REFLECTOR: Engine Selection

[Douglas Holub]

To each his own.  You can always go faster with a bigger engine, but to me the weight and fuel consumption penalty for anything over 200 hp in a plane this size isn't worth it.  That's just me.  A lot of guys like to build the biggest, baddest airplane they can.  I love it.  More power to them (literally.)  It takes all kinds of people to make up a world.  I'm one of those "less is more", "think smarter not harder" kind of guys.  I'm shooting for 180 mph and 25 mpg at 9,000 feet with my top door, short wing, fixed main gear, retractable nose gear Velocity.

I'm disappointed to hear that propellers are not more efficient at lower RPMs. I was hoping that extra efficiency would give my diesel a little free speed boost.

Doug
  ----- Original Message ----- 
  From: Al Gietzen 
  To: 'Velocity Aircraft Owners and Builders list' 
  Sent: Thursday, June 17, 2004 11:22 AM
  Subject: RE: REFLECTOR: Engine Selection


  Just a couple of comments on this power, efficiency and speed thing.  Torque is a measure of force; HP is a measure of work; force times time - or acting through a distance.  So it is the HP that does the job.  Hp is simply torque times rpm.  You can have high torque a lower rpm but if it gives you the same HP you've gained nothing; unless the prop was more efficient at lower rpm.  I thought this was true as well - until I studied some prop performance charts and found it wasn't true.



  160; 180; or 200hp - IMHO, these are all low for a fixed gear 173.  Getting 161 mph at 5500 ft with 160 hp translates to 173 mph with 200hp (remember; speed goes as the cube root of power).  That's 153 kts.  Hardly impressive.



  Al



  Subject: Re: REFLECTOR: Engine Selection



  Plenty of power. He's got a 173 RG. The Velocity was originally designed for 160 hp.  The DH180A4 is 180 hp up to 18,000 feet. The DH200A4 is 200 hp at 18,000 ft. Plus, the diesel has better torque at lower RPMs than a Lycoming, and propellers are more efficient at lower RPMs. Plus it weighs less if you take into account that it is 30% more fuel efficient, so you don't need to carry as much fuel weight to get the same range. A DH160V4 is in the factory's test airplane.  With the 160 hp engine they clocked it at 202 mph at 15,500 feet, and 161 mph at 5,500 feet. And that is with a fixed pitch propeller.



  The DeltaHawk has half the moving parts of a Lycoming, no spark ignition to interfere with the radios, and burns readily available and slightly cheaper Jet A.  It is much smoother because it's a two-stroke. Plus, since the DeltaHawk test platform is a Velocity Std RG, the firewall foreward package is pre-designed.



  No, I don't own stock in the company. Just excited about the first significant improvement in general aviation powerplants in 50 years.



  Doug Holub

  Std Top Door, 50% done, 80% to go

    ----- Original Message ----- 

    From: NMFlyer1 at aol.com 

    To: reflector at tvbf.org 

    Sent: Tuesday, June 15, 2004 9:18 PM

    Subject: Re: REFLECTOR: Engine Selection



    nice idea Doug... but not enough power scotty 


----------------------------------------------------------------------------

    _______________________________________________
    To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector

    Visit the gallery!  www.tvbf.org/gallery
    user:pw = tvbf:jamaicangoose
    Check new archives: www.tvbf.org/pipermail
    Check old archives: http://www.tvbf.org/archives/velocity/maillist.html



------------------------------------------------------------------------------


  _______________________________________________
  To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector

  Visit the gallery!  www.tvbf.org/gallery
  user:pw = tvbf:jamaicangoose
  Check new archives: www.tvbf.org/pipermail
  Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.tvbf.org/mailman/private/reflector/attachments/20040617/5dd09134/attachment.htm