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PostPosted: Sat Nov 16, 2013 9:23 am 
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Chopcat :
Actually there is a great risk that you will fold the hull, (that's what I think happened to Hobie's entry into the EC challenge in I think the 2011 Everglades challenge race). (probably the main reason the jib option was never offered by Hobie).

Unfortunately as with most of my posts which always end up too long, I try to explain in detail the reasons why I do the things I do, so that others understand and then you can make your own decisions on how to proceed based on knowledge and understanding of the problems, and come up with your own solutions, and/or improve on the ideas.

There are 3 or 4 design problems with the TI that make it unlikely that Hobie will ever offer a jib or jib/spinnaker option, however all of these shortcomings can be easily overcome.

1. The weakest area on the TI is the bow, caused by the huge opening created by the front hatch. With a jib mounted on the bow, the extra stress causes the bow to wave around making the front hatch leak like a screen door in a submarine. This needs to be overcome by adding external bracing. Your idea of using Yakattack mounts is fine, however I suggest you mount two up near the bow, then two more just in front of the front AKA brace (the strongest area of the boat). Then your aluminum V shaped external brace which needs to clear the hatch area will support the weak area of the bow (the hatch opening), most of the rest of us used 3/4 sq aluminum tubing for the external brace, which is plenty strong). So bottom line, your vision of becoming a poster child for Yakattack will work just fine as long as your OK with drilling holes in the hull, and you mount them as I described (the rear mounts behind the hatch).

2. The front lifting cleat would probably work fine for adding a 22sq ft Hobie Kayak sail, but not much bigger (a 22 sq ft jib might be a little small for a TI (but perfect for an AI). It's not a good idea to mount a huge spinnaker ( or a spinnaker/jib combination) to that cleat. Since you are planning to use Yackattack mounting, as long as you mount the sail(s) to your brace vs the front cleat you should be fine whatever size jib or jib/spinnaker combo you put on. I actually like your idea, as long as your willing to drill your hull (BTW, those drill holes are actually easy to fill with the Hobie welding system if/when the time comes). Most of us follow the Hypocritic oath just like doctors (thou shall do no harm), which is probably silly (especially coming from the guy with the most modified TI's out there LOL)

3. If you look at the TI you will notice that the main sail is mounted really far forward on the hull. This severely limits how much sail you can add to the boat. That's why I added a 2 ft bow sprit to my TI, for two reasons, the first being if you have both a jib and a spinnaker there is simply not enough room for both up there. The second reason is with the main sail mounted so far forward on the boat, when on a downwind the bow of the boat gets pulled underwater (nautilus mode). By angling the jib or jib/spinnaker and moving the base forward, this creates lifting force that lifts the bow out of the water. When I added my bow sprit I completely eliminated the need for my hydrofoils so they were removed (their now sitting in my garage collecting dust). Just to clarify, this is a problem only to the TI, the AI mainsail is mounted much further aft, so adding an extended bowsprit to an AI might only be marginal (the hull bracing is still needed though). I like Jims setup, which I think is perfect for an AI. The AI and TI are different boats with different problems and solutions.

So now you have the bow sprit and the necessary hull re-enforcements to start adding additional sails, where do we go from here.....
Here are 3 or 4 more things to keep in mind when adding sails to the TI.

1. The mainsail on the TI is a boomless furl-able very modern square top sail design ( a really good design), specifically designed to work best on a very flexible carbon mast. This is direct contrast and opposite from the design of almost every other sail/mast design out there. The last thing you want to do when adding additional sails is to destroy the built in abilities of the basic mainsail design. By adding all kinds of side and rear stays making the mast rigid, basically destroys the mainsails ability to work efficiently. You could actually go backwards if not careful, making the boat slower instead of faster and more capable. Now you have the hull prepared for the future whatever design you decide on, keep in mind not to interfere with mainsails basic design, and in my opinion it's best to keep whatever you add sail wise as simple, easy, and fast to rig/take down, and use as possible (KISS principle), otherwise you will get bored with it quickly. And keep in mind a jib designed for say an H16 (with a rigid mast) may not work as well as it would on an H16 unless you can design around a few things.
2. Whatever you add to the TI sail wise you have to be aware that the mast holder in the bottom of the boat, was only designed to withstand the forces of just the mainsail, adding too much sail will over stress that small 1/4" bolt on the bottom of the mast holder unless you can relieve some of the forward force. As an example if you were in a strong downwind run (15mph plus winds) with the main pointed to one side and say a 40 sq ft jib pointed to the other (a batwing setup), the stress on that small bolt would be too much and it would snap. With a setup like that or adding a spinnaker you pretty much have to add a rear stay line to the top of the mast to prevent it from bending forward too much, and also to relieve some of the stress on that little bolt. The design of Hobies metal brace system inside the hull regarding side to side stress goes is ok as designed, it's just forward to back that you have to adjust for. As far as side to side force goes, the mast will snap long before the braces give out so your reasonably safe. The Hobie mast is extremely strong and well designed. If you are only planning to add a smaller jib (under 25sqft) and not adding a spinnaker you can probably forego that rear stay line, however you'll need it on anything larger especially on downwind (my rear stay line is actually slack when on an upwind or on a reach).
3. Keep in mind that the flotation on the AMA's are only sufficient for the mainsail only in winds under 12mph, otherwise the boat tips over. That's why you have to furl the mainsail on a reach in higher winds currently. If the boat were slightly wider it would help but it's not. This means whatever sail area you add this will require you to hike out to counter balance the boat in higher winds. If you ever watch videos of Tom Kirkman on his Weta (or any cat or A class mono for that matter, you will see the crew hiked out, you will also have to do this (an rudder control/extension rod is highly recommended), and either Haka's or tramps (something to hike onto), and this pretty much eliminates driving the boat from the rear seat (your pretty trapped back there anyway). With the bow sprit and the additional lift it provides to the bow (because of the increased angle of the jib/spinnaker), the boat performs perfectly fine from the front seat (plus you have better access to the sails and sail controls from up front anyway).
4. It's a very good idea for safety reasons, that the main mast and the jib are independently furlable, and whatever you add doesn't interfere with the furling ability of the stock mainsail ( a mast topper design like mine or Jims does all this). I recommend you use a halyard line to raise and lower the jib to the mast top, this allow you to raise and lower your jib or change jibs/spinnakers while out on the water, and also makes it easy to drop the mast if needed to go under low bridges. If you do get out in really strong winds, the halyard also gives you the ability to take the jib down and work your way home with the main furled almost completely, while your hanging on for dear life (we have all had to do that). That's the main reason for yours and my Honda Motors (LOL). My TI actually has two halyard lines, one for the jib, and the second for the spinnaker that also doubles as the rear stay line, (remember the rear stay is only really necessary for the spinnaker, or a really big genoa sail, and only on downwind, upwind it does nothing).
Hope this helps you.
Bob


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PostPosted: Sat Nov 16, 2013 1:22 pm 
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After doing lots of reading of this and Capt Chaos' thread, I really want a to add a jib to my AI. I was thinking of doing a similar hybrid set up for the frame too. I'll be watching with interest.


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PostPosted: Sat Nov 16, 2013 2:16 pm 
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So here's a question: it's not ideal but how much drag would a couple of 1 in webbing straps around the bottom of the hull cause? We're talking thin seatbelt material here.


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PostPosted: Sat Nov 16, 2013 2:29 pm 
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Not sure how much drag, but beaching would wear through the strap quickly i would think.


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PostPosted: Sat Nov 16, 2013 3:09 pm 
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DM06 :
Think of the bow brace/bowsprit system as something similar to the hood on your car. Attached at the back (on the AKA braces, just like the hinges would be on a car hood. When the hood is open you can barely move it back and forth, and you cannot move the hood forward or back, you can only swing it up to open or close it. Now think of the joint up front as the hood latch, it doesn't do anything structurally for the hood except hold it down. All you need is something to hold the brace down at the front, all the strength is in the brace itself, you can do it anyway you like, I'm sure there are a hundred ways to hold it down, I was just suggesting something easy cheap and fast that I've been using for several years now with no issues or problems. The webbing that I explained to go around the front of the bow of the hull traps the brace down, it's just not necessary to go under the hull (the strap is above the waterline). Since the brace is attached to the AKA bars at the back it cannot possibly move forward, backward, or side to side. So when the strap is cinched up around the front of the hull it holds the front of the brace down. If you want a little extra assurance just pass a pin thru the front cleat (the pin would act as kind of a safety latch like on a car hood). A small portion of the upward force on that cleat is not going to hurt the cleat. All the side to side and forward/backward force is taken by the bow brace instead of the cleat. The bow brace prevents the front of the hull from waving around and possibly folding the hull, and also helps keep the forward hatch sealed.
Besides 90% of the force on the bowsprit when the sails are working is side to side, very little up and down. The only time the up and down strength is needed is when you pick the boat up by the bowsprit when loading and unloading.
I'm pretty sure Jim (CaptnChaos) doesn't have a strap, I believe he just attaches the front of his bow brace to the cleat with a D ring.
Hope this helps
Bob


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PostPosted: Sat Nov 16, 2013 6:21 pm 
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One of the things I have no idea about is selecting a sail. I have a friend who is an upholsterer with industrial sewing machines so he might be able to make one up for me.

I've downloaded the sail CAD program http://www.sailcut.com/

Any ideas on some dimensions to start with? I've put in the boat LOA, Rough Fore triangle base J & Fore triangle hoist I. As for the rest????

Image

Image

Image


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PostPosted: Sat Nov 16, 2013 8:16 pm 
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Here is a quick mock up of how I'm thinking about doing the bow frame.

Image

Image

Image


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PostPosted: Tue Nov 19, 2013 5:56 am 
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Ok chaps. i have had the sketchup out and here is the plan.

here is the front of the boat
Image
add the yakattack rails
Image
some tube down the sides for the anti fold strengthening
Image
fixed to the rails with some braces (the rear one might not be needed
Image
add in a tube to hold the bowsprit
Image
and finally slide in the bowsprit
Image

there you have it . will it work? I think it will ....possibly

Image

Image

Image

Image

CC

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PostPosted: Tue Nov 19, 2013 11:56 am 
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CC- nice concept. Aesthetically, a simplified version of this could be mounted INSIDE the hull. Only 3 stainless threaded posts need to project. Perhaps even quick release fittings for an optional jib plate or longer bowsprit for a spinnaker.

The bigger challenge still remains. Designing simple, affordable and durable rigging/control sheets around our flexible, furling masts.


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PostPosted: Tue Nov 19, 2013 1:08 pm 
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Well I'll tell you one thing. Getting your metal from a distributor is going to cost me literally 1/4 of what it would cost from Lowes or Home Depot. Yowsers!


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PostPosted: Tue Nov 19, 2013 1:17 pm 
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I'm not sure if that's good or bad

CC

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PostPosted: Tue Nov 19, 2013 6:50 pm 
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Sorry, haven't mastered the art of posting with a crawling baby yet. Have to get posts in before running to save him from himself.

I was simply trying to point out that aluminum at the big box hardware stores is expensive in comparison to a local metal distributor I found in my area. Conversational in nature, not good or bad.


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PostPosted: Fri Nov 22, 2013 5:04 am 
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NOHUHU wrote:
CC- nice concept. Aesthetically, a simplified version of this could be mounted INSIDE the hull. Only 3 stainless threaded posts need to project. Perhaps even quick release fittings for an optional jib plate or longer bowsprit for a spinnaker.

The bigger challenge still remains. Designing simple, affordable and durable rigging/control sheets around our flexible, furling masts.


you might need a vertically challenged person to get inside and fit it!
CC

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PostPosted: Fri Nov 22, 2013 6:58 am 
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John_h:
I used that same program originally when I started trying to design and make my own sails, I looked and I didn't keep or save any of the info. Anymore when I start designing a new sail I usually grab an old version and update ( I design everything in Solidworks or Pro-engineer in full 3D) and am not good at saving my old stuff, (it was 3 1/2 yrs and many computers ago LOL ), I have a photographic memory (but not that far back (too much crap stuffed in there LOL)).
Here is a pic of my original jib from I'm thinking summer 2010, this was version 2 (around 30 sq ft) version 1 was square topped (like the main) and was 40 sq ft, and way too much sail for the TI. With the old twist and stow rudder system I was getting severe weather helm, and the boat wanted to tip over even it 10-12 mph winds on a reach so I cut it back to about 30 sq ft.
Image

I started out with an old worn out Hobie kayak sail that I had laying around, then just added to it. Notice the vertical battens coming up at an angle, those battens with fiberglass rod in them were adjusted a few times to get the sail to work correctly (trial and error). Because of the super flexible mast on the TI most programs for designing jibs and conventional jibs (like from an H16 or a Laser) don't work all that hot ( a lot of trial and error).
If I remember correctly I believe I had a 1/8 dia fiberglass slipped into the rear vertical edge (leech) of the jib (the full height). The jib still furled without any difficulty. I had an aluminum mast (made from a telescoping painters pole). The kayak sail already had that sharp angle on the bottom and the clear mylar so there wasn't much I could do to change that part of the sail (my Pfaff sewing machine couldn't sew thru the mylar so I pretty much had to work around it).
Basically making a jib for an AI (which is different from the TI) is going to be a trial and error thing, basically you have to start somewhere, just measure up and cut, then try it and adjust accordingly. Most on the forum only need to see a video of the sail working to make suggestions on how to fix problems (add a batten here, or nip and tuck there, etc). Having experienced sailers take it out and watch it work then comment is very valuable. It always takes me several adjustments to get the sails to perform the way I want.
Actually single layer sails and jibs are pretty straight forward, and easy to make. I usually start out with inexpensive rip stop nylon, get everything the way I like (trial and error), then make the final Dacron sail using the expensive material once the design is proven out.
My best friend (from Sweden (typical Viking, it's in all their blood LOL) who is an uber experienced sailer and has captained some giant tall ships would go out with me and tell me what adjustments to make ( ie.. nip here, tuck there, you need battons here, here's how you fix this problem etc).Just go find a Viking to help you ( LOL).
I'm now into wing sails, unfortunately they are 1000 times more complex and way more difficult to design and build, plus you have to throw out most existing sailing knowledge (that works on different principles), so there is no help out there. I wish I had known that going in ( LOL)
Image
Bob

Edit:
After looking at the registration number on the hull on the pics I posted above, the top picture was my second TI (not the first as I thought) so must have been taken mid 2011. The last picture is of my 3rd TI (which was bought in July 2012) so that photo was likely taken last spring (2013). Too many boats, too many sails LOL.


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PostPosted: Fri Nov 22, 2013 8:16 pm 
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Thanks Bob, I'm now leaning towards just getting one of the Hobie kayak sails to start with and then go from there.

Incidentally, the brass 1 1/2" tube you used for your mast topper, does not appear to be an item used here in Australian plumbing. Must be something to do with our plumbing regulations? I spent a couple of hours going around my local Masters and Bunnings Hardware superstores and did not find anything comparable.


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