Is there any sort of cassette or shim you could put in the daggarboard trunk to allow the use of high aspect daggarboards?

Or would you have to rip out the trunk and install a new one for the new HA board?

You could probably just make a filler out of wood. I think somebody told me the Glaser's did that with their Infusion to run the wildcat boards.

That's kind of what I was thinking. Might make the older Blade design a little closer to the newer designs in terms of upwind performance/angles?

I don't think its that far off the pace as is. The achilles heal of the Blade is more its capacity to take a heavy team. The volume just isn't there like it is on the Falcon.

Talk to Matt, see what his thoughts are.

I didn't find the Blade to suffer from heavier crew weight (range seemed pretty wide) ... big difference is that you can push the Falcon alot harder than the Blade without fear of pushing the leeward bow in.

Semantics?


If you go with a thinner board, might be able to build some cant into your shims. Random thought.

I got on Seth's Blade(may have been a Falcon) at that Windy T-winds a while back and we didn't do too badly (other than I kept knocking him off the back) up or down, but I think there was only one or two Falcons there to compare to, and they were driven by rock-stars so I didn't even think to analyze the performance minutia. We were probably #370-#380 combined

I've raced the Blade 2-up at over 350lbs and it wasn't very competitive in <12kts against the uni teams and 290-300lb 2-up teams. I think in big breeze it'd be fine upwind but downwind lack the buoyancy. Sailing the Viper 1-up in breeze is a handful, I was near the ragged edge a few times but managed to keep it upright. I think she'd handle weight better than the Blade but a solid team on either will do well. The 2-up Blade at our club does well when the breeze is up, they were first to finish a 30 mile distance race in big breeze against some decently sailed N20's (we didn't put the pro team on the water, may have been a different story).

I got a reading on the class rules and there is no limit on length (or area that I could find). Rules permit up to 6 degrees of cant.

So, I was thinking about building a set or modifying a set from an F18.

Comments?

A set of wildcat boards would be perfect on the F16, high aspect and less area than the other F18 foils, would work really well on the smaller boat.

I've had that exact thought.

Thanks Macca.

A set of Wildcat boards is over $1,600 for the pair new. That's out of the question for a 6 y.o. boat.

What would it take to build a set at home? Anyone done it?

$1600 for the pair seems cheap to me. Source? I say this because the Infusion Mk. 2 long boards are $1200 EACH. I think there may have been a first generation Wildcat board that was shorter? Those I can believe would be $800 a piece?

As to building your own, I've considered it but decided against it. I currently have $2K in tooling and easily another $3K in carbon lying in my shop to build 60" molded model airplane wings, so I have a pretty good handle on what manufacturing carbon things costs. There are several techniques to build good foils but the issue is we are now in a super high load case with a relatively thin foil. To build these strong enough, high modulus pre-preg carbons are likely in use, along with compression molding techniques. Even if wet layups are being done, through resin infusion or simple hand layup, and they are building a somewhat hollow structure, you still need molds capable of post-cures in excess of 175 degrees; i.e, you need aluminum molds. Lets add up the costs:

1) Set of aluminum daggerboard molds: $2K for the aluminum, plus machining time, so ~$7-10K by the time you are done.
2) Machined end-grain balsa or high compression strength foam: Since you're doing it twice, maybe $500 including machine time.
3) High Modulus uni-carbon: $200 worth might cover you
4) Regular carbon for rest of board: $150
5) Gallon of MGS epoxy: $250
6) Pint of gelcoat: $40

Still think its cheaper to build a set at home? Hotwire foam core won't work, melts in the oven. Maybe you can bag a set over a machined core but you still need several hundred dollars worth of materials, and several hundred more dollars worth of vacuum equipment.

Thanks for the input.

Source was a local Hobie dealer who prefaced the conversation with the statement that the Wildcat is a "rare" boat so he may not have the latest price. The price you quoted doesn't surprise me.

I'd be more inclined to look at plywood first. Two layers of veneer, laminated at 90 degrees would be stiff but I've no idea if it would be stiff enough or hold up for any appreciable time.

I've kicked around building a laminated daggerboard and rudders out of wood just for fun. I could make em' purdy....

I do not think I could make them nearly as stiff though, at least not with straight wood. Now If I could bury an aluminum I beam or something.

and, wood is stiffest with the grain. You might want the layers offset a bit, but not much. Just a gut feeling, but I'd say 45*; would be too much even. You'd want the grain to be pretty much vertical.

I think it would be do-able, aircraft props have been made from laminating wood for over 100 years. IIRC they were all pretty much parallel.

If the boards were short enough then for sure you can do it in wood, but with the aspect ratio and foil section shape of current F18 foils..... no way is it possible to do in wood.

Most builders are struggling to build unbreakable foils even in carbon.. If you want them to be perfect then you need to spend big bucks to build them right.

I reckon 1600 USD is pretty ok for a pair of wildcat boards, they will be really good in an F16

Well, again, I have some things keeping me off the water. So while I'm on hold I may just cobble up 1 board 50% longer, drop it in the trunk and see if it does any better than the stock board. If there is any appreciable difference I would be satisfied with that. I won't be collecting any pickle dishes so there isn't much point in throwing a lot of money at it.

Fwiw, I read the Bernard Smith book "The Forty Knot Sailboat" many years ago and he seemed to think fat foils would work. But I'm not a rocket scientist, he was.

http://www.sailrocket.com/node/518

"Some things just didn't fit into the high speed sailing forensics puzzle and we refused to neglect them. We had been constantly told how thin foils were the only way to go... and yet our big, 'fat', Mk1 foil had repeatedly hit over 50 knots. When we applied the theories and associated numbers that sent us down the path to superthin foils to the old Mk1 foil it showed that we would be very optimistic to even achieve 40 knots. It was obvious that something was wrong..."

I suspect you'd have to break a lot of boards to make home-building them, according to your plan (aluminum molds, etc), affordable.

I can only imagine the cringe on any long-daggarboard owner's face when they become "bottom feelers"...

The Charlotte Sun Herald newspaper had you with 3rd place at the Charlote Harbor Regatta and you weren't even there to pick up your pickle dish.

This isn't your grand daddy's airplane prop...dagger board foil sections and loads are all completely different.



What about carbon over a cnc milled wooden core? This to me is actually very tempting. Does anyone have a rough idea on the laminate schedule for a board?? Foil section is the other big question, I doubt they are running NACA0012's? Last time I dug and dug for this data it was unubtanium and NACA sections came out ahead in my 2D analysis.

I wasn't there to race either so I guess it all works out.

Is this of any help?
http://www.hobieclass.com/site/hobi...01_Wildcat_daggerboards_for_comments.pdf

Still missing the foil section. Plan form dimensions are useful. In my case I would literally take my existing Infusion short boards and add length till I had the same area as the long boards. I'd do some tweaking to keep an elliptical plan form at the tip (lower induced drag). The reason for doing this versus say copying the Mk. 2 long boards directly would be so I can interchange boards at will.

Looks like an Eppler section on these A-Cat foil (note the ridiculous amount of carbon): http://lindahlcompositedesign.weebly.com/install-curved-boards.html

Here's a layup for some F18 shortish boards: http://www.youtube.com/watch?v=k6AzcUBHEzU

CNC cutting a wood core is possible, you would need to have some recesses in the max chord area to allow the required uni fibres to fit in, there would be a lot of finishing work to do, but its certainly feasible.

As a rough shot, I reckon around 8 layers each side of 300gsm uni IM or HM uni fiber is pretty much the bulk of the structural part done. then you need some RC200 biax or similar to hold it all together and you are good to go... remember that this is for around a 1.8m long foil with similar dimensions as a wildcat foil. Oh, and you need plenty of sand paper if you are going to do it this way!!!

Also, the wildcat foil is around 17mm thick, and you will get a lot more strength if you made yours at 21mm or so, its a bit more drag, but its easier to build a strong foil at this thickness.

Good Lord! No wonder they're so expensive.

The boards I have are the stock, short stubby boards. I'm guessing most anything would be an improvement so I see me laminating some cheap, throw-away plywood, shaping it with a rasp until it's time for a nap. Then, if that shows any improvement while actually sailing, I'll make a set out of better materials.

Bless all of you willing to go through the complexity of engineering. It definitely ain't me!

I just priced some UHM fabric per Macca's laminate schedule and it comes out to $700 to do 2x boards!! I would have to find some IM or HM at half that price to make it worthwhile.

I'll stick to wood. This looks like it might work and can surely be done with a belt sander on plywood.

how about a Sunfish centerboard?

That is an asymmetric foil, i.e it produces more lift at positive angles of attack than negative angles of attack. My understanding is current straight foils are symmetric. Otherwise you would have to tack the boards when you tacked the boat.

Thank you for the assistance, it is appreciated!

what's one more string to pull!?

Seriously, that may be the best idea to come out of the days discussion. Asym, tacking boards. Set up properly in shouldn't be too big a problem, particularly if there is a bigger gain to be had.

For the phantom boards we use some very special UHM uni's and I think the material cost is close to $700 per board.... But we do have the stiffest foils by a big margin.

Strength wise you will be achieving the same with standard modulus stuff, but it will just be more bendy.

Plywood is definately not adviceable for use as a high performance foil. On total I have four plywood foil breakages before going to strip-plank solid core. We even covered one set of foils with 600gsm triaxial S glass but the plywood core was unable to handle the loads
Strip plank solid spruce did the trick on the Tornado. For an F16 the rudder foils could be done the same way or even with a laminated hollow wooden core like Marström.

For the daggerboard wood is probably doable if you dont go to radical with the length and thickness. Old 18squares etc used wood based foils with success but they can be heavy and flex.
Covering a wood core with carbon is certainly doable, if you dont go too extreme. You can go extreme but it might break. That is what we have structural engineers for, and even they get it wrong now and then.

Wood is good. Carbon is lighter, stiffer and might also break


I just love being helpful...

I think the best approach is to build one board of wood based on the existing profile but longer, then do on the water trials. Question is how much longer?

Why dont you get onto Matt and get one of his F18 boards from the new boat?

Easy and he will be keen to see the difference too I reckon

Matt's busy, I'm not going to bother him with this.

About the only way a homebuilder could effectively make a long dagger without a mold would be to get a machined wood core and lay up carbon on the outside. Even this keeping a fair and constant section is the work of only the most skilled pattern makers and finishers.

I went out with Matt when they were testing the long daggers for use on the F16. They purposely used the same chord length on the boards so it was possible to interchange them and better test varying lengths and foil sections. The one thing about the longer boards was that it made it obvious that board height was a critical setting for performance. Too much board in the water and your vmg went to crap. The board height position is near as important as mast rotation. (very bad deal IMO for beginner and or even moderate skill level crews as now there is even more to do to sail) The long ones did help getting the boat to power up in the transitional speed winds. Once you were moving, you were quickly pulling up some as the wind built. Once double trapping it took nothing to have them up at the same depth as the normal high aspect foils, but now you have the dagger sticking up on your hull all the time, in the way for going in and out and moving crew weight. Never mind the danger of the sharp trailing edge meat slicer way up in the air just waiting to catch the crew sliding forward if you happen to stuff it.

A couple of comments on the above.

1. F18 boards are really heavy due to their length, the rules and the boat's huge righting moment compared to an F16.

2. I have to dissagree with Rolf, for projects like this wood is not good it is great. Built properly a carbon skinned timber cored foil will be about the same weight as the foam carbon alternative and if you're not paying for the labour they're much cheaper (this was demonstrated to me by a very good i14 builder).

3. I agree with Macca with regards to a bit of extra thickness. 2mm (19->21mm) will add over 20% more strength

My grip is with plywood. Plywood have nothing to do inside high performance foils.

Details on "proper" build of a wood core carbon covered foil is most interesting!

What wood (species, fast grown/slow grown, weight pr cm3 etc).
Cutting and staggering of timer staves to avoid warp.
Laminate schedule.

I like wood! As in "I love wood!"
The material is cheap and strong, easy to work with, excellent durability, relatively lightweight, very environmentally friendly and so on.

With the Gougeon book available as a PDF for download I hope more people try their hand with wood.

So, if not plywood then what? As regards plywood, I was thinking Brunzyeel for the finished product but anything from the local box store for a model.

Rolf,

the way I we've built "timber foils" before is.

1. Select straight grained timber with good strength to weight ratio (ie cedar) of say 1" (25mm thickness).

2. Cut into narrow strips, reverse alternate layers glue and clamp back together.

3. Place whole thing in thicknesser and dress until "flat"

4. Laminate solid glass strip up to same thickness (de-bulk and bag)

5. glue glass to front and back edges.

6. Machine to shape (you want solid glass lead and trailing edges)

7. Create rebate for uni strips at maximum thickness point. Note unis can be tapered out between 50mm below hull exit and lower end of board.

8. Fair over unis.

9. Apply laminate.

10. Fair and paint.

Cedar? Here in the U.S. I'm guessing the most suitable species would be western red cedar. Anyone hazard a quess?

Not western red, it has too much oil in it so will delaminate too fast. Go for Spruce, Hughes didn't pick it because he liked the colour.

Hi Scarecrow,


Questions:
7. Uni strips with carbon? How much would you guesstimate is enough for a 1995x21x180mm board?

8. Fairing. How much work is this and how precise is the result? How critical is the trueness to the designed profile?

9. Is this laminate only to make the foil durable so a 120 to 220gsm glass cloth is enough?


In your opinion:

How critical is accuracy to the designed profile. Is a tolerance of 1mm, 0,1mm or even 0,01mm the target?

What about geometry of the foil. Any tapers complicate work. Same with rounding off the tip etc. Yet this is often not discussed even if it is "standard" to aim for an elliptical pressure distribution and to avoid drag from tips.


Thanks for your insights, much appreciated!

Why not a hardwood? It'd be twice the weight, but there isn't much mass to begin with.

FRUIT NINJA!

petrified wood? Talk about sailing a "classic". How about one thousands of years old?

Sitka spruce is pretty much the standard in aviation for its characteristics in weight, strength and flexibility. Marine applications such as this should be much the same.

We are operating at reasonable Reynolds numbers, close to 1 million when sailing at 10 kts. Doing some first order calculations, assuming the flow is laminar (i.e smooth), looking 0.25in (6.4mm) aft of the LE, the boundary layer is 0.098in (2.5mm). Effectively this means any scratches or bumps within that distance would have no effect on the performance of the foil as the water around the foil can't even see them. However, there are A LOT of assumptions made in that first order analysis and you always want to build the best foil you possible can. My #1 tip if selecting a foil for a home build is to go with something whereby the performance doesn't degrade drastically due to imperfections. For example, a laminar flow section like the NACA 63-209 discussed here (http://www.foils.org/hysecdes.pdf) is much more sensitive to surface imperfections and things like kelp than a more traditional foil. The NACA0010 that was designed to operate in a more turbulent flow environment where the boundary layer is even thicker and hence you can get away with even more, besides it is easier to build accurately.

I am not an expert at wood construction by any means. I guess you have to laminate strips together to avoid warping along a grain line?

The smaller the strips, the less warping you'd have. So long as you flipped the pieces, assuming they came from the same stock.

Rolf,

too many variables, to little time to give you a back of the envelope estimate. Design path goes something like this:

1. Determine maximum righting moment.
2. Determine worst case lift distribution from rig.
3. Using above info calculate max side force on foil
4. Calculate lift distribution on foil.
5. Calculate moments and forces on foil.
6. Determine young's modulus and allowable stresses on selected timber.
7. Determine young's modulus and allowable stresses on proposed laminate.
8. decide on allowable flex on fully loaded foil.
9. determine section modulus of proposed foil.
10. adjust number of carbon layers until deflection goal is achieved.
11. confirm maximum stress due to bending in various components.
12. adjust laminate to suit.
13. check shear strength of core (particularly in way of hull exit).
14. Repeat all of the above because I've almost certainly lost a decimal place somewhere.

The exterior laminate makes it more durable but also must take into account hoop stength and twisting, yes you can use glass but it will be heavier.

Profile (meaning the shape of the board when view from the side) is in theory very important, however there is a trade off between efficiency with the foil down and up. If you taper the lower end you can reduce drag, however, it is at the expense of drag when you pull the foils up as you end up with slop in the case or a small amount of foil left down.

Section shape is important but don't dwell on it too much the shapes people use (with the exception of Richard Roake, Martin Fischer and their peers), be they NACA or any other profile are merely part of systematic analysis programs where one variable has been changed at a time, they are not "ideal solutions", so pick one which has the characteristics you want and do your best to match it but your priority should be a fair (consistand curvature without waves) shape.

Rudder and daggerboard section selection is not only important in theory. Some years ago we replaced the original rudders on a Tornado. We changed from the classic thin profile to a thicker foil with higher cavitation resistance but still the same drag level which made a huge noticabale difference to boat handling and speed. It removed all weatherhelm we had a high speed, which was significant and drag from the partially cavitating rudders.

Don't select laminar sections as they are inferior when operated in turbulent conditions and surface water is always turbulent if there are waves. That's why most people are happy with NACA 4 digits sections.

Concave sections are difficult to build, hence better stay with simple convex sectuion. Again a good reason for NACA four digits.

Other than stated here in this forum, skin smoothness or quality is very important, 1 mm roughness would have an catastrophic impact, and 0.1 would be still significant. A foil should be as smooth as possible and smoothness is more important than the section.

Cheers,

Klaus

Thanks Smiths.

Hi Klaus,

as smooth as possible is an "unclear" target In your opinion, how smooth should a homebuilder aim for? The combination of surface roughness and a true section is a challenge if working by eye and hand accuracy.
Is there a crossover point between the importance of sectional trueness and surface smoothness?

A CNC millcan work down to 0.001mm accuracy and some light sanding will give smoothness (or the machine can produce that as well if it is good enough).

I think this bears repeating.

"Other than stated here in this forum, skin smoothness or quality is very important, 1 mm roughness would have an catastrophic impact, and 0.1 would be still significant. A foil should be as smooth as possible and smoothness is more important than the section."

So what degree of smoothness can a home builder hope to achieve using hand tools?

The issue with that is that you need to get both sectional shape and roughess correct at the first try.

Huh? In a wood laminate?

I see it as just the opposite.

Am I missing something? We're talking smoothness as in like glass is smooth, sandpaper is not right?

I think technique is the answer. Once the shape is fair at 220 grit then it is more a case of polishing.

You will get both smoothness and shape right as homebuilder as long as you have enough sanding paper, filler and patients as thousands of homebuilder and model aircraft builder have already shown.
To get the section shape right you can work with a negative template gauge (don't know the right english word for it, a plank where you cut out the sape of section). With that you can easily see where to remove or add material. You have to sand and fill until you have the shape. The section is more sensible to errors at the nose than at the end and more sensitive for errors in streamwise direction than along the span. I hate sanding but I go down to 1000 and then start polishing, but if you after a nice look as well you may even uses finer sanding paper.
The real problem is that a catamaran has 4 foils... but after sanding to hulls you are already into the zen of sanding.

Cheers,

Klaus

"...negative template gauge" as always check Gougeon Brothers, lots of stuff there.

I like to spray the work area with a light dusting of black lacquer, it shows the contours nicely with only a little sanding.

If you think the foil is fair spray it with a high build primer and then wet sand with a cork block and 1200 grit until it looks flat and shiny with no dimples. Look at the reflections. They must all have clean straight lines. Then spray a top coat and wet sand again. I went 800 and then 1200 (don't press too hard with the 800 or you will have probs removing the scratches it makes) and then cutting compound. I would have liked to go over with 2,000grit but couldn't source it at the time. I was making the plug for the rudder on my Tri. There is a pic in a thread on Farrier tris. I started off by getting the reflection of the trees to look straight and eventually got the extremely fine lines on the diffuser of a hand held fluro light to look spot on. Then I felt that I was in the ball park.
Someone mentioned the word ZEN. Forget about the time it takes because it is all about getting it right.Suspend time and get into the zone to get it right. If you don't think you can do that just buy something off the shelf.

So that is what is called "optical quality"

Even if Zen is a goal in itself, I wonder what the real world difference on performance between optical quality and non-optical quality is.

I'm not likely to find out, surfaces with that level of finish are all but impossible to maintain.

I think primer sanded to 320, then painted followed by 600,800,1000 grit wet sanding plus polish. Even then, normal usage will mar that finish so it will be maintained with soap and water.

What Phill gave us was a good method to determine fairness by looking at the surface. I think it was a very good post in its clarity.

With "perfect" fairness and surface finish the performance will still be good as the surface detoriates. If fairness and finish is inferior to begin with the performance will decrease faster while maintenance will be harder.


I have a hard time trying to think of an easy to follow procedure to produce that level of fairness within a reasonable amount of time, by hand. CNC have its advantages.

Next question could be what level of fairness and surface finish an "off the shelf" product has, and how they are produced?

From "back then" I think Phills foils used a homebrew CNC mill to produce cores and moulds. He would finish the cores and moulds by some hand sanding. It has been some time since I read this so please dont quote me and take this as gospel.

During the development of foiling Moths they hand built the foils to "good enough" performance to make them fly efficiently. It is surely still possible if one has the Zen

Imo, the first place to start is selecting a foil shape. How does one go about choosing? Btw, all I've seen are simple line drawings are there more accurate descriptions somewhere?

Pete,
You could buy Profili. Not sure these days but it used to be around 40 euros. You could buy it online. It has a huge database of foils and it will not only give you the offsetts to create the foil shapes but also all the foil characteristics including lift and drag.

Thanks Phil. And I like your slogan, seems we're tuned into the same station.

http://www.profili2.com/

Looks a little complicated. All I have is a simple Epson printer. Has anyone used this with a home pc?

Pete,
It has been quite a while but I have used it on my home PC and personal laptop. There is no problem with processing. If the problem is just printing why not store the file on a thumb drive and take the thumb drive to a plan print office. The last time I got something printed this way it cost me $4 per file.

Regards,
Phill

There is a trial version that can be downloaded and tested. The software itself is relatively lightweight in normal use. It runs fine on my 8 years old laptop.

The software is complicated becouse the topic is non-trivial (at least I find it a complicated subject when trying to do the math by hand)

I liked the new functionality in Profili 2 Pro for saving 3D design files and even producing G-Code for male or female moulds. Take the file to a CNC shop and have the mould or core machined with very little overhead for them ($$$ to set up CAM and produce G-code)

Ok now I'm intrigued. When generating STL files from Profili 2 Pro, can you specify the wing washout at each span-wise station? I have non-linear washout requirements...

XFLR5 is free and worth every penny. Pete, this is a non-trivial subject matter; I have a 4 year degree in Aero Engineering and I still feel like a newbie when it comes to foil design, and an even lesser man when it comes to hydrofoils. Guys make entire careers out of this subject (Tom Speers for example, Boeing engineer and BMW Oracle foil specialist). My #1 suggestion is to call or email Matt and get a quote on the long boards, I think you'll be pleasantly surprised and quickly realize you can't do this for less. My #2 suggestion is start with a NACA 0010. My #3 suggestion is simply extend your existing Blade foils to the desired length.

I'm fearful this will quickly become an exercise in futility for all the reasons you cite.

#3 has occurred to me and will be the first step in any case.

I'm beginning to suspect that using aero foils (if I may use that term)for hydro foils may be a mistake. I cited an article from Vesta sail rocket to that effect.

Bernard Smith may well have the last word in the matter.

Sam,

I belive the "standard advice" for cat foils is NACA0007 for daggers and NACA0012 for rudders.

Then the customization and differences in philosophies starts. From there follows a big debate where I quickly am out of my depth. Some of these discussions seems more like religious debates than fact based ones (you can choose which facts to select and debate from). In the end it comes down to who to trust.

Well, I'm going to start with some cheap materials to make a model. Then whittle away to suite my fancy.

If I can make any sense out of the data I'll try to apply it.

Pete,

Sailrocket is a rocketship, literally. They have custom foils because they are reaching custom speeds!!! You're not doing anything crazy with your Blade and standard airfoils designed to operate in turbulent flow are fine (NACA series). Others have generated perhaps better for our cats but these aren't freely available.

Rolf,

Good to know, that makes sense, thank you. You pay a little drag penalty going thicker on the NACA foils, but the advantage is a higher stall angle of attack, which is why you want a NACA0012 on the rudder. You should never approach stall with your dagger boards unless you are doing something wrong with boat handling, so the key there is minimizing drag. On a long board, you may select a thicker foil for structural reasons mentioned elsewhere in this thread.

I've come full circle and decided I would rather go sailing than build foils. I don't have time to repair boards because my layup was insufficient, nor do I want to deal with broken foils 30+ miles from my destination. Finally, I have a hard time justifying my materials cost relative to a set of production blades. Mold cost is staggering for the required materials; this is with free CNC time on a $50K+ machine! Carbon alone is $800 for the pair of long dagger boards!

I was hoping to go with asymetric boards, thinking this would actually give me an advantage!

Remember F16 is a developement class and I'm using first generation boards (and case which will not accept the new boards without modification) while third generation are available.

Solo sailing with asym boards is a lot of work in the tacks.

Even double handed I wouldn't want to deal with it. Performance increase is likely mitigated by crew work level.

Is the shape of the Blade foils acceptable?

I am a firm beliver in the KISS principle.

Keep It Simple Stupid.

If so,cruise down to your local locally owned hardware store and get a Layout Comb. You can get the profile of the foil and then lay it out on a piece of sheel metal and cut to shape. This gives you a template to shape your foil to.

There's an idea, hadn't thought of that.

Theres been many a debate on assy foils and many attempts to make them work, but then about 1 sailing season on they seem to be replaced with sym foils. On that basis I wouldn't bother.

I've always wondered that with the slight bit of leeway we get and by consequence the boat is a little " crabbed " as it goes along, if you draw those vectors we can see that the normal dagger board has some angle of attack anyway and is creating lift.

I've recently built a carbon ski bike frame from scratch and designed it to be built as simple as possible so that others can copy it. As part of that I simply laid a number of flat layers of carbon on a table to act as the backbone of the frame. I then glued foam to either side and shaped that to give form and depth. I then laid carbon around the profile to give bending strength to the structure. It seemed quite an elegant way to build a very light but strong frame.

Could we not do the same, just lay x number of layers of carbon onto foam, add another layer of foam and compress. Take the block to the CNC man and cut one side, turn over and cut the other. Layup the outer and job done.

Even better there are a number of shops that will cut wing shapes for model aircraft, get them to cut two halves of a wing and glue that to the carbon centre layers.

I gotta give this a tri!

http://vimeo.com/34164014

Foil "V" shape looks interesting. Might make the form rigid without expensive layups?

That's what a triangle is all about...

damn you, geometry!

What are the standard boards for a blade f16? Mine are similar to those on a taipan

Charles who built your boat, there are quite a few flavours of blade and it may well have taipan boards. For the record the Taipan, Blade and Viper all have the same mast.

I believe my boat is Australian built as I live in Singapore, the hull is kevlar with the short boards

Can there really be a standard board? Since F16 is a developement class the boards can change almost at will.

I prefer to think I have generation 1 boards while others are using generation 3 or higher.

fwiw, my boards extend approx. 21" below the case, and have a chord of about 11 1/2", and are approx. 3/4" thick (that's an eyeball measurement).

It appears to be NACA 0006

does anyone build or sell blade foils these days or are they all home builds?

I'd be surprised if Matt didn't have the moulds

Is there an Australian builder still around? just thinking about shipping costs etc

measure your boards and post here (with a photo) so we can work out if they're taipan boards or not then contact ahpc and order either viper or taipan boards. It would also be worth trying windrush, Brisbane cat centre (nacra) and performance sailcraft ( laser/Capricorn 2) and seeing if they can help.

okay cheers, I'll post the info this weekend after sailing

The only builder of Blades in Australia that I know about, excepting plywood boats, would be Marcus Towell (working with the Barrets I believe). But I dont think Marcus used Taipan foils.

I would have contacted Marcus if you want foils built in Oz. Send me a PM if you need his contact info. Marcus is a resource!

If you consider going from Taipain foils (if that is what you have ) to a different foil it might be worth checking if AHPC Viper foils could be installed. You would need some inserts and some epoxy work anway when going for different foils.

Pics of your boat and foils would be helpful and interesting.

I wasn't confused enough, so I thought I'd complete the job.

http://www.boatdesign.net/forums/multihulls/gybing-center-boards-43772.html

Before you get too excited talk to some early Capricorn and Infusion sailors about their gybing boards.

The Viper has gybing boards, as does the C2.

Really, I didn't know that. Are they asymetrical or off set from the centerline of the hulls?

No, and no.

So where does the gybing come in?

The boards twist in the trunk, the leading edge moves, the trailing edge is the pivot point.

How does the performance compare to other boats you've sailed?

Interesting, I know a lot of the early boats (Cap and Infusion) had the foils locked off as the slop was deemed slow, I didn't realise AHPC have kept building them that way. Do any of the other new F18s have gybing boards?

Sailed an infusion Mk1 with gybing boards and loved it. Really felt good in flat water. If it gets a bit bumpy they can flop around in the case but not as much as you think. Didn't really understand when they started locking them off. Was just the fashion at the time I think.

Love the gybing boards on the viper. You can feel them click in and the thing takes off upwind. They never really move in the case even in bump so i guess AHPC managed to get it right.

Aido,

does that mean that there is some friction mechanism to hold the boards in the right angle of attack, or is there something else at play like increased angle of attack, asymentric profile or.. I dunno, but very interesting!

The lateral pressure on the board holds it sideways. With the boat on the beach you can grab the board and move it in the case. Its a very tiny amount and would only change the angle of attack by 1 or 2 degrees maybe less. But its enough to make a difference. In flat water you can feel the board flop over as the boat accelerates from a stop or out of a tack. I feel that the boat really tends to travel towards whatever you are pointing it at with no or very little leeway. Thats what is supposed to do and i think it works.

Nacra didn't get it right and the gybing system resulted in chewed up daggerboards. The lost speed wasn't noticed. I'm glad to hear AHPC got it right it makes sense, the 505's have had gybing boards for a long time.

Yes Aido, but what is the difference between the Capricorn version and the Viper version as the latter by reports now works properly?