UK-Cherub Forum
Cherub Chat => Tech Chat => Topic started by: phil_kirk on March 14, 2012, 08:00:51 PM
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I noticed that marmite had a plastic or nylon insert in the snout tube which i assume is to provide a low friction surface to help the pole go in and out better. What is it Paul and where did you get it?
if anyone else has any suggestions of obtainable low friction tubes or materials that can be stuck on but wont fall off i would be very interested.
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Helicopter tape always worked well for us in the SB3... I'll try and find out where i got it from, we haven't had to replace it in ages!
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I've used Delrin for a lot of yachty things, Not sure how easy it is to get, but its really good for sheaves, bearings etc. I reckon it would make a pretty good pole slider..
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Nylon kitchen chopping boards also work, just cut to the required size. A little heat can help bend to fit.
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Rich Taylor turned some beautiful delrin bearings foe the Deamons.
On Atum and Antidote we used lots of silicone spray and made sure the surfaces were really smooth. Might have used PTFE paper from Tim Unerman for the bottom aft bit.
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Tim kindly gave me some of the PTFE paper but I find that it wears when the pole is possibly partly loaded and I am replacing the paper ocasionally. It coul be that I need to realign the snout and inboard pole support a bit better.
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I now own the Subtle Knife, one of the Deamons.
I do not think that it has been used that much in its 4 year life but the turned delrin bearings are very badly scored, to the point that it could easily be getting fine Hayling sand trapped in the scoring and pressed into the delrin - not good.
I think that Delrin and Nylon are both too soft and that a harder low friction bearing material is needed.
If I was doing a new boat, as I hope too next winter I would use something like an Igus plain bearing:
http://www.igus.co.uk/iPro/iPro_02_0001_0000_GBen.htm?c=gb&l=en (http://www.igus.co.uk/iPro/iPro_02_0001_0000_GBen.htm?c=gb&l=en)
The materials they use are much harder than delrin or Nylon and specifically designed for bearings.
They even have materials designed for wet environments.
They are available in 5mm increments of diameter. I am not sure how what your pole diameter is but their 75mm bearing cost £10 each if you buy 5 off. They can be purchased on line.
Clive
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ill pitch in to buy something with you phil, im in the same boat as you....chortle chortle
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Thanks Clive and John,
I will measure my pole and snout diameters.
I probably need something very similar for the inboard end pole support.
A pack of 5 between 3 of us would be cost effective and give us a come in handy spare or two.
As you know no cherub is the same but they are all quite similar!
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well my pole and snout are carbon copies (the puns keep getting better) of yours phil, so whatever you need, i do too
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Well the inside diameter of my snout is 66mm. However i don't think i can allow for the thickness of the bearing without sacrificing some length of pole out of the boat. So to incorporate the bearing i need to make a slightly larger diameter snout.
John your pole was a bit longer than mine so I expect that your snout will be a couple of mm larger in diameter than mine to allow for the larger diameter of pole at the snout.
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oh ok, ill have a look, its not like my kite flies brilliantly anyway, so i can prob still keep to the same order as you :/
and i was thinking of sandwich wrapping the bearing and doing a single skin of carbon round it, flopping this off, building it up appropriately, attaching to boat, then put in bearing, just so i don't get any resin on it. i dont have any idea regarding the inboard end though
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Thanks for the link.
I think I'm going to use one of these on Madge new snout.
Will let you knew how it goes
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do you want to buy with us for discount?
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I'm likely going to to get two tubes. Outer longer tube to build the snout around then a short insert for the outboard section to deal with the taper.
As I'm building from scratch I have a bit more freedom on length and diameter than you guys do.
Will let you know what dimensions I'm looking at once I get the pole unwrapped in few days after it finished curing in the hot aile at work.
I will keep you posted.
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Right so I have now measured the pole.
S the diameters look like follows.
2.9m -- 7.98
2.8m -- 7.92
2.7m -- 7.70
2.6m -- 7.57
2.5m -- 7.38
2.4m -- 7.19
2.3m -- 7.00
2.0m -- 6.49
0.0m -- 3.91
So I'm Thinking of getting one tube with an ID of 80mm and a length of 60mm. And then a second tube of ID of 75mm to pad out the outer end. To deal with the taper. Thoughts on this?
Once I get the tube I will build out some carbon around them before I put them into the bow.
Having unwrapped the pole I have a total weight of 2.17kgs for the 3m tube.
Our cloth/resin breakdown before the build is as follows.
Cloth 1.05kg
Resin 1.254kg
So it came out very nicely.
Nick
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mine is 70mm at the launch tube
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mine is 70mm at the launch tube
That's nothing to shout about mate. Hayley says she's not impressed.
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Sorta related, I'm in the habit of using offcuts of kevlar in laminates in high wear places. On the sliding seat on the Canoe it seems to be wearing to a very high polish (too high actually which is embarrassing in that application) and I reckon its much longer lasting than carbon. The surface is smooth: it hasn't gone fuzzy like a sanded kevlar surface does.
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mine is 70mm at the launch tube
That's nothing to shout about mate. Hayley says she's not impressed.
she must be incredibly hard to impress then, fair play Mr trim
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I have incredibly high standards ;D
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jimc,
ill try that kevlar on the inboard pole rest, cheers!
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ill try that kevlar on the inboard pole rest, cheers!
Don't forget you'll need to mould a polished bearing surface because you won't succeed in sanding a kevlar surface smooth unless you are a lot cleverer than me (not that big a challenge). At a guess some graphite powder in the resin at the surface will do no harm at all either...
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what would the graphite do?, i was thinking of taking an impression from my pole,l then making a male mould for the kevlar bearing surface from that with something cheap that can be polished up
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Crikey you lot put me to shame. My insert fell out about 2 seasons ago, its on my desk here at work, should I bother putting it back in ?
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what would the graphite do?, i was thinking of taking an impression from my pole,l then making a male mould for the kevlar bearing surface from that with something cheap that can be polished up
Graphite powder in an epoxy mix seems to leave a low friction surface, that also wears OK. I am not sure the mechanism but it seems to work. I have not tried the kevlar bearing surface.
Careful application of parcel tape to your pole will give a smooth surface, assuming the pole is fair.
There will always be some pole behind the support so molding the loop on the pole further down than the final position will give a bit of slack.
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I have just machined a new jib turret for Banshee Ambulance out of Acetal. It seems to be a nice material to work with and gives a nice surface finish.
I dont currently have any inserts in the bow tube. We had a pole let go at the bow where the point loads are last year. I am wondering if inserts to match the pole taper may help stop this happening again?
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yeh, i wish i could order some tapered ones without it being too expensive, i dont want to aftermarket machine taper into ones that ive bought for alot of cash, especially since the bank of dad has folded in the current economic climate!
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Having a tapered pole support, with increasing flexibility towards the end of the support will be best. However with a tapered pole if you don't get it fully out then it won't fit the pole inserts properly and you get a point load.
if your pole is designed and constructed with a safety factor low enough for this to be critical then I suspect it won't last long in use.
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I would not recommend doing that - it suggests a tight fit at full extension. This may stick when the pole is out. Even if it does not, you are vulnerable to a single sand grain getting in there.
~5mm of space sorts that problem out, but leaves you with the point load issue. This can be minimised by flaring the inside (very slightly) and by increasing the distance between the front and back supports. I think we were at 340mm for this distance.
Lots of hoop fibres in the last ~400mm of pole is probably the major requirement though.
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Even if it does not, you are vulnerable to a single sand grain getting in there.
Thinking aloud I suppose what one really wants is a bearing surface that exactly matches the pole on say 40% of the diameter which takes the load, and a fair degree of play on the rest of the surface... So on the fore end like the attached, at the aft end the same but inverted. I suppose it wouldn't be totally impossible with generous amounts of parcel tape... Or is there some obvious drawback I've completely missed?
Not something I anticipate having to worry about in the forseeable future though.
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it seems you cannot order from the company discussed on the first page, without proving you are a business or reseller :/