canard discussion

General Discussion
1

    Been doing a lot of twinzers lately and discussing different positioning/sizing of the canard fin. I have done all mine based off of Wil Jobson’s positioning and layout, i.e. a pretty tight cluster. 

    I have also been reading on some other forums (aerodynamics) about wing layouts and the relation of the canard to the main wing in positioning and size. Here is a link to a canard positioning calculator for a model glider.

http://adamone.rchomepage.com/cg_canard.htm
The issues and reasoning for this position is going to be different for surfboards I understand.
-What I want to know is how the size of the canard will effect drag reduction on the main fin ?
-WHat is the optimal percent reduction of surface area from main fin to canard? 
 -ANyone active on here explored the options? 
THe superchargers look considerably smaller than the canards that Jobson prefers.
What about a bonzer runner as the canard, the surface area is spread along the base rather than in height?
2

try them ALL , Pico , and please let us know YOUR findings !  and how they surfed , mate !

 

I have tried PLENTY of different four fin setups [including a bonzer runner as the front side fins[?canards?] , and enjoyed THAT ,

 

  but with the walden , because the plugs are so far apart , and are so far forward of the tail pod , it would be a different feeling / result from a 'standard ' quad , or  a 'twinzer' setup , too.

 

  I hope people post [shots of] their setups here too , as a lot of the hydrodynamic / aerodynamic 'pseudo-science' discussions here often  leave me scratching my head ...

 Personally , I prefer seeing and reading about how the fin setups FEEL , when SURFED ...the practical stuff ! 

THAT is why I come here , and one of the aspects of why I SURF !   [....all the other over-ANALysing stuff  , and theoretical wanking , and arguments threads ... I basically couldn't be  bothered  with  them ! To me , they are just  blah blah blah , in most cases ... achieving no positive outcome , and just making enemies . Mostly , they are often nothing more than  just ego-jousting nonsense * ]

 So, Pico ...please keep up the experimenting , and post photos , and ride reports of all your twinzer experiments , ... I , for one , absolutely  LOVE that stuff !

cheers mate !

  

  ben

 

* there is no substitute for time spent in the water

3

hi , good timely subject for me , i tried my homemade herbs superchargers about 5 years ago , they definatley added something to the board, it just seemed smoother all round ,

i like bonzers in general and that is what i ride the most of the time , the bonzer front runners are like carnards in reality,

i normally glass on the front two runners just because its easier but the last bonzer i made i wanted to use plugs so i could try different fin set ups on the same board , with the board as the constant it would show up what fin set ups were better than others ,

on a 6ft 6ins bonzer the rear of the larger front fin is about 11 inch from the tail , this is about the same as a thruster and also somewhere around the same placement for a quad so already there is similarity going on ,

the bonzer distance between the two fins is 1 1/2 inch ,a bit further away than a twinzer set up but somewhere around a quad type board m

my stance on the board is quite narrow and i find further front fin placed boards seem to work better for me as well ,

in generall a lot of quads are shorter and wider with the rear fins set behind the main fins ,

meaning your foot needs to be right back over the cluster ,on a bigger board of any fin set up your feet just naturally move up to balance the board,

i made some bonzer runners out of lexan polycarbonate ,the fin tabs can be bent to your angle with heat ,this enabled me to set the fcs plugs ar 6 degrees and the then bend in the angle for the bonzer fins ,

the bonzer set up went fine ,about what i expected it to go like , i tried the board as a 2 plus one with different side fins of different sizes and different rear fins ,

i tried different combinations of front bonzer a rear fcs and vice veresa

some set ups went a bit better than others in that some lacked a bit of drive ,

in the end the set up that was so much better than the others ,bonzer set up included was plastic g5 in the front rear postion with homemade glass fins in the front forward posistion , this fin was a copy of the griffin rears that the five fin boards use,

the rear fin was a 6 1/2 inch narrow slightly raked that camr from a wind surfer ,

these two forward fins are canted at 6 and have 1/4 toe,

although the board has so much more fin area like this it just felt so much drivier ,looser,faster ,free,

i think the slot effect just adds something really extra , i can/t explain why then the more forward fin postioning suits my stance on a 6ft 6 board ,

i have another board , a 6ft 8 thruster i made a couple of years back that just lacks drive , its quite light and the tail is narrow and the front wider ,its a hybrid type board ,

i think my feet are just to far away from fins so have added some more plugs in front of the front fins to see if i can replicate the set up on my bonzer and see if i can get the drive back ,

whether my board will go even better with smaller carnards a bit closer to the main fins i don/t know ,i may try it sometime but i am quite happy for now

so my own conclusion even though i have never ridden a true twinzer is that the slot effect has some real benefit ,

ps some pics especially for ben pete

 





4

there must be a distance between the canard and main fin which is optimal. 

also there must be an a relationship in size for the two fins. The rc airplane guys say the canard should be no less than 15% the size of the main wing. the superchargers look smaller than that to me. Has anyone ridden a true twinzer and the supercharged setup? how does the ride vary.

the ride on a twinzer to me is like a twin fin but more stable and doesn’t lose speed coming out of turns. would running a longer fin base as the canard lose the ability to flick the tail around? and be more likely to track?

also why no roving  on Jobson’s canard? 

 

5

Did a lot of tweeking of  Canards on windsurfing boards. Don’t really know the science be hind them but most all of them were less than 15 %. Don’t understand the need for them on a surfboard as  mostly surfboards do not reach high enough speeds and canards work best on boards that are intended to track and really screw up the turning of a board. I used them on all my fun bump and jump boards but they didn’t work well on wave boards where I wanted to do a lot of turning. You kind of had to sail your board off the tail and couldn’t use the rails much in your turns. I did experiment with them on windsurf wave boards but they just didn’t work well in the waves but it’s allways fun to try them !   The issues and reasoning for this position is going to be different for
surfboards I understand. -What I want to know is how the size of the
canard will effect drag reduction on the main fin ? I don’t think it has anything to do with drag reduction , rather the canard was to prevent ventilation which would lead to cavitation and the failure of the fin to hold. In fact they did a good job of stopping cavitation . I think there was an increase in drag but because the canard stop the cavitation the board could go faster and not spin out .

6

wow , that is GREAT , Pete !

 

  thanks so much for the photos , as well as the detailed fin setup and ride report post !

 

  THESE are the sort of PRACTICAL POSTS  that I  learn from , there is no 'pseudo-science' theoretical mumbo jumbo over-complicating the simple act of riding a wave , in this post !

 

  keep up the good work , the simple language , the experimenting , and the test ride reports !

 

  good on ya mate !

 

  cheers !

 

  ben  

7

cheers wood ogre !

so...

[ now the million dollar question ...wait for it....]

  DID you ever use them ['twinzer' setup[s] ] on your surfboards , at all ?

I'd be keen to see / hear how they go in hawaii ...do you know [m]any surfing on twinzers on your island ?

 

 Because , I'd be keen to hear their feedback [the down the line point waves there might provide enough board speed for any positive effects to be clearly felt , is what I am thinking ]

 

  cheers

 

  ben

8

With my first board built I went the single fin route thinking that less fins meant less drag, more speed - made sense.

I then took a test ride on a Takayama Scorpion with a quad set up (relatively close set up) and was blown away by how loose and fast it was. When dropping in it felt like there were no fins (or a least like it was under finned), but it turned no prob’s and didn’t loose speed in turns.
I needed to investigat this further so I started looking around and read someone mention jib/mainsail interaction as a factor, this lead me to this site which has a lot of info on this phenomenon. - http://www.arvelgentry.com/techs.htm

As far as fin set ups go I don’t think they benefit from any ‘power’ gains like a sail boat does but they would definitely be benefitting from the reduction in cavitation/increase in smooth laminar flow.

Roughly translated, the front fins directs water over the back increasing the flow along the base and smooting the laminar flow over the whole back fin, this increase in flow then also ‘pulls’ the water along the front fin to do the same. This is awesome!

Obviously there is infinite set ups to achieve the desired effect but I believe most close fin quad set ups work this way to some extent.

I’d love to set up a tanks and do some testing…

9

thanks wood ogre, the reduction in cavitation makes sense to me. As a twinzer surfer i have to say I believe they do work, but your information was very helpful.

Mick d I really appreciate that link. Now I’ve got some more reading to do.

I have also been thinking more about the foil relationship. I read somewhere that Jobson is foiling out the tips of the main fins 80/20. 

what would happen if the fins were single foiled with the foils facing each other? thrailkill style.

I have decide that I will add a couple plugs and start making a bunch of different canards to test.(just for you Chippy61) ill even post some pics in the future.

 

10

[quote="$1"] what would happen if the fins were single foiled with the foils facing each other? thrailkill style. [/quote]

Synergy.

11

yes. this I am stoked to try out. I am a little concerned with the overall flow since the first fin to direct the flow would have a non foiled face. perhaps a double foil on the canard to promote synergy and direct flow to the main fin. I also imagine this would work best if the toe in were more relaxed on the canard, rather than Jobsons increased toe format.