking pictures.
The venue was Grahamstown Dam again. Early on the wind was gusting 15 knots, and as the forecast was for wind in excess of 25 knots in the afternoon, I chucked in a reef. However, the first reef removes a massive chunk of sail, and it was just too docile for my liking and I was having trouble punching through the waves so I went ashore and removed it. Aah, that was better. More scary, but much better! I have the standard sail, but I think the oft talked about mod that makes the first reef a lot smaller is a good idea.
We had two races around a triangular course of two laps each.
There were plenty of boats today, but I sailed with the Lasers as they are much closer to the speed of the GIS. Four Lasers (1 had a radial rig) and a Goat today! Conditions were much more suited to Lasers, but I didn't do too badly. By the time we started at 2:30, the wind was up to 20 knots. For me on my own, this was survival conditions, but I decided to have a go as it was a much steadier north Easter than last weeks “all over the place” southerly. A predictable breeze is always so much better, even if it's too much.
In the first race I got a crap start and gave away about 20 metres to two of them, which I couldn't pull back. I was pointing really well, but I was struggling with the conditions and could not power up the sail enough to catch them. The next leg was a close reach, and again, I was spilling too much to really make a difference, but they didn't extend. At the wing mark I had three Lasers in front of me, and the radial behind me. The next leg was a run and I gained somewhat on the leaders. On the next beat I lost a position and was fourth, and this is how we finished.
In the next race I got a better start, but was 3rd again at the top mark. The waves were now much bigger and the Lasers were starting to struggle on the downwind legs. The wind shifted slightly and the third leg of the course became a broad reach instead of a run. On that broad reach, we were all hit by a savage squall. Too bad the leg wasn't longer because I was screaming along, hiking from the rail at the 4th bulkhead to keep the bow up, surfing the waves and catching the 3 Lasers in front rapidly. They we starting to nosedive into the waves, and when they did I'd make huge gains. However, they would just eat me upwind as they could manage the strong wind better than me. On the 3rd leg of the second triangle, the wind was from dead behind so we needed to gybe. I got all my gybes right, so that was a big plus that I can take from a difficult day, and I didn't capsize! The Laser immediately front of me capsized when executing his gybe so I was able to scream past and get 3rd. I have never planed that fast on a run in the GIS! It was scary, and the boat was vibrating like a guitar string. How I stayed upright I don't know. I had recently installed new, bigger 10mm shock cords on the rudder stock, but the rudder was still lifting on that mad reach in the squall. I was gobsmacked, because not only did I have the bigger cord, but it was tight also.
If my daughter had come along today, things might have been quite different, and I'm sure the Lasers would have been toast. I was knackered after the second race, and I just know that I'll be sore tomorrow. Because I was so tired, a capsize would have been bad for me, so am very glad that I was able to execute my gybes well.
But today was just a buzz...! Just sorry I don't have video or pics for you
PS. One of the guys who has only recently started sailing and is learning in access dinghies has just bought the plans for the OZRacer, so he will probably be along here one of these days. He's in the RAAF.
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