Rolf, at 40 I was invincible, at 50 it was oooh things are not the same as at 40, at 54 I'm worried about the speed of the rate of that change. You will notice a real differnce beteen 40 and 50's, I certainly have. Still trying to keep fit and enjoy the wilder side of life, sadly given up endurance motorcycle racing after finding the rate of recovery from injuries was affecting my work hours but do a bit of Mtbing, ski ing and now beginning to get to grips with http://www.lenzsport.com/gallery_focus_ski.php?gallID=12. Here is Bitsa 4 http://www.skibike.me.uk/2011_04_01_archive.html scroll down to the 15th April.

Oh the Auscat Flyer 4s is listed as having 0.1 sqm of board area in the SCHRS listings, I think mine has even less as it has had the boards changed to high aspect ratio boards. mmmm.

Thanks Wayne!
I felt invincible and immortal in my 20s. In my 40tieth year I know I am very much mortal and subject to stresses of all kinds.
Guy who taught me mountaineering/climbing was in his 70s back then. 20 years later he is telling me that he is beginning to feel the age. Still active in off-piste skiing, climbing and ocean swimming through his 80s. Similar quotes from others with more experience who still are motivated and active give me hope Avoiding flab and retaining max strength seems to be the key?

Snowbiking!! Now why is that more fun than skiing or snowboarding?? I mostly go backcountry with my snowboard and I have a problem seeing myself enjoy the ride down again on a snowbike

A-cat sail area incl mast is ~13.94m2 with 0.1m2 of board area in total?
Higher AR should increase efficiency but some area is still needed. Would be very interesting to have some numbers on this.

At 40 I could diet moderately, do some walking, lift a few weights and see an immediate result.

From 60-62 I was not able to gain any measurable strength after a quick modest gain. No amount of work produced a weight loss. Only severe caloric restriction produced any weigh loss at all. Frankly, I'd rather be fat than give up cookies and milk.

Cheers!

I believe diet is the key to 90% of staying well as time passes. Diet is however a very controversial topic. It is so personal to many people and there is no best practice. Choose your poison

Working out for sure helps this tender 40 year old.

Snowbiking came about for very different reasons. Two of my friends could no longer come sking with us due to a damaged knee and the other a car accident damaging his tibia and knee joint. Ski biking gives them an opportunity to join in with the fun and so we all decided to learn together. I've been skiing for a very long time so was quite keen to give it a go. After 6 days we were competant enough to tackle most slopes, the learning rate was quite fast.

yep, better live happy and short than long and sad

Rolf,

basicaly board area depends on two factors:
* avoid stalling at low speeds (e.g. being manouvrable at the start line)
* avoid cavitation at high speed
Both depends on the force which the rudder or board has to produce. The force depends on the boat balance and leeward force from the sails. The leeward (or better sideslip) force of the sails depends on their efficiency and the righting moment of the boat. Since a A-cat has a higher mast and a more narrow platform the sideforces are considerable less (especially compared to a double handed F16). I know this from my boat: The board size is just fine double handed, single handed up-wind it is a bit too much so I can drop the traveller a bit to get a more reasonable sail angle of attack. It may be a bit cryptic what I say, so don't hesitate to ask if you want to know more details.
The foil which I posted here some time ago was for the Tornado (which is now history , like us human beings, boats don't get fitter with age...), where we had high speed cavitation problems (I am really not wondering, even todays Tornado rudder look like F104 sections for me, you know the aircraft they called a rocket with wings). Maybe you want to go with a bit more low speed focused section. Again, don't hesitate to ask. I have started a small report about foil design for boats, which I want to finish a publish hopefully soon.

Foil planform is as important as the section, but much simpler. You can go with all those fancy shaped boards, we have seen, but you can achieve the same with a simple trapez. You can achieve it even with a rectangular shape with some forward sweep, if you dare to do something others don't do. The basic idea is to have an elliptic shape. You can do this with an elliptic planform or with a trapez with a 0.4 chord ratio and zero sweep at 25% chord. If possible from a structural point of view, the rudder should have the same depth as the board. Don't stick too much about aspect ratio, absolut depth (draught) is more important than aspect ratio and a larger rudder can have less drag than a small one.
I personally think that a homebuilder can make a good foil only with a simple trapez planform, because the surface of the foil is only single curved (unless you have a buddy who has a CNC machine). Already a small change in thickness distribution will ruine the hydrodynamics (1% percent change in thickness has lot of effects, 1% is equal to 1mm on a board with 100mm chord).

Cheers,

Klaus

Wayne,

that makes perfect sense. Creative way to continue enjoying downhill skiing!


Klaus,

thanks for writing up that info.
I always thought the ideal was to have ellipitcal pressure distribution over the foil, not neccesarily to have an elliptical foil. Reading what you wrote I think that is still valid.
Doing anything but a parallell sided rectangular foil is prone to errors without a CNC. I found this link which looks like my best shot with no CNC. Especially as a good friend offered to laser-cut templates on a CNC laser cutter.

http://www.duckworksmagazine.com/09/howto/foils/index.htm

Doing a cut after routing and then sanding/fairing before pulling off moulds is a real option. The same for rounding off the tip by hand at the bottom. Getting the proper section in that area will be hard. Dont know if the gains outweights the extra drag and loss of lift I will make with my unskilled hands.


I have done three sets of foils earlier by hand. Wood, plane and sand. Free hand.. None of them turned out really well. Partly becouse of design and partly becouse shaping wood by free hand is difficult.

Tornado rudders from Marstrøm was pretty good compared to my homebuilds. Yes, they did cavitate some times. Not a pretty sight when double trapeezing. I always thought the class overloaded the rudders with the mast rake. We sailed with less rake to overcome cavitation problems. They still happened, but not so often. Sheeting out a handful reattached flow.
I am really really surprised that you think the T rudders were designed for a speed much higher than obtainable by the T. With the amount of resources invested in producing a faster T around the course the foils is a very logical place to do research. The centerboards were of course very hard to optimize due to the class rules defining their planform.

When you mention forward sweep, you advocate installing the foil with a bit of forward sweep? Not seen that in a while
The idea is to produce elliptical pressure distribution or to delay ventilation? Cavitation should not be an issue with a daggerboard operating in turbulent flow under the hull?


Looking at the "state of the art" daggerboards in the F18 class, they have gone for higher AR and shorter chord. I think the Wildcat from Hobie have daggers with an 180mm chord! Effective length when fully down 1130mm. Pretty extreme compared to older designs and probably a handful on the starting line.

What I really would like is to buy something ready made with reasonable performance for a reasonable price
I have been unsuccessful in finding that and nobody is sending me plugs or moulds in the mail so it looks like I will have to shape something myself. A "good enough" planform that is easy to shape with a relatively robust profile (building in the garage, able to handle the starting line, tacks and jibes) with adequate lift and reasonable drag. Hmm, sounds like mission impossible..

I would be very grateful for any suggestions or help on this


PS: I definately would prefer to live long and happily!

What is your diet like?

The Zlin Z42 is the classical example of a rectangular wing with near to elliptic lift distribution. The benefit is to have only one sort of rib, instead for each section at different rib.

I would not take F18 as an example. Since the foil (and hull shape) is the only "unlimited" part of the boat, builder try to differentiate here, well I think that's why you put the quotes around it). At the end they have very different daggerboard and rudder length, so induced drag is not as good as one may think. I guess that shapewise A-cat (before c foils) is a better example.

Actually I think the foil looks like a section of a Mach 2 fighter aircraft from the sixties and hence totally unsuitable for a boat. They are very thin and pointy at the nose and this causes the early cavitation. I guess in the beginning without spi and single trapez it was fine, but once the boats got faster... My friend had an old (30y, Panthercraft I think) T. Later he bought some of this wood core rudders. Very beautiful, but as thin as the old once. So I didn't see evolution in the rudders.

I think I would ask a carpenter with a CNC machine to cut me the wooden core and laminate glass or carbon around it and sand and sand and sand... I don't have the talent to cut and carve it or cut and fill it (as in your link) by myself.
Other possibility, ask the carpenter to cut a female mold or cut your female mold from wax or foam with the hot wire method (not sure if it works for high aspect ratio). Or take an existing one and take a negative of it...
I don't like the female mold method because it is difficult to get a reasonable core or framework in the rudder. That's the reason why so many boards are heavy like stone, overcame the core weakness with extra skin thickness. If you have a wooden core you can go with glass and you are still lighter than many carbon boards.

From a structural point of view the ultimative boards are extruded aluminium: Topcat
You may ask the dealer for a price.

Cheers,

Klaus

Well Bitsa deservidly has been back on the water this year after quite a revamp. Back on with the A rig after the really unbalanced F16 low aspect rig created so much drag at the back, move the travellor foward to accomodate the much shorter foot giving me a chance to remove the gantry rudders at the back and go more conventional, fix the hole from the damage caused by the extra drag from the T foil / gantry, rejig the main sheet to a cascade system, and move the main sheet to the front.
http://imageshack.us/photo/my-images/401/bitsa006.jpg/

So a very different boat. With the A rig on Bitsa is very well behaved, with almost neutral helm with just a touch of Lee helm when the spinny is really loaded up. I do like these A Rigs and despite being only 14sqm it is just as fast as the 15sqm F16 rigs. The class is really missing a trick here as A rigs are available secondhand with the early masts being more than strong and stiff enough to cope with the spinny + the development of sails and masts will always mean a steady supply of S/hand and huge amounts of development

I do like the very foward position of the sheet for the single hander.
http://imageshack.us/photo/my-images/40/bitsa005.jpg/
Everything you do is facing foward out of the boat, and right where you want to be pulling from, out on the wire upwind your feet are locked on and if you pass the sheet foward of the rear stay, you can edge foward to the front beam.

I can only recommend the cascade system as being not only cheap to build, effective but buttery smooth.
http://imageshack.us/photo/my-images/507/bitsa004.jpg/

The new rudders have been good, maybe a bit old fashioned in aspect ratio but do the job. I do need to be careful as they can be pretty effective brakes if you turn them too much in a tack.
http://imageshack.us/photo/my-images/444/bitsa013.jpg/

So to sum up things then, yes I am pleased with the way the boat is beginning to shape up. In comparison to the new Nacra F16, it would seem pretty on par if not better upwind, just a fraction slower downwind and that I suspect is more the spinny rather than the boat. So no excuses, down to the skipper then

http://imageshack.us/photo/my-images/405/bitsa009.jpg/

Wayne,
She looks beautiful! What is the final blk with the cam cleat? I don't recognize it. At the rear you've got single/becket at the clew, a double at the traveller, what's inside the boom? What's the sheave inside the boom that turns the sheet forward? I like your simple rotation control arm. Thanks!

Dave

Dave, sorry I can't remember what the final block manufacturer, it was an Ebay special I bought some time ago for about £20.00 brand new, I think Lewmar springs to mind. Most of the blocks I use have been Holt Allen, great blocks at low low prices. The through deck block is http://www.force4.co.uk/ProductImages/088.jpg, Harken xxx although this is a really low tensioned line, these seem to last forever without really ever failing.

Inside the boom I have a 30mm at the front against the gooseneck and a 30mm with becket at the rear creating a 3:1. Not really sure whether this is a 12:1 or 9:1 you can discount the last block at the front as it has very little effect, but it is nice and easy on the forearms.

There are a number of do's and don'ts with cascade systems, they can be a bitch to set up to get maximum travel, but worth while.

The biggest don't is to make the rear boom block at the back fixed inside the boom. The mainsail with tension on can grip the boom and turn it just a few degrees beyond the best working angles causing alsorts of binding problems. I solved this by using a tie on block mounted onto the outhaul pulley, the tie on allows the block to always be at the best angle.

There is an interesting discussion on SA re the mid mounted sheets for A classes, lots of interesting litle nuggets of info there.

All excellent, thanks Wayne! I'll give SA a view.

Dave

Well a relatively interesting season racing at Datchet, without breakage. Despite my best efforts at knocking the main cleat out repeatidly and forgetting to release the downhaul, the A mast is still intact.

Another racer commented on just how flexible the top of the mast above the hounds was one night whilst racing, for me to realise that I had been both forgetting to release the downhaul and the mast rotation and having problems with the main jammer seizing open. Virtually every reason to break the mast.

Changed the mainsail as the sail I had clearly was not suiting both my porky frame and the older style stiffer mast I have and what a revelation. Very much now able to fly the hull from about 6 - 8 knots of wind and downhauling pretty hard now when into the 15 - 20's. Despite only 14msq in area, the high aspect and the years of design knowledge far surpass the F16 compliant sails I had been used to.

This really is something the class needs to address or should consider perhaps within its rules to help the solo sailor. In direct comparison to the equivalent sailor on a Nacra F16, Bitsa probably is faster upwind, something it shouldn't be and I put that down to the sail mast combination. I am very much a believer that we should be allowing the A mast and sail combo on single handed F16's. Cost is not the issue with there being very little difference in price between an equivalent F16 and an A carbon mast. The upside is all that free development that has taken place. On handicap terms it makes virtually no differnce with the higher aspect rating cancelling the 1 less sqm of sail.

Learning all the time and really starting to notice the angled dagger boards. Bitsa is probably too old fashioned in hull design and has too little volume, but at speed with both upwind and downwind, I need to move far less around the boat than I did with the Stealth and one would seem to be further foward in the boat. That could be due to a number of reasons such as the beam and COE is further back, certainly upwind I have to be nearly as far foward as the front beam to get the bow down and use the full water line length, which seems to get the boat into a nice groove, downwind its faster to stay off the wire and fly the hull going more downwind than to try and hot the boat up on the wire, again probably something to do with hull volume I would suspect. What is very evident though is that you cannot be more than a foot out of position in the boat as it simply will either lift the front out or try and dive the bow, those angled boards are having quite a bit of effect.

Lots of design ideas going on in Bitsa and it is quite contrary to a lot of modern design, but its no slouch and certainly the Nacra and Bitsa are pretty evenly matched with the Nacra being faster downwind. The snuffer is certainly causing a lot of head turning and seems to work very reliably when going downwind and doing everything as a single hander should. The minute you turn upwind that fraction too much such as leaving it a bit late at the mark, it turns into a real horror story. The need to bring the spinnaker around the stays just slows the retrieve enough to suddenly wet the sail and then cause it to drag just slightly. The boat then over runs it and you end up trying to pull in a great big wet blanket. I have a simple mod, that of fitting a snuffer ring just ahead of the stays on the spinny pole, that should solve it, but then we are suddenly increasing wind drag.

So learning Bitsa's foibles, and probably in all truth its a better sailor than I, very very balanced now that I have shortened the spinny pole a tad and can upwind, almost put the tiller down whilst adjusting the downhaul etc,downwind a bit of lee helm but not significant and probably means that I have put the dagger boards a touch too far to the rear.

But and a big but, its bloody great when someone asks is that an A Class and I say no, an F16, upon which they will immediately ask, which make then, upon which I say Bitsa. "Never heard of them" they often reply and I guess that must be the case as there just aren't many around.

Hi Wayne,

what is the mast length of the rig you are currently running? Is it class legal?

Last night Frode and myself cut down the mast section we are going to use from 9.2 meters to 8.49 meters. It hurts but after crying a bit we tossed the cut-off into the alu scrap bin and started drilling new holes for the fittings.

Looking at your pics and the rudder forward rake, it seems like quite a bit of rake there?

Apart from the user errors on the snuffer, do you think the reduction in drag from the snuffer is worthwhile?

Very interesting post you made!

Sadly the 9.1m mast I have would take me outside of class limits but then the 13.95sqm total of mast and sail combo, under SCHRS handicap will give a slightly lower handicap than the 15m F16 so all is fair (approx). Bitsa is slightly underweight at 100kgs and only 2.3m wide as well so it balances out nicely to just under the true F16 handicap, under SCHRS.

Why only 2.3m wide, I think we have gone over wide on the solo boats as with a low aspect 15m main at 95kgs I found it really difficult to fly the hull in anything less than 7-9 knots of wind. Less RM will allow that hull to fly earlier and on the water I would say I have substantiated that with both Bitsa and the early Stealth ( which was only 2.3m wide ) flying the hull earlier than their wider brothers. I think also there is something about less tripping and diving also with the narrower boats.

Its been long known that I feel the jib gives the dual handed boats more drive than the weight penalty of another body on board and that really shows at low speed where the jib smooths the flow over the main. All the knitters loom of wires and snuffer etc can only make the bottom of the uni main even less effective, anything we can do to at least give something back to the bottom of the main can only be a good thing. This winter I plan to build a blade jib and fit it to Bitsa to test out my theory's.

Why the foward angled rudders. Most vintage aircraft with leading edge pivots on their rudders have foward angled rudders to balance the rudder and prevent flutter. Water being a lot denser means much lower speeds before the potential of flutter. How many times have you sailed some of the Hobies to simply feel the rudder " spin out " and you have to slow somewhat before you get full rudder control back, thats flutter setting off ventilation. On Bitsa I tried to get as much board ahead of the pivot as behind to try and prevent this and give a nice feel to the rudder. As a bonus the foward lean prevents a lot of the ventilation problems we often see, the moths certainly have had to do this to prevent air leaking down the leading edge and getting to the hydrofoil. There is a really good You tube clip made by a guy called Bulgari which shows this happening. I'm sure SmithCats would be able to put a more finite analysis on whether I'm right or just luckily wrong as the rudders are really light and nicely balanced at the moment.

Interesting what you say about flutter. On the Tornado we regularly lost grip with the leeward rudder when flying a hull and hauling the main tight when going upwind. I dont think there were any flutter as there were no noticable vibrations and no escalation. Rudder loads were light and we did have positive rake on rudders vs pintles/angle. However we were sailing with 200kg on the trapeze and class standard mast rake. This problem went mostly away when we used less mast rake. My conclusion back then was that we overloaded the rudders and experienced loss of lift as the poor rudder was asked to balance too much total load.
I am fully with you on the foil balancing to avoid a heavy helm and flutter as it is defined here: https://en.wikipedia.org/wiki/Aeroelastic_flutter#Flutter

Cudos for your willingness to experiment! Wires are a worst case for drag I think. But seriously, we should look at our bodies and how we dress onboard as well. Drag reduction is the game for optimization!

For width I always enjoyed the curves showing righting moment vs angle of heel. Decreasing the max widt also decreases max potential RM. By going less wide the boat should in theory not be faster and heel angle should, again in theory, be controlled by crew positioning. What I think you imply is that we, the sailors, are not good enough at getting our positioning correct (we dont move our "behinds" inwards from the hulls)? Where do you notice the most difference with a less wide boat. Upwind, downwind or even?
We drilled the beams for max width when assembling the platform, but beams are affordable


Thanks for sharing Wayne!

As virtually all my racing is based around SCHRS handicap racing then Bitsa has to conform to the pecularities of a rather antiquated one calculation fits all system. We as solo sailors are penalised in my opinion and few Uni boats can conform to their ratings, one only has to look at the F16 rating between solo and dual, both being the same rating. Can a solo boat beat a dual boat, I think with the new powerful rigs and sail handling systems available, it is now very very very unlikely.

So how do I "trick" the boat out to try and get any sort of advantage. The only real way in my view is to use very well developed mast and sail combos ( A Class ) and hull design to suit the Uni sailor rather than the hull designs which suit the dual sailors weight ( RM ) and extra drive of the jib.

I chose to go to the narrower beam for a number of reasons, pricipally it helps a lot in reducing the handicap rating in SCHRS, enough to allow a lighter boat and more high aspect rig. Secondly to get a faster hull ( in theory although I think some of the new designs are proving otherwise )one has to increase the hull width to waterline length ratio. Once we go to a finer hull as I have tried to do, immersion from the RM becomes a problem ( drag through the water )however by using angled boards creating lift this can be reduced somewhat ( think A class with their new C boards ). So lots of design factors here being influenced by a handicap calculation.

Last but not least, when I moved from the Stealth 2.3 to fitting the full 2.5m beams, it was very noticable in the handling at just how that 200mm effects the boat. The boat became much easier to control the heel, it became much more likely to bury the nose in a tripping sort of way, it became much more sluggish in handling,it became possible to over load the boards and start going sideways rather than tracking true.

So by choice wishing to compete under SCHRS handicap, I went narrower and probably would go narrower even further on real life experiance. It would certainly make for a very lively boat and probably only the very experianced sailor would be able to get the best out of it, but it would lower the handicap significantly and allow even finer hulls that would benefit from C boards.

Bitsa has become about the package under SCHRS I'm afraid to say, one cannot compete at F16 meets due to the anomoly of our class rules so one has to compete on handicap.

Hi Wayne,

I dont know your rating system. But if it is formula based a coefficient for solo F16 might be a solution? Dont know how to incorperate this though..

Rules are what they are. Some parts are excellent, others are not. But the rule is what makes this interesting and at the same time frustrating?
We need friction brakes on the spi halyard for non-solo boats. To be serious, it would be very good to see some statistics on the performance of solo vs. 2-up with boats and sailors of comparable skill. Perhaps there are some things that can be done?


Interesting that you have optimized BITZA for your rating system instead of just getting an old A class. I bet you have learnt a lot during the progress.

The SCHRS is the official ISAF handicap system and although it is good, like all handicap systems, some boats seem to pop out the side of the system and flag up errors. Its been long proved that single handed F16's cannot now compete with the duals, when one of the top A Class sailors in the world tried at the 2010 Europeans ( ? ) at Garda to sail solo when his crew became ill, it was very noted that he went from top 3 to 17th. That was certainly an eye opener and in later discussions with SCHRS it was very apparant that even they consider that the duals have some advantage. But hey thats another story.

I did sail an A Class for the 2010 season just to learn the basics about mainsail control and have learnt a lot. However the A is no match for all the spinny boats at my club and for that reason have moved back to Bitsa. A single Uni sail cannot compete with the spinny boats in just one small part of the race, just as you transition from upwind to downwind. The spinny allows them to just slide slightly below you whislt you are trying to hot the A up onto one hull, at that point they are in control and you inevitably lose 1 or 2 places on every leg. The power of the new mains on the likes of the Hurricane 5.9's which predominate at my club, means they are a near match on the upwind legs which always means that you are slowly but surely going down the fleet. I think the very good guys are perhaps able though to sail the downwind legs on the A's far better than I, where the spinny on Bitsa at least gives you a chance to maintain your position.