T-Foil rudder on Merlins?

20/07/2007 17:05:56
Andy C
Have just finished reading a fascinating article in the latest Y&Y mag about T-foil rudders. 
I had never realised that as well as their positive impact on reducing the effective displacement of the boat, they can also recover wave energy produced by the hull as it passes through the water, generating additional forward drive.

This got me thinking; has anyone ever experimented with using a T-foil rudder on a Merlin? Judging from the article and an excellent reference website (www.tspeer.com) I don't think it would take a very large foil section to create a significant downwind speed advantage. It is unlikely that any speed advantage would be gained upwind because the hull speed needs to be >6.5knots for a 14ft waterline hull. In fact it is more likely to harm upwing speed, so a compromise would have to be found in terms of foil size.

Alternatively, it could be used to great advantage by heavier than normal crews, as a way of reducing hull displacement. Has anyone got any experience of these things, I feel like a bit of DIY coming on to try them out!

20/07/2007 17:52:54
Andrew M
er, yes it has been tried.  If you have a look in the class rules on the latest yearbook you will see winged rudders have been specifically banned.

Mr King turned up at Salcombe with one about 3-4 years ago. The experiments didn't suggest it was going to have the same effect on a Merlin as in the I14 and the committee stamped on it to prevent another expensive arms race. If it ain't broke etc.

20/07/2007 18:38:24
Andy C
Thanks for the reply Andrew. I've checked the rules in the latest yearbook and on the RYA website and, unless I missing something, the only reference to rudders I can find is in the general section prohibiting "double rudders and similar contrivances".

20/07/2007 18:41:29
I might be out of date, but I thought there was attempt to ban them a couple of years ago at Salcombe, but the decision was taken that at that moment in time they didn't seem to be conferring much advantage (Phil King/Linton and Simon and Al Warren all tried them), and the full facts weren't in so a 'wait and see' approach was adopted.  Since we don't all have them, maybe that sums it up!  There were certainly weed issues, particularly around Salcombe...

21/07/2007 07:35:01
Chris M
I agree with deepy, we did put a motion in place to ban them due to the potential for very inflexible hull shapes that go against the ethos of the class (Though it has been done before).

Obviously inland on restricted water and anywhere where weed is a problem they are not a good idea, and with the circuit such as it is any building of a boat that will only work with a Tfoil rudder is a seriously expensive bad move.

They have certainly been tried a number of times, and since at the moment to my knowledge nobody is using one it would seem that they don't really work for us.

21/07/2007 07:37:09
Chris M
I forgot to add that the motion didn't get passed, it was decided to see what happened first.

21/07/2007 20:42:54
Andrew M
Oh yes, that was what happened.  A bad day at work that was and now looking at the year book we didn't ban them (I was getting confused with double rudders) but nobody has tried again recently.  Suggests that it's another experiment (wing masts anyone?) someone could revisit.

22/07/2007 10:50:06
There are plenty of people in the class with money....but for the past 5 years, they have had more sense!

22/07/2007 20:58:29
Andy C
I don't think it will involve a lot of money. Around £50 should cover it! 
From Chris's previous comments I'm assuming that this rudder modification is within class rules?
I'm thinking of constructing a sleeve foil for my Driver fixed rudder. This way I can experiment without damaging the standard rudder. It also means the foil can be removed for light winds/unsuitable conditions.
Apparently for optimum efficiency in energy recovery mode the foils needs to be as close to the water surface as possible without cavitating. This means it will be located on the parallel portion of the rudder blade near the head, so attaching the foil sleeve will be relatively easy.
I don't see why the current Merlin hulls shouldn't be suitable for wave energy recovery gains from a T-foil, but the proof of the pudding etc...
I'm thinking of pivoting the foils on a rod/tube either side of the rudder so I can alter the angle of incidence, maybe via a screw arrangement to the tiller extension. I think tuning the foils' angle of attack will be critical for generating maximum forward thrust.
I'll also need to modify the rudder pintles slightly so the force doesn't lift the rudder right off!

22/07/2007 21:24:53
its a development class.
if its within the rules, try it!

good luck with the 50 quid.

23/07/2007 08:13:45
Measurement Man
Please, Don't go there!!!

One of the greatest strengths of the Merlin is its ability to be competitive anywhere, sea, river, estuary etc, and although in the past some folks have tried to develop a 'sea boat' for championships, there has been, overall, limited success at achieving this.

It is a great concern that if T foil rudders were permitted we could see a championship boat designed specifically to sport a T-foil rudder that would not perform anywhere else, but in the right condition on the sea be extremely quick and beat a standard boat. This could effectively kill the nationals and divide the class.

Whether or not such a boat could be produced and this would actually happen is speculation, since as alluded to earlier it was tried on a standard boat and was not successful, as much as anything because the riders couldn't get the weed off it! However; we are in a really strong situation currently with good numbers of new boats on order, second hand prices holding up well, good entries to the Nationals (over 70 pre-entered) and good open meeting turnouts; anything which risks compromising this situation unnecessarily should be avoided.

Please do not rock the boat with this train of thought; even if we could get a few knots more from the boat it would not make the boat more competitive to rac, it would merely take us back to the dire have/ have not scenario of a few years ago when those with the early carbon masts were stamping all over everyone - a situation from which we have only recovered in the last 3-4 years.

The Merlin Rocket is a Restricted Development Class, and the 'double rudder' description in the rules is adequately ambiguous for the RYA to support a ban on them if required - as discussed at a previous AGM - but it would be better for the class to avoid the need to consider doing this. The strength of the growth in the class in the last 6-7 years has been the result of gradual non-divisive evolution - a period of stability if you like - and the outcome is envied by those classes who have gone down the 'radical' routes.

Lets keep our 'be comptitive anywhere' reputation strong.




23/07/2007 09:28:16
On looker these days.
You mean "Foreward but slowly"? Or are you arguing for no more development? A Winder one-design?  Just like the Conservative Party of old. In the past a lot of odd ball ideas have been tried and very few survived the first outing. If it's faster either everybody will have 'em or you'll ban 'em, if its slower no-body will bother, if it's just very complicated and awkward to use for a minimal advantage people will get fed up with it!

23/07/2007 10:20:15
Richard Battey
Graham, you are spot on.

If you want to sail a boat with T-foils go sail a 14 or Moth but you ain't going to get them on a Merlin.

The posts who have hidden their names (sadly) I can't comment how long you have been involved with the class if at all, but I can remember the difficult times that Graham refers to when the class went through a bumpy stage competing against the mass produced RS 400 etc, but 60 years on and the class is the strongest it has ever been. Boat sales are high both new and second hand and championship turnouts are on the up and the Vintage wing gets stronger and stronger. Everyone who owns a merlin be it old or new enjoy good competitive racing, so don't rock the boat and leave well alone please.

23/07/2007 11:37:24
I agree partly with the 'don't rock the boat' philosophy, but with some reservations.  Firstly, I don't think a little experimentation is going to kill the class.  Secondly, I don't think that many would argue that the class isn't better for carbon masts, larger spinnakers and the other developments of the last 10 years.  Without those mods, we'd be sailing expensive wooden boats with unforgiving metal masts that were damned hard work upwind in a blow, and not so rewarding off-wind.  Or we wouldn't: the class would have become moribund and we'd all be sailing RS400s.  Progress happens, although I absolutely agree that it should be at a carefully considered and manageable rate.

23/07/2007 12:00:57
Richard Battey

I agree. But right at this moment in time there is a very healthy balance. You can pick up second hand sails,carbon masts and booms all 'two a penny' at the moment and that is what has attracted so many pepole to the class recently that do sail on a budget but want a good, racing boat.

Experimentation is fine but as soon as you implement a costly change like the foiled rudder it means more expense less competitiveness at the bottom end and the numbers peel off again.

I would re-iterate the Merlin is at an all time high at the moment. Lets keep it that way rather than get greedy and watch the class spiral into free fall over one or two radical knee jerk decisions because thats what a 'minority' want.

Having said all that if people had turned up to the AGM at Salcombe this one could have been put to bed pretty quickly!

23/07/2007 15:23:52
The Natioanl 12's have also tried the T-foil rudder arrangement. Graham Camm at the front of the fleet had one for a season or more. Recently I noticed that he doesn't use it anymore. Whether that is because inland it doesn't help, or whether it doesn't help anywhere - not sure!
It does seem odd for people to argue against developments in the Merlin fleet. Carbon spars are frighteningly expensive for people who have paid less for a full boat, but they were allowed in. A T-foil rudder can be adapted / used / tried without affecting other things on the boat - and it has to be home mnade and cheap, 'cos there is nowhere to buy them!

23/07/2007 16:16:57
Richard Battey
No one is arguing against development, on the contrary, after all it is a development class. All one is saying is that currently there is a period of stability in terms of development of the Merlin, we have carbon masts, booms, poles, decks, bouyancy tanks and all singing all dancing sail materials and with a steady but healthy growth of members let not rock the boat! By all means make a T-Foil, I believe Kevin Driver made a fine specimen a couple of years ago, fully adjustable wings et al at a cost, and give it a blast around the course but I suspect it will be moth balled as the majority are content with what they have got for now!

23/07/2007 17:44:18
Andy C
Wow, that certainly generated a bit of lively discussion!

For everyones information I have been with the class at club racing level for the last 35 years on and off. My father and I were actually the ones who helped introduce Alan Jackson to Merlins way back in the early seventies at a tiny lake in Welwyn Garden City, Herts. In those days he was a cabinet maker in St Albans as I seem to recall... I'm now sailing Chris Martin's old boat, Armed Forces, and thoroughly enjoying it.

Anyway, I think this discussion sums up the somewhat polarized views that the class seems to have at the moment. Chairs, CJ and Deepy, I'm fully in agreement. This is a development class after all. If nobody had rocked the boat we would all still be sailing 4' wide hulls with wooden masts and cotton sails.

We should be encouraging legal experimentation and exploitation of new technologies, not trying to dampen down enthusiasm and maintain the status quo. There seems to be a view in some quarters that development is detrimental to the class and the membership. I actually believe the opposite to be true.

For those at the top of the fleet with the latest gear it is a fact that every development means spending even more money to remain competitive. But hey guys, isn't that what belonging to a development class is all about? For the majority of club sailors who don't own up-to-the-minute equipment, developments like this are potentially a way of increasing performance of their existing boats using ingenuity and resourcefulness. The trickle-down of technology also means that in time everyone can benefit from the improvement.

Something like the T-foil could be a relatively low cost way for older Merlin designs to be more competitive with the modern boats. I've always raced development classes:- Merlins, National 12's, International Moths, because as well as being enjoyable and exciting to sail, they not only reward good sailors, but also the application of good engineering and design principles. I hope this continues to be the case.

Anyway, out to the garage now to start experiments....

23/07/2007 18:11:50
mad jack
In my opinion the T-foil won't work on a Merlin as it does on a 14.  The 14 planes upwind and the T-foil effectively drives the boat harder by increasing the wavelength.  For it to be effective, the Merlin would have to be capable of planing upwind.  Also, its good for the 14 because it helps prevent nosediving downwind and in flat water, it can be used downwind to soak down lower.  The Merlin doesn't behave in such a way upwind or downwind that would lend itself to it. They're also a bugger to handle for launching and capsizing, so unless a real benefit can be made, don't bother!  The Merlin's fine in this respect, so don't change it.

If Andy C really wants to get in his workshop and get mucky with epoxy and carbon, why not try something more harmless like a carbon GNAV? It'll give your crew much more room, for which they'll be eternally grateful!

23/07/2007 21:18:32
Andy, I think the topic wandered off whether you should build your own rudder, and went off at a tangent regarding rudders in general and the fleets future!

Definately have a tinker with a rudder in your garage, but it's just that the committee would rather you didnt build an entire new hull with it!!!

23/07/2007 21:48:55
Doubt it
Yeah, put a Gnav on.  It will do really nice things to the mast that you spent 1500 quid on just so that the 8 stone chick in the front will be able to have 8" clearance under the boom instead of 3" under the kicker.

23/07/2007 22:45:43
Alan F
I guess we could keep the puller on on the beat and change the cut of the jib so you can still tack.

23/07/2007 23:02:13
Pat 2121
Andy - just don't bother trying it on Shearwater - you'll be flying over the dam!! We barely have space to get the kite up let alone foil :-(

Would love to see the end product though. A willingness to explore and experiment is a sign of a healthy class.

24/07/2007 08:21:31
If there is any progress on the winged rudder, I'd suggest that it should be registered on the certificate - i.e. you have to use the same design of rudder all the time... (with the obvious repair/emergency exemptions).


24/07/2007 08:50:49
The lift off the foil is a function of velocity squared, so the benefits only come into play at higher speeds,when the reduced drag from the reduced effective displacement and wetted area of the hull make up for the extra drag of the wetted area and induced drag of the foils at low speeds the extra wetted area and section of the foil creates more drag than a conventional rudder.  This may work in boats with a high power to weight ratio, I can't see it being effective in a Merlin, but don't ban them, enjoy the diversion.

24/07/2007 09:44:21
Long and short of it the Merlin is a development class, i think it is a positive move. Either way its within the rules so there is no reason why you shouldnt. The cost of developing a championship boat now adays would seem to prevent any sensible person going down that route but developing foils i think is a great idea.......tinker away.

24/07/2007 10:24:19
Andy Hay
www.aardvarkracing.co.uk do a nice (!) carbon GNAV fitting, oh, and T Foils. Very tasty daggerboard style rudder in black carbon too.

I thought about a T foil for my Phantom some years ago to give the aft end a bit of support, but it all gets a bit much. Rather concentrate on getting around the course upright, hitting the right wind shifts and getting a first rank start than all that!

Actually, the rudder performance would probably be better aided with a "fence" plate to stop cavitation / air being drawn down from the surface. Small flat plate about 1" to 2" below waterline should do the trick (like on an outboard motor). Two effect (theoretically) - a. plate end effect means that aspect ratio of blade effectively increased, so smaller blades = lower drag = more speed & b. might help steering in those death roll, downhill trip outs that seem to happen with small rudder blades.

Trust me I am a Naval Architect ..... (!)

24/07/2007 13:39:21
John Dalby
All very interesting.....
I tried a fence at the top of a rudder on my old 1034 some years ago - it caused a lot of interest at an Inlands at Bala. I did not notice any difference. It extended approx 6" aft of the TE and was approx 6" wide, nicely faired to the blade. I expected that people would complain about an increse in effective boat length but they didn't. It is a tweak still worth thinking about. There used to be a lot of rudders with small fences on the leading edge, never did understand those (unless as a turbulence generator).
I would not want to see T Foils banned and have often thought of having a go.
If Graham Camm of the N12 fleet reads this then he may enlighten us as to the latest N12 experience. He made a very nice example which he showed at the Dinghy Exhibition 3-4 years ago which he reported offered benefits. It was variable incidence and the control - an old motorcycle throttle lever on the tiller, was calibrated fast, faster and very fast (so it must have been a Vincent throttle!)

24/07/2007 14:13:32
I recall that Jude's old Empi rudder use to have a 'fence' as you call it top and bottom of the foil.

Interestingly various boat builders I have talked to think the fin shaped rudders we use have very little effect in reducing turbulence, and that traditional curved bottom more effective. Is it Scantally Clad that also has a fin centreboard, only one I know of?

24/07/2007 19:47:13
Not sure about the effect and haven't read the article but after reading this thread one thing I would point out is it doesn't matter what the committee think about it, it is the membership that decide!


25/07/2007 13:48:28
You are quite right of course, but I think it would perhaps be nicer to reword that so it doesn't sound quite so insulting to those who volunteer their time on the committee! They're not just a bunch of killjoys!

25/07/2007 14:30:12
The voice of the people is not always a reliable tribunal, 2007 years plus a bit they (the people.) crucified the son of God, but then it give give The roman Catholic Church a business!

25/07/2007 15:19:40
Chris (3062)
Vox populi vox deus?

25/07/2007 15:39:01
Nec audiendi qui solent dicere vox populi vox Dei quum 
tumultuositas vulgi semper insaniae proxima sit

25/07/2007 16:49:58
Richard Battey
God! My parents paid all that dosh for a decent education and I still don't understand Latin! 

anyway.........and what was that sir, Big Mac, large fries and a strawberry shake?

25/07/2007 17:33:35
vade mecum
quidquid Latine dictum sit altum videtur

25/07/2007 18:51:16
Richard Battey
would vos amo ut per chips?

ahhh, its all coming back to me now.

25/07/2007 18:54:24
Richard Battey
usquam tergum ut thema of t foil rufus. dont silicis navis nimium!!

wehey its flooding back. Thanks mum, thanks dad.

25/07/2007 18:55:28
Well done Richard, found the web site then!

25/07/2007 18:57:35
Richard Battey
bugger you've blown me cover and I was feeling quite intelligent for a nano second. Is nano Latin? LOL

25/07/2007 20:04:46
Andy C
JA LYH fiksu perse , kanisteri te aikaansaada rikki mikä langauge nyt kuluva asettaa on kotona? ;)

25/07/2007 20:16:41
Andy C
Clue: It's not Rudder-ish, but it's close!

25/07/2007 21:16:30
No it's Greek.

26/07/2007 15:12:55
The Judge
As Ned Sparrow would say 'TAHW A DAOL FO SKCOLLOB'

26/07/2007 15:20:40
Pauline Fowler
I prefer my Rosey foil wrapped...

26/07/2007 18:56:27
Bored in drizzle at home.
Foil wrapped Rosey? - Pray explain.

27/07/2007 10:37:18
Pauline Fowler
I'm a cockney don't you know...

27/07/2007 10:52:58
Richard Battey
Rosey Lee (TEA), my old china... ya see, T foil, ge'it?

27/07/2007 13:28:59
Bored in drizzle at home.

28/07/2007 22:08:01
As a former Merlin sailor and now 14 crew (morrison 12) i can vouch for the t-foil rudder, it has saved our bacon more han nce but on a merlin, i dont think so, we use the t-foil more to keep thge bow out of the water on down wind legs! yes it helps with speed slightly b tricking the water that the boat is slightly longer but it would not work well with a merlin first of all the merlin is much slower therefore the tfoil would create more drag then lift!  I also think that it would require major structual work to get a T foil working due to the loads (look at our gantry) it would just shear the pintles and rip the transom off a Merlin.  Finally making a sleeve for your existing rudder for £50 is never going to work, as stated earlie you need to strengthen the transom and rudder stock, also how do you propose to be able to adjust the pitch of your t-foil in a fixed stock (you adjust the angle for different lift carcs.  etc.)  Bieker spent years developing the t-foil and you want to coble up a sleeve system in your garage???

29/07/2007 17:59:55
some photo's! would a merlin have lift or downforce?

http://aolsearch.aol.co.uk/aol/redir?src=image&clickedItemURN=http%3A%2F%2Fwww.philsfoils.com%2FDesigns%2FDevelopmentClasses.html&moduleId=image_details.jsp.M&clickedItemDescription=Image Host URL
26/02/2019 20:58:57
Silly idea...
More than 10 years on since the last post.  Can’t believe the cost can be significantly different to Moving the jib tack / self launchers / lazy guys or other “must haves”.

Why not have a go?  The clear consensus is that they won’t work!  Or maybe they might

27/02/2019 08:39:40
Might work on a Merlin but would it work for the class?

Take a look at the N12 Fleet now.......

27/02/2019 20:55:40
Following the introduction of T foils in the National 12 class a few years back, the possibility of using them on Merlin Rockets was discussed at the AGM. They were banned. See rule C.8.2.

27/02/2019 21:15:25
Rod & Jo Sceptical
Hi Keith, & quite so.
We sail, distantly, both Merlin & N12, & are members of both classes. Due to intelligent control of rules evolution over the years, Merlin fleet remains in excellent shape,- N12 class is in big trouble, though I have immense respect for  the few individuals who are trying now to save it.  
It would be silly to say that the 'T' foil rudder is the only cause of this difficulty, but it sure hasn't helped.

28/02/2019 15:43:01
what about putting foils on the rudder stock? whoops i mean fences - like you see on outboards.
What is the rule on the rudder foil? We could add foils to the rudder stock any length /size as long as they count as fences on the stock?

28/02/2019 15:55:21
are we allowed fences on rudders?

28/02/2019 23:05:18
Scam, yes it would appear so, a few boats are sporting them and i checked with Dan Alsop last year to confirm (for my own interest in adding one).

28/02/2019 23:20:49
...with a nod to Keith's post, my other reason main for checking was that C.8.2 wasn't clear to me
"C.8.2 Daggerboards, bilgeboards, double rudders, winged rudders and similar contrivances are prohibited"

02/03/2019 08:34:35
David Gates
As the wings need to be near the surface of the water, why not attach them to the stock this way they do not have anything to do with the blade. you could have a vertical foil section that drop down clear to each side of the rudder and take the foils off these, or extend the stock into the water with the lower part being a foil section. this way the rudder integrity is not affected, and if you used a lifting rudder this could still work. All the controls would be through the stock.
Only issue with current boats would be how to make the transom strong enough. Re comment on I14 and structural frame, the Merlin would probably not produce any where near the same forces from a wing, more in line with a N12.
Have a great show guys hope it all goes well.

02/03/2019 08:35:04
David Gates
As the wings need to be near the surface of the water, why not attach them to the stock this way they do not have anything to do with the blade. you could have a vertical foil section that drop down clear to each side of the rudder and take the foils off these, or extend the stock into the water with the lower part being a foil section. this way the rudder integrity is not affected, and if you used a lifting rudder this could still work. All the controls would be through the stock.
Only issue with current boats would be how to make the transom strong enough. Re comment on I14 and structural frame, the Merlin would probably not produce any where near the same forces from a wing, more in line with a N12.
Have a great show guys hope it all goes well.

02/03/2019 09:24:58
Exactly what I was thinking on my lifting rudder stock....

02/03/2019 10:51:16
Roger Cole

I must support Keiths post here and look at the rule. The last few words are "and similar contrivances are banned".

This means in English, that if you stick a wing on your rudder, stock, hull or anywhere else that affects the flow of water,  you have a "similar contrivance" and your boat is out of class.  Sorry, but that's what the rule says.


02/03/2019 18:22:27
Graham Cranford Smith
This idea would be a real pity. 

Winged rudders have all but killed the Twelve class.  I voted against the motion at the Twelve agm where this idea succeeded. The Twelve class was terrified of the rs200 at the time with good reason as it turned out.  But they'd have done better, like the Merlin by staying conservative. Ditto single floors by the way, imho. 

Besides winged rudders are such a pain when coming ashore or leaving a confined place such as Batson. Never mind weed issues and transporting them.  And they add, what, exactly? 

Do we have to do this to ourselves? Let's not.  

I hope the class rule is sufficiently robust. 

02/03/2019 20:11:13
current foiling moth new is approx 30,k, its not in the hull, bugger all materials...bet most is in the foil costs....suggest we leave well alone...

04/03/2019 09:02:30
R Geek
I believe that winder already have started putting 'fences' on their stocks / foils? when does a fence become a foil or "contrivance" another strangely worded rule, no? It would be better if the class want no foils or "contrivances' to include "A hull appendage attached to a keel, bilge keel, canting keel, fin or
bulb, primarily used to affect leeway and/or lift." 
World sailing rule (yeah yeah, you are a national class; so boo boo to world sailing rules, however!)
E.1.1 Hull Appendage

Any item of equipment – including the items listed in E.1.2– which is:

wholly or partly below the sheerline or its extension when fixed or when fully exposed if retractable,

attached to the hull shell or another hull appendage, and

used to affect: stability, leeway, steerage, directional stability, motion damping, trim, displaced volume,

Any of the following shall be included in the hull appendage:

corrector weights,

integral ballast, and

associated fittings.

For this addition to the rudder blade to be considered an additional hull appendage it needs to meet the three requirements laid out in the first part of the definition. In the case of rudder fences:

Is it wholly or partly below the sheerline – yes

Is it attached to the hull shell or another hull appendage – yes

Is it used to affect any of the listed items above – yes
fences are? a: legal or b: illegal?
you pay your money, you takes your choices... 


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