UK-Cherub Forum
Cherub Chat => Tech Chat => Topic started by: kokopelli on June 27, 2012, 09:00:03 AM
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Re:- Sweet Dreemzzz makeover. . . Having not studied the pole kite launch systems . . . what system should I go for? What is the preference for a 'sprogglett' (a small lightweight crew) on spinny uphaul and pole launch? Is it the combined launch which pull both together (which i think takes a longer halyard and needs more muscle) or the separate launch done in 2 stages - pull out pole and then kite- (think in that order)? What systems are yer using and what can yer recommend? Kokopelli uses the combined system but the pole is shorter and Joe struggles without any assistance. I guess the helm could tug out the pole whilst the crew spinny launches??? Help!!!
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On Evo we have fitted a 2:1 advantage system for the pole, see diag below. This makes it much easier to get the kite to the tip of the pole, but the danger is that the kite goes forward rather than up (and trawls). This is avoided by a distinct lack of anythign causing friction anywhere up the mast. Finding a "clear" route from the return block to the top of the mast is vital for an easy hoist in any case. This also works as a take up for the halyard.
The other thing that makes the hoist and drops easier are the patches on the kite. Two appears to be easier than three, but the real key is to get the overlap correct. If you get it wrong you are pulling the kite inside out past itself in the sock during the launch, personnaly I've been slow on this and only really thought this through with the new kite - getting it right makes a real difference. If you can get the bottom patch to the back of the sock and the the top patch to never cross it - the hoist and drop get easier and the kite "folds" nicely into the sock. The fold also ensures the top goes up first.
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I am sailing with Alex (11) We have a combined system. With lots of regular lube he seems to cope.
I did initially come close to changing the system so that the pole pulled out separately, so that I could do it and help however there is very little room in the cockpit during a hoist, and I am not convinced that it would be better.
I how shout at him a bit louder. This seems particularly effective if there are other young crews close by and we are in a direct hoist match. I also try to run very deep during the critical parts of the hoist so that the kite does not fill and make it even harder.
I am looking at putting a sheave on the end of the pole rather than the trumpet end. I think that sacrificing an inch of pole length will be worth it for the reduced friction .
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an alternative (sort of) to the above system attached
This is how it's done on Atum. Especially good for tricky drops with the block at the back of the sock that the helm can give his complaining crew a bit of a hand. Also if you ditch it with the kite up, pulling from behind the drop block can give you a bit less resistance when trying to get the kite in in the water (can be done when standing on the centreboard depending on which way you go in).
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At the risk of sounding very non-technical (I'll leave that to Roland - see post above), whatever we have just done to Evo worked brilliantly last weekend. I don't think I've ever hoisted and dropped so quickly, easily and smoothly. It came as quite a shock. Admittedly the fact that we were fast running out of lake lent a certain urgency on occasion (people on the shore got a very good view and noted that the drop was PDQ), but the fact that the helm thought he could leave it quite so late suggests he has a lot more confidence in the system.
Unfortunately if your kite sock rips along its entire length, the hoists and drops don't matter so much - it's keeping the kite in the boat going upwind... ::)
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I am keen to try this piece of rope between the 2 patches as I have heard it mentioned a few times. Previously when it was me doing the hoists and drops I kept things basic and simple and just strapped a pair on when required, but to keep things running smoothly and being the loving husband that I am I would like to make things easier for Kate!
So the burning question of the day... how long is the piece of string?!
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It would be smutty to quote that bit
Not sure if the sketch above is clear, but with the new kite i followed:
1) Hang kite by the ring on the bottom patch from cieling or other high object i.e. the bit the kite halyard goes through. Tack and clew should be together, if not patches are not in correct place or you have the kite upsidedown.
2) Hang kite via strop to upper patch form the same place (at the same time). Adjust strop so all three corners of kite come to same point. By the system I've targeted for the new kite the strop should be needed on top patch. If not I'd reccomend moving the patches.
3) Tie Halyard onto Strop and through ring on bottom patch, it will enter the sock in the same folds as it hangs (ish).
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Ronin has the same system as per the Atum sketch. We spent a long time checking that everything ran smoothly and upgraded some of the blocks as well. Loads of Prolube also works wonders. We tie a large bowline (6") in the kite downhaul to stagger the patches in the spinnaker sock as per Rolands suggestion. We also have found a couple of times that if something snagged or loaded up Peter thought he had got the kite to the top and stopped pulling which normally ended with a trawl, to solve this we have a very big mark on the spinnaker halyard that is just past the cleat when the kite is fully hoisted. He now just keeps pulling until he sees the mark.
The biggest gain I have found is to bribe him with chocolate for each good hoist and drop, it worked wonders :-)
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Having just changed from a three patch kite to a two patch (it's the same kite but now with measles) I can agree that is certainly easier for the crew to hoist and drop with less bunching around the chute. i had not gone down this route thinking that I needed a longer sock to accomodate a two patch system. We always staggered each patch by 30cm. In three patch mode the top and bottom patches were 1.9m from the corners with the middle patch in between the top and bottom ones. The kite could be drawn deep into the sock.
I managed to squeeze it in by having the top patch go to the back of the sock followed by the lower patch. The reason for this is that the bringing the top patch down still allowed much of the leach to be drawn into the sock. If I had made the bottom patch the longer bit this patch wouldn't be much further up the kite and I would have still needed three ptaches.
Our sock is 2.7m from the bow to the inborad end and 2.3m from the mouth of the chute to the inboard end. I allowed all the corners to be in front of the mouth of the chute. So the top patch is 2.6m from the head of the kite. The bottom patch is about 2.4m from each lower corner.
I like EVO's additional purchase. It requires a bit more halyard to pull but if it's much faster and can be done hand over hand it will be quicker. If the tack goes out first I would question that the bottom patch should go to the back of the sock because you will be pulling the bttom of the kite past the top bit.
Good thread though.
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Marking halyard - yes. We had thin halyards which were fat only where they hit the cleat when the kite was right up, so that kinda marked itself.
Patches - People have different views. Two patches means a longer sausage and probably means a slower hoist for that reason. Three patches might be expected to be harder, but if everything really works we found it fine.
Patches - we put the ring of the bottom and middle patches on strings. 450mm and 300mm from memory. This had the effect of separating the three patches as they go into the chute. I do not recommend having the patches moved so that the corners are all equal when you stagger the patches. This is because if the corners are all at the chute mouth at the same time they may jam up and cause difficulties. It is also because (we think) you actually want the head to go in first, followed by the clew and then the tack. If the head is furthest out, the motion when going upwind may pull it out. Similarly the clew, esp if the sheets get in the water. With the head in first, when you hoist, you pull the head section back past the other bits of kite, true, but we think this is better than the slower (though probably less trawl-risky) two patch approach.
Three patches became the norm in 2005, but I guess there is no obstacle to 2 patches, except for sock length.
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roland, what does the triple floating block on your system look like, i like the idea!!!
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Also the size and angle of your hoop makes a huge difference we have a large and relatively upright hoop making a big mouth to fill. We have 3 patches - bottom one has a string about a foot long. No strings on the others but we have a knot with a bobble about a foot down from the top patch to separate this from the middle one.
Getting this right was about the only thing on the boat Jill was concerned about and it has received her seal of approval.
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Thanks, ab fab for the pole/spinny thead... i think i know what to do now (ish). Today i have been cutting up sails and 'sailmaking (of a fashion)'.
the older 97 main was too long for the mast so i got the scissors out! I now have the option of 2, 97 rigs and an 05 rig. After some measuring I can now sail 97 rules on 2 totally different sail set ups. Large main and Small jib. Small main and Large jib. (The 05 is large and large but I am not thinking seriously of that option yet). I am really looking forwards to testing these in August. What experiences have yer had with these variations?
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The 97 rules change was designed so that you could upgrade from 1990 area by putting a snout on and using a large jib with the same main.
Once the new build 97 rules boats started appearing they typically had smaller self tacking jibs matched against a larger main.
so both have history of working, you just have to try them and see what the balance feels like.
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The modified Sweet dreams rig has a very high hounds height. It's less than 1m from the top of the mast with the mast fitting the mast cap limit.
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After a bit of lateral thinking Joe and I are going to experiment with a bag system.
Our thoughts for this are mainly due to the fact that we sail on a puddle.
Problems we have encountered so far necessitate getting the kite down fast and not able to bear way enough to balance the boat safely enough in extreme tight areas (ie running out of water and land being too close to miss). we also have problems with massive windshifts, gusts and racing courses not suitable for overpowered assymetric Cherubs.
Therefore part of the idea is so that we can de-power quickly and bring the kite in on the windward guy and stuff into the bowbag. Joe maybe able to do it still on the wire!!! (well not really but I'm positive thinking about the mechanics of it) I also think the benefit of both on the windward side and not loosing track could be an advantage.
I am thinking of the pole being separate to the uphaul and on a bungie bringing it back in. Therefore the tack is bagged as well.
Our hoist system is currently crap as i havent changed it since getting the boat and its all wrong anyway. (It could have been I I got the set up all wrong though)
If it works on our trials we will be playing with it at the inlands so you can see if it works as well.
Has anyone tried bagging on Cherubs before and if so what were the results. I have sailed loads of other spinny boats with bag systems but never tried assyms. I see the 18s do it so it must work if set up well. Any other thoughts greatly appreciated...
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Bagging a kite is much harder and its only done on 18s because the kites are impractically large to use a sock system, it also becomes much much harder to do if you try to stay high
Why cant you drop it from the windward side currently?
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Hi MK. Is that Matt Kiddle? if so can you PM me. We maybe bringing both Kokopelli and Sweet Dreamzzz boats to QM. I need to know if you are still interested in Koko. I cant access the members areas and get peoples contacts or update photos and stuff on the site so u need to PM me as i cant u.
Anyway.. Back to 'baggin' I think our launch and retrieve set up is not good, its too slow and takes too much effort. So, therefore, we need to change the system anyway. I think i will still try baggin. Obviously there will be a learning curve and dropping the kite will need to be synchronized and practiced to work effectively. I guess, i think, what you are R saying is don't bother trying its doomed to failure... From your own experience is it worth trying???
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https://www.youtube.com/watch?v=qoJCSmkaXus&feature=plcp (https://www.youtube.com/watch?v=qoJCSmkaXus&feature=plcp)
You can see from around 35 seconds into this the two stages of a bag drop, it is quite uncommon for the middleman to do the pull round part and obviously in a double hander you do not have this option but it is a good example to show how physical a job it is, the resistance of pulling the entire kite round the forestay is significant (Of course this part is removed if you gybe drop each time), and keeping it in check for the drop without a trawl is quite a skill
I would not try it if i were you, sort your chute system, widen the hoop, align blocks if necessary, hayley is an expert on this sort of thing hopefully she can come along with some tips
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yes thanks i can see from the youtube the physical strength needed. joe just wouldnt be able to haul it at all. cheers ade.
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The biggest problem with a bag drop from my experience in the 12, is what happens when you capsize with the kite up. With the boat on its side you have no hope of bagging it into the leeward bin, as it's now underwater. So the whole big, wet, heavy kite has to be dragged up out of the water, round the forestay into the upper bin. A real arm-killer. The Platypus design Cherub now known as "Therapy" (2656 I think) was originally built with a bag system for a '91 Rules kite. The fact that nobody copied it says something though.
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I tried bags (without the bags) on Mango for part of a season when I first fitted a big kite. It was possibly fractionally quicker to hoist but slower on the drops. It was easier to trawl and as Neil mentioned took more effort to put away than a chute if you capsized with it up. You also have plenty of halyard to do something with when the kite is up.
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Thanks for the info guys. Your experiences are an invaluable source that leads me to focus on re-designing the chute entry and re-doing the uphaul/downhaul systems - so to make it easier!
I think we will go and try it out just for the craic and the extra experience for Joe to have tested (struggled) and formed his own opinions through trying.
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There is no harm in trying even if it to prove to your self that another way is best.
We changed the chute mouth on slippery from a trinagular shape to a semi circular shape. It meant you could recover a trawled kite and generally made things easier for the crew.
As above we also found on E-numbers that a bigger chute bigger sock and fewer patches make a big difference. Our halyard systems have always been aligned well because I spend to much time on that sort of thing and in a sad sort of way enjoy it.
I think it has been said before that with the two string system the pole also launches the tack which with a long pole has to pull a lot of kite out of the sock. Set this up ashore and get joe to try this first stage. You may also find that this leads to a trawl unless the halyard is hoisted very soon afterwards.
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Yes, at the nationals Joe and I did a lot of trawling and I had to reverse the boat a few times, which was tricky, just to get the bloody thing out of the water. We still have some sorting to do. I have already changed the uphaul system to a 2 to 1. Whereby 1 pull brings out both pole and kite and Joe says it is a lot better than before. He needs to move and pull much faster i think it is time in the boat Joe needs and we dont get enough of it! I now have 2 patches and the knot spacing between the 2 is about 30cm. I am still not happy with it but intend making a semi circlular chute entry approx 45* elevated to help launch but more importantly retrieval. I have carbon but would rather use a kelvar mix. Does anyone have any going spare? I need about 50cm by 25cm. Swaps or buy???
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Kevlar won't help that much, it will just end up furry. I would go for using glass as this is far better at wear the Kevlar and can be filled when there is some.
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I was about to try and make a spinnaker mouth for the new boat.
I have brought some 31mm silicone tube:
http://www.ebay.co.uk/itm/290742298928?var=590074415541&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649 (http://www.ebay.co.uk/itm/290742298928?var=590074415541&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649)
I will cover it with carbon braid and epoxy:
http://www.easycomposites.co.uk/carbon-fibre-reinforcement/braid/carbon-fibre-braided-sleeve-40mm.aspx (http://www.easycomposites.co.uk/carbon-fibre-reinforcement/braid/carbon-fibre-braided-sleeve-40mm.aspx)
and form to shape with a ply jig.
it may be necessary to pack the silicone tube with sand to help stop it collapsing. It just about bends to the desired curves
I am hoping that when the epoxy has set I will be able to get the sand out and then pull out the silicone tube.
If I have to leave it in it will not be a significant weight
Any one tried any think like this before?
I believe that things like carbon bike bars (drops) and frames are moulded over silicon formers that they manage to pull out.
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I did a chute mouth moulded around a bike inner tube and it worked out OK, I did a write up on the process I used.
http://www.uk-cherub.org/doku.php/tech/new_chute (http://www.uk-cherub.org/doku.php/tech/new_chute)
I did the first layup with one layer of glass, so if it went wrong, there was not much waste. For the outer surface I have been painting the mouth with epoxy and graphite powder, seems to wear OK and feels low friction. It is also easy to repair, or recoat if you get a cut from the haliard
I have previously setup an auto trip on the haliard cleat, so as soon as the retreaval line is tight, the kite starts to come down. It defnatly helped on some of the drops.
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Kevlar won't help that much, it will just end up furry.
Funnily enough my experience is that it doesn't go furry in wear situations like it does when you sand the laminate. I don't know why not, but that's how it seems to have worked out for me. I use it for wear surfaces on the canoe sliding seat setup and it just seems to polish up. I also used it on the wear points on Halo's last chute and don't recall it going furry.
I agree with the rest about bagging the kite, it is IME more effort than a really well set up chute, the fly in the ointment being getting that really good setup, and I've never managed one I thought was really good, so bear that in mind with what I say... My impression is that large radii are really helpful, as is avoiding bunching, both when coming down and when going up. Sometimes a setup that goes in smoothly will bunch like crazy coming out again. I've usually moulded chute exits round styrofoam. I suggest trying graphite powder in the outer layer of the layup: not only should it be lower friction per se but it also takes a good polish.