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 Post subject: Larger skag
PostPosted: Thu Aug 07, 2014 10:27 pm 
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Joined: Mon Jul 23, 2012 8:56 am
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Wondering if anyone has ever tried to enlarge their skag/daggerboard on a TI.

With project jib going well I can now point, but I still get blown sideways WAY more than what I am used to on a monohull. I was thinking about clamping a hunk of aluminum plate to it or something, but was wondering if anyone has come up with something better.

Maybe a second one that I could drop into one of the mirage wells?


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 Post subject: Re: Larger skag
PostPosted: Thu Aug 07, 2014 11:39 pm 
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Joined: Sat Nov 05, 2011 1:58 am
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Location: Forster, NSW, Australia
Couple of thoughts...
The design does not lend itself to going to windward like an America's Cup 12 metre, and while adding a jib might make apparent wind angles smaller, leeway is bound to increase. It is all a compromise.

I am sure you could double the side area of the centreboard by adding material on its front edge, but because of its pivoting mechanism, any extra area will not fit inside the slot, so you would have to be prepared to have a large amount of the bigger centreboard hanging down under the hull, even when raised. This would be a major pain when putting it on the trailer or roof.

Personally, I would rather just accept the limitations of the design, enjoying the versatility that the compromises provide.

(btw, the centreboard is quite different from a skeg. The latter would be located at the rear of the hull (traditionally, skegs were fins in front of the rudder, holding the bottom bearing for the rudder)

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2012 Tandem Island "SIC EM"
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 Post subject: Re: Larger skag
PostPosted: Fri Aug 08, 2014 9:47 am 
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Location: Bellevue, Nebraska
Baratak wrote:
Maybe a second one that I could drop into one of the mirage wells?

Maybe adding something to the mirage drive plug? What about just leaving the mirage drives with the fins sticking down instead of up against the hull? I know they aren't huge but having both sets sticking down should do something?


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 Post subject: Re: Larger skag
PostPosted: Fri Aug 08, 2014 11:13 am 
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Joined: Sun Apr 20, 2008 6:18 am
Posts: 1311
Location: Sarasota,Key West FL
Baratak :
I don't think there is any need to add more centerboard to the TI, there are many other things you can do to improve the boats performance and pointing ability.
First off it's probably a good idea to never remove the mirage drive (especially the one you are sitting next to), as the boat is a pedal boat first and a sailer second, removing the mirage drive handicaps the boat quite a bit, (especially if running with an empty drive pocket, this create way more drag than the mirage drive, putting the drive plug in helps but I don't think enough to leave the mirage out).
The boat is kind of designed to pedal even when your sailing ( you can pedal very lightly and it still works). By pedaling lightly you increase the performance and pointing ability of the boat considerable (basically what it was designed to do). You will notice much less side slip, and the boat will point higher, and require less rudder (too much rudder steals a lot of your power). Even if you just leave the mirage drives pointed down it has similar benefits if you flat don't want to pedal.
Keep in mind the more you add under water the more drag it creates ( I had a 50 lb weighted center swinging keel (kind of like on monohulls) on my TI for a while mounted in the rear mirage drive socket, and it caused a lot of drag).

Adding a jib also contributes to more side slippage because 1/2 of the power of that jib is lost as side force and heeling force. Unless you go to a wing type jib which doesn't have hardly any side or heeling force at all. I've had jibs on my TI now for over 4 yrs, and find when running the jib I pretty much have to pedal 100% of the time in order to counteract the additional side force (one of the prices you have to pay), which I don't mind doing since this is my exercise program anyway.

Always keep in mind that the TI is not a sailboat, it's a pedal boat/kayak that also sails well, it's not intended to be handled like a laser or sunfish, it has it's own strengths and competing 1=1 with lasers and H16's is not one of them, the TI has a higher purpose ( LOL).

This video shows my TI in 5-7 mph winds sailing mostly up wind (about 15 degress off the wind) so there isn't going to be a lot of side slippage anyway when your pointing that high. But if you look at the boat wake you will see there is almost zero side slip. If I were to stop pedaling the side slip would increase, and eventually the boat would round up into the wind and stall (basically you have to pedal to maintain that artificial trim condition)
https://www.youtube.com/watch?v=a1OjgyqBsXk
[youtube2]https://www.youtube.com/watch?v=a1OjgyqBsXk[/youtube2]

In the video I think I was traveling around 9-10 mph up wind into a 5-6 mph wind (1.5x windspeed), the apparent wind across the wing (and on my face) was around 15-17mph, the wing in turn directs a very nice organized slipstream across the mainsail forcing the main to work more efficiently. Of course the motors are part of the equation in this situation, but if I were to take the sails down and stop pedaling the motors running at 1/4 throttle would be propelling the boat at around 5mph upwind in these conditions. I much prefer traveling 10-12 mph with a 17 mph wind on my face keeping me cool when it's 90 plus outside ( LOL). Basically the fuel cost for that day was somewhere between $.50 cents and a buck for the day, I gladly pay that to have fun and actually get somewhere (if just sailing only without the wing, motors or mirage drive (on a stock TI), my forward speed would have been 3 mph at best).

I totally cheat and admit it.......

Bob


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 Post subject: Re: Larger skag
PostPosted: Fri Aug 08, 2014 3:16 pm 
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Joined: Thu Aug 16, 2007 2:25 pm
Posts: 2005
Location: Central Coast NSW Australia
fusioneng wrote:
First off it's probably a good idea to never remove the mirage drive (especially the one you are sitting next to), as the boat is a pedal boat first and a sailer second, removing the mirage drive handicaps the boat quite a bit, (especially if running with an empty drive pocket, this create way more drag than the mirage drive, putting the drive plug in helps but I don't think enough to leave the mirage out).
Bob


I can't agree with that Bob ...unless the winds are very light.
Removing the MD when sailing in winds >8knots or so, improves sailing. The boat tacks better and sails faster (drivewell plug in of course), especially if you leave the seat and hike out on haka.
You also don't get that annoying fluttering vibration from the fins that occurs at speed and less chance of picking up weed that adds drag.
Sailed this way the Islands are very capable sailing craft. :)


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 Post subject: Re: Larger skag
PostPosted: Fri Aug 08, 2014 4:27 pm 
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Joined: Sun Apr 20, 2008 6:18 am
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Location: Sarasota,Key West FL
stringy :
I'm sure you are correct, unfortunately I never see winds like you describe around here so I have no idea.

Bob


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 Post subject: Re: Larger skag
PostPosted: Mon Aug 11, 2014 2:27 pm 
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Joined: Mon Jul 23, 2012 8:56 am
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With stringy here, in low winds, I may leave them in, but as soon as the wind picks up I pull them out and drop the plugs in. There is a grand amount of drag from the MD.


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 Post subject: Re: Larger skag
PostPosted: Tue Aug 12, 2014 9:28 am 
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Joined: Tue Jul 22, 2014 2:21 pm
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Location: Clear Lake Area, Houston, TX
I'd also like to add I don't think the mirage drive (MD) fins perform very well as a centerboard. A centerboard, when on a reach, develops higher pressure on the leeward side and a lower pressure on the windward side, preventing leeway and increasing the efficiency of the boat. It needs to be rigid. The MD fins are quite flexible, making a great propeller when used as intended, but I believe they just create drag when under sail. The drag is relatively low in lighter winds, however, and I often leave them in under sail. The plugs allow more room to move while preventing objects from falling through the MD hole and I suspect the boat sails best with the MD out and the plugs in.

I have noticed more leeway than I like when sailing on a reach or even close hauled and would love to experiment with additional centerboard area. I wonder how performance would change if an identical centerboard were added to the other side of the hull? I sail with a stock setup and tramps, no jib.


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 Post subject: Re: Larger skag
PostPosted: Tue Aug 12, 2014 1:04 pm 
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Joined: Tue May 18, 2010 2:31 pm
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Location: Kailua 96734
Tip: If the fins are in, use them. Slight pedaling can improve your speed and pointing dramatically, especially in light winds and waves.

When the going is good, pull them or lock them tight against the hull. Downwind they should be pulled, along with the dagger, to get you another knot or so of speed.

Course, if you are fishing or in traffic, leave them in. Speed is not the issue then.

Wait!,..that's 3 "tips". :roll:


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 Post subject: Re: Larger skag
PostPosted: Tue Aug 12, 2014 7:52 pm 
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Location: Lake Macquarie NSW AUSTRALIA
NOHUHU wrote:
Wait!,..that's 3 "tips". :roll:


You really are the gift that keeps on giving NOHUHU !

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Don't take life too seriously................it ain't permanent.


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 Post subject: Re: Larger skag
PostPosted: Wed Aug 13, 2014 8:39 pm 
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Joined: Mon Jul 23, 2012 8:56 am
Posts: 16
Cheap test, I think I have a line on a sunfish daggerboard that I can modify to fit in the front MD well and lock in place. If I get my hands on it, I will post pictures and results.

Oddly enough while searching for daggerboard I found this:

http://www.akff.net/forum/viewtopic.php?f=58&t=30240


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 Post subject: Re: Larger skag
PostPosted: Wed Aug 13, 2014 11:17 pm 
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Joined: Sat Nov 05, 2011 1:58 am
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Location: Forster, NSW, Australia
Baratak wrote:
Cheap test, I think I have a line on a sunfish daggerboard that I can modify to fit in the front MD well and lock in place. If I get my hands on it, I will post pictures and results.

Oddly enough while searching for daggerboard I found this:

http://www.akff.net/forum/viewtopic.php?f=58&t=30240

Now THAT is clever! It might be a 5 year old idea, but its a bloody good one!

Image

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Tony Stott
2012 Tandem Island "SIC EM"
www.scenefromabove.com.au


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 Post subject: Re: Larger skag
PostPosted: Thu Aug 14, 2014 7:32 am 
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Joined: Tue Jul 10, 2012 10:22 am
Posts: 25
This is a topic I've been thinking about a lot lately. I was initially thinking about adding surfboard skegs to the amas, but was having trouble real thinking of a decent way to do so that would work. Along the lines of TI-Tom's idea, I have recently ordered some 9" longboard skegs and fin boxes from a surfboard supply dealer. The idea is to epoxy a fin box into the bottom of a Mirage Drive well plug and then put the skeg to the well plug. I am thinking of doing this twice, once for each well in the TI.

All the stuff is on order, so I hope to be able to post some photos, etc., within the next few weeks (these projects always take me a long time to actually do).


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 Post subject: Re: Larger skag
PostPosted: Wed Aug 27, 2014 10:33 am 
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I just managed to find a daggerboard off of Craigslist. It isn't a nice foil shape, but since it is wood it shouldn't be hard to fix that. It is about 1' x 3' in the water. My plan is to modify the top a bit so it will drop into the Mirage Drive hole in the front seat. I have the jib added so the center of side pulling (I am sure there is a more technical term) is moved forward a bit anyhow.

Hope to start sanding tonight.


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 Post subject: Re: Larger skag
PostPosted: Tue Sep 09, 2014 10:21 pm 
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Joined: Wed Aug 20, 2014 2:51 pm
Posts: 6
I like the idea of the center board a lot. I think it's a no brainer.
One of the previous post someone said that they tried it in the rear drive slot and it created too much drag?? It makes no sense to me, to put a center board in the rear drive slot when you think about a boat and the need to turn it. So that person's test doesn't tell us much.

A center board in the front slot would almost certainly make this boat sail much better at almost any angle while still allowing it to turn.

I would also like to request that if you feel the TI is just fine how it is, then perhaps the "personal modification forum" isn't the best place to be reading and chiming in. I have noticed the same couple of participants here shutting down ideas about improving the TI, claiming that it's fine how it is. That's true, it's great how it is, but for many, small improvements are very welcome and this is a place where we can all brain storm together and share ideas. Let's keep it productive.
Please, if you don't think modifications are necessary, there are plenty of other areas on this forum for you to participate.

Thank you, and I look forward to more discussion about things like a center board and a small rear seat hike out bench that possibly has a traveler on the aft portion.

Cheers


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