UK-Cherub Forum
Cherub Chat => Tech Chat => Topic started by: Neil C. on March 15, 2011, 11:09:57 PM
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2658, initially named "Cellulite" by Duncan Barr in honour of her Nomex construction (I think!), and later known as "Lost in Space" is now resting in my garage. She's in need of some serious TLC. She's not quite the ship she once was:
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Duncan built her using Nomex core for about 97% of the hull. In fact the only non-Nomex bit I can find is the daggerboard case. With all the paint off the hull is now strangely translucent, you can see right through the honeycomb with only a light covering of glass on either side of the core. The areas where the side tanks have been carved up give a good view of the construction technique:
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So, what next for the Honey(comb) Monster?
John, the previous owner chopped off most of the side-tanks with a view to building some Cheese Before Bedtime style racks. (Also whipped off with the anglegrinder was the entire central tunnel and the top 3-4 inches of the daggerboard case). But on measuring the remaining hull, I only need to increase the gunwale width by about 10cm on each side to bring her up to '05 rules beam. Duncan was very smart with the original design, in that the mid-length beam measurement point in force at the time lies a short distance in front of the main bulkhead. The gunwales aft of this point are flared out a long way.
So I guess the options are:
1. Laminate all the removed chunks of side-tank back on as a simple restoration job. John kindly provided all the bits he chopped off in a black bin-liner! But this will no doubt add weight and misses out on the opportunity to get up to the 1.8m beam.
2. Do a Cheese and start building some scaffolding.
3. Fit some flat(ish) wing panels in the style of Shiney Beast, which might fit more or less into the cut-outs already provided.
I'm leaning towards option 3, but don'y know for sure yet.
Thoughts anyone??
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Option 3.
I'd see this is more like Nautilus - single skin flares. The annoyance with this is on what you have is the need to remake the gunwale.
Option 2.
No scaffolding required as the structure is all there and almost un-molested. The concept for the boat was a slug crossed with at 12, so now it look more Atum than Born Slippy. This gives you a boat with semi-racks and has to be the quickest route back onto the water for this boat?
As per the attached sketch.
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I am not keen on the solid sloping wings, I find them very difficult to trapeze on.
What I would do is trim the outer flairs back to the inner chine, and then cap the top of what is left of the side tanks.
Then i would add tube wings it might need a bit of a rebuild of the transom, and you would also need to cap the end of the boyency tank at the front.
I think you could end up with something structured very like the way Pocket Rocket ended up.
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Thanks for the suggestions chaps.
Roland's idea is simple and certainly has merit. I'm not sure it would look very pretty but it ought to work. I'll certainly be giving it some consideration.
I agree with you Phil that flat wing panels which slope down and in at a heavy angle are probably a bit of a nightmare for trapezing off. Our 12 Footer is a stage worse, in that the cockpit is single-skinned and is actually quite concave when viewed from above. There is a small kick-bar half way up the cockpit side, but if you miss that it's nearly impossible to get any purchase with your feet on the concave floor to get you out to the gunwale. It's not so bad for the crew who can use some hands to help but for the helm, particularly downwind when both hands are already occupied it's very difficult.
On the other hand I'm not too enthusiastic about fitting racks with only a small gap between the inside of the bar and the outer edge of the hull - looks like a case of leg or body entrapment waiting to happen.
I was quite impressed with this 14 at the Dinghy Show the other week. It doesn't show up so well in these photos, but the wings were actually a bit convex, sloping slightly down towards the gunwale - which was really just a 90 degree turn to the outer edge of the wing giving a 3 inch vertical lip. This would give you something to trapeze off and I guess adds a shedload of stiffness to the outer edge of the wing. The overall geometry is different from Lost of course. But I think if I built up the height of the inner wall of the old side-tank a bit it might be possible to do something sort of similar, with a reasonably horizontal convex panel running from the new inner tank side, across the outer rim of the hull topside, and on out to the new gunwale position 10-12cm outside the hull. The transom would probably need re-building to match.
The whole business needs a fair bit more beer-assisted head-scratching before I get the rubber gloves on, so any further smart, wild or just plain looney ideas will be gratefully received.
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This picture shows the convex wing shape a bit better. Taken from in front of the wing it also shows the attachment point for the main shrouds (complete with big purchase system - not something I'd be looking to copy!).
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It looks like monkey magic.
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I agree more with Phil A.
Cutting the flairs back to the vertical sides of the hull would give you a better inboard trapeezing point and a big enought gap to avoid foot entrapment. If the hull has a low floor you may want to build up the inboard side of the side tanks to maintain a flat top to the tank.
While weight is important I would also ensure that the modified boat looks right too.
If the shroud points are not affected the transverse rack tubes do not need to go all the way to the centreline.
i understand Roland's point but would personally add some big kick bars to give a good footing on the concave hull side.
There is noting stopping a flat or even convex extension to the flairs to give the max beam.
It all comes down to how much time you have and when you want to get sailing.
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I agree more with Phil A.
??? I'm confused - I think my sketch and Phil A's comments are exactly the same ???
(i.e. resulting in a boat with racks at the back and looking like a N12 at the front).
Granted you could also do something similar and leave the skin in and have a flair.
I think Phil A's experience of sitting in the new Pocket Rocket confirms the sit on racks as a comfortable goer, hence the skin was "greyed out" for removal.
From the short crew's union - Hayley says racks are much better for the crew and makes getting in an out far easier with the inner gunwale to go off first.
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Doh! I'm a complete eejit. Sorry Roland, I didn't twig from your diagram that you meant the upper part of the hull skin / topsides should be cut out. Suddenly it makes a lot of sense. I'd end up with effectively a lowered side-tank with a flat top, a reasonable gap and then the new rack bar sitting a few inches outside where the old gunwale used to be. I like it!
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For some reason I thaught Roland's diagram left the flairs on the boat.
If you are going to cap the rear of the tank, rather than remove it completely I would make sure that it does not have a big vertical face on the front. PR's aft wing support is vertical and you get some serious wave slap going down wind if you do not keep the boat flat, or use the T to lift the back.
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Phil A - do you have any recent photos of Pocket Rocket you could post up? Also, any idea how much freeboard you've got at the back end?
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Hi Neil,
I will take some more pics at the WE and measure the free board.
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Hi Neil, How is project infinity getting along?
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As ever, these things take about 4 times as long as you think they will. Also, real life has a habit of getting in the way of the timetable. Nevertheless, I've finalised the design plan. It will be a little different from other boats - I took some inspiration from a First World War front line trench! More to follow :) Spent the last couple of weeks sorting out the garage and workbench. 7 P's - proper planning and preparation prevents pi** poor performance. Have received my delivery of foam from Impag/Trident, got resin from SP and a load of glass cloth and other bits and pieces, so now about to get sticky! I'll try to remember to post the odd photo along the way.
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Project Infinity continues to make slow but steady progress. This is a number of weeks out of date now, but I only just got round to transferring the photos from my camera onto the PC. Before sealing the new deck panels down I thought it would be a good idea to see what the structure under the false floor looked like, such as configuration of bulkheads, daggerboard case construction etc. There was a small gap between the edge of the false floor and the inside of the hull, just big enough to get my hand and a small digital camera into. I was amazed to find this little guy hiding on the central spine, just behind the daggerboard case! I don't know what his name is or what he's doing there, but the poor fella has been stowed away in there for the past 17 years. I've locked him back in again now, poor bloke.
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The 2658 rebuild is coming along. She's now watertight, so officially a boat again. I still need to do a pair of side-deck / gunwale extensions to get her up to the 1.8m beam. I put her on the scales this afternoon and she's currently weighing in at 42kg with bowsprit installed. The question is how much weight do I need to allow for paint (she's down to bare glass / kevlar at the moment), and fittings? The remaining weight margin will be what I have to play with for rebuilding the gunwales.
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We put in 12 kg of tubes, fittings, progrip and paint onto Atum. We could have saved loads by having no, less or thinner progrip alone.
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The top coat originally sprayed onto E-Numbers was about 1kg. if you roller then it will add a thicker coat. Probably at least double.
Primer/sub coats allow about another KG as this will on average be equivalent to a normal coat.
from a bare painted hull to a measurement weight we put 10 kgs of fittings (including pole), sock, control lines and progrip.
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Hmm... That all sounds a bit ominous. Think I might have to inject a few kilos of anti-matter into the hull somewhere!
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We used a similar amount of paint on EJ as Phil and Sarah did on E-numbers - perhaps a little bit less. We used a filler primer - much of which was then sanded off again - and then a couple of coats of colour. When we sprayed Born Slippy the first time we were much more stingy with the amount of paint because we knew we didn't have much margin and wanted to keep her to weight (had to stay true to the "mega mega light thing" philosophy), so the paint was very thin - transparent in places. Post the recent modifications BS got a much better coat as we had lost weight from elsewhere. With EJ we had much more margin and so gave her a good layer of colour, and of course with a racked boat you only have to worry about a much smaller area of hull. Pro-grip is a real killer on weight. You may find grippy paint a lighter alternative, putting pro grip only where it is essential and using the very thinnest stuff. Much may depend on how vociferous your crew is - I insisted on a certain amount of pro-grip to cushion the blows!
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We decided that we would make things as easy as possible to sail, slipping on the boat and falling over is alot slower than an extra kilo of weight. Not that we have a weight problem, we could use an extra bit when the wind gets up. Does antimatter get hevier when wet?
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Does antimatter get hevier when wet?
Antimatter must get lighter when it gets wet, because, as I understand it, it should violently explode, eliminating both the matter (the water) and anti matter in equal proportions. Whilst this will certainly save a great deal of weight, there is a small question mark in my mind about resultant structural integrity.
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Had a pleasant afternoon drifting about at Derwent in the sunshine this afternoon. Then spent an hour or so getting sticky with 2658 in the garage this evening. Epoxy resin gets very gooey when the ambient temperature drops doesn't it?
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Antimatter must get lighter when it gets wet, because, as I understand it, it should violently explode...
.... there is a small question mark in my mind about resultant structural integrity.
I think we'd be wondering where the universe had gone rather than the boat?
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I need to finalise the position of the rack tubes on Lost in the next 24 hours or so. In terms of aesthetics, they look about right with the upper surface of the tube flush with the horizontal extension of the plane of the old side-decks (which are now mostly missing). However, when I look at photos of other older boats which have been racked (Cheese, Suicide Blonde) mostly the racks are positioned a bit higher than that, with the lower surface of the rack tube flush with the side-deck line extension or even a bit higher.
A higher rack position will mean a bigger step up/back to get onto it when trapezing. But on the other hand I guess it will keep the rack out of the water for a bit longer as the boat heels over. Is there anything else I'm missing here?
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consideration 1. If there is a reasonable gap between the rack and the gunnel you may want to use the gunnel as a step or possibly trappeeze of the gunnel. If the rack is too high you may not be able to get much of your foot onto the gunnel without wiring very high. The modern boats have quite a gap between the rack and the gunnel so the racks can afford to be a little higher without stooping you from getting your feet comfortably on the gunnel.
If the racks are quite close to the gunnel as in Suicide it may not be possible to trapeeze off the gunnel anyway. No problem.
Consideration 2. With the racks higher can you still get control lines into cleats and cleat the jib (if using a self tacker?
The rack needs to be a few cm's lower than the line through the cleat to the last turning block.