LIGHTWEIGHT F18 V3 BUILD - DAY 3

Finished up my RC Powers F18 V3 "skinny build" today.  I had a bit of glitch getting the rudder servo setup to work.  Initially I wanted to put the rudder servo underneath between the intakes and run the dubro micro pushrods up through the intakes and wing plate, but I need more practice with this setup.  I decided to go with the servo between the vertical stabs behind the prop slot.  This will give me a little bit of interference in the prop wash and some weight back a little further than I want, but it gives me great travel on my rudders which I want/need for high alpha steering.

I achieved my goal of being under 19 oz, my final AUW with 1600 Mah 3 cell battery is 505 gr/17.8 oz... :)

So now my wing loading will be 5.4 oz/sq ft as apposed to 7.7 oz/sq ft on my first "heavy weight" build...

Using the CofG that worked on my last F18, 1/2" behind stock, I have a very slight nose heavy plane with the 1600 Mah battery right up against the bulkhead, so that should be perfect to start off on the maiden flight and then I can adjust from there. 

Here are the basics of my build -

• 6mm depron built with Foam Tac (a couple of little dabs of hot glue here and there when needed), score hinges done with Foam Tac instead of tape;
• 4mm dollar store foam Kf4 airfoils top and bottom, glued on with 3M Super 77 spray adhesive;
• "paint scheme" is "old school" with dollar store permanent marker to give me a pattern I can see and keep track of in the sky (added less than 1 gram of weight);
• finish is done with bevelling and sanding, no filler at all this time;
• motor is Grayson Hobby MJV3 with Turnigy Plush 30A ESC;
• receiver is a HK 6ch compatible with my Turnigy 9x;
• servos are all HK HXT 900 9gr plastic/nylon gear servos, two for elevons, two for ailerons, one for rudders, five in total;
• pushrods are scratchbuilt with nylon clevis from Hobby King, 2mm cf rod, on rudders I used some pieces of micro pushrod wire connected to the cf rod with Foam Tac, dental floss lashed around that and then covered with shrink tubing;
• battery is 1600 Mah 3s 30-40C discharge;
• for control surfaces I have elevons, ailerons with spoilerons mixed on a switch for high alpha and rudders, all control surface hinges done with Foam Tac.

These are the mods I made from stock -

• I used a 4mm cf rod for my wing spar instead of a 3mm cf tube, it cost me 8 grams of extra weight, but my wing is rock solid, even stiffer than the 3mm cf tube "triangle of strength" method I used on my first one, so I am happy those 8 grams of extra weight will be very useful ones;
• I put 3mm cf tube reinforcements in my elevons, perhaps not needed with this setup, but if there is one set of control surfaces I don't want to fail it is my elevons, so the extra 2 grams is worth it in my opinion;
• I opened up the prop slot, cutting it back square to the "v" that is on the plan;
• I added two cooling vents behind the bulkhead underneath the leading edge extension to allow more airflow through my electronics bay and help get a little more air back to the prop in whatever way possible.

Anyway, I am very excited to see how it flies at this weight with this motor setup, I have never used a MJV3 before, so this will all be "new ground" for me.

Using this chart from the GH website as reference http://www.graysonhobby.com/catalog/images/MicroV3-Stats.jpg, I should get about 23.5 oz of thrust from the MJV3 motor, giving me a thrust to weight ratio of 1.32:1, so I think that should be pretty decent and with the light weight and low wing loading, I am excited to see this baby perform!

Since this build is so much at the opposite end of the spectrum from my first build, I plan on doing another "walkaround" video to discuss the different techniques, this plane is 215 grams/7.6 oz lighter than my first build, a 30% reduction in weight!

I kept a fairly detailed weight log of how each stage of the build added or subtracted weight which I will share in coming days.

Cheers,

Scott