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Xion Wing Lock – Pt 3 – Can’t recommend

After another couple flights on my Wild Hare Slick on Saturday I have lost a second wing lock.  Once again, no harm as I have clips on my anti-rotation pins and they once again stopped the wing from sliding out far enough to cause any issues.  I had the wing locks very snug and I believe installed these correctly so I can’t account for how they managed to exit the airplane.

Because of this, I can’t recommend this system.  While I love the idea of quick connect and disconnect and somewhat easier installation than the nylon bolts I was using…. I can’t positively identify why mine have now twice been lost in flight.  If these had been the only thing holding on my wings I would have trashed an airplane… twice now.

I’ll have noticed the studs from Xion seem very sloppy in the blinds that are in my wing so maybe this is somehow contributing to the problem.  Is this just a case of cheap blinds with to much play in them?  I don’t know but I’m done risking my plane to find out.  If you use these successfully I’d love to hear about what you did to make them work but I’m done with them for now.

For my earlier posts on this item, please see:

Part 2

and

Part 1

 

 

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Parkzone T-28 – My 3rd

I picked up a new PZ T-28 to replace the one I retired a couple months back.  I started having motor issues and had at least one servo starting to chatter, plus the foam was showing a lot of wear.  Additionally it was the US Air Force color scheme which is beautiful up close but very hard to see under anything but perfect lighting conditions.  I like to fly this plane near dusk and sometimes far up and out at times and poor visibility is an unnecessary limiting factor so I had been wishing to get back to the Navy scheme since about 2 days after I bought the last one!

Since I was pulling a new ARF out of the box anyway I thought I’d post some comments.  First, it seems that PZ really knows how to pack an airplane.  The packaging kept the plane very secure and I found no dents or dings at all.  As you can see here, its very nicely packed.

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Second, the manual (which I didn’t need, since I’d done this twice before) is well written, apparently by a native US/English speaking person (at least the US/English portion, I can’t comment on the rest of the languages) which I find refreshing compared to some I’ve seen.  No offense intended to those who are native speakers of other languages but I would expect a product sold in a particular country should have a manual that is written clearly in the native tongue of that land.  Everything seemed to be present and accounted for so assembly was pretty quick.

Looking the airplane over there are some drawbacks.  The paint job suffered from a bit of over spray and the decals have quite a few wrinkles and bubbles.  While I still like the overall look of the airplane, it could look better with a bit more care in production.  Here is an example.

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That aside, I have now flown the new plane a dozen flights or so and just as I remember it is a hard to beat little airplane.  Somehow it seems to fly bigger than it is.  While not capable of unlimited vertical… no hovering for this bird… the plane has enough power to climb rapidly and quite a bit of aerobatics are within its flight envelope.  Even better, the plane flies super stable (without needing a stabilization system) and can handle a lot more wind than you would imagine for a 2 pound foamy.  I can fly around all day doing knife-edge or simply putt along making wide sweeping turns and making low passes and it will do either equally well.  It just flies great.  It also will fly with a wide variety of battery packs.  I’ve flown them with everything from 1500-2200 3S packs from 15C to 45C discharge rates (static testing showed about 14A, so 15C is sufficient) and any of them will work.  Lower capacity batteries which are lighter and high C rated packs improve performance but the lower end (cheaper) batteries work well and keep costs down so suit yourself!

In the past I had typically hand launched the T-28 as the small wheels are not always conducive to upright landings and smooth takeoffs.  I have been a proponent of getting rid of the wheels from the beginning as it also lightens the plane up a bit… always good in an airplane that doesn’t have unlimited vertical anyway.  This time, however, I decided to get back to some wheels takeoff and landings so decided to put them on.  They were a problem on our grass field.  Not intolerable but occasional flip overs and difficulty taking off with anything less than full throttle and full up elevator.  I like a nice easy takeoff and upright landings so I recently changed them out for some Dubro lightweight wheels that I’ve seen others use on the other similar size PZ aircraft.  Here is a comparison of the old (smaller) wheels and the newer, larger set. (Dubro 250MS)

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Here is the complete set installed.  The existing axle caps unscrew and so can be reused but I did need some wheel collars to add inside the wheels to keep them from rubbing the wires.  I also had to drill the wheels out to 7/64ths to fit the wire axles.

 

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I flew at the local field using these the other day and it really makes a difference.  Much easier to roll on the grass and landing went great.  The nose occasionally will dip as the landing gear bends back but not a big issue and I think extending the nose gear just bit will help with that as well.

One final construction note.  I have noticed in the past that the wing tends to rock just a bit when installed, even with the machine screw at the front nice and tight.  In order to keep the wing snug, I add some wing saddle tape to the body before I install it.  This tightens things up remarkably.

Since I had an extra Telemetry receiver lying around….  I had to install it, and an altitude module, and… well I’m still working on the rest!  Don’t know how long I’ll leave it in there but it’s fun to gather some data.

 

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“Bargain” battery? Maybe now it is..!

While working with a new pilot at our club field the other day he mentioned that in order to get his charger to properly work with the battery he was using for his on board glow (a pretty standard 4.8V NiMH pack) he had to bend the wires just right and/or stick pins in the connecter, etc…

I immediately told him this was NOT the norm and he should not continue this practice.  This is a warning that something isn’t right and we need to figure out what and why.  He took the battery out and we tried to check the voltage and sure enough the connector was almost impossible to get a good connection on…  I volunteered to take it home for further investigation and likely swap out the connector.  It was clearly labeled as a 2300mah NiMH from one of the more recently arrived web based resellers and a quick browse showed claims that it is a low discharge NiMH variant.  Some call these Hybrid NiMH and there are other terms.  The nice thing about this type of NiMH is that have a low discharge rate when stored so they don’t tend to drop their capacity between flight sessions like many NiMH batteries do.  I wouldn’t use a standard NiMH if I could avoid it because I just can’t count on them to be ready when I am and I don’t always know I’m going flying, sometimes until a couple hours before leaving for the airfield.  Standard NiMH with their high on the shelf discharge rates just don’t work for me.  This is especially true when you combine that with the low charge rates most will tolerate.  I can’t store them fully charged and expect them to hold for long and I can’t fast charge them…. just doesn’t fit my flying habits at all.

This battery looked like a nice combination of low price and a reasonable battery technology for our needs in RC aircraft.  Combine that with a low price and maybe there was something to be happy about here.  But what about that connector?  When I got the battery home I decided the connector was just not very good quality.  The pins (sockets really) were moving to much in the plug and didn’t appear to have been crimped evenly.  Next I noticed that the wires were significantly smaller than the average servo wires I’m used to.  Maybe 26 gauge instead of 24?  I’d rather replace the lead than splice it anyway so I took off the outer shrink wrap and this is what I found….

photo 2

First of all, I wonder if using what appears to be masking tape as the insulator to keep the wires from laying directly on the battery ends is the best choice or just an economical one?  I guess it’s not terrible since I presume it’s there to prevent chafing more than electrical insulation or perhaps just to aid in assembling the battery.  I’m used to seeing strapping tape/fiberglass tape here.  Seems like the masking tape might attract some unwanted moisture though.  Anyway, that isn’t so bad but the wires being so thin I did not like.  Seems like some slightly larger gauge silicon wire would be ideal but I guess you can only expect so much for single digit (dollars) pricing.

I then started to strip the tape and de-solder the wires when I noticed the following.

photo 1

Do you see the insulation cut on the black wire?  This was caused by the outer shrink wrap around the battery cutting into the insulation on the wires.  Either the shrink wrap should have been applied differently/softer heat shrink used or perhaps a wire shield/wrap/guard of some sort used around wires.  I’ve seen others use a nice rubberized sleeve (maybe just some appropriately sized heat shrink) to keep this from happening and add some stress relief in this area.  Hmmm… bad connectors and questionable construction/poor quality control…  Makes me think the savings on this battery might not have been such a bargain after all.

My point here is really just a long winded way of saying that very often in this hobby, “you get what you pay for” applies.  Even when you are buying something as mundane as a basic 4.8V NiMH pack.  I have no idea how good the cells that make up this pack really are.  Time will tell.  But even if they are top end like Sanyo Eneloop, the short cuts they took to make this pack more of a “bargain” could easily have resulted in a high cost to the user.  If the cut had been in the red wire and it had shorted to the negative can of the battery it was sitting on top of, the best cells in the world wouldn’t have helped.  Same for the connector that wouldn’t reliably do its job.  Every little bit of quality I can get in my airplane products is welcome.

Hopefully, with the new lead attached and a few wraps of some decent quality electrical tape, this “bargain” battery pack really will be.

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Building the Top Flite Giant Scale P-40 – P5 Wiring

I’ve finally gotten back to some work on my friend Kelly’s P-40.  Lately I’ve gotten the plumbing done on the fuel tank and sorted out the electronic kill switch, battery and switch wiring.  Here’s a shot before I buttoned up the throttle servo tray. 2014-06-01 10.51.59

The A123 2300mah battery is bundled up in the blue foam and tucked up against the bulkhead just above the back of the tank.  With a couple of custom fit foam spacers to hold it in place it has no where to go.  The circuit board for the ignition kill is also sandwiched in between the battery foam and the spacers.  The ignition kill indicator light projects up through the fuselage just forward of the instrument panel but is protected inside the canopy.

Here’s another with things a bit more “buttoned up”.

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Not quite finished up… throttle linkage is hiding in the sidewall, one of the remote receivers is not plugged in yet but most of the wires are wrapped up and the radio/servo tray is in place and hopefully will not need to be removed again before the end of this build.  One more short session buttoning up the wiring, fuel tank and ignition and I should be able to finish up the fuselage and move on to the final steps to complete the wing.  From there we will be nearing flight ready!

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Building the Top Flite Giant Scale P-40 – P4 Cowl Mounting

After we built the first P-40 (this one being round two) and got a few flights on it we began to immediately see problems with the cowl mountings.  It seemed impossible to keep the screws from backing out and even around the ones that didn’t the vibration immediately started chewing up the mounting holes.  No amount of reinforcing of the fiberglass helped and while bonded washers have proven to be effective in this role they would have completely trashed the scale lines of this bird.  So when cowl number two arrived I got creative and decided we needed a better mounting system that didn’t result in having to put a bunch of (I don’t remember the exact number  but it seems like 20) holes in the cowl.  I came up with a system of mounting using blocks epoxied inside the cowl with 2 guide pins and two bolts.  It seemed to be working quite well… right up until an unfortunate lack of airspeed, altitude and ideas destroyed more than just the cowl.  So fast forward to today and I had to recreate the mounting method.

This time I thought I’d document a bit in case someone else wants to try it.  It worked well but it’s a bit devilish to get the alignment right.  It’s amazing how tightly it holds though with only two pins and two bolts holding it and zero holes in the cowl to mar the great looks.  The basic idea is to use the two bottom mounting blocks on the firewall for alignment pins, then using the the blocks on the bottom front of the motor box to accept bolts that are reachable via the (already needed) exhaust cutout.

Here is one of the firewall mounting blocks after drilling and the addition of an “alignment pin”.

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Then I marked and drilled a block with a matching hole.  Where I was careful not to drill all the way through the firewall, this block can be drilled all the way through.  I matched it up to be flush with the outside edge of the block attached to the firewall and also beveled the hole so that the locator pin could be inserted easier.  Here it is after the initial fit.

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The tricky part is to then put the cowl on and get it aligned as perfectly as possible.  Using the spinner back plate helps.  Once it’s right, mark the inside of the cowl and get prepared to apply some epoxy.

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Importantly at this point, where the block is going to be glued to the inside of the cowl, you need to clean the cowl inside surface with something that will cut through the mold release agent (think wax) that was applied when the cowl was made.  You can use some acetone (caustic stuff so be careful and make sure you have good ventilation) and/or sand the surface before applying epoxy.  Standard clamps can hold these blocks in place until they are set.  If you do this in the general area before you mark the block locations it will make you life easier in the long run.  Ask me how I figured that one out!

Similarly, the forward mounting blocks must be carefully aligned, marked and glued in place.  These I pre-drilled to snugly pass an 8-32 bolt and drilled and tapped the existing bottom motor box blocks to match.  Thin CA (very thin preferably) will harden those threads nicely, though you may have to re-run the tap 15 minutes later to make sure the CA didn’t block the threads.  Here is one method of holding the forward blocks in place while the glue dries… This method used masking tape and a “cut to length” dowel.  If you look closely you can see the holes to pass the bolts through have already been pre-drilled.

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In order to be reachable from outside the cowl the bolts are inserted from the bottom.  Happily this results in a very firm mount.  I used allen bolts which require a fairly long ball driver to access in this position.  Once you have these all in place you may (if your like me) find the blocks don’t perfectly match the surfaces to which they are attaching and one or more may need to be redone.  Sometimes a little sawing or sanding to make the surfaces match will suffice.  Otherwise a hammer will remove the block and a layer of the fiberglass with it (if you epoxied it well).

I’ll edit this post in the next few days to add a picture showing the mounting bolts in place.  I’ve done this twice now and it probably took me 3-4 hours to get it right, even the second time.  It’s time consuming and painstaking work but it leaves no marks and the cowl seems rock solid when it’s done.

 

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Xion Wing Lock – Pt. 2

Last weekend at the field during the IMAC contest I lost one of the cams and the washer on the port wing of my Slick.  No big deal really… I have clips on my anti rotation pins on each wing so I needed a click of aileron trim and all was fine.  After the flight when I went looking for the reason I spotted the wing gap and on investigation found that the cam and washer were gone and the stud had rotated out a bit.  I didn’t have my spare so that wing went back to the nylon bolt for the rest of the day.

So what happened?  While it is impossible to tell for sure, I believe the problem was rooted in not seating the wing down snug against the body.  So when I locked the cam down it pulled the wing in a bit but not enough to put pressure against the cam and therefore with some vibration the cam escaped.  Maybe the stud rotated enough to further loosen as well.  Possibly contributing to this is that I have not glued the washers down inside the body either… perhaps if I had the slack in the system would not have been enough to allow the cam to escape??

The only other issue I can see is that perhaps the stud managed to pull out of the blind nut embedded in the wing root.  I am really not fond of blind nuts in any case.  I find most of them to be ill fitting/loose.  When used in conjunction with a standard bolt there just seems to be a lot of play and I have seen a bolt manage to walk itself out a thread or two before without rotating at all because of vibration and slop.

I have continued to use the system through another 6 flights or so and so far have not had a sign of any movement.  I may add some plumbers tape to the studs to cut down on “rattle” between the studs and the blind nuts before my next trip to the field.  Otherwise I will keep with it and see how it goes.

(Don’t recommend these anymore… see part 3)

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