Reducing TE cup on 19deg-38bar abc

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Rod Fonda

Active Member
Joined
Apr 30, 2021
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44
Is it best to just backcut TE,,or blend it down along the TE cup face to reduce some cup on a 2217- 19deg-38 abc ?,,would it be better to reduce more closer to hub and leave more at the tips ?,,,cheers
 

shoboat

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Joined
Jun 23, 2002
Messages
7,083
Rod,

I would grind it out if I was you, but you need to check it
with a good pitch gauge while you are doing that operation
to make sure it is equal on both blades. If you decide to mill
the trailing edge out make sure it is equal on both blades.

Thanks,

Mark Sholund
 

dwilfong

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Joined
Jul 1, 2008
Messages
5,711
What is the prop doing?
If it is not reaching good RPM because of to much load go to the 2215.
I found that if you take to much boost pitch out of the 38 bar props thy lose there efficiency.
If it dose not launch good take some off close to the hub and leave it alone at the 50% pulse mark.
Be careful taking it off towards the tip the boost pitch has bin reduced on the newer castings.
I have a few that are junk now from removing to much boost pitch.
 

Terry Keeley

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Supporting Member
Joined
Jul 24, 2002
Messages
6,557
What is the prop doing?
If it is not reaching good RPM because of to much load go to the 2215.
I found that if you take to much boost pitch out of the 38 bar props thy lose there efficiency.
If it dose not launch good take some off close to the hub and leave it alone at the 50% pulse mark.
Be careful taking it off towards the tip the boost pitch has bin reduced on the newer castings.
I have a few that are junk now from removing to much boost pitch.
Why not just put it back in?
 

Rod Fonda

Active Member
Joined
Apr 30, 2021
Messages
44
Rod,

I would grind it out if I was you, but you need to check it
with a good pitch gauge while you are doing that operation
to make sure it is equal on both blades. If you decide to mill
the trailing edge out make sure it is equal on both blades.

Thanks,

Mark Sholund
So either way is ok,but preferably grind out,Thanks for the advice Mark
 

Rod Fonda

Active Member
Joined
Apr 30, 2021
Messages
44
What is the prop doing?
If it is not reaching good RPM because of to much load go to the 2215.
I found that if you take to much boost pitch out of the 38 bar props thy lose there efficiency.
If it dose not launch good take some off close to the hub and leave it alone at the 50% pulse mark.
Be careful taking it off towards the tip the boost pitch has bin reduced on the newer castings.
I have a few that are junk now from removing to much boost pitch.
Yeah,, doesn't launch well and bogs down on rpm,(JAE 45),I am probably trying to make a prop work that is a tad too much for 30% nitro and a .035" stroked Kand B(.55cc head vol .012" clearance, 180 ex),,I was trying to buy a 2117 , but could only get the 22,,,hard props to get here in Aus and Walt is out of stok..I also thought of cutting down the leading edge for a bit more slip and lift,,I'm an old boater getting back to the hobby, but new to prop mods and pitch gauges and all the mad scientist stuff lol,,I suppose I'l learn making mistakes and having fun experimenting,,Yes,it does seem to have less pitch at the tip,I will be careful and just remove a little bit near the hub to the 50% and test,,,Thanks David
 

John Beardslee

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Joined
Apr 20, 2011
Messages
1,599
Cheers John,,looks like a good method,and not too aggressive if you slip a bit on the blade,,thanks for the tip
I use, 60 or 80 grit flap wheels in my battery powered dremel at the pond, you can dial them it right on the boat if you need to. If you take to much I add more cup/pitch to about an 1/8” of the trailing edge from 70% point of the blade out to the tip. It’s a matter of pitch over square inches of blade area.
 

Rod Fonda

Active Member
Joined
Apr 30, 2021
Messages
44
I use, 60 or 80 grit flap wheels in my battery powered dremel at the pond, you can dial them it right on the boat if you need to. If you take to much I add more cup/pitch to about an 1/8” of the trailing edge from 70% point of the blade out to the tip. It’s a matter of pitch over square inches of blade area.
That's quite a cheeky way to do it John haha,,love it,,I suppose the number of props you've done in life,your eyeballing pitch progression on both blades would be pretty good,, like an internal pitch gauge lol,I better not take too much off
 

bermudadude

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Joined
Feb 3, 2003
Messages
229
30%? k&b? 180deg? 12thou? u need a 450 lol
yea u better ease off the prop load on that ole girl...poor thing .
as i was told u only cup (im imagining thats the word boost is replacing) the last 75% of the dia of the blade. sounds weird saying it that way but i never 4get it cause its a odd way of remembering .
dont worry about both blades being identical just take off material a bit at a time,even 1 blade at a time when u get close ,till u get the engine to do what u want .
heh heh funny ,,,,some people asymmetrically cup their blades on purpose
 

Rod Fonda

Active Member
Joined
Apr 30, 2021
Messages
44
30%? k&b? 180deg? 12thou? u need a 450 lol
yea u better ease off the prop load on that ole girl...poor thing .
as i was told u only cup (im imagining thats the word boost is replacing) the last 75% of the dia of the blade. sounds weird saying it that way but i never 4get it cause its a odd way of remembering .
dont worry about both blades being identical just take off material a bit at a time,even 1 blade at a time when u get close ,till u get the engine to do what u want .
heh heh funny ,,,,some people asymmetrically cup their blades on purpose
Hehe,,I am a bit mean on the ol girl,,the cranks I made with .035" extra stroke gave her some more grunt and only ever blew 1 conrod lol,,funnily I used to run a sprintcat on 50% and a 450 and no one could catch me haha,,,Yeah John mentioned adding cup to 70% of blade dia, if you take off too much boost ramp at the edge,,I have seen the debate for asymmetrical blades and indexing prop to engine,interesting,,,,,
Well the way the new ABC props are made it's just a boost pitch on the trailing Edge that's almost impossible to pinch 5 degrees Boost pitch back into a prop on the trailing Edge
30%? k&b? 180deg? 12thou? u need a 450 lol
yea u better ease off the prop load on that ole girl...poor thing .
as i was told u only cup (im imagining thats the word boost is replacing) the last 75% of the dia of the blade. sounds weird saying it that way but i never 4get it cause its a odd way of remembering .
dont worry about both blades being identical just take off material a bit at a time,even 1 blade at a time when u get close ,till u get the engine to do what u want .
heh heh funny ,,,,some people asymmetrically cup their blades on purpose
 

Rod Fonda

Active Member
Joined
Apr 30, 2021
Messages
44
Well the way the new ABC props are made it's just a boost pitch on the trailing Edge that's almost impossible to pinch 5 degrees Boost pitch back into a prop on the trailing Edge
It does look impossible to pinch it back,,Those abc blades seem quite thick,around .040" 1/4" down from tip and 1/4" back from edge,maybe grinding a .020" deeper cup with 5/16" dia stone, blending to edge might restore some efficiency and make the prop usable,but I'm guesstimating lol
 

John Beardslee

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Apr 20, 2011
Messages
1,599
That's quite a cheeky way to do it John haha,,love it,,I suppose the number of props you've done in life,your eyeballing pitch progression on both blades would be pretty good,, like an internal pitch gauge lol,I better not take too much off
Rod, I use a Woods pitch gage when pitching but when you are removing a cast in cup it’s pretty easy to blend the area to match the rest of the blade. I also use small crescent wrenches 4” & 6” to pitch. I grind a radius on one of the jaws so to not damage the prop face. I also put scale calibrations on the jaw so I can keep the wrench on the blade the same amount. Later when I have time I’ll post some pictures that will help clarify.
Thanks John
 

shoboat

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Joined
Jun 23, 2002
Messages
7,083
Rod,

I think you should reduce the diameter a little bit more for your
nitro % and K&B power plant. I have three 2117’s in stock if you
want me to sell you one? It helps to go down in diameter sometimes
instead of grinding or sanding all the face of the propeller blade down.

Thanks,

Mark Sholund
 

Rod Fonda

Active Member
Joined
Apr 30, 2021
Messages
44
Rod,

I think you should reduce the diameter a little bit more for your
nitro % and K&B power plant. I have three 2117’s in stock if you
want me to sell you one? It helps to go down in diameter sometimes
instead of grinding or sanding all the face of the propeller blade down.

Thanks,

Mark Sholund
Yes thanks Mark,I should've tried asking you if you had a 2117,,been waiting on Walt to get some in stock,,I got the 2217 from a local supplier here in Aus ,but couldn't get a 21 ,,my address is 67 Prince Edward Ave Earlwood NSW 2206 Australia ,I'm assuming you have paypal,give me a price and your details,,cheers
 
Last edited:

Rod Fonda

Active Member
Joined
Apr 30, 2021
Messages
44
Rod, I use a Woods pitch gage when pitching but when you are removing a cast in cup it’s pretty easy to blend the area to match the rest of the blade. I also use small crescent wrenches 4” & 6” to pitch. I grind a radius on one of the jaws so to not damage the prop face. I also put scale calibrations on the jaw so I can keep the wrench on the blade the same amount. Later when I have time I’ll post some pictures that will help clarify.
Thanks John
Yeah,,be pretty hard to get things right without a gauge when pitching,I see what you mean about removing the cast in cup,I was going to put some tape near the edge to protect the face ,I'm not too bad with a dremel in hand lol,,Hey thanks for sharing your Knowledge John and others that have chimed in,,Ive learned a lot in a cpl days,,luckily Mark has offered to sell me a 2117 prop so I don't have to go mad grinding the 22 down and save it for future high nitro tests,,cheers
 

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