why shorter lines are harder? This is not the answer.

[Skihack]

Long line 36 mph is a tough one. 15 and 22 were so easy after starting at 34 mph long line. If I had to choose between 32 off and long line 36, I would go with 32 off.

[ForrestGump]

The answer to this subject is along the same lines as "is the chupacabra real?"

[Horton]

Yes

[skidawg]

The faster you have to go behind the boat, but the more time you have to take in the turn and stay in control.!!! Thats why it gets harder. going faster is easy, taking more time in the turn is not.

[scuppers]

@gator1‌ That idea seems like it would provide real data. Looking forward to the results.

 

[gator1]

@scuppers: "one engineering test is worth a thousand engineering opinions" - Ed Zillman, legendary Honeywell engineering guru.

 

We're not up to a thousand opinions yet.....but as soon as I get the data I'll post it.

[Porkfight]

@gator1 said

I'm going to make a big protractor, lay it on the motor box, and video the rope's position as Tim runs 22 up to 38. ZO beep will give me guide ball locations, and I'm going to assume the boat's speed is close enough to 34 mph that it doesn't matter, or at least consistent in its speed variations.

When I posted that angle chart the other day, I was looking into Flag Slalom, which is based entirely off of rope angles. This protractor comes with their flag system.

 

http://www.propellergraphics.com/flagslalom/images/visual%201.jpg

[SkiJay]

Some of the confusion in this thread seems to stem from a lack of definition of which distance is being discussed. The distance the handle is traveling in arcs relative to the pylon is one distance, and the distance/path the skier is traveling relative to the ground/water is another.

 

Clearly, the length of the arcs scribed by the handle around the pylon get longer as the line gets shorter. The skier, on the other hand, travels a fairly similar path through the course, relative to the ground, at all line lengths.

 

As for loads and speeds, the shorter the line gets, the further the handle has to fall back on the boat from ball to wakes before generating any real load or acceleration, the narrower the work zone behind the boat gets, and the higher the loads and speeds have to be in the narrowing work zone to maintain a 16.95 second course time.

[gator1]

@OB‌ I have been concerned about the lack of sensitivity and political correctness that you have shown in previous posts, and am happy to hear you have grown emotionally, and now are interested in moving to a non-judgemental format for your event. May I also suggest that we all eliminate perjorative terms like "22 off" and "longline" from our vocabulary as hurtful and unkind. Lets award the medals based upon how the participant feels after their turn, and if we must discuss rope lengths lets use terms like "rope length disadvantaged", and "rope length neutral".

 

@skijay: Skier distance traveled about the same. Check. Higher loads due to higher acceleration rates and speeds. Check. Higer acceleration and speeds needed due to shorter arc in work zone. Check. We be on same page again.

[Gloersen]

Trigonometry

 

from a prior thread.

 

definitely >delta V's

 

regardless of why; it's just plain harder.

[ToddF]

A...... B....... C....... D....... E...... F....... G......

75... 60.. . 16.7%... 471... 78.5... 4.7%... 0%,

15... 77... 21.4%... 377... 80.6... 7.5%... 2.8%,

22... 90... 25.0%... 333... 83.2... 10.9% ... 3.5%

28... 110... 30.6%... 295... 90.2... 20.3%... 9.3%

32... 120... 33.3%... 270... 90.0... 20.0%... -0.3%*

35... 140... 38.9%... 251... 97.6... 30.1%... 10.1%

38... 180... 50.0%... 235... 117.8... 57.0%... 26.9%

 

A is rope length off

B is degrees of swing required for pendulum to move 75 feet point to point( straight line not the arc)

C is percentage of the full circumference based on the rope length required to go 75 feet (sl)

 

D is the full circumference of the circle (in feet) if we skied a circle around the boat.

 

E is the distance the handle or end of rope must travel to swing the 75 feet

F is the percentage increase the handle must travel. (Really should be read as 104.7%)

 

And finally G: this is where I think the shorter rope length becomes much more tell tale.

15 and 22 off have relatively small percentage increases in X and oddly enough 28 and 32 are basically flat.

 

Then 35 jumps 10% over 32 and 38 well it jumps nearly 27% and I can say this mirrors my feeling on the course

 

So I am going to call Call Column G: Degree of difficulty increase

 

Now none of this takes into account a moving boat, just the increases of travel over a shorter circumference.

[mwetskier]

@ToddF -assume in the first row the initial value of ' 75 ' is not feet off but rather deviates from your stated convention to indicate a full length rope?

[mwetskier]

@scotchipman -its been explained to me that nelson dismisses the pendulum analogy only in so far as the standard equations applied to ' small ' pendulum calculations do not apply to slalom. hes not saying the arc described by the handle relative the boat is not a pendulum but that the standard pendulum pattern is not an accurate way to discuss the handles path thru the course. i take this to be because a simple pendulum cant input additional acceleration or willfully change direction the way a skier can. but that does not alter the fact the ski handle follows a semi circular path around the pivot point of the boat pylon and in that manner very much describes a pendulum like path relative to the boat.

[9400]

I love it when the pendulum physics discussion starts every year. It means ski season is here.

[Gloersen]

:)

[Onside135]

This thread is awesome and ridiculous at the same time...

[ForrestGump]

F it. Just turn and lean.

[Horton]

Funny I started this and even I can't read it anymore

[Drago]

To me it's simple.Gotta go faster to get (nearly) perpendicular to the boat. Gotta carry that speed through the turn or you will fall over/not get around the buoy. Yes, it's a narrower/later path viewed from above, but we (I'll include myself in this group for conversation, even though I no longer ski short line) are practicing a feeling at the longer line lengths, not a path . If we have to make a longer arc because of the speed, where do you propose we do that? I'm going to do it in front of the buoy when there is very little slip angle instead of after the buoy when there is tremendous slip angle.

I propose it's harder because people are over-analyzing it in order to make it easier, and many are too worried about slowing down when the physics slow you down anyway. This is a pendulum effect, or a pendulum feeling. It may not be a true pendulum on paper, but we aren't on paper.