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ACRO E-mail Archive Thread: [Acro] RE: [Serious-Aerobatics] MT's new 80" b ...


Thread: [Acro] RE: [Serious-Aerobatics] MT's new 80" b ...

Message: [Acro] RE: [Serious-Aerobatics] MT's new 80" blades for the S-2B

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From: Dave Swartz <djswartz at>

Date: Sun, 21 Jul 2002 05:06:43 UTC


  On Saturday, July 20, 2002 10:58 AM, acroguy at [SMTP:acroguy at] 
> To All,
> Sorry, accidently hit the send key on that first post.   Has anyone installed
> the new 80" blades for the MT propeller?  If so, do you notice any
> performance improvement?
> That's it,
> Jack Stovall N2MK

I've had the 80 inch MT for 7 months now.  I previously flew about 20 hours 
with the short blades and did not like the performance trade-off with those 
blades.  The long blades gives me a maximum speed about 10 MPH faster than the 
short bladed MT.

Comparing the 80 inch MT to the 2 blade metal Hartzel, I see the following 
advantages with the MT:

1.  The crank shaft is less likely to break
2.  Reduced vibration causes less wear on airframe and accessories
3.  Better low end acceleration (accelerates faster from 60 to 140 MPH)
4.  Faster cruise speed ( a surprise..... 165 MPH at 2200 RPM/25 MP vs 160 MPH 
with the 2 blade at the same setting)
5.  Reduced torque allows longer uplines without torquing off
6.  Deceleration with power pulled to idle is significantly higher

Like most things, there is no free ride.  On the minus side, comparing the 2 
blade with the long MT:

1.  Max level sustained speed is reduced by 5 MPH (I get 180 MPH at 1000 feet 
full power with the 2 blade and 175 with the MT)
2.  Acceleration from 140 to max speed is slower
3.  Take-off performance is noticeably less aggressive (but the same is true 
comparing an Extra 300L to the S2B with a 2 blade)
4.  Since there is a torque reduction, many figures will require different 
control techniques than with the 2 blade - it takes some time to acclimate to 
the differences

The plusses far out-weigh the negatives for me.

Dave Swartz
Fort Lauderdale, Florida


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