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PostPosted: Sat Mar 30, 2013 10:59 am 
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Puget:
No problem.
The bow sprit is a fiberglass pultrusion, if you were to place a brick on each end a 200 lb guy can stand and jump up and down in the middle (we actually used to do that in the factory where we made them) so they are extremely strong. This one had been sitting in my garage for 20 yrs or so. It was a sample left over from when I designed the crazy things, then designed and built the molds. I think if you go to Home Depot you can find ax replacement handles. The right ones are a fiberglass core with a polypropylene cover molded over the top of the fiberglass. What I did was just took a knife and cut the polypropylene off and used the fiberglass pulltrusion (I'm not likely to ever chop any wood anyway). I then took 1/8 x 2" x 24" piece of aluminum and drilled and tapped eight 8/32 holes evenly spaced into the bottom of the pultrusion and through the aluminum and bolted the pultrusion down to the aluminum. I tapered the front of the aluminum a little to make it cool. I then took another piece of 1/8 x 2 inch aluminum (available at Lowes or Home Depot) and carefully formed it in my vise to fit the shape of the bow about a foot back from the front. I glued onto the inside some of that anti-skid rubber shelf liner stuff so it wouldn't scratch the hull. I then bolted the back brace to the main piece of aluminum.
I then cut a slot into the bottom of the aluminum main aluminum plate (and also a little bit into the bottom of the pultrusion) in order to clear the lifting lug. The lifting lug prevents side to side motion so it needs to be a little snug on the side. I then took some 1/8" x 1/2" (about 6 ft long) aluminum bar and bent it around front AKA bars right on the ends (behind the plastic cover). It was actually pretty easy. I wrapped it around the bar then bolted it to itself with 8/32 flathead screws.
I then ran the 1/8 x 1/2" up to the bow sprit and bolted it down to the bent brace and the main brace (creating a truss) with more 8/32 stainless flat head screws. You will notice there is some bend in the long 1/8" bar, this is because it was a cold day and the boat itself grows and shrinks an inch or two depending on the temperature, so you want to fit it at the desired temp you use the boat in most often (mine was adjusted to the 90+ temps down here in Florida during the summer). CaptnChaos used I think 3/4 sq alum, which is much stronger. The straps to hold the thing down are 1 inch wide (800 lb) straps like you would use to hold your kayak down to your roof. I have two layers, I sewed mine together to make it more fancy, but that's not necessary. I filed a slight indent into the bow of the boat to hold the base of the strap (the hull is about 1/2" thick right there so a .100" groove isn't going to hurt anything). I then ran spectra string (rudder string, which is around 400 lbs test) to basically tie the bowsprit to the bow. The angles of all the strings and webbing give everything its strength, I'm guessing it would take 800 to 1000 lbs lifting force to break it. To test it out I set the bow sprit on a bucket, then went back to the passenger compartment and put most of my weight on it (of course I didn't sit in the boat (not sure the hull itself would withstand that).
I made the thing several years ago and it's been on all 3 of my TI's and I have had no difficulties with it so far in over 2000 sailing miles. As I mentioned earlier I lift the boat by just grabbing the bow sprit on the end and hoisting it up over my head and setting the front of the boat on my T-bar hitch receiver.
If I were to do it again I would probably make it more like Jims using 3/4 sq alum.
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Good luck
Bob


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PostPosted: Sat Mar 30, 2013 10:08 pm 
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Location: Puget Sound, Washington USA
Bob,

Thanks! I see part of my original confusion now in your first post. In the picture I thought there was just a line or rope of some sort running to the aka. It was the 1/8" Al with a slight bend. And wow -- my boat grows & shrinks an inch or two. I had no idea is was so much.

Puget


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PostPosted: Sun Mar 31, 2013 4:12 am 
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Puget:
Yes if you look up the coefficient of expansion for polyethylene it is .000111" per degree per inch. So at 40 degrees the boat is one length then at 90 deg it is 1.2" inches longer. This is why the rudder steering lines are sometimes tight and sometimes loose depending on the temp of th hull.
Hope all this helps.
Sorry I tend to try to say too much in my responses.
Bob


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PostPosted: Sun Mar 31, 2013 1:39 pm 
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Location: Clearwater, Fl
Puget wrote:
Keith /Jim,So from the picture it looks like the brace is fastened to the akas aft, and forward to the two little screws holding the forward handle. Doesn't that mean that much of the force of the wind is transmitted to the hull through two little screws holding on to some plastic? I've been nervous just lifting an empty bow by that handle because I don't see how it could be strong enough. And doesn't Hobie put a caution in the manual about putting too much faith in bow and stern handles. What am I missing?

There is very little force applied to the bow padeye. The aluminum bow frame is loosely attached to the padeye in front and it doesn't move much. In the early tests, a bungee was attached from the frame to the bow padeye just to see what happened. That's when I learned there wasn't as much upward force applied from the jib to the padeye as I thought. I believe the brunt of the pull is transferred from the frame to the akas.

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PostPosted: Sun Mar 31, 2013 5:50 pm 
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I think your jib frame and furling setup is brilliant, Jim. Tight integration.

To recap - are you using any stays?

How would you describe the forces at different points of sail? What direction and energies are exerted?

I'd like to explore this mod for the AI a little further, if you don't mind.


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PostPosted: Sun Mar 31, 2013 7:08 pm 
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Puget wrote:
Doesn't that mean that much of the force of the wind is transmitted to the hull through two little screws holding on to some plastic? I've been nervous just lifting an empty bow by that handle because I don't see how it could be strong enough. And doesn't Hobie put a caution in the manual about putting too much faith in bow and stern handles. What am I missing?


Just to clear this up Puget. The two little screws are attached to a molded in brass fitting. They are not just screwed into plastic. They should be as strong as the mainsheet padeye. I haven't heard of too many failures. I know of a couple who were towed in their Oasis by a tinnie for 36km and reached 20km/h. The towline was attached to the bow padeye.
The main problem with hanging the kayak by the bow padeye is that plastic creeps over time when constantly under pressure and temperature changes.


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PostPosted: Mon Apr 01, 2013 4:17 am 
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NOHUHU wrote:
I think your jib frame and furling setup is brilliant, Jim. Tight integration.
To recap - are you using any stays?
How would you describe the forces at different points of sail? What direction and energies are exerted?
I'd like to explore this mod for the AI a little further, if you don't mind.

Thanks NOHUHU,
I have used stays but never for this particular configuration. I rigged some up 2 days before the race but just before leaving I had a change of mind and removed them. They are kind of a security blanket but I'm not sure how effective they really are. On the beach I asked Jim from Hobie about them and he was more concerned about supporting the mast with a rear stay than side stays. Kind of like the way Bob does his (FusionEng). I was surprised to hear this since Jim's earlier jib on the TI incorporated side stays. Although his side stays were somewhat behind the mast and provided some rear support. In the EC, I noticed Jim's spinnaker had a rear stay but the way it deployed from the top of his mast would always be hitting the mainsail. I imagine that was quite annoying for him during the race. Wish he would comment here and share how that went for him. Especially when the wind was flipping the mainsail from side to side all the time.

The problem with the AI/TI and rear stays is how to extend your mast topper to keep the stays from hitting the mainsail. I started to fabricate a mast topper like Bob's but wasn't comfortable with the weight of his design. He has a really slick setup on his TI but I felt that mast topper was too heavy for me and would make demasting at sea almost impossible. And it seems to me that extra weight on top adds more to the mast stress. I needed a jib design that allowed easy demasting at sea to get under bridges.

I am not an engineer and really don't know what I'm talking about, but feel a TI with a jib may stress the mast holder more than the smaller AI sail. What happens in my setup is there is a good amount of downward pressure on the mast topper in most points of sail. I'll try to be more observant in the future though. The carbon fiber mast flexes pretty good when it's blowing with the jib exerting that downward pressure.

Sailing with a jib is a lot of fun. Especially when the design is simple and both sails furl and deploy easily. Of course there's always a risk of breaking the boat but it's a risk I accept and the more I use it, the less I worry about breaking the boat.

My latest plans include buying a TI and transfering this setup to the TI with some modifications. I'd like to add a bow sprint like Bob's and possibly a rear stay. I'm working on an idea for a lightweight method to modify my aluminum bearing topper with a rear stay extension.

But first I need to buy a reasonably priced TI. Anyone in Florida with a Papaya TI and trailer for sale ????

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PostPosted: Tue Apr 02, 2013 4:08 pm 
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fusioneng wrote:
Puget:
Yes if you look up the coefficient of expansion for polyethylene it is .000111" per degree per inch. So at 40 degrees the boat is one length then at 90 deg it is 1.2" inches longer. This is why the rudder steering lines are sometimes tight and sometimes loose depending on the temp of th hull.
Hope all this helps.
Sorry I tend to try to say too much in my responses.
Bob


Don't be sorry. The detail helps me understand. .000111 seems like such a small number that I had to multiply it out. And you're right. Now it amazes me that anything on the boat fits!


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PostPosted: Tue Apr 02, 2013 4:15 pm 
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stringy wrote:
Puget wrote:
Doesn't that mean that much of the force of the wind is transmitted to the hull through two little screws holding on to some plastic? I've been nervous just lifting an empty bow by that handle because I don't see how it could be strong enough. And doesn't Hobie put a caution in the manual about putting too much faith in bow and stern handles. What am I missing?


Just to clear this up Puget. The two little screws are attached to a molded in brass fitting. They are not just screwed into plastic. They should be as strong as the mainsheet padeye. I haven't heard of too many failures. I know of a couple who were towed in their Oasis by a tinnie for 36km and reached 20km/h. The towline was attached to the bow padeye.
The main problem with hanging the kayak by the bow padeye is that plastic creeps over time when constantly under pressure and temperature changes.



That makes a lot of sense. Hobie has more sense than I was giving them credit for. I'll start using that padeye a lot more. Until now I've been attaching my bow line as a Y to the aka brace.


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PostPosted: Tue Apr 02, 2013 5:34 pm 
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Puget wrote:
Until now I've been attaching my bow line as a Y to the aka brace.
I tie my bowline to the front crossbar and thread it through a shackle attached to the bow padeye. Nothing to do with the strength of the padeye - it's just easier to get at from the cockpit.

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PostPosted: Wed Apr 03, 2013 1:19 am 
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The interesting thing is that Hobie actually built a faster trimaran sailboat as the predecessor to the Adventure Island. I have seen the prototype sitting in the Hobie factory yard and the Plant Manager told me that he and other Hobie staff still sail it for fun. He said it sails quite a bit faster than the Island boats but Hobie chose to go with the versatility of the kayak island configuration that we have today.

So if Hobie wanted to release that boat it likely would fill the spot for additional performance in a trimaran that this thread is calling for. I got the feeling that its still a wet ride though.

Barry

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PostPosted: Wed Apr 03, 2013 4:46 pm 
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A 12+ knots bow shower? You'll get no complaints there.

That's what sprayskirts and "copilots" are for. 8)


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PostPosted: Wed Apr 03, 2013 7:07 pm 
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I just built my first spray skirts this week--3 sets of them. I'm ready.

Keith

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Last edited by Chekika on Thu Apr 04, 2013 6:10 am, edited 1 time in total.

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PostPosted: Wed Apr 03, 2013 8:54 pm 
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Oh good - we're still talking. :wink:

I've seen a WETA with sprayskirts too, and they work quite well. Plus, you get a slightly drier, "hiking out there" Haka-style ride.

The real point is, once you push +10 knots, sitting near the water on ANY little sailboat is going to feel like a ride though the ultra carwash. :mrgreen:


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PostPosted: Thu Apr 04, 2013 6:13 pm 
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aussieonyak wrote:
The interesting thing is that Hobie actually built a faster trimaran sailboat as the predecessor to the Adventure Island. I have seen the prototype sitting in the Hobie factory yard and the Plant Manager told me that he and other Hobie staff still sail it for fun. He said it sails quite a bit faster than the Island boats but Hobie chose to go with the versatility of the kayak island configuration that we have today.

So if Hobie wanted to release that boat it likely would fill the spot for additional performance in a trimaran that this thread is calling for. I got the feeling that its still a wet ride though.

Barry
Aussie, did you see this one too?

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