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PostPosted: Thu Sep 25, 2008 2:53 am 
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Location: Central Coast NSW Australia
One of the great benefits of the mirage drive is the centreboard effect the fins give when in the down position while sailing. They help make any Hobie pedal kayak a true upwind sail boat. The only problem is that when underway the fins won't remain in the down position unless you hold them with your feet. On a long upwind trip this can get tiring. You could of course keep pedaling but I find it very relaxing to just sit back and enjoy the sail when conditions are right. :)

By using a stainless eyebolt through the drive adjustment holes you can lock the drive in the fin down position easily and it can be quickly removed when necessary.
Image
This is a 6mm diameter eyebolt with a few layers of heatshrink added to cover the sharp threads and fit the holes better. An 8mm eyebolt will fit but it is bulkier/heavier.
It's easy to tether it with a loop of bungee through the pocket net.
Image


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PostPosted: Thu Sep 25, 2008 4:06 pm 
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Hi Stringy,
I'm familiar with that problem, and I solved it my way a few weeks ago (I use a bungee), but I like your solution better!


Without bolt or bungee, you have to hold the drive with your foot.
Image

My bungee does it's job well...
Image
.. but I think it's less easy to fasten and release than your bolt, and it is not tethered!
I will definately gonna try you idea!

In my experience upwind performance without any pedaling is quite poor though. My rough estimation is that it is about 70 degrees (actual course) with my oasis (without hindering chop). As far as I know, most sailboats (this is a yak ofcourse, so I don't complain) can do between 45 and 50 degrees, some even a bit better. So I think I will go experimenting with aluminium "socks" (eliseo-style) or something like that...

PS: low tech: I like that term! ;)

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PostPosted: Thu Sep 25, 2008 8:07 pm 
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Hey Scooby Hey Stringy
I would not state this as an absolute 100 percent fact , however I do think my larger homemade rudder and winglet does tend to function somewhat as a centerboard in certain favorable conditions.

In other words I can still sail upwind with the fins folded up against the hull and the boat goes faster than it used to without a noticable amount of lee helm.

There are times of course in strong currents or tides when this is not the case and both fins down or just pedalling like crazy is the only way to go.

This effect was something I just started noticing this season with two sails , good winds and no currents.

So now whenever sailing I always fold up the fins for awhile to test my theory and see if folded up is the faster way to go. :wink:

That leads me to a new question I have now which is this.
How could sailing our yak be improved if we had a large sailing rudder in the bow as well as the stern which functioned linked together via one rudder handle ? A double rudder system if you will.

Seems to me we might point higher track better..carry more sail in more wind and go faster without pedaling than we could having just one rudder with the fins down or pedaling?
Just food for thought for you master craftsman in case either of you want to build one. :wink: 8) .

Have fun out there
Kepnutz


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PostPosted: Fri Sep 26, 2008 8:16 pm 
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Stringy, great idea! :D


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PostPosted: Sat Sep 27, 2008 4:07 pm 
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G'Day Skua and Kep,
Since I got an AI I haven't solo sailed the Oasis and I haven't gone on to develop some of the ideas I was working on when it was my only kayak. Sailing the Oasis now is always as a tandem and with both drives down I am happy enough with its upwind performance. It definitely points higher tandem!
Skua, you may have seen my old post about adding the daggerboard to the front drivewell. That did improve pointing solo and was useful on long upwind runs but being so far forward was a pain to reach. Before that and following on from some of Roadrunners advice I was going to mount the daggerboard as a leeboard. I made a bracket that attached to the sides to hold the daggerboard but it didn't have enough lateral resistance. I was going to get the Sidekicks and mount the daggerboard as a leeboard to the crossbar so that it pivoted within easy reach but then I got the AI instead.
Do you think the Sidekick crossbar has enough strength in it to mount a leeboard?
PS- I had you in mind with the post title. :wink: Keep us posted with your testing.

Kep- your forward rudder is an interesting one. Have you sailed with the drive removed? You do go faster. My next project when time allows though will be to add the outriggers and sail from my AI to the Oasis seeing as Hobie didn't release a double AI this year! :(

Roadrunner - Thanks!


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PostPosted: Sat Sep 27, 2008 11:42 pm 
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How Ya Going Stringy
An AI Oasis Hybrid is just what Im looking for too.
I hope they could blend the best of both models into a new hull design.
I like the stable dry ride of the Oasis but would prefer that mixed with the sleek and speedier traits of the Adventure whether using the pedals or the sail.
What about you since you have one of each model to muck about in?
Do you think the Oasis hull is capable of going any faster even with an AI Sail ?
Sure would be fun to find out.
Take it easy
Kepnutz


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PostPosted: Sun Sep 28, 2008 5:10 am 
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Hi Stringy,

I've seen your "daggerboard plug", and I want one! But I'm afraid it is a bit too high tech for me to make it myself. Also I fear that in my case the center of lateral resistance would be too much to the front when I would put it in the front drive well (the center point of your twin sails combined is much more to the front than is the case with my rig).
Besides, ever tried to use it lifted up for tracking when paddling only (solo, without rudder)? Is the daggerboard long enough to "repair" the tracking of the mirage kayaks (when it is lifted up) when purely paddling them?

Besides the "alu drive sock", I was also considering a lee board. I was thinking along the same lines as you do: using the sidekick crossbar.
My crossbar is nicely fixed to the boat with an aluminium backing plate. I'm quite sure that that is strong enough! The bar itself feels a bit like the paddle (the paddle fits!). There is clearly an end to its strength, but I think it is strong enough as long as the forces are distributed in the right way, the lateral force should be directed as much as possible directly to the hull and close to the attachment points of the bar. Then it should be no problem. I think a lee board should be quite long (since it sits higher) and broader than the daggerboard for it to work. With my sailing rig, I think the position at the crossbar would be close to ideal with respect to the helm.

I'm very happy with my oasis, but it's inevitable: I'm also dreaming of an AI (don't tell my wife!). I also did some fantasizing about putting the ama's and sail of the AI on the oasis. Will your oasis front sail mount will be strong enough for the AI mast? That would be the best place (to retain the tandem functionality). Or do you consider a front plug mast mount (eliseo style)? That would be a very interesting project!

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PostPosted: Sun Sep 28, 2008 9:58 am 
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Sum of U are moving in the rite direction and I'm excited watching the experimentation of sails both home crafted and purchased(wind paddle) as I know this is what the Oasis needs is a bit more sail area I have hi-hopes that 1 of U tries the items from a AI on a Oasis but it is my belief that the guys working with the multi sail set-ups once dialed-in will get the best all wind performance but the large AI sail will give gr8 performance with better ease of use.

Pleez 2 proceed U gr8 experimenters and inventers I watch and wait as a Oasis is my next purchase hopefully Hobie is also working on a solution to this as well.

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PostPosted: Thu Oct 02, 2008 4:34 am 
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kepnutz wrote:
Do you think the Oasis hull is capable of going any faster even with an AI Sail ?

G'Day Kep,
I doubt that the Oasis would sail much faster with the AI sail and outriggers. As you know it's difficult to push the Oasis over 6mph. What I would hope is that the average speed sailing would increase. In my AI most of my sailing is done at speeds of 5 to 8mph. I would be very happy if I could get similar results with the Oasis under sail. As much as we enjoy sailing the Oasis with the two sails, the hiking out can get uncomfortable on long sailing trips (we still don't have sidekicks!:wink: ).
For me the AI's great strength is in its ease and comfort in sailing long distances. That is what I am trying to achieve with our tandem AI conversion. :)

Skua,
I haven't tried the daggerboard in the raised position while paddling as we only paddle when the water is very shallow.
I am hoping to mount the AI sail in the same position the mast step is now on the tandem, with the x-bars mounted fore and aft of the rear seating position. A quick measurement check shows it is possible. The main problem will be bracing the mast. The AI has a V-brace that takes the place of the plastic mast tube. I am looking at reversing this V-brace so that it is above the crossbar. The other big problem is that the shorter length of the tandem makes it difficult to mount the rear sheet block. Maybe the opposite to a bowsprit is needed - a stern sprit of sorts!
I am also hoping that I can still use the smaller front sail with the AI sail! :wink:


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PostPosted: Thu Oct 09, 2008 12:31 pm 
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Stringy,

I was curious how the AI ama's would look at the oasis at the position you indicated. So I did some quick and dirty (but close to proportional) photoshopping:

Image

Finally, the Oasis Island! 8)

I don't know if it is possible to mount the AI sail on the standard mast step position. Bracing sideways should be no problem, but there is very little room front and aft of the mast step. But if you manage to do it, I am more than interested. For the strength of the mast step is my biggest concern and reason I am very cautious when sailing with the (furled) jib in moderate winds.

If you mount the mast in the position of the front mast, the rear handle would be just right to position the sheet block. I guess that solution will be easier in that respect.

BTW, I made an alu sock already. The oasis seemed to point better, the drag seemed significant (could be a show stopper), but there was not enough wind to really try it out.

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PostPosted: Thu Oct 09, 2008 11:24 pm 
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Stringy, I was thinking about your AI sail mounting options for the Oasis. I'm afraid with that sail, if you mount it aft, you may end up with uncontrollable weather helm. But if you mount it forward (along with the amas) you may have a more dangerous uncontrollable lee helm. There are some countermeasures you can use to correct this to some extent, but possibly with a less than optimal upwind performance.

Your twin sail rig with amas may end up being your best option, if not as fast. An alternative might be a forward mounted sail with a longer foot -- perhaps a Bravo sail (if it's not too big).

A couple of other thoughts -- if you mount the sail aft but with skegs on the rear of the amas, it should help. Whether that would bring your Center of Lateral Resistance back far enough is a big ?. Or conversely, it may be possible to mount the sail and amas forward and (if necessary) twin skegs under the bows of the amas.

Between the two, the forward mount may give you the better performance (as skua suggested) with your daggerboard permanently replacing the front Mirage Drive. Your rudder would have a longer purchase and better control. It might be more comfortable for the front passenger. The forward position of the amas may give the bow some reserve buoyancy (some adjustment in mounting height may be necessary) and also stow easier along side of the boat when not in use. The sheeting angle would be easier to control. You may be in the way of the mainsheet, but you could get around that by using a traveller aft.

It's a tough problem, but if there's one person who can pull it off, you're the one who can do it! 8)


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PostPosted: Fri Oct 10, 2008 7:18 am 
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Hey Stringy How You Going ?
Sounds like a great project if you have the patience and a plastic welder to add raw material and beef up strength where needed. 8)

I wonder if skegs on the amas as well as some longer ones on the bottom of the main hull located on both sides of the rear scupper hole would improve sailing performance ?

I have often thought about a couple of say 24" long by 3" deep Rib/Skegs , plastic welded on the hull, might help tracking and sailing upwind by enlarging the center of lateral resistance and function as a keel does on larger monohull sailboats.
It could be easily done in a few hours time but I just hope I could still turn the Kayak when needed. :lol:

If you do manage to run the AI sail on our Tandem Oasis that would be a big increase in the center of effort to contend with compared to our standard Hobie sail.
I might consider a even larger sailing rudder modfication to go along with everything else.
I feel I have gained so much more kayak sailing improvement by enlarging the rudder than almost anything else, short of using two sails.

It would be cool if you Roadrunner, Apalach ,Skua, Tracker and a couple others all lived close by, then we would have this little monster built in less than a week. :lol:

Have Fun
Kepnutz

P.S. In photo number two at the top of the page are those wing nuts and bolts locking your pedal crank arms down to the drum?


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PostPosted: Fri Oct 10, 2008 8:41 pm 
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Thanks for all the input.
Skua,
I like your Photoshop mock up pic. Its very close to what I imagined when I measured the Oasis up with the AI ama's. They do sit more aft than I would have liked.
The alu sock sounds interesting. Any pics?

Roadrunner,
As usual you bring up some important points and have got me thinking. What I am trying to achieve is the effortless, relaxing sailing that the AI has. At the moment our sailing is not effortless as with both sails up we are constantly shifting our weight to keep an even keel and not turtle. It is fun but not relaxing and not something I would want to do on an extended trip. I know the solution is outriggers but I have never liked the idea of inflatable sidekicks for long distance sailing. Adapting the AI's outriggers seemed the most logical to me especially as I have them on hand! What I could do is mount the outriggers first (it's simpler) and use the twin sails. Then if that works OK maybe try to adapt the AI sail as well. I don't want to have to modify the ama's. Thanks for your vote of confidence -it's much appreciated. :)

Kep,
I would like to keep this simple so plastic welding is out! I agree with you on the benefits of the larger rudder so I may have to copy your design if I need to go bigger! :wink:
Yes, they are wingnuts and through bolts on my wife's earlier drive. We suffered the elongated drum hole problem on both our Tandem drives. I'm pleased to report the V2 drive that came with my AI has been problem free. :lol:


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PostPosted: Sat Oct 11, 2008 7:10 pm 
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I bought a 1' x 2' piece of 1/4" white HDPE plastic (like kitchen cutting board material) for $10 and drilled a hole in one corner of the HDPE plastic board to hook a bungee onto, then, once out on the water, I just hook an approx. 1' bungee onto the hole at one end and onto the sail's mast at the other end, then drop the leeboard into the water on the lee side and it's ready to go until I come about, at which point I transfer the board to the new lee side.

The board stays in place laterally because the force of the water tends to push the bottom of the board inward against the hull which forces the top of the board outward which is held in place by the bungee which provides flexibility, which is good, because when a huge gust hits, the board absorbs the "hit" instead of "holding its ground" and causing a capsize.

And the board also stays in place longitudinally...maybe because of either gravity or friction against the hull or both.

The HDPE material is perfect because it is strong and yet flexible enough to not be brittle so it is nearly indestructable.

I've streamlined my board, etc., and I'm sure that other improvements could be made, but just the above alone provides a really cheap and easy leeboard.

Oh...and although the HDPE plastic board floats, the bungee will cause it to sink, so attach a length of foam pipe insulation onto the bungee so it won't sink your leeboard if you lose it into the water.

You COULD just make two boards and not have to switch the one board from side to side, but storage space on my kayak is more important to me so I only use one.

This leeboard makes my Oasis a better sailer, but it still doesn't achieve more than about 70 degrees off the wind when sailing upwind. Also, it removes some of the stress on my Mirage drive flippers.

My guess is that more sail area and/or the ability to be able to lean the boat way over (hard to do in a kayak) might be the true key to better upwind performance...but that is just a guess.

Anybody know the answer to that one?

Jerry

[quote="stringy"]G'Day Skua and Kep,
...I was going to mount the daggerboard as a leeboard. I made a bracket that attached to the sides to hold the daggerboard but it didn't have enough lateral resistance. I was going to get the Sidekicks and mount the daggerboard as a leeboard to the crossbar so that it pivoted within easy reach but then I got the AI instead.
Do you think the Sidekick crossbar has enough strength in it to mount a leeboard?


Last edited by Soyjer on Fri Jun 03, 2011 8:35 pm, edited 1 time in total.

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PostPosted: Sun Oct 12, 2008 2:38 am 
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Soyjer, that sounds like an great idea! It is even simpler than I thought it could be done! I would love to see pics of your solution. Have you tried to sail with upwind, without any pedaling? If so, how did that work out?

kepnutz wrote:
It would be cool if you Roadrunner, Apalach ,Skua, Tracker and a couple others all lived close by, then we would have this little monster built in less than a week. :lol:

That would be very cool indeed, Kepnutz!

Roadrunner, as stringy said, you bring many relevant points to think about in a project as this. Of course you are right in stressing the importance of the the helm balance in this. This surely must be taken into consideration. I think it is possible that the original idea of stringy, with the AI sail in the aft position and the small sail in the front position could work out with respect to this. The front sail wil bring the "mean point" (sorry, I don't know the correct term in English) of the AI sail a bit to the front, and the "mean point" of the sails combined could come close to that of one small sail in it's original position (If necessary the AI main should be furled a little, to reach that.) And with the "mean point" over there, the balance is managable (with sailing rudder) as long as the front flippers are out or up, or if the front passanger pedals actively.

Other placements of the sail need other measures of course. The possibilities to adapt the oasis to are amazing though, because of the two drive slots (and with a "dagger plug"). One of the many reasons it is so much fun to play around with this boat!

Stringy, Alu sock pics will surely follow, but later on...

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