I have bought Cf landing gear from hobby king for my phoenix extra. These are the 28cc variety. Earlier I had got the20 cc ones but used them on my us40 as the part where the axle mounts is not too wide

Now, to use the 28cc ones I have 2 concerns- firstly the part where the axle mounts still feels not wide enough- i.e. in a hard landing the axle may twist or shear off. Secondly, when tightening the axle, the washer tends to grind into the CF surface. How do I avoid these two problems?. should I sandwich the surfaces which receive the bolts/axle between MS flats, may be 0.5mm thick?

ameyam

CF tends to be strong along the grain axis, so you really DO NOT want anything "grinding" into it too much or upsetting the grain.

Use washers to prevent damage and if necessary do exactly as you've said and utilize another material that will not grind into the CF.

BTW:

In my old Funtana S90 I puchased and installed second party CF axles.

I did not need to do anything to the axle mount area... but one day because of a VERY hard landing, I did exactly as you said and sheared off the "tab" the axles bolt to.

I ended up gluing ( on both sides for appearances ) a small 1x1" square of CF over the broken area, after I put it back together... I then redrilled the axle holes through the new material, and finally added thin 1" CF rods alone each side of the square vertically.

I've since hit it even harder on bad landings and it has held up VERY well with no cracks or breaks.

So if you are concerned you can do something similiar, but I doubt you really need to... CF is stronger than you think.

when i used the earlier 20 size CF LG, i used standard dubro MS axles. i think the threaded potion tht goes thru the CF tab was 6mm & the tab was 20mm wide. so there wasnt too much to shear. one side of the axle was already flattened, so didnt need a washer, the other was with nylock nut, i added a washer to increase bearing area and. a spring washer for safety. when i tightened, both sides dug into the Cf. thinking of putting ms flats on both sides.

they tell me at the field CF is strong but brittle- it cant take a less than perfect landing. how true is that?

ameyam

It is less forgiving then alum or fiberglass. Stronger and lighter than both but like you said more brittle. I may be biased as I have paid big money for two sets of it and neither lasted the season. And I thought I was pretty easy on landings. The first set delaminated at the curve 5 flights in. The second set was a dead stick landing, but not hard enough to flip the plane over or even dammage the wheeel pant. Hard enough to delaminate the gear though.


david