BBA/Winter Build 2017/18 - Top Flite Corsair

[PsyBorg]

Congrats on another success Joshua!

That looks great in the air. I would have to say you are correct saying it flew well after seeing the cockpit footage. Very smooth turns and hardly any turbulence or porpoising. That is a great testament to not only your build skills but your pilots skills as well specially considering that was not an FPV flight.

Hopefully the damage is minor and quickly repairable so this one sees its share of air time this summer.

Seeing those wheels turned in like that reminds me about snapping a tie rod on one of my cars back in the day after finding a huge pot hole the hard way.

 

[Namactual]

Congratulations on the successful flight, that build looks great!

 

[Tench745]

That landing was HARD even if the gear hadn't spun. Looks like you were coming down a little fast and gave elevator to flare, but were still carrying too much speed so it jumped back into the air. That looked like a good place to attempt a go-around. It's hard to tell from the video if there was a down elevator input in an attempt to plant it, or if it was an imminent stall Either way, it's not too surprising that the gear was unhappy afterward. Glad to see everything held up well.
Of course, it's easy to be an armchair pilot when you weren't there; you were on the sticks, not me.
I'm really interested in that telemetry data. Do you need a logger of some sort for the PWM or is that a base feature of the X9D? Obviously airspeed is from your pitot system.

 

[willsonman]

All of the FRSky radios can log telemetry of the entire radio system. Whether you have sensors or not, you can log the flight controls. It's a nice feature that has come in handy more than once to evaluate a maiden flight.

Keep in mind that this airplane is nearly 3 POUNDS over the recommended flying weight so she has to carry speed to some extent but then factor the nose-heavy CG and it makes these kinds of things more complicated. Also worth mentioning again is that the EXPO on the elevator was on 60% so I was having to be fairly heavy-handed with it in an area where the expo was a bit more sensitive toward the middle of the expo curve. Once I dial this back to 40% the control on landing will be much better. The roll-out would have been fine and honestly, had it just bounced again, I would have done another go-around.

I learned a lot about this airplane from this flight and given that the airplane can go much slower I'll be able to trust her more on my future approaches. If you'll notice, I had excellent control at the 30MPH with flaps and at the end of the graph you can see I was coming in at 40-50MPH... quite hot. Rest assured, future flights will go much better.

 

[PsyBorg]

Bottom line is did you enjoy what you got out of it from the build to the flight to all the attention it brings. Crashes are gonna happen and knowing you have the skills to figure why and fix what the issue was as well as repair the damage to fly again is a great place to be in the hobby. I know I enjoyed watching you work thru this to this point and I learn things nearly every time you post. Seeing these special builds from all you guys documenting it is like being there and hanging out with you as you do it.

 

[Tench745]

All of the FRSky radios can log telemetry of the entire radio system. Whether you have sensors or not, you can log the flight controls. It's a nice feature that has come in handy more than once to evaluate a maiden flight.

Keep in mind that this airplane is nearly 3 POUNDS over the recommended flying weight so she has to carry speed to some extent but then factor the nose-heavy CG and it makes these kinds of things more complicated. Also worth mentioning again is that the EXPO on the elevator was on 60% so I was having to be fairly heavy-handed with it in an area where the expo was a bit more sensitive toward the middle of the expo curve. Once I dial this back to 40% the control on landing will be much better. The roll-out would have been fine and honestly, had it just bounced again, I would have done another go-around.

I learned a lot about this airplane from this flight and given that the airplane can go much slower I'll be able to trust her more on my future approaches. If you'll notice, I had excellent control at the 30MPH with flaps and at the end of the graph you can see I was coming in at 40-50MPH... quite hot. Rest assured, future flights will go much better.

Fair enough. I always enjoy hearing the background info and decision making that goes along with video. I know I'd rather come in hotter on a maiden than risk the dreaded approach stall. I don't fly with expo on most of my models, so I'm not very familiar with it. 60% seems like a lot. Is that usual for maidening a bird like this?

 

[willsonman]

I usually maiden with 60% expo as a general rule. Sometimes you just get nervous and your hands start to shake and making the center of stick more "dead" helps to mitigate this. Most folks I know fly with 30-40% max. My flying style is more buttery smooth scale turns and approaches so the higher expo helps me to achieve that easier.

 

[OkieDave]

Unfortunately that means a bit of surgery and may leave some ugliness.

It's not "ugliness," it's "authentic battle scars!"

 

[nhk750]

Nice flying plane, looks great, glad not too much damage.

 

[willsonman]

Thanks! Been really ragged trying to recover from SEFF. Got more sleep last night so I'm easing back into things to make the repairs and final touches.

 

[willsonman]

Let's get back on this bird.

The oil cooler vents incorporate a grill to keep debris out and this is a small detail that took all of 15 minutes to do and I SHOULD have done it prior to SEFF but I neglected it. So, to start off, I took some balsa and cut/sanded it to shape. I used some screen door material to simulate the grill. I sprayed the balsa with Super77 and applied the material.


I'm just using black acrylic paint here. Nothing fancy. Applied with a brush. I applied some to the sides to hide some gaps that may be there.


I scuffed up the balsa in the pocket and applied some medium CA.


The pieces press in and the balsa to balsa quickly sets with the CA. It really completes the look of this area and it's these small finishing touches that add up to make a great-looking model. I think it looks a little too clean so I may go back and dry brush on some graphite powder to dirty it up a tad.

 

[willsonman]

Moving on to address the landing gear issue. From the maiden video, clearly you can see how the oleos twisted on my rather hard landing and fast approach. I was able to find a dremel and grind flat spots in the mounting wire but I noticed a lot of play (twist) still that was isolated to the bottom part of the retract. So, the WHOLE gear needs to come out. I drew some cut lines with a pencil. The pencil marks can be removed easily but I'll try to blend in the cuts later. I have to cut the balsa skin away in order to access the screws and remove the retract.


Here are the cuts to remove the portions of balsa. Gentle cuts to remove what was needed and that is all.


So, here is the deal. Take your FREAKING time with retracts. I DID make this flat spot in the base prior to the initial installation... I just forgot to put loctite on the grub screws. The 7-800 mile trip there loosened it up and I noticed that our trip home made it worse. SO, I re-installed the retract with loctite and torqued everything as much as possible.


With everything re-installed and checked, I used more medium CA to put the balsa pieces back in. Again, I'll blend this a bit with some paint. You can also see the slight damage to the right from travel. Minor damage that I reinforced with thin CA. Some paint touch up there as well.


So, now I need to do the other side and I can move onto the cockpit. The last part that I am now debating is the tail gear doors. I may or may not do them. I've not entirely decided. I can do them but it may prove one of the maintenance things that keeps this bird grounded more than any other thing. I want this to be a regular flyer so yeah, I need to make that call eventually.

 

[willsonman]

So I tackled the other retract last night. Wow, I really messed up there. The geared part in the retract that provides the twist had absolutely NO flat spot in it at all. So I ground that down and straightened the part out on the vise like the other one. Only took two hits with the hammer. In addition to this, I realized that the air line to the front part of the retract was partially binding with the gear for the twist so I re-positioned that as well. With the new flat spot on the main pin, I had to adjust the flat spots I ground down at SEFF. Both wheels have the same amount of slight toe-in now. For those who do not know, slight toe-in on tail draggers helps to keep this tracking straight.

With everything re-installed I painted the wheel wells with some white acrylic paint. It was bare wood before and with possible wet conditions I wanted to make sure that it was somewhat sealed but also complete a more scale look. These wells will naturally get dirty over time so I'll let nature take its course. I did some additional paint touch up after this shot, both one the white and on the blue to cover the skin damage.


To wrap up the wing issues, I then examined the ailerons. Referring back to my maiden video, The ailerons were not centering entirely. I was making a counter-clockwise circuit for the maiden and she just wanted to keep rolling right when I would level off. The culprit was slight binding of my internal linkage for one aileron. The aileron would get bound up a little and I would have to over-correct to get her to fly level. The fix was simple: get out the #11 blade and trim things out a bit. You can see in this picture the removal of some wood from the bottom edge of the wing where the clevis protrudes and connects to the horn in the aileron. That was the trouble area. It's all cleaned up now and is completely smooth in operation.


So, with the wing repairs out of the way, I'm ready to put the wing away and focus on the fuselage again. The canopy slide was a bit of a rush job and one side of it does not close quite right. I need to cut a new mount for that side and make it perfect. I'll start working on the rudder pedals first and work out their animation with the UMX servos. This is going to get interesting so stay tuned.

 

[willsonman]

So, I'm still fighting the canopy closure. I'll get it but it really tests my patience.

Moving on... The cockpit is a vacuum-formed kit supplied by Top Flite. Since I've never really done this before I chose the easiest part to do... The throttle lever. This stuff is REALLY small for my big hands so this is very much uncharted territory for me. You can see the balsa tabs I added to slightly elevate and secure this servo. Pulled from a UMX-something.


I cut the styrene panel to have a slot for the throttle lever. I had a bunch of pins in my stash and a red one fit the bill nicely.


From there, there was a lot of work done for this next shot. The wood support was drilled out and a copper bushing was placed in it. That was secured with thin CA. a slightly smaller OD copper tube was used as a torque rod. The red-head pin was inserted into one end with CA, crushed with pliers to secure it and bent 90-degrees to stick up from the pivot point. The rod was cut to length and I used styrene bushings and CA to keep the torque rod centered on the wood mount with the bushing. A double-layer of scrap styrene was CA'ed together to make a control rod and was stuck to the other end of the torque rod with CA. THEN the whole thing was stuck in place to the panel with CA. A balsa backing was mounted for the servo to rest on.


And the panel with it all mounted... from the front side. Obviously, more details to come.
View attachment

 

[willsonman]

Had a fun weekend with the family. We had a little vacation and went to Hershey Park and had a wonderful time. Now I need to re-focus and get this cockpit wrapped up. I really need to get the electronics bit under control as I need to get the servos centered as I install them permanently. I'll fire up the soldering iron this afternoon. I have a voltage regulator to keep the volts lower. I'm running the main system on 6V and the UMX servos have an input range of 3.2 - 4.2V. My regulator is for 3.5V so that will supply the voltage for all the servos and the signal inputs will go to a separate connector to go into the S.Bus board.

 

[PsyBorg]

Ohh I soo miss being closer to Hershey Park. Back when we were kids that was like a ritual thing at least every other year. What do them huge 5lb Hershey Kisses go for now about 100 dollars hehe. Ill bet a lot has changed since I last went back in the 80's

 

[willsonman]

The 5-pound Hershey bar was $50 or so... My daughter wanted the 2-pound Kit-Kat. That was only $20. I'm not a big fan of their chocolates as my palette has become accustomed to finer vintages from Belgium, Austria, and Germany. It is still a very fun experience and worth the day in the park.

 

[willsonman]

Ok, I got the Pololu board wired up. I stand corrected... output is 3.3V. Many thanks to Jon (rockyboy) for suggesting this board. SUPER tiny and does the job well. I picked out a scrap connector from my computer parts box and I will use that to make a header for the 4 channels to plug into. For now, I've got a way to get the servos centered for installation and check max throws to make sure my pivots are at the right point. What you see below is two servos wired together. The servos are slightly different model numbers and coincidentally, they operate in opposite directions... perfect for my rudder pedals.


For the pedals, I started by inserting blasa with CA into the back of the main stalks to provide some support. After that I took measurements of a tab on former F5 that would normally accept the balsa former for the cockpit floor that would be higher if you opted for no cockpit. 3.5cm wide and the former is 1/8" thick. I made a hole in a piece of balsa 7cm wide as a platform to mount the pedals and servos to. I dry fitted it and cut off the excess that would protrude into the cockpit area, obstructing the instrument panel. This way I have two hard mounting points, former F5 and the instrument panel former. I trimmed away the excess plastic and sanded to round corners here and there. 1/16" balsa squares were used to slightly elevate the Dubro hinges so that the hinge did not bind. The hinges were CAed to the squares and then to the pedals. They dangle like strings now with no resistance. This was absolutely crucial as these UMX servos have no torque at all. I'll get them installed with control rods and horns later today.

 

[willsonman]

I completed the rudder pedals. I used some reference pictures to help me determine if I needed to trim more plastic. Turns out that the pedals are not even close to the same as the full-scale. So, I trimmed a little more off the bottom as I thought that I could have possible binding issues with the false floor that will go in. I got the servos connected to the pedals and they work perfectly. I also finalized the mount of the throttle servo. The push rod's hole on the arm needed to come closer to the pivot point to get full movement of the lever but Its all worked out now.


Moving on, I started making preparations on the yoke. The false floor will incorporate the roll and pitch axis servos together. The roll axis will have a torque rod mounted under the floor so I needed to stiffen the plastic a bit. Some balsa and CA stiffened this up nicely and provides good mounting points for additional hardware.


The pitch axis servo is just small enough to fit underneath the mount for the seat. I'll have to trim away some of the plastic for this but it will give a scale look to the control of the yoke this way. The seat will be affixed to the mount using some velcro. This will allow better access to the SD card for the camera without breaking anything. The idea is to get the main torque rod installed next. This will provide a mounting point for the yoke to sway left and right, Then I will focus on the pitch axis. I trimmed away the plastic for the yoke to protrude. There will be a hinge point in this location.

 

[willsonman]

Needing to get an idea of how these parts go together I did a dry fit of the panels. I had to make some cuts for the camera to get the back panel in but that was quick work.


The side panels needed to be trimmed to account for the canopy slide rails. they will sit flush against the brass and give a clean look.


The seat is only roughly cut right now but clearly it is too large, even in the stock location, it is too tall. I will trim it a bit and also trim the depth to account for this size change. The camera circuit board makes the seat move forward a bit but this does not change that the seat is just too big. It will be removable via velcro so that I can have access to the SD card to offload flight footage.


I was glad that I trimmed the bottom of the pedals. The clearance looks good and the pedals will have free movement with no obstructions. They are also in a very scale position.


The base needed to stiffen up and the balsa does the job well with very little weight. it also provides hard points. You can see here also that I have permanently glued the base to the back plate. This was necessary as the yoke roll axis servo will be mounted there. I used CA to do this and drove pins through balsa in the back plate into the balsa of the bottom plate. Also note the two inset balsa tabs that are locators for the front of the bottom plate. There hare holes that allow the front end to be locked in this way. The guide tubes give support for the main yoke roll-axis torque tube... just a sullivan push rod. very little friction this way and a hole was drilled through the balsa at the rear. A small piece of brass was shaped and drilled to screw into the torque rod. this will provide movement of the stick in a side to side motion. I had leftover (many) APC prop centering bushings and I'm using two on the sullivan rod to keep it from moving fore/aft. they ahd to be trimmed down a bit but the fit is good and I get no binding this way.


Here you can see how the top of the brass piece protrudes. The stick will pivot side to side from this but also fore/aft on another pivot.


Another view of the mockup.