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Discussion Starter #1 (Edited)
I have seen many different oar tower configurations. Colorado frame companies place them on the outer edge of the frame with a tilted cast head to mount the lock. Flagstaff companies have the elbows turned inward towards the tubes with the straight oar tower tilting out. Northwestern rigs have their designs as well. Does anybody know if putting the towers and locks in these different configurations makes a big difference in leverage and handling of the raft?

I also see people tilt their towers way out past the edge marking the lock further away. They do this even though they have the tilted cast head on the tower.

Is this just preference or is there any mechanical knowledge that can back it up?

Ultimately, I just wanted to start another thread to waste valuable time reading

Cheers

Tda
 

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Well, you sure waisted mine, I’m gonna need about three fiddee for that...

Lots of geometry goes into where you put the fulcrum point, narrow little frames tend to need the tower further out, you can make an oar that is to short work, if the tower is angled to the inside, but if you really want to understand it all, it’s gonna take one of these smart people on the site, to explain it all, ( which I very much am NOT!)
So about that three fidee :D
 

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My big water frame is very wide and I have the tower of the Hollander fitting on the inside of the frame. My narrower large frame has the tower outside the frame. I can use the same oar on both my large frames without moving the oar stops(critically important oar rights:)).

Your second photo of the blue NRS with the tower to the inside would not suite my preference. The general rule of thumb is for the fulcrum to define thirds with one third toward the oar handle and two thirds of the oar toward the blade. Consider the following thought experiment. If I had the fulcrum at one foot from the oar handle you would have no leverage and the oar blade would be difficult to lift and would almost be impossible to pull through the water. Thirds tends to define the sweet spot for most people.

Without putting a tape measure to these oars it looks to me like the fulcrum defines the oar almost into quarters. These Smokers would likely feel very "heavy" in my opinion especially considering that they are not counter-balanced. Pulling them through the water would feel hard and slow. If the towers were on the outside of the frame I think it would be more properly configured. But, to each there own.
 

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There's a lot geometry, measuring, etc. etc. Here's an idea, take you're boat, oars, and a wrench to a lake, row your boat and adjust it until it feels right for you.
 

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Lots of geometry goes into where you put the fulcrum point
^^^
It's really a matter of oar leverage and balance more than how it looks on the frame.


I don't claim to be a geenyus, but I am very curious and I do tend to overthink oars. OK, I'm an oar slut. Here's what I've learned:




Conventional wisdom for oar stop placement for work boats and pulling craft (not necessarily whitewater only, but it represents a much wider/older history of use than whitewater rafting) are 2/7 the length of your oar, 30%, and the 1/3-2/3 Rule we see recommended for rafts. This isn't much percentage difference. 2/7 is 28.57%, 30% is 30%, and 1/3 is 33%...but it makes a perceptible difference in use.

2/7 needs a counterbalanced oar with light blades (Squaretops), but we don't really need "high gear" as we aren't rowing a pulling boat and we don't coast that well in a raft between strokes.


1/3 works with heavy blades and wide oarlock spacing (unbalanced Smokers, Cataracts, Carlisles, etc.).


I think 30% is a good target for whitewater boaters if you have balanced oars.

For a 10 foot oar:


  • 2/7 is only 34.2" of oar inside the locks, or say 69" minimum between your oarlocks
  • 30% is 36" from handle to oar stop, or 73" minimum between the locks
  • 1/3 is 40" or 80"+ between the locks.

For a 9.5 foot oar:


  • 2/7 is only 32.4" of oar inside the locks, or say 65" minimum between your oarlocks
  • 30% is 34" from handle to oar stop, or 69" minimum between the locks
  • 1/3 is 38" or 76"+ between the locks.
What does this mean?

Oar length and balance are important to determine frame/tower width. If you have poorly balanced oars and a narrow frame, you'll be working hard to get the blades out of water and you'll have a bad day. If you have well-balanced oars and a wide frame, it's easy, but your "gearing" is pretty low.


My big water frame is very wide and I have the tower of the Hollander fitting on the inside of the frame. My narrower large frame has the tower outside the frame. I can use the same oar on both my large frames without moving the oar stops(critically important oar rights:)).

This makes good sense. If your oars are balanced well, you shouldn't have a different pin width from boat to boat.


The general rule of thumb is for the fulcrum to define thirds with one third toward the oar handle and two thirds of the oar toward the blade. Consider the following thought experiment. If I had the fulcrum at one foot from the oar handle you would have no leverage and the oar blade would be difficult to lift and would almost be impossible to pull through the water. Thirds tends to define the sweet spot for most people.
I'd argue that if you have a balanced oar and can skinny up the inboard dimension, it feels a bit better than a full 1/3-2/3.
I'm curious to know your dimensions and oar type.


Without putting a tape measure to these oars it looks to me like the fulcrum defines the oar almost into quarters. These Smokers would likely feel very "heavy" in my opinion especially considering that they are not counter-balanced. Pulling them through the water would feel hard and slow. If the towers were on the outside of the frame I think it would be more properly configured. But, to each there own.
Troof. Smokers have very heavy blades and shafts. You can remove almost 1# of wood from the blade without weakening them or causing performance to suffer.


 

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I currently have my frame set up with the oarlock to the inside but plan to change this because of two reasons.

1. I just got a bimini and with the oar tower on the inside of the frame I can not fold down the bimini without interference from the oars. This will be fixed by putting the tower on the outside of the frame.

2. I believe that if the oarlock is going to be shifted out of its preferred vertical alignment it would tilt into the boat. This would be problematic because it would result with the hollandar fitting sitting below the plane that the frame sits in and would rub on the boat. I feel that this situation would not be as critical with the lock on the outside of the frame because there would be more wiggle room for the lock to sit out of plumb.
 

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Wider is better ... period
 

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I like them positioned where my oars will not break, smash my thumbs or have them pop and hit me in the head or private parts. Relative Bearing Grease on the pins helps out, immensely too. Personal preference works also. Have fun.
 
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