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PostPosted: Mon Jan 30, 2006 12:00 am 
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sols wrote:
Ronnie,

I think that would really reduce bar pressure but what about the hands?

What about grabbing a pulley or a line after a one handed trick or a

handlepass?

There could be something like an extra bar below a bar with the pulley

system you displayed, or something... too heavy then, i guess...more

drag....more this , more that...


I'm sure Cabrinha would have considered this possibility. I'm only guessing what this 'mod' will be, not trying to provide a solution.


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PostPosted: Mon Jan 30, 2006 7:57 am 
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ronnie:

If you pull the bar down by 1cm the rear lines will still be shortend by 2cm. And your proposed bar modifaction doesn't offload some of the rear line pressue to the front lines. So nothing will change when it comes to bar pressure compared to the original Cabrhina setup (if we ignore the additional friction).

Because the "effective center of force" (or whatever you want to call it) moves backwards on the crossbow when you sheet in and a higher proportion of the total forces are transferred to the back lines you need to come up with some solution that effectively moves the front attachment points at the kite backwards when you sheet in. Simon (sq...) mentioned one way do it.

This reminds me of early 80ies windsurfing sails without full batten support where the "effective center of force" moved back and forth in gusty conditions. The only way to keep the forces on the front and back arm roughly equal was to move your hands back and forth on the boom.


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PostPosted: Mon Jan 30, 2006 12:32 pm 
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high123 wrote:
ronnie:

If you pull the bar down by 1cm the rear lines will still be shortend by 2cm. And your proposed bar modifaction doesn't offload some of the rear line pressue to the front lines. So nothing will change when it comes to bar pressure compared to the original Cabrhina setup (if we ignore the additional friction).


I only said it moved the force, not offloaded it. It does not change the effort needed to sheet in or hold the bar in position, but it will reduce the force needed to steer the kite.


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PostPosted: Mon Jan 30, 2006 1:04 pm 
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Location: Gold Coast Australia
ronnie

I am drawing some sketches to post with some pics right now. The solution I am currently using does precisiely as you suggested "offload some of the rear line pressure to the front lines"

You will kick yourself when you see how easily and cheaply this is done.

At last a Crossbow with light bar pressure. This will certainly protect our resale value.

Fitzy - Gold Coast OZ


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PostPosted: Mon Jan 30, 2006 1:16 pm 
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ronnie - Your design would actually increase bar pressure to a genuine 2:1. The current design starts as 1:1 with the bar out and increases as you sheet in, approaching maybe 1.75:1. You will also lose the increased ratio on the steering, slowing it back down to 1:1. The worst of everything!

thekiterider2000 - Get on with it you frickin' tease! LOL


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PostPosted: Mon Jan 30, 2006 4:03 pm 
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Location: Gold Coast Australia
CROSSBOW BAR PRESSURE FIX

Sorry to have teased you guys for so long. We just had to make sure that the system worked under a few different conditions and on a few different sized crossbow kites.

I have been very frustrated as have many Crossbow users with the bar pressure. A forum aquaintance of mine (Paul from Melbourne) wrote to me recently and alerted me to the fix I have been getting quizzed about. He was also reticent to share the knowledge without firstly testing that people could understand and make the necessary changes.

If you are not confident with knots or loops and haven't played around extensively with bridles, lines etc., you should get assistance from someone who has the appropriate knowledge BEFORE making the changes listed herein.

I was so dissappointed with the bar pressure on my 16M Crossbow that I used it very infrequently. I have a 12M Rapture 1 which is my favourite kite due to the enourmous depower. Bar pressure has not been an issue with this kite due to the CC Bar setup.

I purchased a 16M Crossbow thinking that as it was a newer kite it would be better than the Rapture. Elbows ached after each session.

I modified an old bar incorporating a spinlock cleat which allows you to lock the bar in any position but this still did not fix the bar pressure problem. Just gave some respite while riding.

I have had an absolute Sh*tfight with my camera tonight thanks to Mr Microsoft and a recent service pack upgrade. So rather than wait any longer I have done three sketches to explain the changes needed to FIX THE BAR PRESSURE ONCE AND FOR ALL.

Essentially you will be replacing two sections of your bridle on each side of the kite with a single piece of bridle line in each case.

You will also be incorporating an additional small pulley onto this new piece of bridle on each side of the kite.

This new pulley allows the pressure involved when you sheet in and out or turn the kite to be transferred and shared more equally between the front and the rear lines.

The current front line setup has a fixed attachment point which causes high pressure at lower wind speeds.

This is well documented and accepted as truthfull by all except those on the forum who like to pretend that they are tougher than most. Some respondents on the forums just call anyone who mentions the pressure a whimp or some such equally useless name. Its best to look for answers rather than just Pooh Pooh the problem.

I was concerned about the resale value of my kite as well as its usability.

You will need to purchase two Ronstan RF 13101R-2 Kite Block Pulleys or alternateively two Riley 302 Pulleys.

You will also need a few meters of spectra bridle line. Thats all.

The problem fix will costs less than $20. (I personally think Cabrinha should send out a free retro kit)

Lay your kite on the ground and work on one side at a time. Lay out the bridle and detach the bridle lines as shown in the attached ilustrations Lay them onthe ground in front of your kite in approximately the same position as they were originally placed.

Loop the two pieces of bridle together that you will be replacing and measure the overall length. Add to this measurement, sufficient line to make a loop on one end and a pigtail knot on the other.

Buy your line and pulleys.

Make a loop on one end of the new piece of line. Attach this end to the kite. Thread your pulley onto the new bridle line and tie a pigtail knot on the other end.

Reconnect the remaining bridle lines back together.

Repeat this process for the other side of the kite.

This fix really does work. The bar pressure is similar to an ordinary C Kite and I have found that my 16M turns slightly better and relaunches very easily.

This fix has been tried in a variety of wind conditions and gives the most improvement in bar pressure on a 16M kite. There is also a large improvement in the 12M model.

It has not yet been tested on a 9M Kite.

Have a look at the following sketches. Sorry for the quality but it's 12.30 am and I am dog tired.

PM me or write in this forum if you need any further info. Any resourceful young person who needs some extra cash might even benefit from making a "fix pack" to sell to their mates.

Good Luck and enjoy your Crossbow fully at last.

If you don'y like the fix just put the old pieces back and work on your forearm muscles !!!!!!

Regards - Fitzy Gold Coast OZ


Attachments:
File comment: Old Bridle Setup
SAVE0023.JPG
SAVE0023.JPG [ 54.43 KIB | Viewed 12106 times ]
File comment: Seperate the necessary bridle pieces and measure new required bridle line length
SAVE0024.JPG
SAVE0024.JPG [ 65.1 KIB | Viewed 12096 times ]
File comment: Fit new bridle replacement section and pulley then reattach bridle components
SAVE0025.JPG
SAVE0025.JPG [ 88.6 KIB | Viewed 12104 times ]
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PostPosted: Mon Jan 30, 2006 4:55 pm 
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Nice work Fitzy,

I was looking at the bridles the other day and trying to figure out the exact same thing. Here are my observations.

Your extra pulley basicly moves the centre of effort (not sure that is the right term) back a bit as you sheet in.

I think that this might even make mid air inversions less likely, because as the kite depowers the tow point would move further forward which would make the kite less likely to backwind ahead of the towpoint which seems to be what causes mid air inversions.

What kind of rope are you using for the replacement bridle? I have never seen the exact same rope Cab uses in any store around here. I have easy access to amsteel, and spectra core line of a similar size.

How did you make the loops? Just knots, or did you splice & sew them?

Cheers,
JJ


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PostPosted: Mon Jan 30, 2006 5:09 pm 
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Location: Argentina - Los Angeles
Thanks thekiterider2000, for sharing your improvement with us.

I have to say that your explanation is very clear....little scary at the begining.

I'm a crossbow rider, and of course I can ride with the original setup...but if there is something out there that generate less bar pressure, keeping the perfomance of the kite with no compromise in security...we should try it....

I will write a big Congratulation if this works.....anyway Thanks for sharing this with us...

I have the same question than Jatkinson

"What kind of rope are you using for the replacement bridle? I have never seen the exact same rope Cab uses in any store around here. I have easy access to amsteel, and spectra core line of a similar size. "


Fernando


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PostPosted: Mon Jan 30, 2006 5:18 pm 
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Location: Minnesota, USA
Kiterider, thanks for the research, great job!


Here is one source for the Ronstan Block in US:

http://www.apsltd.com/Tree/d6000/e3490.asp

Layline should have it but it's not on their website.


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PostPosted: Mon Jan 30, 2006 5:20 pm 
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Excellent! That looks really interesting. I can't wait to try it. Unfortunately I had 4 spare pulleys but I've just glued them together to make some replacement for my slightly worn "double pulleys". I'll have to get a few more.



You've also answered something I've been thinking about for a while. I hadn't posted it as the whole bow scene is already confusing enough and a real pimp zone.

I had been thinking that the majority of the difference between current bows is in the bridling (and whether the bar has pulleys). To me this means that it's theoretically possible to modify and "upgrade" your kite to some degree. (e.g. If the '07 Crossbow differs mostly in bridling, could you upgrade the bridle? If the Sonic turned out to be the way to go, could someone design a Sonic-style bridle for the Crossbow?)

I think you've answered that!


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