Super Aussie Fruit Bat (SAFB)

Plans

Click on the images for a larger picture

SFB Engine Detai.jpg (105226 bytes) This is the latest evolution of the Aussie Fruit Bat (AFB). The Super! (or SAFB) It's the AFB with a 3 mm Coro cambered wing. Read the AFB build instructions as well. You will need 5mm and 3.3mm (or thinner!) Coro to complete this aircraft. Note that the C-of-G is further forward on the SAFB than the AFB
SFB Engine Mount.jpg (35218 bytes) This is the engine mount made from HDPE (High Density Polyethylene) - or your wife's plastic cutting board. The old AFB used two pieces of thin wall alloy and a commercial engine mount - Radioactive Mfg (RAM) or Thunder Tiger adjustable worked well. The small slot in the mount is 14-15mm wide to suit 3 thicknesses of coro. The wide slots are cut to a size to suit your engine. Before you mount this on the plane, squirt some hot glue into the coro slots where the screws will go. Let it harden - it gives the screws something to bite into, stops the coro from crushing and generally make the whole thing work better.
FB Finished.jpg (75529 bytes) To attach the mount, I used 2 long self tapping screws right through the two sides of the mount. I drilled clearance holes on one 'arm', inserted the screws and then 'self tapped' through the fuz and into the opposite arm. I then made a small alloy plate underneath the wing/fuz, drilled some holes into this and inserted shorter self tappers through the plate, wing and into the engine mount. This helps during "arrival" aka "landing"

Engine size is ~.25 to .36. This picture has my beloved OS 32SX with whom I am well pleased. I took it out of storage after 6 months, fuelled it and it started 1st flick. Please note Mr OS - this is a wonderful engine but they are TOO bloody expensive! A Thunder Tiger 36 PRO is half the price, 15% more grunt

Click on the navigation link for the plans everything is in 5mm (4.9 actually) Coro except for the wing uppers. These are in 3.3mm (about all we can get in Aus) - pretty simple really. Should take about 10 minutes to cut out. Note that nothing is set in stone re the dimensions. The only 'given' is symmetry about the centre line. I have chopped 40% off the height of the tail in the past - it still flies well! See the prototype page! If anyone builds one with 2mm Coro uppers can they let me know how it goes?

SFB Coro Components.jpg (28436 bytes) This is the almost complete 5mm coro bits. The only 5mm pieces missing are 2 strips 500mm long by 3 flutes wide as the 'spars' - they don't support any weight so are not really "spars". The flutes in the fuz/tail are running vertically. The flutes on the fuz doublers run length wise. One daring experimenter on our field - Chris - has hinged the tail to form a rudder. On the original (flat wing) AFB it would flat spin with this killer enhancement. Haven't tried it with the new improvedd version

I glue every thing together with 'Selleys Gel Grip' This is an Aussie brand so I'm not sure what is called overseas.  It is ordinary "contact cement" (yellow rubbery glue)  used to glue Formica laminates to kitchen bench tops (amongst other things). The gel version versus the liquid seems to much easier to use. It sticks like s..t to a blanket, is very low mess and is ready to joint in 5 minutes - much faster that the liquid version. Use your old busted props as spreaders. An old 11x5 is just about perfect. I clean my coro off first with "Prepsol" Its the stuff used by automotive painters to clean wax and oils from car panels paintwork prior to painting

SFB Mortice & Tenon This picture shows the 'mortice and tenon' arrangement for joining the fuz. Again the dimensions  do not need to be exact. Just down the centre line! Glue the doubler to the wing first (using Gel Grip) and then cut the mortises. Don't do the final join of the fuz to wing until you have cut and glued the wing uppers. I used to glue fuz and wing together but some well positioned zip ties will hold it all together just as well. I have tried Hot glue in the past - zip ties are better!
SFB Wing Layout.jpg (41004 bytes) This is how you layout the upper wing surface. Place the wing on top of the chosen material for the "uppers". Ensure that the Leading Edge (LE) of the wing is parallel to the flutes of the uppers. Allow a 'fold over' (shown in the photo) allowance of about 35 mm and then mark and cut your upper surface around the wing plan. Make 2 of these!
images/SFB Spar.jpg Mark out a glue line on the bottom of the wing to help locate the uppers. It helps! Glue the LE of the uppers to the underside of the wing using your choice of glue (see above). They stick out at a funny angle for the moment but don't let that deter you. The fuz is now attached using little zip ties. The 'spar' is then hot-glued in position. It doesn't take any weight but just keeps the airfoil section from collapsing. (Actually it might not even be needed!). I like to pop a tiny zip ties into the end of each spar - just to keep em located! You can now fold the wing uppers over the leading edge and check the overall fit. If you score the inside of the uppers with a blunt instrument, it will fold over easier. You may need to trim the uppers a bit around the fuz and trailing edge (TE) near the elevon area.

images/SFB_Radio_Layout.jpg

This is the radio layout. The C-of-G on the SFB is a bit of guess work. Around 320mm from the TRAILING edge is in the ballpark( see below). The control horns are ~200 mm out from the centre line. They are simply screwed on to the elevon. I use the control horns that have little backing plates that the screws bite into. The elevon servos are on 200mm push rods. Note the throttle servo is behind the battery. Servos and receiver has 3M brand double sided mounting tape behind it and is secured with 2x zip ties. I use a small phillips headed screwdriver to punch holes in the coro. Elevon throws are about 12mm each way. Add some exponential if your radio has it - about (minus) -30% should be enough.

I don't use a switch. I just push the battery connection into one of the servo connections. Simple but effective. Update - I changed the battery pack one day and left the battery lead flapping in the breeze - big no-no - the lead pulled out mid flight - Bugger - SAFB augered in and smashed the engine mount.

Flight update.. With an SX32 on the front the C of G using the layout pictured is about 60mm too far back.. Push the throttle servo, radio and battery forwards. With a TT36 Pro this layout is probably not so bad!

Do the final fold over of the uppers and cut relief holes for push rods, servos etc. I join the trailing edge (TE of the uppers to the fuz using little zip ties (again). It means that if I want to lift the uppers for access to the electronics then its almost too easy.

You are now about ready to fly!

Launching this is per the AFB plans. I fly Mode 2 so I grab the SFB with my left arm, hang on to the right stick/tranny and somehow bump the throttle up to 100% with my chin. Seems to work most of the time. Make sure you have lots of 'up' elevon initially.

I always launch underarm - it never fails. Actually launching this baby overarm would be hard as it has nothing underneath to grab on to! If you really, really need to launch overarm then bore some hole just forward of the c-of-g (a bit like a bowling ball!) Give it full throttle and a gentle push should see it well on its way. If you are brave you can launch overarm and inverted!

Please let me know if you have built and flown a SAFB. Its the cheapest RC fun I know of.

tglynn.at.hotmail.com (do the usual - replace the .at. with @) - I get enough spam as it is