[SPAM] FW: Re: Abbra first fly report

[vicenterc at comcast.net]

Good question Brian,
 
My friend Pat has been flying the gasoline version a lot these past two or three weeks.  He can give you his point of view.  However, I helped Pat during the first fly and trimming.  My first recommendation for those that are planning to use the gas engine is "DO NOT install the rudder and elevator servos in the tail".  The balance would be just fine using one servo for elevator and one for rudder located in the canopy area.  You could use the ignition and the airborne battery to balance the plane.  You would save some weight on servo extensions, and believe me every fraction of an ounce counts in the gasoline set up.  When we flew the gas version the first time was extremely tail heavy.  We had problems to keep the header in place and the header came loose during the first fly and moved to the back in the belly pan making landing interesting experience.  The plane was at that moment very tail heavy and engine died.  We landed in tall grass damaging the landing gear.  The landing gear was replaced and the batteries were move below the landing gear plate.  The plane is flying very nicely now.  The weight now is a little over 11 lbs.  However, we know that replacing the prop and the receiver will take it down below the 11 lb. mark.  The impression in flying are difficult for me since I have not flown the complete master schedule back-to-back with both planes.  The difference in weight is large (around 14%).  I noticed that landings feel a little heavier with the gas version.  Also, the up lines are a little lazier but should not be a concern.  As far as I can see, the gas version is a viable option for those that would like to go gasoline power pattern plane.  There is a weight penalty but that is compensated with fuel cost.  In the gas version, I will say that the positive incidence should be more around 0.5 degrees due to the additional weight.  The trimming comments for this version are similar than for the glow version but mixing amounts were a little higher.  The mixing amounts could be reduced now since we r
eadjusted the CG but we haven't done that yet.
 
Some more recommendations to save weight.  The ignition battery that Pat has in his plane is 5 cells NiMh 1100 mah with regulator.  You could save weight using 4 cell smaller capacities (900 mah or less) and save the weight of the regulator and the additional cell.  Also you could save weight by using smaller receiver and a wood prop that is lighter.  Doing all this the plane will be for sure below 11 lbs.  I think the penalty of electric is approximately equal to the penalty on gas.  Therefore, it is clear to me that the Abbra electric and gas versions will be below 11 pound but you need to monitor the installation closer.  Final recommendation, use standard duty servo extensions.  I don't think we need it for this application.
 
Final comment.  The current engine has soft mount provided in the kit as additional cost.  I think the rubber amount of that mount is not enough to dampen the vibration of the ZDZ 40 engine.  I will strongly recommend trying Mr. Hyde soft mount if you are going to install a gasoline engine.  I am not sure if someone out there has done this.  I know that Mr. Hyde will custom made the mount.  The only problem is the additional weight of the mount but I think it would be OK following the recommendations above. 

Have a nice weekend,
 
Vicente
-------------- Original message -------------- 

Thanks Vincente.

I cant wait to see this plane, and the comparison to the gasoline versioned one.

Brian

vicenterc at comcast.net wrote:
Abbra glow version 1st. Fly report

Yesterday, June 3, 2005 I flew my Abbra the first time.  For those interested in the equipment please see Bob Pastorello web page.  The version that I flew is the glow version using OS160 engine.  Final weight is 9 lb 14 oz.  I know that I could reduce the weight a little more by using lighter wheels and smaller receiver.  It is OK for me since this plane is my first 2 m class plane less than 10 pounds.
 
First Fly impressions:  Clearly the most constant speed plane that I ever flown.  I can fly closer to show a better presentation.  It is going to take some time for me to get along but definitively I like the change.  Please understand that this is my first wide body plane.  For those flying already wide body planes probably won’t be a big change.  The down lines are a pleasure to watch.  I felt as a pilot that I have more time to make corrections.  Slow and snaps rolls are fantastic. Landing is a pleasure.  Not sure yet about spins since I did it once only.  I really didn’t like the break.  I think I need a little more up elevator since I lost some travel amount after the elevator trimming.  
 
First Trimming Impressions:  As soon I took off I knew that I need down trim.  I got fixed and finish with 28 bits of down trim in my JR 10 X radio.  Also I finished with 4 bits of left trim.  Ailerons and elevators were set up for 10 degrees travel.  After the first landing, what a landing it was a 10 using the old rules, I checked the elevators and found that one half was a little more up than the other half.  Also, I found the same problem in the right aileron that was a little more up. When I say a little is almost difficult to see at naked eye.  Definitively the plane was telling me that I need a better mechanic.  This was clearly mechanic error (me!!).  I checked the CG and the plane looks fine now.  If you ask me where it is the CG now “I will say I don’t know”.  I am one of those guys that check the CG in the air.  I put the battery behind the firewall so I knew that I was a little nose heavy.  The plane requires a little pressure when flying inverted.  Right now I need more time to finish CG adjustments.  My taste is a little tail heavy so I will start to move the battery but I want to correct the positive incidence first.  I will check the actual location for those that want to have the information.  The rudder was set to about 30 degrees.  I think is OK.  I did the master schedule one time.  I feel now that I am OK for travel.  Probably, I will need to get a little more up for the spin but I did it only once yesterday.  In the second fly, I did finish with 8 bits of down elevator.  I know that my plane was set up for 0.75 degrees positive incidence.  I also know that you can order the plane now using 0, 0.25, 0.50 and adjustable that you will need to install.  It is clear to me that 0.75 is too high and probably I will go 0.25 in my next Abbra to reduce the down elevator trim.  The positive incidence and the elevator trim causes that the plane requires rudder with up elevator mix to hold knife edge in both sides.  In this regard, it is clear the plane requires opposite aileron also.  This is not a sur
prise to me since I never had a pattern plane that didn’t require any mixing during knife edge.  I still tweaking with rudder mixing with elevator and rudder.  The final information will come in the future.  My next step in trimming the plane is to try to reduce the positive incidence to 0.25 degrees to minimize the mixing and the down elevator amounts.  Also, I will increase to 12 degrees the up elevator to improve the break on spins.  On lateral balance I don’t think that I have to adjust.  The plane tracks very well in loops but I need to check a little more.
 
Tomorrow, I will have a judge calibration section.  The judges will tell me if my impression of fantastic landings, snaps and slow rolls are realistic. 
 
Vicente Bortone
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