Hobie Cat Forums

It is currently Fri Oct 31, 2014 8:03 am

All times are UTC - 8 hours [ DST ]




Post new topic Reply to topic  [ 29 posts ]  Go to page Previous  1, 2
Author Message
PostPosted: Wed Nov 13, 2013 7:56 pm 
Offline
Site Rank - Captain

Joined: Thu Jan 10, 2013 6:50 pm
Posts: 64
I have a windpaddle for sale (large size yellow) for sale in Norcal if anyone wants to add it to their downwind arsenal. http://www.windpaddle.com/cruiser_sail.htm


Top
 Profile  
 
PostPosted: Wed Nov 13, 2013 10:49 pm 
Offline
Site Rank - Captain

Joined: Fri Feb 26, 2010 2:03 am
Posts: 144
Location: ACT Region, Australia
CaptnChaos wrote:
Sorry about that John. This is an older thread and that jib video showed an earlier inferior attempt so I disabled those videos to not misdirect those who are trying to come up with a jib on their islands.

For awhile I was using a Hobie kayak sail (from I14T) as the jib and it worked ok especially in downwind but not the greatest overall as a jib. It was fun but not that much better performance wise. In fact it may have even slowed me down in some situations unfortunately.

So the current version has gone back to using one of my earlier jib sails re-sewn with a better shape and to allow a PVC pole to go through the luft/leading edge to hold it's shape better. Especially when furled. The PVC pipe keeps it from being a lumpy inefficient mess when furling. It seems to work pretty good now.

Currently the whole system has been removed from the AI so I can't take any current pictures. The following pictures show the furling system and show the inexpensive ($80) ronstan furler on the bow frame as well as the mast topper which is what allows independent mainsail furling as well as jib furling. There are several cleats mounted to my haka extensions (not shown) that I cleat the jib sheets to.

Image


How have attached the front of the frame to the bow?

Do you have a rough dimensions of your current jib?


Top
 Profile  
 
PostPosted: Thu Nov 14, 2013 12:52 pm 
Offline
Site Rank - Admiral

Joined: Wed Jan 25, 2012 5:30 am
Posts: 270
Location: Clearwater, Fl
John_h wrote:
How have attached the front of the frame to the bow?

Do you have a rough dimensions of your current jib?

Something like this miniature stainless D shackle is how the frame loosely attaches to the bow
Image
I wouldn't recommend copying my jib dimensions. It's just what I had available which may or may not be the best efficiency.

_________________
Jim


Top
 Profile  
 
PostPosted: Fri Jun 27, 2014 11:06 pm 
Offline
Site Rank - Captain

Joined: Sun May 25, 2014 4:35 am
Posts: 69
Location: Naples, Italy
Could Jim or one of the other experts on Jim's jib bow brace solution please clarify something for me?

From the photos and descriptions I've seen, it's clear that the aluminum tubing running from the bow to the akas is designed to reinforce the hull laterally and not vertically.

Are the increased lateral forces caused by the jib (and wave action?) really so high that without the reinforcement, the hull could buckle sideways? This seems odd given that the hull is deeper than it is wide and that the front hatch hole must reduce vertical stiffness in the bow far more than lateral stiffness. From the posts I've read about the front hatch leaking, it appears that one of the main causes of leakage is precisely this; the bow flexing vertically when (partially) submerged, so I'd have thought that the vertical loads on the hull caused by jib forestay (and optional main backstay) tension would be a bigger factor in causing the bow to buckle (vertically).

What am I missing?

_________________
Simon


Top
 Profile  
 
PostPosted: Fri Jun 27, 2014 11:37 pm 
Offline
Site Rank - Old Salt

Joined: Sat Nov 05, 2011 1:58 am
Posts: 1534
Location: Forster, NSW, Australia
siravingmon wrote:
Could Jim or one of the other experts on Jim's jib bow brace solution please clarify something for me?

From the photos and descriptions I've seen, it's clear that the aluminum tubing running from the bow to the akas is designed to reinforce the hull laterally and not vertically.

Are the increased lateral forces caused by the jib (and wave action?) really so high that without the reinforcement, the hull could buckle sideways? This seems odd given that the hull is deeper than it is wide and that the front hatch hole must reduce vertical stiffness in the bow far more than lateral stiffness. From the posts I've read about the front hatch leaking, it appears that one of the main causes of leakage is precisely this; the bow flexing vertically when (partially) submerged, so I'd have thought that the vertical loads on the hull caused by jib forestay (and optional main backstay) tension would be a bigger factor in causing the bow to buckle (vertically).

What am I missing?

I think that your assumption that the frame is there to reinforce the hull laterally is incorrect. The frame ensures that there is no horizontal load imposed on the hull from bow to hatch area. As a bonus, the frame will also reduce any lateral forces on the bow area.

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


Top
 Profile  
 
PostPosted: Sat Jun 28, 2014 12:36 am 
Offline
Site Rank - Captain

Joined: Sun May 25, 2014 4:35 am
Posts: 69
Location: Naples, Italy
Thanks for the quick reply, Tony

By horizontal loading, do you mean the horizontal component of the load caused by the jib forestay tension, meaning the aluminium braces are in compression?

If so, I'm afraid I still don't get it, as the forestay is much closer to vertical than horizontal, so I think the main component of the load would still be the vertical load on the bow, causing it to bend upwards.

The alloy braces don't appear to be designed to deal with vertical loads, given the shackle attachment at the front and the U bolt attachments at the aka end, which don't seem to be able to offer much resistance to the alloy tubes rotating upwards about their aka axis.

Really happy to be proved wrong! :-)

_________________
Simon


Top
 Profile  
 
PostPosted: Sat Jun 28, 2014 5:52 am 
Offline
Site Rank - Admiral

Joined: Wed Jan 25, 2012 5:30 am
Posts: 270
Location: Clearwater, Fl
The weakest area of the bow is around the hatch area. I heard about an AI in our area with a jib or spinnaker (can't remember) which ran into a sandbar. From what I heard the hull buckled in the hatch area and destroyed the AI. So that's why I made the aluminum frame. Because I didn't want that to happen to my AI. And it does seem to transfer some of the horizontal force to the aka mount bar.

I've since sold my AI and now have a TI which isn't modified yet. I'm hoping Hobie comes out with a jib or spinnaker option with the new models in August/Sept. I believe there may be changes coming as I was by the Hobie factory in San Diego a couple months ago and they couldn't allow tours that day because of all the sensitive new model changes in the work area.

_________________
Jim


Top
 Profile  
 
PostPosted: Sat Jun 28, 2014 9:02 am 
Offline
Site Rank - Old Salt

Joined: Sun Apr 20, 2008 6:18 am
Posts: 1375
Location: Sarasota,Key West FL
Simon:
Unless your planning to add 250 -300 sq ft of sail area to your your TI (if you have a TI), you don't need to modify or add anything at all to your boat. Many people have added just the Hobie kayak sails to their AI/TI's with no issues. I think one mis-conception everyone has about adding just a jib to you Adventure type boat is that it will increase your speed greatly, it doesn't, it will add maybe 1 mph to your top speed and that's it (hardly worth the effort for that). However the reason I always fly a jib is the jib allows you to sail closer to the wind, instead of 45 deg off the wind you can get closer (maybe 30-35 deg) upwind. As long as the jib is under around 25 sq ft (maybe a little more on a TI), most everything will still work fine. If you fly the jib in a batwing configuration on downwind runs you can increase the downwind performance slightly (without having to add a giant spinnaker (which also has it's own issues, and adds much complexity to the boat for no real reason).
You also have to keep in mind by adding a standard jib you are also increasing the lateral force on the boat (the force trying to tip you over), so as winds increase you have to furl the sails in earlier or run the risk of burying the AMA's or tipping over.

I don't know much about the AI's, as I've never owned one so I can't comment on them. But on my TI if I didn't have the bowsprit (I didn't used to have that stuff) and I try to go on a strong downwind (> 15mph winds) flying 260 sq ft of sail, because the main sail is mounted so far forward the bow of the boat completely submerges (what I used to call nautilus mode). Basically your sails are generating about 50 hp and the bow goes underwater and just stays there until you release the sails (and I would never do that ( LOL)), I would just fly along like a submarine. Before adding the bow sprit I had hydrofoils mounted under the boat to create some lift to get the bow to raise, but later on figured out by angling the fore sails to an extreme angle so they can also create lift as well as forward force, this solved the diving problem and I was able to remove the foils about 3 yrs ago and haven't had them back on since except when I go out in extreme winds and want to foil around (just screwing around). But the winds have to be over 15-20 mph for all my foiling stuff to work correctly, and it can get very dangerous, so I don't do it much. Before attempting any of this extreme stuff it's probably a pretty good idea to massively harden the TI for offshore use and rough conditions as the AI/TI only has an EC 'C' rating and is not suitable for offshore use, if you want to do that stuff get something else.
I don't pretend to understand the engineering, but I do have eyes, with my original setup with no bowsprit and no bow brace flying 260 sq ft of sail, I could watch the bow flex up and down 6 inches, and I would take on easily 5 gallons of water into the hull in under 30 minutes in not super extreme conditions.
Here is a video of the bow in light conditions with the first version of the bow sprit, it was designed as a truss to prevent side to side stress, and the forward pulling stress from the huge 135 sq ft spinnaker but not up and down, as the bars
were only 1/8 x 1/2 aluminum, so they only helped pull force, and side to side force (because they formed a truss) but no compression force.
[youtube]https://www.youtube.com/watch?v=ZGCdveLxDME[/youtube]
https://www.youtube.com/watch?v=ZGCdveLxDME

Keep in mind It's basically a rubber like boat 20 ft long with a triangle sticking 18-19 ft in the air which is held rigid at the mast holder and a completely flexible mast, as the boat rolls through the water and waves it all bends and flexes all over the place, the top of the carbon mast flexes forward, back, and side to side 3-4 feet easily.

Now here is a video with a sq tubing bow brace sailing in light conditions (winds were 5-6 mph and the sea was pretty flat). Watch the bow of the boat, it doesn't flex or waver at all. Think of the bottom of the hull as rigid, then the braces as rigid with about 1 1/2 ft in between, think of the front section of the boat as a cardboard box with the hull bottom as the bottom of the box, the braces as the top of the box, and the side walls of the hull as the sides of the box. Now glue the box to a wall by one end (with the wall you are gluing to simulating the super strong mast area of the boat). Now go to the end of the box and push it up and down, you will see the sides trying to buckle a little as you add more force but the top of the box remains fairly straight. Now take that same box and cut a giant hole in the center of the top almost to the edges in the center (that's your hatch opening). The front of the box (simulating your bow) will wave up and down and back and forth like a flag. Now lay a rigid piece of plywood on top of the box loosely. When it's sitting still the plywood remains sealed against the top of the box (exactly the same as the hatch cover does). Now pull up and down and sideways on the front of the box (simulating wave action). You will see massive gaps forming in the opening continually as it moves around, this is where the water rushes like a flood into the hull. The actual seal type name eludes me right now, but think of a canning jar and a rigid lid, both the canning jar and the lid must remain rigid for the seal to work. Now think of the boat as a Tupperware container (flexible), and try to seal a rigid metal lid on top (doesn't happen), that simulates the hatch seal system that Hobie uses. Now go back to your cardboard box still hanging on the wall in your living room for no apparent reason, and your wife is about to leave you over this ( LOL). Now make a foam plug about an inch or two thick that fits perfectly into the opening of the box. This is what they call a cork in a bottle type seal (the same type seal used in the 8 inch twist and stow hatches). Now wiggle the end of the box up, down and sideways. You will see that the seal is much more solid, and the flex on the box is similar to when there was no hole at all.
Sorry it took so long to get there with the explanation, and soooo much detail, but I can't explain it any other way.

[youtube]https://www.youtube.com/watch?v=HjJ-9rvDOi8[/youtube]
https://www.youtube.com/watch?v=HjJ-9rvDOi8

We were averaging around 8-9 mph, and I think top speed for the day was around 11mph. I always measure the amount of water I take into the hull, we were out around 3 hrs that day and I took in about 2-3 cups of water into the hull (I have no idea where it comes in (probably a little from everywhere)), and we used about a dollars worth of gas (powersailing).

Even with all my hardening my TI takes on a lot of water in rougher conditions. Her and I went 3-4 miles offshore a couple days later in 12-15 mph winds and 3 ft rough chop offshore where I opened the boat up and pushed it pretty hard (which I normally don't do since it is mostly rigged for the very light conditions we normally have in this area), at times we were hitting 15-20 mph. Even with all the hardening I took in about 3 gallons of water into the hull in about an hour (even with all my junk the boat is still not suitable for offshore in anything over 15 mph winds and 3 ft chop). Of course I carry a nice pump on board (LOL), and all the required safety stuff, a Boat US membership, and triple redundant everything .
Seriously if you want a boat you can push hard offshore, I would be looking for something else (just my opinion).
Bob


Top
 Profile  
 
PostPosted: Sat Jun 28, 2014 12:01 pm 
Offline
Site Rank - Captain

Joined: Sun May 25, 2014 4:35 am
Posts: 69
Location: Naples, Italy
Thanks Jim, i could see why you'd want to play safe! Interesting to hear Hobie are planning new models - I hope the AI I've put a downpayment on won't become 'the old model' overnight, particularly in light of mmillar's comments that there wouldn't be any changes to the Ai in 2014

Thank's Bob, your exhaustive cardboard box explanation made perfect sense to me; I get it now :D Interesting to see the difference in even light winds. I also remember you mentioning in an earlier thread that even with the AI and the Hobie kayak sail as a jib you thought the bow reinforcement was worthwhile, so if/when I fit my jib I'll do just that. I won't be looking for extreme conditions but plan to sail/peddle to the island of Ischia for weekends and from my kayaking days I know the weather on the way back doesn't always fit the forecast so I want to be prepared. The wind early morning on the way out however is often negligible so a jib sounds like a good idea. At any rate it's only a 30 km trip with the island of Procida in between and the longest open crossing is less than 5 km so I'm not too concerned :-)

_________________
Simon


Top
 Profile  
 
PostPosted: Sat Jun 28, 2014 12:46 pm 
Offline
Site Rank - Old Salt

Joined: Tue Jun 19, 2007 6:14 pm
Posts: 1903
Location: South Florida
siravingmon wrote:
Thanks Jim, i could see why you'd want to play safe! Interesting to hear Hobie are planning new models - I hope the AI I've put a downpayment on won't become 'the old model' overnight, particularly in light of mmillar's comments that there wouldn't be any changes to the Ai in 2014


Siravingmon--what is the source of Matt Millar's comment about the 2014 AI?

Keith

_________________
I sail: Biscayne Bay, Everglades to Cape Romano, Ft Desoto, Cedar Key

"Any intelligent fool can make things bigger and more complex ... It takes a touch of genius and a lot of courage to move in the opposite direction." A. Einstein


Top
 Profile  
 
PostPosted: Sat Jun 28, 2014 1:09 pm 
Offline
Site Rank - Old Salt

Joined: Sun Apr 20, 2008 6:18 am
Posts: 1375
Location: Sarasota,Key West FL
Simon:
Like I said I have never owned an AI so I defer to Jim and Keith for any information (they are both very sharp and experienced). If I remember right I think I said in an earlier thread that upon observation I thought the AI had a longer and thinner bow than the TI, so my logical conclusion was an AI might benefit from a bow brace as well. It's also pretty common ( I think, at least from what I'm reading on this forum) for AI's to take in more water thru the hatch vs TI's, however I don't know if that has more to do with the seal design itself (which may be a different seal design on some models) or because the bow is longer and more slender, I defer to Jim and Keith.... (hopefully they can explain without mentioning boxes ( LOL))
Now go remove that box from your living room wall before your wife gets home. Now I'm giggling thinking about an old Saturday Night Live skit with Justin Timberlake that involved boxes (English humor sorry)
Bob

PS The 2015 model year comes out in September, the 2014's have been out since last September and there were no major changes in either the AI or TI for the 2014 model year.
I'm just speculating here, but I suspect Hobie will be releasing a more hardened version of the AI/TI hopefully with a CE 'D' rating, and optional jib and spinnakers, I'm willing to bet it will be much more expensive though (because none of that extra stuff is cheap (ie... furlers, sails, carbon masts, new sail designs, stronger AKA bars, etc)), and I highly doubt they will be walking away from their bread and butter (the current AI/TI design), which from where I sit looks to be one of the most popular boats on the market today, and in my opinion has indeed changed the playing field. My 2 cents..


Top
 Profile  
 
PostPosted: Sat Jun 28, 2014 3:15 pm 
Offline
Site Rank - Old Salt

Joined: Tue Jun 19, 2007 6:14 pm
Posts: 1903
Location: South Florida
This is beginning to sound like ESPN Sports Center speculating on the NBA draft (now done) and Miami Heat James/Wade/Bosh futures (they've all opted out of their contracts as of today)--all of which leaves me speechless. I'm waiting 'til Sept/Oct to see what Hobie is really doing. However, I have heard enough to think that Hobie is indeed coming out something new in boats.

Fusioneng--I don't have a feel about whether the AI or TI takes on more water. I had one friend sell his TI because it took on so much water he said it was dangerous. Since I installed my ROIDs front seal on my AI, I've not had significant (more than a pint or quart) of water egress into my AI and most of my sailing is fully loaded with gear/supplies for camping. My wife's AI has never leaked even that much, although her front hatch seal now needs work. If it is true that the AI takes on more water than a TI, in general, and I CANNOT CONFIRM THAT IS TRUE, I suspect it would be due to the fact that the AI is more prone to diving and cutting through waves than the TI. The TI just sets higher in the water, I believe, especially the bow. I was amazed after I started using hakas on my AI, diving (submarining) was greatly reduced. In recent times, I've have begun to load the rear of the hakas, and open rear storage with heavier gear/supplies in an effort to keep my AI bow up. Diving/submarining is pretty much a thing of the past for me, as is water in the hull. Of course, it is also true that when I do sail WITHOUT camping gear/supplies--i.e., just a day sail, diving is minimal and water in the hull is negligible.

Keith

_________________
I sail: Biscayne Bay, Everglades to Cape Romano, Ft Desoto, Cedar Key

"Any intelligent fool can make things bigger and more complex ... It takes a touch of genius and a lot of courage to move in the opposite direction." A. Einstein


Top
 Profile  
 
PostPosted: Sun Jun 29, 2014 2:34 am 
Offline
Site Rank - Captain

Joined: Sun May 25, 2014 4:35 am
Posts: 69
Location: Naples, Italy
Thanks for all the responses guys, all very useful info!

(Keith, see Matt's comments here:http://www.hobiecat.com/forums/viewtopic.php?f=71&t=48604&p=216717&hilit=2014#p216717)

_________________
Simon


Top
 Profile  
 
PostPosted: Sun Jun 29, 2014 5:37 am 
Offline
Site Rank - Old Salt

Joined: Tue Jun 19, 2007 6:14 pm
Posts: 1903
Location: South Florida
Simon, Matt's comments about no changes to the AI were made a year ago and were with regard to the 2014 model--the latest model now in Hobie shops. Those comments may turn out to apply to this year's new model (2015 due in Sep/Oct), but I don't think there is anything on that from Matt. No comments this year may be the most telling. Now, I have some tea leaves that I'm looking at....

Keith

_________________
I sail: Biscayne Bay, Everglades to Cape Romano, Ft Desoto, Cedar Key

"Any intelligent fool can make things bigger and more complex ... It takes a touch of genius and a lot of courage to move in the opposite direction." A. Einstein


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 29 posts ]  Go to page Previous  1, 2

All times are UTC - 8 hours [ DST ]


Who is online

Users browsing this forum: Exabot [Bot], Yahoo [Bot] and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group