Flat edge

[Richard Larsson]

Hello!

I have just repaired and painted four of my runners. The 6mm(thick) long stainless inserts has taken me very fast round the course some times. I have also had spins several times. When i checked the edge flat length i see it is very short, only 7-8 inches. I am a heavy sailor and like speed conditions. I wonder what would happen if i made a longer flat edge on the runners.

Do a long flat edge make more or less friction?

Do a long flat edge give me more or less traction? I have seen that some sailor sail with platerunners in fast conditions. Could the reason be that it is a short flat edge on them and the pressure increase on the edge with increased traction?

S807

[Richard Larsson]

They have 90 degree angle and i keep them always sharp.

S807

[Rolley]

I picked up some "short track" runners last season.  These are shorter Sarns plate runners with a shorter flat section presumably for sharper turning, I guess.  I like the shorter front runner because it turns with a lot less effort, especially in crust. The shorter rear runners tended to slide slip more than I like (and screech loudly while doing so).  This is with an IceFlyer.  I have no opinion on straightaway drag.

[Bob Gray]

    There is a lot to properly sharpening runners but here are the basics for what your are looking for. 90 degrees is what most runners are sharpened to. I'm no good with metric conversions so I'll leave that to you. First of all let me tell you how to check and measure your runner bottom edge side profile. Take your runner and place it edge down on a true bar (flat surface) . Place your hand over the bolt hole and press down. With good back lighting you'll be able to see the profile.  The vast majority of us do not want any true flat but rather a nice even smooth curve.  What we measure is the crown or the distance of the curve between two points. You must now be totally confused but it's actually easy to measure. Again with the runner on the flat surface and your hand over the bolt hole, take two .008 inch thick ( about the thickness of a busness card) shims and run them in from the ends of the runner until they touch the sharpened edge. The distance between these two points is your crown ( some people used to call it the flat). 
    The desired crown varies between types of runners but here are some basic mesurements:
         a. For 26 inch plate runners 10-12 inches
         b.  "   30   "    runners  14-16 inches
         c.  "   36   "        "        17-18   "
These are average lengths of crown , I have a set of 36 inch runners at 16 inches and another at 20 inches. The numbers above should get you started.
                                                                  Bob

[Richard Larsson]

Thx for info, but the queston is how they behave at the ice in high speed. How do a 10inch feel and how do set of 20 inch feel? I got some thaughts from a swede that helped me a lot. The long, flat ones rides up on the tops on the ice more and does not rock (rotate) as much. Therefore they are faster. I am happy with that answer and make the conclusion that a long crown makes less drag straight forward.

[DN5358]

"...but the queston is how they behave at the ice in high speed..."

You're hoping for a simple answer?  There isn't one.  It all depends on the ice.  Long and flat work sometimes, short and high work others.  I unfortunately do not have an answer for you but will gladly get back to you when I figure it out!

Can someone give us a general guideline for when you would use different length / width runners and different profiles?

David

[Bob Rast DN1313]

I have 1 set 1/4 440 insert  20"rocker   smooth ice heavy air
          1 set 3/16 440 insert with stiffeners 18" rocker medium air crusty snow shorter course

          1 set 1/4 plates 16" rocker dont like to use them but short course light air snow
Steering runners 30"  3/16 440 14 "rocker  1/4 32" 440 14"rocker

shorter rocker 13 to 16 inches turns better in light air than a 18 to 20 inch rocker which will slow you down in lighter conditions when turning

Thats my primary regatta runners trying to keep it simple  2 good sets 1 set plates

I do have a old set of Sarns Inserts I sharpened to 95 degrees for lighter air but that s it
Thats about 150 lbs of runners enough to haul

Happy sailing

[DN5358]

Thanks Bob!

[Bob Gray]

A couple of years ago I asked Matt Struble what he uses. He said his primary runners were 18" crown 3/16" inserts for most all conditions. I then asked him what he uses in lite air. The answer 18" crown , 3/16" inserts. A very highly rated sailor told my buddy this year that he likes 17" crown runners for smooth ice in most wind situations and the rougher the ice the longer crown he likes to use.

Runner selection can be a tough call. If you have a set of 3/16" inserts with 17-18" of crown, a set of 3/16" ,30 inch inserts with 14-16" of crown and a set of 26" snow plates, you can cover 95% all sailing conditions.

[Bob Rast DN1313]

A couple of years ago in The NA at Menomonee I got lazy on the second day and after listening to the weather idiot who predicted light air I decided to sail out to the course with my short 304 plates  and left my good inserts in the trailer.The course was like a mile off shore and you had to drag your boat over a big crack on some plywood. When we got ready to sail the wind s were like 20 mph , Im thinking Im screwed. The first race took me about a lap to get the boat wound up and going to windward if I sheeted block to block  the side runners would break loose like a camaro in the snow with bald tires.
I finished in 11th,
Waiting for the star of next race I was in  11th Place.looking down the line I was the only boat with Plate  runners.
I was a little pissed at my self for not bringing my inserts. Jan Gougeon was walking by and looked at my boat and said Plate runners.?
I commented ,yeah a big mistake ,Jan the optimist said yes but your 11th.I said yes you right .
So if I had brought my inserts I probably would have picked up a few places, overall I did finish 7th.
Lesson learned, bring your best equipment to the line , short runners and long not a big  difference in performance but enough to get you a few more places. I did beat about 20 boats with inserts in heavy air.
.Have some fun.

Bob Rast
favorite quotes From the Wizard of OZ
"if I only had a brain"
Talladega Nights
"Seconds Last Dude"

[DN 5449]

Bob I like your attitude.You remind me of a sailing Buddy of mine who uses the expression "don't get itchy underware".

[Rick Lemberg]

now to confuse everyone their is also the amount of flat in front and in back of the bolt hole,you can center it up or put 8'' in front and 10'' behind for an 18' flat. their has been several theories on this , what do you think !.                   Rick DN4155

[Bob Gray]

I believe Ron says 60/40 front/ back. I personally wouldn't screw up a real nice profile to move it an inch or two forward or back.

[Richard Larsson]

Now i got some nice info! Thx guys. It seems to me that a long crown mostly is faster and more grip. Probably it is most efficiant on bumpy ice. Easy!

[KB [us5219]]

After all these years, even certain top sailors I know are still studying the effects of different types of runners on different ice in different wind ranges. 
The shocker was last years worlds in Sweden when the shortest profile runners were the fastest.  there was a little snow on the ice, but there was a nasty "hoar frost" coating on what was once beautiful smooth, flat ice.  I describe the ice surface like dragging runners across asphalt.  There was no glide.  Even in races where there was plenty of wind to power-up, still the short runners came out on top.

It didnt matter if you used minimum T's (as I tried).  The shortest profile runners - even if they were 1/4" snow plates were the fastest in these conditions. 

But you are generally correct!  Longer profile runners can give more grip in heavy air and can be tolerated on the smoothest, flattest ice in fast conditions.    Also longer profiles help smooth out the bumps on less than ideal ice, but beware they will slow you down more quickly in the turns or if you are dodging drifts and other hazards.

Remember when working on your runners that you do NOT want them sharp at the "entry" and "exhaust".  I use marker to show where the front and back edge of the "flat" of my runners are, and from those points out, I gradually dull the runners (with paper or stones).  By the time you get to the ends of the runner they are quite rounded off and smooth.