UK-Cherub Forum
Cherub Chat => Tech Chat => Topic started by: Banshee Ambulance on April 25, 2009, 09:24:00 PM
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Outline plans: As much as I my love current boat, my mind keeps wandering when i'm at the sailing club. Don't take this the wrong way (I dint think anyone to thing that I have ideas above my station/all talk no chance of action etc.) but the idea of building my own boat keeps springing to mind. Im sure it is not a real possibility or though it may be depending on job and thus pay! So, here it goes.
Imagine a banshee, make it a little wider at the back (to increase stability), then add r class L3 style spray rails half way up the sides (again to increase stability by adding reserve buoyancy when heeling and to improve downwind wake profile), add a deep cockpit (so it sits lower in the water when capsized and so the boom can be lowered and thus lower the center of effort) and add a concave for deck ( partly because it looks cool and partly to give the crew somewhere to sit in the light stuff) and thats what I'm thinking.
If anyone has any thought this please get in touch, although, no rush as it is very much an intellectual exercise for the time being.
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Congratulations, you have caught the bug, I think most cherubers think about designing and building their own boat, it is part of the fun. You will get there in the end.
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The current trend is to be as narrow as the chine rule allows.
You need some freeboard to avoid spray hitting the racks and your feet so the deeper cockpit would provide that if you increased it with a deeper hull. The self draining floor needs a good slope so it will drain in light airs when the boat is trimmed forward.
The other current trend is to keep the bow angle of entry narrow and push maximum beam aft.
Making the boat easier to sail will make it quicker round the course so ideas for increasing stability and crew space are positive. Understanding the trade offs against outright speed is the key. It is possible to make the boat technically slower but easier to sail at 100% but knowing if this would be quicker than a really fast boat that is difficult to sail at 90%.
A build takes a lot of time but is very rewarding.
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Between revision I have found the time to start doodling. Cant work out how to put the spray rails in at this stage though and don't really have the time to learn. Anyway, here is my first attempt:
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Any pics of the underside?
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That's pretty cool for a first go. I know that I go through many iterations when I'm designing before I'm near happy. Are you keeping an eye on the wetted surface area and hull drag? I'm sure the program you're using can produce this information.
Why would you want to make the back of the hull bigger than a Banshee as it is already 880mm at the transom? I would avoid spray rails if you want to add reserve buoyancy as; they make construction difficult hence either a heavy or weak hull, spray rails are only marginally beneficial in a narrow range of conditions and the rest of the time they are slowing you down. One thing you really don't want is a big brake coming onto play as the bow starts sniffing. Any reserve buoyancy when heeled or otherwise needs to be progressive and this is best achieved using topside angle and curvature. If you have trouble with the cockpit draining too fast don't have an open transom.
To add to Phil K. you will find that a quick boat (around the race track) is an easy to sail boat or the crew are gods. For us mere mortals applying the KISS principle (keep it simple stupid) is a must.
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The spray rails will be about half way up the topsides (which are quite high as it is) so will be out of the water most of the time anyway. I guess they could be seen as a bit of a gimmick but don't think they will do any harm/add too much weight.
As for making the boat wider at the back, this is a to make it a little more stable and also give more buoyancy further back. This should make it a little less frustrating/more comfortable in a drifter (probably no faster).
As for transom arrangements: " Proper " transom to take wings but with false floor so self draining.
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In the light airs you will want to trim the boat forward and heel to leeward to reduce wetted surface area and lift the transom. Therfore the transom will not provide much stability in this mode and may make the boat more sticky in light winds.
Obviously hull design is a matter of ballancing various aspects of the design against each other and ensuring that it sails well over the intended wind range and speed range.
Designs intended for 97 rules were different from those now designed to the 2005 rules. The thought being (if i am right) that a twin wiring 2005 rules boat can develope more power across the wind range and will plane earlier than a single wire 97 rules boat. The 2005 rules boat can therefore tolerate the lighter conditions a bit better and so are optimised a bit more towards the top end of the speed range.
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The spray rails will be about half way up the topsides (which are quite high as it is) so will be out of the water most of the time anyway. I guess they could be seen as a bit of a gimmick but don't think they will do any harm/add too much weight.
As for making the boat wider at the back, this is a to make it a little more stable and also give more buoyancy further back. This should make it a little less frustrating/more comfortable in a drifter (probably no faster).
As for transom arrangements: " Proper " transom to take wings but with false floor so self draining.
Making things more comfortable in a drifter has more to do with freeboard and false floor height. As Phil has said you will be sailing in 4th? mode ie crew up the front, heeled and lifting the transom. If you design a boat with a false floor like the E5's ( curved ) it makes for a lot of crouching. If you design a boat with a false floor and half deck ( or foredeck ) like my Banshee and Loco. The crew has somewhere to sit. The helm simply traps on the racks in front of the mast and the crew balances him by sitting on the half deck.
As for a full transom to stop the water draining out quickly. This is what Ben and myself did with Loco and it was a nightmare. The considerable amounts of water sloshing around that couldn't escape basically made the boat very unstable after a capsize. It was also a ***** to get upright. As you got so far and then you were working against a ton of water. Then when you got in it, it all came rushing across the other side! We cut much bigger holes in the transom.
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The transom is more there to give a simple way of mounting the rear wings. There will be more substantial drain holes than in loco perro. I think the best way to visualize it is to think of you're banshee ambulance but with a fore deck (like aqua but concave) and a transom similar to loco, with spray rails half way up the topsides as the foiling L3 R-Class.
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I think that the ergonomics and construction efficiency of the hull is at least as important as the shape of the hull, a boat that is aqward to sail will make getting around the course quickly difficult.
If the spinnaker runs under the foredeck then it will either increase the freeboard or force the false floor down, there needs to be quite a lot of space for the spinnaker to go through.
I quite like the idea of having a high false floor like Antidote but with the spiniker running in a trough under the deck, keeping the cockpit really clear, althoug this goes against the goal of keeping the construction as simple as possible, if it does not make the boat faster then it should not be there.
When I changed Primal from the false floor below the inner gunnals to one level with the gunnals I found the boat much easier to sail, I could balance on the edge of the hull better when going into tacks.
If you are thinking of building then try and get sailing on as many different types of boat as you can and take the best bits from all of them.
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In my boat, I really like the 'side decks' they're wide enough to stand on, trapeze from, sit on... and they go in front of the mast so it makes navigating the play pen that bit easier. Plus, you can sit/squat to windward from there and walk about if you need to. Will see if I have a pic somewhere...
(http://www.sailingsource.com/cherub/test/lib/exe/fetch.php/boats/2694-20070303b.jpg?cache=&w=360&h=480)
(http://www.sailingsource.com/cherub/test/lib/exe/fetch.php/boats/2693-20070130c.jpg?cache=&w=900&h=675)
Rich later put on pro grip down the edges, and I have since removed the pro grip and done a full coating of hi-build so it is incredibly grippy everywhere now. (at the expense of skin!)
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a plan is forming:
1) sell Flat Stanley
2) buy carbon mast penultimate 14
3) sail penultimate 14 lots
3)b BUY HARDLY SLUGGISH
4) build hardly sluggish hull (like the deamon but with fore deck and transom.
5) put the two together
5)b Replace mast and sails with something more appropriate when finances allow.
Is this sensible?
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Yes, but not until after the Nationals. This will give you 7 months to build the new boat after the end of this season to be ready for next seasons events. Coming to the Nationals will be invaluable, and you will be able to sail lots of different boats and speak to lots of people so you will have a better idea of what you want to achieve with your new build. That's my tuppence worth anyway!
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I would love to come to the nationals but lack of vehicle and un-roadworthy trailer make it a little difficult. I am around as far as I know so maybe I could weld up a new trailer but the law has changed on that recently. mmm
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I would heartily recommend buying a boat that you can practise getting sticky on as the intermediate step. Ideally this would be glass/carbon and with stuff you do to it - snout, kick bars, tail pipes, t-foil give a huge ammount of knowledge for the actual build itself. This is what we did with Born Slippy and the Kirk's with Slippery When Wet (although the new boats are not yet proof that this results in finished boats).
As a benefit you can also sail the Cherub, monster and have an absolute giggle. Peni's always seem to suck away the cash and still remain uncompetitive in the meanwhile.
The Kirks prove that a dog in the right hands is still on the pace (although less said for us in a slug). I'm guessing that both of us will have to part with our boats post nationals and I'd highly reccomend racing stanley this year and keeping in touch with the potential boats out there that are goign to come up for sale.
<<Declaration of interest - I may have to selll my boat in the near future when the one in the shop is ready, but I think I already have the next home for her arranged>>
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I would love to come to the nationals but lack of vehicle and un-roadworthy trailer make it a little difficult. I am around as far as I know so maybe I could weld up a new trailer but the law has changed on that recently. mmm
No trailer and no car should not be a bar to getting to the nationals.
PM me in a few weeks if you are still short of suitable wheel options, but for now I'd suggest you reply to the "How do I get to the nationals thread".
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I would love to come to the nationals but lack of vehicle and un-roadworthy trailer make it a little difficult. I am around as far as I know so maybe I could weld up a new trailer but the law has changed on that recently. mmm
New laws?! Interesting! I think I will not research this so I can act oblivious if and when I get stopped by Mr Plod!
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Don't go thinking any problem of the trailer/getting there/need a tent/need a crew/need an object nature need be an obstacle.
Ask on this forum, don't be too feeble, and we will find a way to get you there.
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Don't go thinking any problem of the trailer/getting there/need a tent/need a crew/need an object nature need be an obstacle.
I must have done at least 8 or 9 championships beg stealing and borrowing lifts when I only had a bike license...
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Obviously the above offers apply to you Jim as well! It would be great to see Queenie. In recent years there have been old boats aplenty - Peanuts in 2006 was the oldest I think. In 2007 it was Plan Jane and in 2008 No Sweat I think.
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The thing about buying a second hand boat is that i would be looking at a budget of £2000. I would be prepared to spend more on a build for the fun of actually doing it. Monkey Magic is a little to odd looking and more importantly too expensive and I cant see anything else that would suit.
On the nationals, I would love to come and hopefully I can sort something out.
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We will be parting with Slippery shortly. if you are interested we would preffer the boat to get use and not sit in a boat park somewhere.
What we have found is that reduced crew weight (we are about 120kgs) will compensate for the reduced sail area. We still find it exciting and a bit challenging in a blow.
For fleet racing it would obviously help having more power and a mast extension would allow more main area and a big kite.
if we were not building a new boat we would look at replacing the gantry and fitting a t foil. There is room for some weight reduction there and the t foil would add a bit of upwind speed.
We went down the new boat route because i wanted to see how we could perform on a level playing field and without the excuse of an older boat for when we get it wrong.
Good starts, going the right direction for tides and shifts will count for a lot.
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The Flying Kipper is also for sale at the moment, it has a mast to the 7.1m limit and can take a larger kite which I do have. Also with a longer boom the 05 main that I have would fit.
I have a lot of fun with the boat in 97 rules mode and it makes a great learning platform
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Can you clever boat designers offer any comments?
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Monkey is £2k now!
If you are concerned about the looks (or any other aspect), why not have a trial sail?
W
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I am thinking more about Taking Liberties actually. Seems more of a project boat which would do me nicely. My own designs are more just a bit of fun at this stage. Although I think if I were to buy Monkey Magic it would have to be re named "Thunderbird IV" because it does look bonkers.
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For the money, Monkey Magic really is excellent. Even for £3000 its still very good VFM.
It has a basically brand new set of 2005 rules sails, a nice C-Tech rig and the hull is obviously newly refurbished so everything should be hunky dorey. It's a bistro hull shape so easy to sail and if you were to design and build a new hull, you could just transfer the rig and sails straight onto it and you would have a very similar setup to that of Dans boat or Subtle Knife.
Taking Liberties is my old boat so I obviously have a soft spot for it too
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If your going to upgrade I'll FS back!
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If your going to upgrade I'll FS back!
SWAP SWAP SWAP! One of you gets a project boat, the other gets his old friend back
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Yea, I'll swap!