Cessna 152, Balsa 30% Scale Rescue from Hostetler Plans

[Joker 53150]

After marking the firewall and the mounting points for the engine I drilled some holes, installed some T-nuts, and tried installing the engine.

.....and found out I mis-measured the mounting post requirements, I actually need slightly longer posts. The engine sort-of fits right now, but the prop is a little too close to the cowl and the cylinder head cooling fins touch the nosewheel mounting screws. I'll build a simple base to move the engine out slightly and the problem will be solved. Either way, it's a great feeling seeing a motor in it! When the spacing is finalized I can do the job I'm really dreading - installing the throttle servo and pushrod. It's really going to be a pain as the servo needs to be moved to the other side of the fuselage.

Note the cowl mounting holes around the outside of the firewall. Most of them are stripped out and in pretty rough shape, so those will need some attention as well. The other option is to leave them and drill all new holes for the cowl, but that would leave a bunch of empty holes in the cowl. No easy solutions on that one, it'll be a lot of little fiddly work to make it all work. I'm considering adding some blocks to the firewall that I'd bolt the cowl to, which would let me move the cowl forward a bit. That would also require even longer spacers for the engine, but it would look a little better as right now the cowl looks like it's mounted too far back.




A 20 x 10 prop looks right for this size plane, and it's also one of the recommended sizes for this 58cc engine. It'll easily swing a 22" prop, but that may be long enough that it cuts grass which I'm hoping to avoid. Working on the plane with the wings on really helps me get my steps in for the day, as no matter what tool I need it's on the other side of the bench forcing me to walk all the way around!




This plane has 9 servos: throttle, 2 for ailerons, 2 for elevators, rudder, steering, and 2 for flaps. I also need to connect the throttle kill switch to the receiver, run power to the receiver, connect a switch to control the lights, plus who knows whatever else comes up. I could run the elevator and aileron servos on a Y-harness to free up spots on my 8-channel receiver, but am not a fan of that with such a big plane. I have an extra 8-channel receiver from FrSky so I'm going to look into connecting them to give me 16 channels. I think I heard somewhere along the line that I could split some of the critical servos between the two giving me some degree of control if one of the receivers dies. Or maybe I'm wrong...

Although I don't yet know the true CoG recommended for this plane yet I think I'm going to be in good shape using a few less pieces of lead than it came with. Making an educated guess shows it just a tiny bit tail-heavy currently. One the exhaust & cowl are installed and the engine moved forward slightly it should be even closer. Those two pieces of lead weigh more than the flying weight of some of my planes!

Wilsonman, that big Xoar prop was $5 at a swap meet. Thanks for the recommendation on using them, they're fantastic props!

 

[Joker 53150]

I broke down and ordered new navigation lights from www.spudgun.com, a guy who's main business appears to be selling spud-guns. They look almost identical to the 10mm LEDs the plane came with and fit just fine. Thankfully I requested long wires as it really makes feeding the wires through the wings and into the fuselage much easier.

I pulled the new lights out and stripped the ends so I could test the lights with a 5v receiver battery. The green worked great, but no-love with the red. I tried a few things with the wires but couldn't get them to light up. Black wire is negative and green is positive, they didn't short out, the red light works, etc. I e-mailed the vendor and had an answer back in about 10 minutes: "Reverse the wires to see if it was simply wired backwards, if that doesn't work a replacement will be sent out tomorrow." With nothing to loose I tried it, and SUCCESS!

All plugs were soldered and the wings re-installed. A charged battery was hooked up for the navigation and strobe lights and they all work perfectly! However, now the plane is sorely missing landing lights, so I'll look at adding those as well.

 

[Morgan]

Can't wait to see this fly!!!☺

 

[Joker 53150]

Can't wait to see this fly!!!☺

You and me both! It took a step closer with new engine spacer blocks being made today (after I was done screwing around with the lights). There is now good clearance all around and over the next few days I'll get around to gluing them in place, running the new throttle cable, etc.

 

[Joker 53150]

Here's something new (to me) - running two receivers for one plane! So far it appears to work well and I'm getting feedback on the best way to connect everything. Currently it's set up with a single battery for testing but that may be changed to dual batteries. I'm also tentatively going with programming to split control surfaces between the two receivers which may help keep control if one of the receivers dies or loses signal.

The setup right now:
Receiver 1
Channel 1: Throttle servo
Channel 2: Left aileron servo
Channel 3: Left elevator servo
Channel 4: Rudder servo
Channel 5: Left flap servo
Channel 6: (open)
Channel 7: (open)
Channel 8: Receiver power from Receiver 2
Receiver 2
Channel 9: Steering servo
Channel 10: Right aileron servo
Channel 11: Right elevator servo
Channel 12: (open)
Channel 13: Right flap servo
Channel 14: Ignition Opto-kill switch
Channel 15: RX battery input
Channel 16: Jumped to power Receiver 1




Right now I'm needlessly using up Channel 15 for convenience and will eventually supply battery power to both Channel 8 and Channel 16. I'm not sure if it'll be done with one battery or two yet... I'm also not sure yet if I'll use one of the channels to turn navigation lights on/off yet. Keeping them on their own battery will help avoid draining the receiver batteries, but maybe I'll run them through a receiver-controlled switch now that I've got some open channels.

 

[Joker 53150]

Arrrrgh, there is some ugly construction coming up, you've been warned!

A lot of wires come out of each wing - aileron servo, flap servo, strobe, and navigation light. These wires have to be fed into the wing's center section and then down to connect to the electrical systems. The holes in the wing and "ceiling" inside the fuselage are small and pretty-much just ripped into the balsa, so feeding all these wires is a bit of a trick. The plan was to simply smooth them out and enlarge them a bit, but the more I worked on it the more I decided that the only way to do the job properly is to do some fairly aggressive surgery. That'll just have to wait, as there is enough work to do on this plane for now and it's still functional.

I also removed the pilot's door as there is limited room to get at the electronics with it installed. It's all sitting fairly ugly and roughed-in at the moment as I get the fuel tank and plumbing installed. I'll need to order receiver batteries and build a tray for them and can then tidy up the electrical mess. Every time I get mad about the "rough" construction I just keep reminding myself that I got the plane cheap and that it's worth it. I don't know if I believe the BS I say at times...




And this is the ceiling above the pilot's head - holes are just punched through the balsa sheet for the wires. This makes me wonder what I'll find when I eventually strip the plane down for a full re-build!




With all that said, the engine is almost ready to fire up for the first time. The ignition system is wired and uses a dedicated battery along with an opto-kill switch to shut the engine down in case of problems. The original gas tank was cleaned out and all new components added to it including an external fill-port. The original throttle servo location was re-used and a new pushrod was run for it - if it works as I think it will I can add a little internal structure to finalize the install. It only needs new muffler bolts to complete it.

 

[roversgonemad]

The original builder was either not much of a craftsman, or just a rank amateur. Make sure it's structurally sound and fly the crap out of it! that's what I say! I am sure the price was good. I have picked up a few planes that I really only intended to take the engine and a maybe a few servos... Some I have flown quite a bit, a few others just got gutted and put in the rubbish bin. I picked up one plane just for the Saito FA 50 on the nose. It looks like your 152 has flow before, so in spite of some ugliness, it looks like it will be a flyer! Can't wait to see a maiden video.

 

[Joker 53150]

It has flown, but maybe not the last few years based on the sludge in the gas tank. The builder was an older guy who had help finishing it so it would be done and flying before he passed. My guess is that speed and “good enough” we’re the orders of the day! Overall it is structurally sound where it matters.

 

[Joker 53150]

With most of the work done while I'm waiting for batteries I decided to do something about the doors. Both are removed and both need plenty of work. The handles are gone making them hard to open, the windows are scratched up and ugly, the covering is fugly, they're super-thick and not very realistic looking, and the hinges are set in too deep keeping the doors from opening fully. Other than that they're perfect!

Step one in reconditioning them is removing the covering so I could see what I have to work with.




Next I cut off about 1cm of thickness around the top of the door so I could verify the thinner door would open/close easier, which it did. With that experiment complete I faced the bigger task of cutting off extra thickness at the bottom of the door.




As I cut the excess material off the door bottom I kept looking back at the face of the door. It could be smoothed out with some balsa filler - LOTS of balsa filler. Glue joints were broken in a few spots so those would need to be fixed as well.




To clear my mind I cleaned up the covering around the door opening a bit. Previously it was a mess of excess covering with uneven edges and major wrinkles. I'll need to add some new covering to help seal the newly cut edges, but this cleaned it up a lot. It also was the kick I needed to realize what needed to be done with the doors...




So I'm scratch-building new ones! The old door was used as a rough template since I don't have the original plans. Once the glue on the basic framework is dry I can round the bottom edges and test-fit it in the door opening. The hardest part of this will be getting a slight curve at the bottom of the door where the fuselage curves slightly. New plastic will be installed for the window as well.

 

[rockyboy]

LOL! Glad those 'perfect' doors that came with the plane were good for something

 

[Joker 53150]

A big reason these doors need to be re-built is due to how they were hinged. This was also a problem I ran into when I re-built a Balsa USA 1/4 scale Cub a year or so ago. If the hinge placement isn't done right the door simply can't open properly. When the hinge is recessed too far in it lets the door hit the door frame causing binding and stress on the hinges. That eventually causes the hinges to fail or to simply pull out of the wood they were mounted in, such as this:




It looks like these hinges were placed before the final sheeting went on, meaning they were recessed too far into the door jamb. After I cut out this broken wood and glue in some replacement stock I'll re-cut the hinge slots in a manner that will allow the door to open fully. Well, as fully as it can get since the wing strut will stop the door once it's open about 90 degrees. Previously the door would open maybe 60 degrees before it started to bind.

The new doors will also include some spring-loaded latches to keep the door closed. The original used a magnet which may be re-used as a backup. The new doors are also about half as thick as the old doors so I'll need to add new structure for the door to close against inside the jamb. That'll help the door close evenly all the way around as well.

 

[Joker 53150]

I failed to mention it earlier, but the framework of the door is made from heavier/stronger balsa. With the frame done I could sheet the outside and test-fit the door. Note I added a couple internal braces where you see the extra pins. Small shims were added around the perimeter of the door to make sure there was an even gap. Front and rear are good (although it's hard to tell because of the ragged edges on the covering) but top to bottom needs a little final sanding.




Sanding and fitting are about done. In the previous picture you can see the top left corner of the window frame sticks out a bit due to the curve of the fuselage. To fix this I made a small cut in the frame that allowed the window frame to be bent in just enough to fit properly. The cut was then glued and will be braced for strength soon.




As mentioned, there is a slight curve to the fuselage and a flat paneled door just wouldn't look right. To help recreate that curve on my flat framework I added some thin balsa sticks and sanded them just enough to create a gentle curve from top to bottom. This is the inside of the door, which will be sheeted once the door latch mechanism is installed. A little extra material will be added where the door hinges go so there is plenty of "meat" for the hinges to be glued to.

 

[Joker 53150]

Yes, I'm eventually going to replace the crooked "152" numbers. They're bugging me, too.

 

[rockyboy]

It's less the 152 number specifically, and more all the red wrinkled parts.

And the white wrinkled parts are a little skeevy too.

Yeah, pretty much the entire covering job.

But make her fly first, then make her pretty.

 

[Joker 53150]

The covering absolutely is screaming for new covering, but it’ll have to wait. The numbers are easy to replace and will make it look 1.3% better from a distance.

 

[Joker 53150]

On the inside you can see the extra bracing added to support the sheet material. Also, a latch has been added and epoxied into place which will give me a much more secure door closing. The magnet will also probably be re-used for an extra level of security. The left edge of the door is where the hinges will go, so extra material was used to beef this area up.




From the outside all that'll be visible is this simple handle to open the door. The slot needs a little clean-up, this was the first trial-fit of the handle. Before adding the sheeting to the inside of the door I'll add a little Gorilla foaming glue to the back of the latch to secure it fully. I may also recess a thin piece of ply across the front to help prevent hangar rash around the handle.

 

[rockyboy]

I thought adding thin ply around the handle for hangar rash would be a way overkill idea.

Then I remembered last night I slipped pulling off some masking tape and made a big gouge in the side of my tele fuselage with my thumb nail.

Now I'm a believer. :black_eyed:

 

[Joker 53150]

Yeah, it doesn't take much to dent balsa. Compound that with a spot that I'm constantly reaching for to open the doors and it could get ugly fairly quickly, and this plane already has enough ugly! If I add it, it'll be super thin ply - maybe 1/32" or so. Just enough to strengthen the area. I may find similar results by just soaking the sheet with some thin CA or even brushing on some thinned epoxy.

 

[willsonman]

Yeah, I'd probably just smear some 5 minute epoxy around it. Hard enough for fingernails and non structural.

 

[Joker 53150]

Here is how my hinge placement differs from the original door. You can see the slots from the original are inset about 1/8" from the outside edge which is why the doors wouldn't open fully - the door would hit the door frame. I've moved the pivot point of the hinge out so the pivot point of the hinge is inline with the exterior skin of the fuselage. Without the wing struts installed I may be able to open the door 180 degrees compared to the approximately 60-ish degrees it could originally open.




Here's a tip when installing hinges on doors or control surfaces: make sure they all line up! If they don't you'll have binding or stiff movement of the surface. I'll need to fabricate some structure for the door jamb that will hold the other halves of the hinges as much of that original material is ripped apart and un-usable. The original door wasn't actually even held in by the hinges when I got it, the door was friction-fit (slightly too big for the door opening) and "secured" with masking tape. Nothing but the best!




Right above the door latch is a small recessed edge. The plastic I'm using for windows will sit on this and fill the recess. When covered it should be nice and flat across the height of the door, just like the original Cessna. The new door latch works very nicely, by the way. The door jamb will need a small piece of hardwood glued into place to receive the bolt as I expect the balsa currently there will wear with time making for a sloppy fit.