|Nov 30, 2007, 08:54 AM|
Fly Fly F-86 Sabre complete build thread A-Z
I just finished building and flew the new giant foam Sabre by Fly Fly. The directions are good but combine about 6 steps into each of 10 single picture diagrams. This thread is to fill in the gaps and save you time.
If you find the thread helpful then please give it a rating in the top right corner.
Available at EJF.com for $189. Retracts are $90.
Wing Span 55.5"
8s flying weight 6lbs 3oz
6s flying weight 5lbs 12 1/8 oz
All but battery weight 4lbs 7 3/8oz
Stronger control rods than those provided (one 24" rod will do)
1 HS 3115 servo for the retract valve (HS65 is not strong enough, I tried)
(edit) I eventually gave up on stock air valve for Robart valve and HS65 servo
5 HS 65HB servos of dual ailerons, dual elevators and steering
Throttle extension 12"
Aileron extension 30" (two)
Elevator extension 30" (two)
Nose gear extension 21"
Retract extension 6"
Battery wire 14"
Horizonhobby.com has the above servos, extensions and Robart air valve.
36mm diam. motor (1600kv from Medusa Products.com)
ESC (Phoenix HV85 for over 6s w/ BEC, Venom HV80 for 6s)
Longer wing bolts than provided (need 40mm of thread length) 2
BEC (I'm using a 3.5A BEC from Medusa Products.com)
I wanted to make the plane resistant to finger nail marks and give the wing some strength but I'm tired of smelling Zpoxy fumes and have heard that Polycrylic Minwax takes a long time to dry completely and does not provide much fingernail/hangar rash protection. I decided to attempt something new and tested Elmers wood glue mixed 1:1 with water, WG mixed 1:2 w/ water, Polycrylic straight and plain white Elmers glue mixed 2:1 w/ water. All tested side by side using .75 oz fiberglass over packing foam. The WG mixed 1:1 did the best with the white glue a close 2nd.
I've tested the Wemotech Midi, AP900 and the supplied fan. I've tried all of Medusa's motors, the Mega 22/30/3E for the AP900 and the AP outrunner motor. The Midi is the most efficient. It produces equal thrust at a lower watt input. My choice was the Midi with Medusa's 36-50-1600 motor using the Phoenix HV85 to get me over 6s lipo use.
I'll start with what's most important. Video! If it doesn't fly well then nothing else matters!
These two are from my 2nd flight and are in a 12mph wind. The plane takes off in a very short distance (100feet) and will go into straight vertical with the 8s set up I'm using.
8s 3700mah PolyRC 20C packs (same as EVO and Polyquest)
High speed and low speed passes. Radar at 107mph twice w/ the wind.
|Nov 30, 2007, 09:00 AM|
I did not follow the order of the instructions.
For the retracts I dremeled a flat spot on the rod where the strut allen bolt would tighten against it. This should help prevent the wheels from turning to the side on landings.
I also need to remove the servo mount plastic piece from the fixed gear and put it on the retract gear. Remove the screw and it slides off to the side.
I used thin CA to coat the wood retract mounts. It soaks in and makes them stronger.
|Nov 30, 2007, 09:10 AM|
|Nov 30, 2007, 09:16 AM|
The large front opening is more than a retract bay. It is a big cheater hole. While it maybe helpful on less powerful systems I believe it is a drag on any set up with much power at all. It may slightly increase static thrust but in the air I swear I can hear it catching wind. I believe it is slowing the plane. I will eventually test this by covering this area. The inlet is plenty large for this fan size.
|Nov 30, 2007, 09:24 AM|
I cover the face of the motor with tape then sand the motor shaft long ways to rough up the surface and prevent the adapter from turning on the shaft. The fear isn't that it will pull forward but that it will twist free of the shaft and then it will quickly work its way forward. Sanding long ways discourages the adapter from twisting. Clean the shaft with alcohol THEN remove protective tape.
I do not use fan rotor caps/cones. They tend to cause more trouble than they are worth. Some will disagree. Do what works for you. My tests are all without the cones.
|Nov 30, 2007, 09:27 AM|
This is with 3 coats of wood glue mixed w/ water over 3/4 FG of entire plane. Weight gain seems minimal. I checked several items before and after FG.
Both elevator halves with servo installed
1.5 oz together before
1 5/8 oz after addign FG and 1st coat of WG
1 3/4 oz after 2nd coat
didn't check after 3rd coat
Rear fuse glued together
6 3/8 before
7oz after 1st coat
7 1/8 oz 2nd coat
Wings together with retracts and servos
1:2 5/8 before
1:4 3/8 1st coat top and bottom
1:5 2nd coat
1:5 3/4 after 3rd coat
The thrust tube comes with an 86mm inlet and 78mm exhaust.
The Midi fans FSA is 80mm. Generally you'd want the exhaust to be 85-90% of the fan's FSA or 68 to 72mm diameter exhaust. I did several tests with different battery combonations and exhaust diameters. Here is the need to know stuff.
On 6s there was nearly no difference in thrust by changing the exit diam. from stock (78mm) to 68mm. The amps increased from 45A to 48.7 and watts increased from 973 to 1069. The batteries had a slightly higher charge voltage on the 2nd test so that explains some portion. A smaller diameter creates more back pressure for less thrust but higher eflux for more speed. That also was a factor. Thrust stayed the same at 64.2 oz while I'm sure speed went up.
On 8s w/ decreasing exhaust diameter using Midi's inlet ring.
86mm 64.7A, 104.1oz T, 1811W, 37,625rpm
78mm 69.2A, 106.4oz T, 1931W, 37,050rpm
68mm 72A, 94.1oz T, 1999.5W, 36,350rpm
I ended up using 72mm exhaust diam. to take advantage of thrust while generating higher eflux for speed. Installed it pulls 2,080 watts at 72A. Things change (inlet and therefore efficiency) from the test stand to intalled.
I also tested the included fan on the Medusa 1300kv motor to find;
6s 3700ma, 42.3A, 58.7oz T, 959W, 24,875rpm
8s 3700ma, 60.8A, 86.5oz T, 1713W, 29,775rpm
This test done using Midi inlet ring and using about a 9" thrust tube I used for a great deal of Medusa motor testing on AP900 and Midi. The will have all test data on their site soon. I believe the 1600kv motor on 6s will put out nicely with the included fan. The efficiency is not as good as the Midi but hey, the fan is free right.
|Nov 30, 2007, 09:28 AM|
Carl - thanks a million! Wow... I'll be visiting this thread quite a bit...
Looks like it flies great! And fast~! 8 cells it is for me...
|Nov 30, 2007, 10:43 AM|
The CG is recommended at 215 -220mm back from the center of the wings leading edge (the gap area). On 8s I was about 3mm ahead of this and thought I may be a little nose heavy. I actually had to give nearly 100% of my trim capacity to lowering the elevators as the plane wanted to nose up acting tail heavy. I flew again after moving packs as far forward as I could (1/2") and found it made little difference. I may move the retract system to the rear so I can get the batteries further forward. The 6s set up will really need moved forward.
The suggested control throws seem extreme.
I used 20mm up and down on ailerons and had a quick roll rate. I use ALOT of exponential on all my throws to make planes easy to fly until I'm very used to the plane.
For elevators I went with 21mm up and 15mm down.
|Nov 30, 2007, 01:03 PM|
Judging from your numbers with the Medusa 1600kv... 6S doesn't even give close to 1:1 thrust to weight Looks like 8S is required for "good" performance with the Medusa 1600
|Nov 30, 2007, 02:07 PM|
i think the last set of numbers carl posted were for the medusa 1300kv...the medusa 1600kv on 6s in the stock or midi fan seems like the best combo for thrust, speed and amp draw...
|Nov 30, 2007, 02:31 PM|
|Nov 30, 2007, 03:40 PM|
64.2oz T on 6s with 1600kv motor in Midi fan didn't change much with change in exhaust diam. though speed would increase with smaller exh. diam.
8s jumped thrust to over 100oz with 1600 Medusa in Midi.
I just got back from flying on 6s set up with Medusa 1600 and Midi. This is a light set up and the plane would literally float with about a 12mph wind at its nose. Radar was 85mph trying to hold a straight line in a cross wind. Expect around 90mph with no wind as the plane will not be crabbing.
In the plane 6s is pulling 945W, 43A you could fly a long time with this set up. This was with 2s pack registering 8.2v so not a full charge.
For those wanting more thrust without going over 6s I would suggest the Medusa 1600 motor in the stock fan. You can expect around 65A draw and 75-85oz of thrust. This is about what the AP900 fan did with 1600kv motor and the performance of the stock fan appears to be right in line with the AP900 from my 1300kv motor test in each. I will test the 1600kv motor in the stock fan when I return 12/10 from vacation. Note that at 29,775rpm the stock fan puts out 86.5oz but requires 1713W. For the 6s set up to hit 1713 watts it would need about 81Amps. Not something you'd want to hold very long on 3700ma packs. The motor is already on its way to me.
I'll post more finished pictures once I get the plane painted.
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