Welcome Dave,
When the wind comes up it's best to reef the sail to control weather helm.
You'll actually go faster with less sail out and the rudder will be more responsive.
I prefer sailing with drives out, especially if there is weed around.
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| Weather helm with/without Mirage drives? http://www.hobie.com/au/en/forums/viewtopic.php?f=71&t=29814 |
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| Author: | davs2rt [ Tue Aug 17, 2010 6:09 pm ] |
| Post subject: | Weather helm with/without Mirage drives? |
I've had my Tandem Island for a couple weeks, and have been sailing it in Clear Lake, CA; a lake with lots of stringy "seaweed". At first I tried to sail with the Mirage drives in, but they (and every other underwater surface) quickly became coated with weeds. The centerboard clears easily, and I've gotten adept at raising/lowering the rudder while underway to clear the weeds. However, when I get to the deep part of the lake, and clear the weed, I still have tons of weather helm in 10-15 knots of wind. Can anyone comment on the value of having the mirage drives in/out to control the helm, and whether the front/back/both configuration matters? I'm suspecting that the mirage fins help to move the underwater center of lift aft, and that I'm going to need to put them in when the wind comes up. As this is my first post, let me also say Hi to everyone. Been reading and learning a lot from everyone. Thanks, Hobie, for providing this forum! Dave |
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| Author: | stringy [ Tue Aug 17, 2010 8:01 pm ] |
| Post subject: | Re: Weather helm with/without Mirage drives? |
Welcome Dave, When the wind comes up it's best to reef the sail to control weather helm. You'll actually go faster with less sail out and the rudder will be more responsive. I prefer sailing with drives out, especially if there is weed around.
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| Author: | dosjers [ Wed Aug 18, 2010 4:53 am ] |
| Post subject: | Re: Weather helm with/without Mirage drives? |
Dave, I don't think they change the sailing characteristics of the boat except to slow it down. Take strigy's advice. When you start to get too much weather helm reef your sail. |
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| Author: | pburling [ Wed Aug 18, 2010 12:37 pm ] |
| Post subject: | Re: Weather helm with/without Mirage drives? |
Dave: Your question about whether the drive fins can affect the center of effort implies, I think, that the fins are in the vertical position while you are sailing. I have always assumed that we are meant to sail with the fins in the horizontal orientation (as they will be if the bungee is hooked to one leg of the pedals.) I think you are correct that vertical fins would affect the center of effort, but I think they would cause an awful lot of drag in that orientation, not to mention risking damage in case of grounding. In any case, the TI sails so much better with the drives out and the plug in that I would recommend taking the drive/s out whenever there is enough wind to move the boat (and you don't need to be able to "motor-assist.") The weather helm could be an excess of sail area as suggested above. It could also be too much down line tension. With two people in the seats, I have been able to sail without reefing in 15 knots without too much weather helm; but I will concede that I have been thinking about reefing at that point. I'd suggest trying both techniques to see which one works best - see if you get a less stiff helm by re-seating the rudder and then reducing downline tension and/or try rolling in a reef. PBurling |
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| Author: | davs2rt [ Wed Aug 18, 2010 2:11 pm ] |
| Post subject: | Re: Weather helm with/without Mirage drives? |
Thanks everyone, I will certainly start reefing the main to deal with weather helm, as several of you have recommended, but some other experiments seem in order, too: more drag if the mirage flippers are up or down? (I'm guessing they might drag more up than down, since the aft flipper would slipstream the fore flipper.) Do they behave as a secondary centerboard, or are they just drag? Will they catch fewer weeds up than down? ...just more reasons to go sailing. |
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| Author: | stringy [ Wed Aug 18, 2010 4:59 pm ] |
| Post subject: | Re: Weather helm with/without Mirage drives? |
Dave, Long before the TI came out there was a discussion of fins and their daggerboard effect that you may find useful. viewtopic.php?f=32&t=10831 Back then sailing the Oasis I always left the drives in. The small sail needed the boost from the pedals. The drive in any position adds drag and any attached weed makes it much worse. The better sailing design of the AI /TI makes the drives redundant when the wind is strong enough. I always take the drives with me though! 
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| Author: | davs2rt [ Wed Aug 18, 2010 5:40 pm ] |
| Post subject: | Re: Weather helm with/without Mirage drives? |
Great thread. I liked the cutting board leeboards, and the aluminum mirage sock. Has anyone successfully made a dagger that fits in the mirage slots? |
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| Author: | stringy [ Wed Aug 18, 2010 8:50 pm ] |
| Post subject: | Re: Weather helm with/without Mirage drives? |
Some more daggerboard discussion. A search for daggerboard will give lots more info. viewtopic.php?f=32&t=3176 I modified a drivewell plug on my Oasis to take the AI daggerboard but since I got an AI (and now TI) haven't done a lot more sailing with the Oasis. I did end up filling the spaces in the plug with a mix of lead shot and levelling compound and replacing the plastic lugs with an old mirage drive axle but it hasn't seen much use. I have pics somewhere I could post if interested.
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