Official Freewing 80mm EDF F-86 Sabre Thread

[Dave Wave]

Do you have link for the .STL file?

Is it only the nose gear with issues? I assumed the mains would have problems without trailing link gear.

[Evan D]

The brace really helps on planes where the gear extend forward. Limited benefit on this. Plus the retract mount on this is pretty well designed…

for the mains, other than the re glueing of the mount they do okay.

[xviper]

Do you have link for the .STL file?

Is it only the nose gear with issues? I assumed the mains would have problems without trailing link gear.

Even on a soft landing (maiden flight), one of my main gear mounts pulled right out. Wasn't glued in very well. Then on the next day's flight with it, the other main gear pulled out. This was landing on GeoTex and rolling up onto the grass. Thinking back, I should have just grabbed each main gear and gave it a good, solid yank just to get it over with.

[Dave Wave]

Even on a soft landing (maiden flight), one of my main gear mounts pulled right out. Wasn't glued in very well. Then on the next day's flight with it, the other main gear pulled out. This was landing on GeoTex and rolling up onto the grass. Thinking back, I should have just grabbed each main gear and gave it a good, solid yank just to get it over with.

If they are re-glued, do you think the gear is suitable for grass?

[xviper]

If they are re-glued, do you think the gear is suitable for grass?

Depends on how you land. If you're still thumping it down, that initial high resistance from the grass could still rip out the retract - actually, it'll rip out the retract housing and the foam it's glued to. If it were me, I would push (and glue) tiny CF rods or strips into the foam almost the thickness of the wing section and then glue the retract mount into all that.
I don't know how much bigger tires you could put on this plane but I would maximize the diameter of the tires to make it roll easier. As with my FW Venom, I also installed trailing link struts but that required some foam removal. I don't fly my Sabre from grass as I do my Venom.

[Dave Wave]

I also installed trailing link struts but that required some foam removal. I don't fly my Sabre from grass as I do my Venom.

I was thinking of going this route. Do you remember which struts you used? Did you just change the strut and use the installed retract? How much foam did you have to remove?

A picture would be fantastic if you have one...

[gooniac33]

Back in the day it was possible to adjust servo centering by inserting a tiny screwdriver through the hole in the output shaft and adjusting the pot. The pot had a screw slot just for this. I don't know if today's servos allow this or not?

I remember seeing this. SANWA had this if I remember right... been a long time though...

[C17loadmaster]

If they are re-glued, do you think the gear is suitable for grass?

With the landing ear extended, pull the MLG servo lead out of the notch in the wing so that it has slack up to the hole in the wing leading to the RX. Then grab the entire completed strut (wheel and retract installed as if it were ready to fly) and gently yank straight down. You will be surprised at the ammount of resistance needed for the entire wing mount to completely seperate from the wing. Then, do the same to the other side. Take whatever glue you want (gorrilla, epoxy, the supplied glue from the factory) and reapply a very generous ammount in the wings where the plastic retract mount was removed. Push the entire assembly back into the wings one at a time and let the glue cure.

-You can just rest the airplane upright on its extended gear so that positive pressure is applied. I personally would set a 6s lipo on top of the wing above both of the retracts during cure time. It will keep the mount seated correctly and you can gently roll the plane forward to ensure there arent any alignment issues.


After that, you can fly off grass all day. Its got to be cut to around the lenght of a golf course "rough", or else it will take up a ton of room and battery to get airborne. If you leave the retracts alone and do nothing, they will evenually rip out on their own just as I explained above. Coming unglued during a landing will guarantee the sharp corners will gouge the heck out of the undercarraige and your flap servos will strip.

Mine is extremely old, and been rebuilt after crashes a few times. Swapping the servos for the flaps from 9g to 17g metal gear was a worthy upgrade.

[Dave Wave]

Thanks for that, I will certainly do that when I get the model. Now I need to decide if it is worth the effort to try to add trailing link gear as well. The combo of the two would probably be bullet proof, but the are certainly some aesthetic and cost issues as well.

[paulrkytek]

The gear back boxes do not have a big enough contact area with the surrounding foam and leaving the bottom out of the back box did not help. I re-fixed mine with gorilla glue and I also
replaced the thin cosmetic silver plastic cover strip with 1/16th ply U Shaped cover strips from a 70mmx60mm rectangle glued to the exposed surface of the back box and the surrounding foam in order to achieve an additional 10mm or so width of pressure spread from the back box to the foam surface. I fly off grass and so far so good. I just finished the ply surface off with peel and stick silver film. I also made the wheel wells a bit bigger and replaced wheels with 2.25 inch wheels and replaced the oleo covers with bent ply covers to match. ( these replaced the ones I cracked when one retract flew out on a pretty gentle landing mainly due to the lack of glue and poor contact area.)

[Dave Wave]

So the C shaped ply is like the top of a sandwich? You just inset it into the foam and glued it to the retract mount?

[paulrkytek]

Thanks for that, I will certainly do that when I get the model. Now I need to decide if it is worth the effort to try to add trailing link gear as well. The combo of the two would probably be bullet proof, but the are certainly some aesthetic and cost issues as well.

I cannot see how you could add trailing link mains gear unless you bend the connecting pin forward and cut out some foam to accommodate the raked forward oleo leg as you cannot move the wheel wells back to accommodate the retracted wheel resting position or there will be nothing to hold the wing fixing bracket in place. Though I suppose you could re fix the back boxes further forward by about 20 to 25mm but its a lot of work carefully cutting the foam as there is not much margin for error before you break through the top wing surface and building back the foam in the original back box hole and then making good the wing surface finish. Good luck whatever you decide to do.

[paulrkytek]

So the C shaped ply is like the top of a sandwich? You just inset it into the foam and glued it to the retract mount?

Yes Dave, ply is glued to both the foam and the top surface of the back box, you may need to trim the wing foam level with the back box top surface. I lifted the actual retract servo about 3mm with spacers to get clearance for the wheels I used so that the wheel did not bottom out and stall the servo motor and kick in the overload sensor. The oleo covers are bent/creased so that the leading and trailing edges sit back into the wing surface otherwise there would be lip. You can still unscrew the servos afterwards using this method. Landing on grass in this video is after the mods

https://www.youtube.com/watch?v=VvCUGzz3e_k

[Dave Wave]

Thanks for all the good info. I think I am going to take the re enforce/ big tire route and see how it goes. Our field is not that bad and if I have issues, I can always try to hack in trailing link if the stock struts do not work out.

I appreciate the help.


-Dave

[xviper]

I was thinking of going this route. Do you remember which struts you used? Did you just change the strut and use the installed retract? How much foam did you have to remove?

A picture would be fantastic if you have one...

I thought I replied to this but it looks like nothing happened. I may have not clicked on the right button.
It's been a while but I seem to recall I got the struts for my Venom from the parts section of another plane - Avanti S or something like that. Since the retracts are the same size, I just used the existing retracts and just replaced the strut and used the same tires. Remember, this is on a Venom, so the length of the strut on the Sabre may not be the same and also, once you change the strut like that, the strut cover will no longer work. As you can see, the area where the spring is and the pivot joint takes up more room, so foam needs to be carved out.



PS. I flew my Sabre with the modded EDF (more power and thrust) yesterday and it flew marvelously. It can come in very stable and land very softly but if it runs off the runway and onto the grass, even with my retract mount re-inforcements, it may not hold up.

[darmokjt]

F-86 80mm main wing installation question: Users Manual, Page 4, shows using the shorter screws for use rearward with the plastic wing brace, and the longer ones for the front. This doesn't make sense to me because seems like we'd want to use the longer screws with the brace since that's where the higher loading is. Users manual right or wrong?

[darmokjt]

F-86 80mm Aileron, Flaps, Elevator, and Rudder low and high rate settings. Users manual, page 13 table has them in millimeters. Does someone have these in degrees for use with Spectrum radios like my DX8, G2? I used trigonometry, and for the ailerons, I calculated 15 degrees for low and 25 degrees for high. Also want to verify my trig method is accurate.

[paulrkytek]

F-86 80mm main wing installation question: Users Manual, Page 4, shows using the shorter screws for use rearward with the plastic wing brace, and the longer ones for the front. This doesn't make sense to me because seems like we'd want to use the longer screws with the brace since that's where the higher loading is. Users manual right or wrong?

its right. You have to go through more foam at the front to reach the screw bite point . length of screws not related to loading its the screw receiver and how the load is dissipated into foam that counts, Also most load is not on the back 2 screws but is more likely to be evenly distributed over the 4 mount points and if anything more load on front 2. I am afraid i think your logic is wrong

[xviper]

F-86 80mm Aileron, Flaps, Elevator, and Rudder low and high rate settings. Users manual, page 13 table has them in millimeters. Does someone have these in degrees for use with Spectrum radios like my DX8, G2? I used trigonometry, and for the ailerons, I calculated 15 degrees for low and 25 degrees for high. Also want to verify my trig method is accurate.

Spectrum radios like the DX8 G2 does not give control surface deflection in "degrees". They give it in % and even that is just a reference. There's nothing more easy and straight forward than measuring deflection in mm. You take the measure of the control surface at the widest part. That's usually nearest to the fuselage for flaps, then nearest the flap for AIL, nearest to fuselage for ELE and same for RUD. Trigonometry? You are waay over-thinking this.

[paulrkytek]

Dave Wave

My Freewing Avanti struts are 110mm from mounting block to Wheel axle, Sabre requires 95mm max from mounting block to wheel axle so Avanti struts wont fit the sabre