Runner Alignment for the DN Iceboat
[Updated 12/2/2006]




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I used two methods to measure the alignment:
Direct  - Pencil marks on a board resting on top of the runner in several positions.
Laser  - Use of a laser pointer.
Other methods
... check and adjust right on the ice.
... use rifle spotter scope.
... square to the plank and hope for the best.



Some things I learned while measuring and adjusting the alignment of the runners on a DN iceboat plank.
(These findings may not hold true for all planks and chocks.)
- The pivot bolts can be tight or loose without affecting the alignment.
- I can swap the runners left for right and they remain aligned.
- Weighting or clamping the plank to the flat or loaded position made no difference in alignment .
- The distance between the runner edges changes by 5/8 inches between the loaded condition and unloaded condition.
- If would be possible to have the runner body in line but the runner edge out of line if a poor sharpening technique was used.

             My runners were sharpened by Jim Wood
             His technique and specially built sharpening rig
             ensured that the sharp edge was centered accurately
             along the entire length of the runner.
- The Direct method provides excellent accuracy as confirmed by a check using a laser pointer.




If you know of better methods, please send me a note.
                





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Direct Measurement
Credits: The method shown below was described by Jon Mattsson

- Clamp plank to a workbench pulling down to the same about of bend expected when under sail.
- Install runners to the same tightness as used when sailing.
- Clamp the runners in a level position.
- Place a small board longer than the distance between the runners on the runners in line with the pivot bolts. 
- Pound one side with a hammer to create a groove.

- Mark the other runner edge position at the other end of the board with a fine pencil.
- Repeat this measurement in three position ... center, towards each end.  Ensure the positions are identical on each runner.
- Adjust one runner as needed (note: one chock made be glued into position ... adjust the other runner).
          (I found scratch marks on the right chock with the note "glued" placed there by builder Dave Klatt.)
- Just for the heck of it, I also measured the plumb of the runners ... they were 90 degrees and 89.5 degrees to the horizontal
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The images are full size.  Page down to see five images.

I used an aluminum traverse rod with a notch filed in one end.




 
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Use of a Laser Pointer

An additional thought ... for this method to work, the runners must be plumb (90 degrees) to the plank.

This method is very easy and which I devised to double check the result of the above measurement and adjustment.

- Place the plank on the garage floor in the inverted position with the runners mounted (bolted tight enough to hold position).
- Place a small board longer than the distance between the runners on the runners in line with the pivot bolts. 
- Pound one side with a hammer to create a groove.

- Mark the other runner edge position at the other end of the board with a pencil.
- Mark the other side with a fine pencil in line with the runner edge.
- Clamp laser pointer to the inside of one runner.
- Place the board on supports (same height) at the opposite end of the garage perpendicular to the path to the plank.
- Align the V-groove so that it is centered in the laser beam (which was about 1/4 inch wide at this distance).
- Clamp the laser pointer to outside of the other runner.
- Check to see if the laser beam is now bisected by the pencil mark on the board.

No adjustment was required.  The pencil mark and laser beam were perfectly in line.  Confirming the accuracy of the Direct method.

The images are full size.  Page down to see three images.
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Note: only the laser beam was used ... the level function played no part in this exercise.


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End View of Runner and Laser Level 

View of Target (measuring stick with V-notch and pencil mark)
Beam is centered in the V-notch

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How to align plank runners for the DN iceboat.
Address of this webpage: http://www.carbondragon.us/iceboat/runner_align.htm