My Cherub Design

[Neil C.]

What amazes me is that nobody has tried it on a Cherub before now. Foiling Moths have been around for years but there has never been a fully foiling Cherub. Whether or not you think it would be a Good Thing is another question of course.

[roland_trim]

The rule "NO FULLY FOILING BOATS" at chew has restricted our efforts in that direction :-)

[JP233]

The rule "NO FULLY FOILING BOATS" at chew has restricted our efforts in that direction :-)

Come to Draycote then

[JP233]

Thanks for all of you input so far.

Phil A, 'Another thing to consider is space to put the kite.' i have looked at the ovi aura skiff from the womens olympic skiff, my thinking is that a 3patch kite would fit in the boat, IF ANYONE KNOWS THE LENGTH OF A KITE SOCK, PLEASE CAN THEY SEND IT TO ME

'it is often worth changing one thing at a time. So if you have a radical hull, and radical rig, and radical foils' i did try and do a 'safe' design, but got told it needs to be much more unique, i agree with your point, it is my usual mantra, but for this project it’s not allowed.

Phil K, come to Draycote with a GPS and we can do some testing.

Neil C, there is the R Class skiff, (basically a 12fter with moth foils) https://www.youtube.com/user/RClassDotOrg?feature=watch
IMO, the R class is too big of a boat to foil, the hull with wings is 29kgs (what's a Cherub bare hull?) but it is too tall, and deep, could just be me though.

Thanks
Jamie

[roland_trim]

Jamie, Will we be looking forward to having more of this conversation at Weston?
 Would be a good subject whilst the wetsuits are drying in the sun and the BBQ is warming up.

[BenR]

The r-class custom made their own foils. The first ones were over 1.5 metres wide! much bigger than Moth foils. There are now about 6 of them foiling and because of this, I understand the cost of joining the class and being competitive has gone up by one pair of foils and a control system. (not an inconsiderable amount as you know from moths)

According to the rules, the Cherub minimum hull weight is 50kg (with all fixed fittings). Although as the r-class guys show, you can make a 12ft hull a lot lighter than this but in order to race as a cherub, you will need to have enough lead to bring this up to the correct weight. Your rig will weigh between 15 and 20kg bringing an all up sailing weight of about 70kg.

So 70kg + 2 people ~ 200kg  if you are kind about the people. Typical upwind speeds are about 9-10kts when fully powered up. Generating this much lift at these speeds is pretty tricky. You will probably need to make your own custom foils too as there isn't going to be anything off the shelf. These will either be very expensive (if someone else does it for you) or maybe you have the kit to make your own, accurately.

Does the 49er have a wand system? Whenever they seem to be going well, the front foil looks like it ventilates and the nose instantly drops.

Cherub kite socks go fairly well down the boat, mine is about 3m i think give or take for a 3 patch kite. The feedback from the rclass guys is that they use a smaller kite when they are foiling as the apparent wind will have more of an effect and you can therefore get away with a shorter pole too.

As a Mothy you probably enjoy the smooth quietness of foiling but a lot of us like the wet and wild contact with the water you get from cherub sailing. They may not be the fastest round a course but they are sure as hell one of the most fun.

I look forward to see how you get on. I hope you manage it as I have thought about it myself a fair bit but not had the time to put any serious work into it.

[JP233]

BS, yeah possible, although it will be near the end of the unit, it depends on if i can get a boat/crew/money/time out travel. we will have to see.

Ben, Thanks for the info, these some good bits i can put in the 'research development' so i can score some more points
im not sure i cant find a lot of reliable info on the foiling 49er
Thanks for the sock length, much apreciated
'As a Mothy you probably enjoy the smooth quietness of foiling but a lot of us like the wet and wild contact with the water you get from cherub sailing. They may not be the fastest round a course but they are sure as hell one of the most fun'
you havent seen me sail have you...

Thanks
Jamie

[JP233]

Should have put these up before... Ooops
The first pic is basically A+E. This is the hull Clive kindly sent me.
The second picture is my version of her.

[JP233]

Here is my version

[Banshee Ambulance]

Bow thing is fashion, not sure it is applicable to such a short boat - Cherub rules have a 200mm vertical bow thing going on...

GEEK BABBLE
If your 3D printer is a MakerBot Replicator 2 then I'd suggest:
- Use ReplicatorG (from replicat.org) to generate your G-code, works better than the MakerBot programme and appears to gives a better logic to the print (especially for circles).
- Use the "print bed" option for anything that is even near big (any dimension more than 1/2 bed size)
- Replace the feed straw with one  about 3 inches longer.
- Look to buy the feed kit ($10) to replace the plunger.

Are you playing with 3D printers? I am going to a lecture by the chap behind rep-rap tomorrow. I will let you know if I find out anything interesting.

[phil_kirk]

E-Number's sock is 2.6m from the bow and 2.3m from the shute and we can get a 2 patch kite into it if the head and tack stick out by 0.3m.  Our kite used to be three patch but was harder to hoist.

Your wave peircing bow concept works if you don't want full sail area but you can still race in 05 rules if you have less than max sail area. Many boats do.

[Clive Everest]

You can always get the area back up by making the boom longer or by going back to a non self tacking, overlapping jib.
We seriously considered this so that the jib tack could be put on top of the kite hoop making hoists and drops much easier.

Is there any chance of this boat being built or is it just a design exercise?

Clive

[roland_trim]

Normal jib at the weekend was a dream. Am seriously considering it for the one in the shed....

[JP233]

BA, yeah, i went to a talk about them on tuesday, i think rep-rap was there, but we left before his lecture.

PK, thank you. True, i hadnt thought about 05 rules, i will have to see. i quite like the square top jib idea

Coxon says the theory for the square-head jib is the same as for the square-top main: It twists out at the head in a gust to de-power instead of relying on mast bend. “In the past you had to ease jib sheet to depower the jib. With the square-top the crew should not have to move the jib sheet as much.”

taken from http://www.mysailing.com.au/news/square-top-jibs-and-other-sail-innovations
This way you can have a big jib and big main, but you would need a prodder, as seen on moths to push the fore-stay forward, would this fit in the class rules?

Clive, its just a design exercise unfortunately, maybe some day when im older it could be built, but the model will be pretty big, just under a meter, with foils, hopefully a full rig!

BS, its tempting, but then gybes become a pain, and light wind tacking, would an inverted jib track work so you can keep the self tacker?

[roland_trim]

but then gybes become a pain

Actually we find the opposite with the gybes.
Next time you are anywhere near BS look at the jib. If you put the clew on the forestay the sheet is very tight between the cleats with the knot to the mainsheet midships. This means you can sheet in on either tack by pulling on the same bit of main.

For the gybe you simply uncleat on the way in and re-cleat when you are on the other side. Uncleated the short jib sheets mean it sets from one side to the other very nicely.

All that said - I am buying a self taker for the next boat...