Build of E5 number 6 (i think)

[phil_kirk]

John's E5 is coming on.  On the 20th we built a new pole and finished the internals of the hull on the 20th.  With snow outside it was difficult to keep the garge warm enough for the resin.  In the end we had to concentrate on warnming a smaller volume to achieve a good curing temperature by constructing a tent over the boat with polyethene sheeting.

the next day we got the pole off the mandrel using a tried and tested tug of war method with the pole/mandrel tied between too cars..  Attempt no. 1 had an unusual result that I manged to pull Nichola's car through the snow.  Swapping over and letting nichola pull resulted in a successful extraction.

We then bonded the deck on.

All went well. 

I'm sure that John's christmas will be filled with lots of sanding and fairing.

[john_hamilton]

Also we ordered deck hardware from Allen through Roland, which came the day after it was ordered, hence I have managed to get the gantry system done and dusted, just waiting for a spindle for twist grip, which will be made in college forge after term starts 

[john_hamilton]

does anyone know a ballpark figure for shrouds, caps, d2s, etc....?

[roland_trim]

Depends entirely on your mast and terminal choice.

If ordering an aussi mast I think it is generally suggested to get them to send the T's - then it is up to your local chandler for rates or call Welsh Harp (they and many others will make shrouds to the length of your choosing).

If you want basement prices then there is always the DIY method offered by BGM. The wire itself costs under £1 per m (I'm sure it is nearer 30p a m, but can't find the last receipt for stainless) and the terminations (eye and ferrel) are about 50p per end. We have no inclination to do T's though as that needs a bigger press (nasty holes in mast precious).

[john_hamilton]

have PM'd you roland.

now  i have been fairly bored recently and have been looking through various skiff sailing books and have found that the optimum jib/main ratio is around 27/73, which equates to around 4.2m2/11.3m2 on a cherub. what has everyone else got?

[douglas_hassell]

I was looking at the I14 website and interested that they go for a 'W' jib track to enable a jib overlap.  I presume this would mean a larger jib than usual?

Doug

[Stuberry]

now  i have been fairly bored recently and have been looking through various skiff sailing books and have found that the optimum jib/main ratio is around 27/73, which equates to around 4.2m2/11.3m2 on a cherub.

Interesting, where did you read that? I think Kevin believe's in something a bit more weighted towards the jib because it gives a better drive/heel ratio. However, a bigger main gives a better drive/drag ratio. So the optimum depends on how heavy you are and how much wind you're sailing in. 

[Ben Howett]

now  i have been fairly bored recently and have been looking through various skiff sailing books and have found that the optimum jib/main ratio is around 27/73, which equates to around 4.2m2/11.3m2 on a cherub.

Interesting, where did you read that? I think Kevin believe's in something a bit more weighted towards the jib because it gives a better drive/heel ratio. However, a bigger main gives a better drive/drag ratio. So the optimum depends on how heavy you are and how much wind you're sailing in.  

Kevin and Stu are on the right track - Theres not really any optimum ratio untill you start to factor in average wind stengths, crew weights etc... Ive no idea what the general trend is in the class but Ive got a feeling that would leave you on the far end with an unusualy small jib/large main.

Doug - the W jib track is very neat and does give you room for a slightly larger jib - but its not a huge difference. Phil has a W track on Pocket rocket and may be along to comment on exactly how much you can gain that way.

[john_hamilton]

Stu I was reading frank.bethwaites most recent book, those.numbers are based on a light-crewed 12 do I thought it may be similar x

[andy_paterson]

Ratio also depends on the total sail area -
With a small sail area ( ie 97 rules ) it was better to have a big main and small jib ( shiny beast was only 3m² jib, + so had a bigger mainsail than everyone else ) more like 25:75.
The 05 rules allowed much more sail, but putting all the extra area on the main was not a good idea, hence a lot of track moving, adding big jib roaches etc to try and get the jib bigger, and keep the main at a managable size.  I believe that the newer boats (built rather than converted to the new rules ) have masts further aft, ~ 5.5m² jibs, and the rigs are slightly undersize ( by ~ 0.5m² )   so about 35:65

[JimC]

the W jib track is very neat and does give you room for a slightly larger jib -

First W track I ever saw was on Tim Dean's Fizzy Shark, think that was long before any 14s... The trouble with paying too much attention to Bethwaite's recomended ratio is that its for a boat with unrestricted mast height. The very aggressive mast height limit in the 2005 rules means you have a lot of tradeoffs to make.

[Stuberry]

I think quite a lot of thought was put in to a W track on Shiney Beast. IIRC the conclusion was that the track has a minimum radius that the car can get around and with the length of the track on Cherubs it ends up with a bit of a flat spot in the middle rather than a full on W.

Perhaps the next step is to find a traveller car system that can cope with smaller radius turns?

[Phil Alderson]

I put a W track on Pocket Rocket, and it works OK, it gets the track about level with the mast, the trouble is that it is a very tight bend radius for the track so they often break them when they are bending them, and they end up slightly notchie.

I have thought about making a track out of a carbon tube moulded to the right shape, and then run a block along the track.
Not sure of the best mould material.

[phil_kirk]

E-Numbers Jib came in at about 4.7m^2.  We weren't to fussed about reaching maximum area so didn't go for a huge roach on the jib.  The overlap is enough for the top jib baten to get caught on the mast in light airs escpecially when sailing downwind when there is little pressure in the jib. As has been said above there are a lot of trade offs.  Our main is only about 10m^2. We opted to go for an efficient shape instead of the max area. For our weight this has proved to be pleanty of power across the wind range. More area in the main requires longer battens and most of the area ends up higher up in the sail.  Controling that area in a balance of mast tip stiffness, sail shape and cap shroud tension with the addition of cunnigham on the water. There are a number of examples where too much main sail roach or a poor match between mast and sail has led to too a rig that doens't work.

Our approach was to rig the boat with the correct rake and mast bend and ask the sail maker to make a set of sails to fit. if you give your sailmaker a clear direction on how you would like to trade off between power, efficiency, weight, ease of use height of boom, he will be able to give you a better set of sails.

[roland_trim]

Allen quote 1.5m radius as OK for their larger track (it may be 1.15 as my handwriting is poor). You can go smaller with their 29er version. Although both o these have balls.

If bending about one axis only (i.e a W in one plane) then the track method we used would be simple, cheap and light.

Cut the track shape you want into a piece of 4x2 wood. Screw this to a sheet of ply. Cover with parcel tape. Vac a few layers of carbon over the top. Demold your z sectioned w and attach to boat. Bolt track hole by hole onto your chosen shape.

Allen tracks/car is about 55GBP + vat