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PostPosted: Fri Oct 26, 2012 12:32 pm 
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Last weekend I trialled a new Splitter - wave deflector. Designed as a solid spray skirt I suppose, the aim was to work out the minimum size necessary to deflect waves. This prototype was all a bit of a guess based on old footage of waves around the bow. I must say, I was surprisingly impressed. I think I'll now start on the Mk2 Clear Polycarbonate version and will possibly make it the same size and trim back if necessary. The method of attachment also worked well.

Appreciate your comments.

https://vimeo.com/52213299

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Last edited by Slaughter on Fri Oct 26, 2012 1:16 pm, edited 1 time in total.

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PostPosted: Fri Oct 26, 2012 1:00 pm 
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My first Sprayskirt I designed with waterproof fabric seemed to work ok, until I came off a small wave and buried the nose, then the boat did not want to surface until all forward motion stopped! :o I cut holes in it with my knife just to continue sailing.

That's one of the reasons why I switched to breathable material. Also, I would move it back further from the bow. In gusty or strong winds, the more extra material that the wind can grab and push at the bow will cause you to not be able to tack (bow across the wind) in lower wind speeds than without it.

Looks nice.

I was hoping from the post description that you had made more of a anti-dive nose piece. :)

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PostPosted: Fri Oct 26, 2012 1:11 pm 
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Very impressive! Looks like it has real possibilities. I have the same question I've had regarding Bob's spray skirts: how do things behave when the bow dives beneath the waves? Have you done that test yet?

It seems that with a solid polycarbonate splitter, you could cut some openings (louvers?) in it to drain water. The angle of the louvers or slits with respect to the hull would determine the amount & direction of splash permitted through the splitter.

As I wrote this, I see KB has posted in regard to the diving problem.

Keith

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PostPosted: Fri Oct 26, 2012 1:28 pm 
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Looks like I have the 2 Hobie wave deflector experts interested. I'm happy.

I thought about the anti nose dive aspect of the design but I'm conscious of the loads placed on the bow or hull itself. I will always sacrifice getting a bit wet over the possibility of adding any extra load to the hull. I really appreciate your comments and hadn't really thought too much about resurfacing if the nose goes under. The main reason for going a little smaller, and manufacturing from polycarbonate, is that poly has flex and will bend under excessive load. The question is getting the right thickness and size but I reackon 4mm thick should be just right.

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PostPosted: Fri Oct 26, 2012 1:40 pm 
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Nicely crafted - and a feasible design. It seems to work great as a shield.

I'm thinking a fabric skirt is likely just as effective, without any down side,

For example:
No added weight
easily deployed/furled
allows full access to bow hatch
no storage issues
less of a drag (wind and water)
safer for boats/swimmers you encounter at ramming speed. :lol:

This design seems both a wave deflector and spray skirt, due to it's large size. My thinking is that a smaller semi-stiff nose wing up front makes a better deflector and a wider porous skirt further back makes for a better spray shield.

I agree with Keith it should be perforated/slotted to help with the wind profile and drainage.

In its present form, it should work great 80% of the time, but would be a real liability when running downwind and stuffing the nose. Possibly a perfect recipe for a pitchpole? You'll know more as you get to test in those conditions.

Regardless if any single design can solve both problems, you are going about this the right way. Good on ya! Thanks for including us in the experiment.


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PostPosted: Fri Oct 26, 2012 5:35 pm 
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I agree with the above comments Slaughter. When you get a stiff downwind and the nose dives, you might be in for one big surprise.

A few months ago I was out in extremely windy conditions and I pitchpoled my AI because of (I think) my custom splash guard. It was pretty scary and I never thought it could have happened. But when the bow dived, my shade cloth splash guard had extra material in the front of the bow held outward with a piece of PVC pipe. Well when the bow dove going very fast, it acted like a shovel and we pitchpoled. My nephew was on the leeward tramp which kind of helped the pitch but if I were you, I'd give your design a lot of consideration. Maybe a flexible thin plastic one like NOHUHU mentioned.

I was with some friends and their AI's a few months prior to that incident and a big storm came in so we went back to the campground. Since I wasn't camping with them, I had to sail back to my truck so I could leave. They witnessed almost the same thing happening to me with that splash guard. I came extremely close to pitching that day but recovered quick enough. And that day I did not have tramps - I had my hakas.

Needless to say, I'd be very wary about your design. I don't think perforations or slotted will help much either. On a warm summer day pitch poling isn't too bad but in crazy conditions and cold weather it could be disastrous. I don't ever want that to happen again. I hope I don't come off negative here and I'm just trying to warn you so you don't make the same mistake I did.

Good luck !

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PostPosted: Fri Oct 26, 2012 5:45 pm 
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Slaughter, it has been my experience that the area which needs "protection" the most is the knuckle in the aka, as this sends up a huge shower of spray when hit by the bow wave. I would therefore be inclined to suggest that you move your deflector back from the bow so the widest part is just in front of that knuckle.

This would also tend to reduce any tendency to pitchpole. (Sitting in the front seat of my TI while solo, I have had to partly furl the sail, going downwind after watching the bow sitting nine inches under green water while forward progress basically stopped...)

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PostPosted: Fri Oct 26, 2012 6:12 pm 
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Good friend, Rick Parks (Intents) offered that he thought a solid deflector in front of the knuckle or pin joint would be sufficient to block much of the bow splash.

Keith

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Last edited by Chekika on Fri Oct 26, 2012 7:40 pm, edited 1 time in total.

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PostPosted: Fri Oct 26, 2012 6:19 pm 
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I played with spray deflectors on my TI. I videotaped the bow as it dived through different waves. That showed me what part of the bow first starts to throw off a wave. On the TI it was much closer to the bow.

I welded on narrow strips of Polyethylene along the bow. The idea was not to completely block the spray. The angle caused the wave to shoot out sideway. The side force would block other water coming up underneath. This also provided some lift. A large plate can be dangerous forcing the bow down in a dive through a wave.

In the end I added Bob's sprayskirt that I use only occasionally.

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PostPosted: Fri Oct 26, 2012 6:24 pm 
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Forgot to add the picture.

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PostPosted: Sat Oct 27, 2012 2:53 am 
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Well, as some of you are commenting about the design, the problem is when the nose are going down. As my child say (optimist racer)..."SUBMARINNING"
I´m thinking about to build the splash in the other way: NO HORIZONTAL BUT VERTICAL. More high on the bow and the lateral flap going horizontal just when reaching the front crossbars.
Don´t know if clear enough...
saludos


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PostPosted: Sat Oct 27, 2012 3:44 am 
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Yes, Alarcas, that would be along the lines of Rick Parks' suggestion.

I'm curious what prototypes Hobie designer/engineers have tried?

Keith

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PostPosted: Sat Oct 27, 2012 4:37 pm 
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Thanks for everyones input. All good constructive comments.

CaptnChaos's comment took me back to a time when I did the same on a HobieCat. To do it in an AI would be far worse and don't worry Captn, this is always in my mind whilst doing this design. Notice I wasn't riding any waves or trying to submarine the nose. With an area that big and also being not flexible, I took a gamble but I was always conscious of the consequences. I should have stressed that the design has always been about being flexible. Stiff enough to deflect water from underneath, yet flexible enough to bend whilst submarining. This prototype was sculptured to just get the correct shape and the bend angles. The key to its efficiency and safety is in the material used, its thickness and its flexibility.

Your comment are confirming and reinforcing my thoughts to go smaller and have a method of shedding water. My method of shedding this water is by flexing.

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PostPosted: Sat Oct 27, 2012 6:54 pm 
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Very impressive metal work there mate! 8)
Keep up the R&D. I'll be interested to see what you end up with.
I like how you designed it to be easy to fit. Looks like it just bungees on.
I agree -flexibility will be the key.
BTW - Even as a prototype it doesn't look too bad. You've shaped it well. The only ugly things on your AI are your legs! :wink:
:lol:


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PostPosted: Sat Oct 27, 2012 9:34 pm 
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stringy wrote:
The only ugly things on your AI are your legs! :wink:
:lol:

Give us a break mate. As you can see, I pumped up those thighs and calves just for the video. :roll:

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