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rpm cruise?

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kr2(at)earthlink.net
Guest

Posted: Tue Jul 25, 2006 2:47 am Post subject: rpm cruise?

Hi All,I had my first flight in my kitfox 4,all seemed to go well considering all my new updates and mods that we did,but I am curious to know what some of you are getting on you climb out and rpm cruise settings?

  I am using a VW mosler 80hp powerplant and I am getting around 600 ft permin climb,this is solo carrying 16 gal of fuel with an empty weight of 753 lbs,I wish I had better climb rate,but maybe I am spoiled from rotax engines in other aircraft and of course it is hot and hummid here in florida.

  I am only getting 75 mph cruise at 2500 rpm even though my engine redlines at 3600 rpm,but on my static run up I am at 3000 rpm full throttle,

 Anyone out there running a VW?,Do you run at cruise at a higher rpm than 2500 ?,can I run at 2900-3200 at cruise.I know other engines guys run a feww hundred rpm lower than their max redline,but does this also apply to a VW ?

  

 Thanks for any ideas in this area.......................

 ps I have attached a picture of my completed bird,another member of the fox family.....

  

  Sincerely     Mark Thomson   N61AC

  

  

 Mark Thompson

 kr2(at)earthlink.net (kr2(at)earthlink.net)

 EarthLink Revolves Around You.

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dave(at)cfisher.com
Guest

Posted: Tue Jul 25, 2006 4:13 am Post subject: rpm cruise?

Mark, 

  

 Very nice looking Kitfox. 

 I assume by the short prop your are running direct drive  ?

 I think the VW like to run higher rpm that 2500 in cruise  so your cruise would be higher in that case. 

 You have a heavy IV at 753 so with the short prop and  heavy weight 600 fpm not that bad really in your climate.   Wait till  cooler days and see how it is. 

  

 I read this ad on the Mosler here  http://www.greatplainsas.com/chooseaircrft.html        --  The claims are far from what you but they claiming a 490 empty weight  as well which I find hard to believe.

  

 Keep us up to date on how your tweaking improves things. I  always like the AeroVee but I don't like to be limited to a short prop as you  will lose your short field performance. 

  

  

 Dave 

  

  

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lcfitt(at)sbcglobal.net
Guest

Posted: Tue Jul 25, 2006 6:51 am Post subject: rpm cruise?

Hey, guys,



The Great Plains site is a prime example of the hype that can trip up a 

prospective engine chooser.  The lightest Model IV I have ever seen weighed 

in at 604 lbs.  Actually there were two owned by the same guy and built 

light for performance rather than trophies.  490 lbs is totally out of the 

quetion - absolutely not doable and 1450 rate of climb is not in the cards 

unless you have a CAP or repitch on the ground for climb tests and then 

repitch again for cruise bragging rights.  It can't be done and should be a 

serious heads up for the other numbers in the claim.



My model IV-1200 weighed in at 704 and undoubtedly weighs more now as they 

always do with the camera mount and other comfort stuff, not to mention the 

tiedown stakes, first aid kit, tool kit and spare fluids I always carry.  My 

climb Saturday in 90° - 1300 ft. weather was 800 fpm and cruise at about 105 

at 5500 rpm. - Rotax 912 UL.



I have no problem with alternative engines.  Please don't get me wrong here. 

I think there are less expensive ways to get a good flying airplane than 

going with certified or Rotax engines and would never criticise a persons 

engine choice.  But what really galls me - almost beyond words - is the 

claims that are made, by the people making the money, using totally 

impossible numbers.   The weight number given in the website is totally 

outside the realm of possibility even if you built with light fabric and 

only one coat of polybrush. Of course if you cut the seat in half, put no 

cushion on it, eliminated the header tank, top and bottom false ribs, used 

only one 7 gallon wing tank and eliminated such things as wing tips all 

fairings and probably a lot more.



Can someone explain to me how this nonssense can continue year after year. 

This happens over and over again.   I think we on the list bare a certain 

burden here.  How can we use our experience in a positive non insuting way 

to clear the air on some of these claims.  I gotta go kick the dog.   ( for 

you animal lovers out there, I don't have a dog, only a bird and she knows 

how to take cae of me)



Lowell



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dave(at)cfisher.com
Guest

Posted: Tue Jul 25, 2006 7:28 am Post subject: rpm cruise?

Lowell,



My Kitfox IV 582 on certified scales is certainly under 600 lbs.

Dry weight is around  570 after new paint this year.



I totally agree about claims that are made by any supplier  that are 

inflated.  The proof is in the pudding. If you got the goods then videotape 

it and show the world.



Dave



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kr2(at)earthlink.net
Guest

Posted: Fri Jul 28, 2006 8:59 pm Post subject: rpm cruise?

Thankyou to all for your advice,I am now wondering can I put a inflight adjust prop on a VW?

  I now that vw calls for a wood prop for the harmonic balance,but can a prop be used in this application using an inflight adjustment/or constant speed?.......

  

   Thanks ....Mark

  

 

  

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