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Zenair CH601HD

phaxtris

(Ryan)
Premium Member
Premium Member
Picked this projects up july 2023, I have finally started to work on it over the last month or so.

Its a pretty old project, the logs i have state the original builder started it in 1992, then sold it to a guy in Hanna Alberta, again in 1992, that guy sold it to two brothers in calgary in 2009, those two didnt do much other than buy parts (yey for me!), i then bought it from them in 2023 when it was time to sell the hangar it was in, firesale prices.

it came with plans, a mostly completed fuselage, logs, new gear, msc gauges, gps, radio, brakes, cannopy hardware, some tools, 2 gantry cranes. I find new things every time i look in the various boxes it came with.

It is a plans built aircraft, it doesn't quite have the perfect fitment of something like a vans and i suspect that will affect the cruise speed, not that this model is a speed demon, im hoping it will cruise at 100mph, but i feel i may be more realistic to hope for 85-90. If i want more speed there is the option to build a new outboard set of "speed wings" that bolt directly on, they are shorter, and tapered, giving it a higher cruise speed, sacrificing stall, take off distances higher landing speed, etc. I have the HD wings, so that is what im going to go with for now.

I have no real timeline for this, im just plugging away at little things until summer hits and i can drill out the wings for the pre-cover inspection, wich looks to have been done, but there is not official paperwork supporting it

Bringing it home
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Bought a 0 time converted corvair engine with mount from a guy in Saskatchewan, delivered it to my door saving me the drive ( does that mean i paid to much?), after replacing the front nose gear (and being in progress of replacing the main gear) i decided to slam it on

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Fabricating the intake for the ma3 carburetor
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fabricating the exhaust, the welds are nothing to write home about, i think its time for glasses
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The odd ball exhaust manifold clamps cut with the cnc plasma, some work still to go on those
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The exhaust heat shield and gascolator bolted to the firewall with the homemade npt-an bulkhead fitting...forgot to take a photo of that
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Had to make new mounts for the brake/rudder pedals, it looks like a few people had a go at making different mounts, extra holes, things crooked, i ended up make mounts that had some additional adjustment options....this isnt really a feature, just more of a way for me to use up all the extra bolt holes and not looks like swiss cheese, moving the rudder pedals would be a job, requiring new nose gear rods, and attachments for the rudder cables
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The throttle arrangement, not as simple as just a Bowden cable, i went through a couple different ideas i ended up with a set up similar to whats used with a 912, and although this is somewhat complicated and heavier than 2 Bowden cables it gives me the throw i want and eliminates the terrible routing i would need with a cable (the carburetor is backwards for various reasons), i also feel it should be pretty much bullet proof. The cranks reverse the direction of the throw, as well as more that double it, with just a cable i would end up with ~35mm from idle to WOT, i felt that would have been far to sensitive, the cranks turn the throw to almost 100mm.

The tension will be achieved at the cranks by tightening the bolts on the delrin washers (cotter pin+castle nut), all of the hardware will be replaced with castle nuts/cotter pins and drilled bolts as well as oversized washers for the rod end and on the delrin washers. I have a piece of 3/8 4130 tube coming to replace the piece of rod that goes across the firewall. Still need to make a bracket at the dash as well as the two knobs.

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A little video of that action, everything is very loose, i dont expect it to be so noisy with the proper hardware


anyways, thats it for now.
 
Hmmmm.... I thought it was a tail dragger?

 
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Hmmmm.... I thought it was a tail dragger or is that a different one?


different plane, i actually bought the zenair before the little taylor, but because the taylor was airworthy it took priority
 
Putting the engine on has to feel like big progress, It’s looking a lot like an airplane!

Good for you re-working the things from the past owners that just don’t feel right, I have even done that for things I have done myself and gone back and looked at.:oops:

Oh, and you’ve poked me to make some progress on mine…….;)

Thanks for sharing!

S :cool:
 
yea putting the motor on was an enjoyable step, and gives me lots to do regarding the fwf stuff

few more little bits and bobs over the holidays.

salvaged what was going to be the throttle bracket and turned it into the mixture bracket, made some knobs for the throttle and a bracket for the rod, started on the step....which the last several builders seemed to gloss over, requiring me to cut some fairing away and climb inside to pop rivets out...good thing im small

waiting on the 4130 to actually fabricate the step, but i was at least able to cut out the plates that rivet to the fuselage, drill, cleco, etc...


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fun climbing in there....have a couple more trips in to deburr the added rivet holes

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still waiting on the 4130 for the step and throttle arm, trying to make progress on some other fronts

the last owners had bought a kit to install a forward hinging canopy as came on later models, i decided that was something i could get some work done, i had to modify the engine mounts, make a mount for the hydraulic lift cylinder, modify the cowl piece and fit the new side cowl pieces. There are still a few items to fit, namely the latch pins, and some aluminum trim, and then at some point i will try to make a plug to form the actual canopy from....a long while from now

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made some panels to fill in the holes for the backrest, there is nothing on the plans for this, some guys make plywood pieces, some guys have riveted webbing across. I had some 18g 5052, figured that would be lighter than plywood, and stiffer than webbing. I think I will rivet in some nut plates to the fuse so that i have a way to hold it tight on the top

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Bought my first Milwaukee packout, decided i needed to organize the growing pile of little aircraft spruce baggies with hardware...it was starting to get out of hand

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thats it for now while i wait for 4130, and decide what to tackle next
 
4130 showed up, made up the new throttle rod, and welded up the "step". The throttle rod is considerably more stiff, and lighter! Thats a win!

step is made from 3/4 x .049 4130 and the throttle rod is 3/8 x .049 4130

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Figured i would try notching the tube in the mill, that way i could use an angle block and have both notches at the same angle...i had enough material to screw up 1 piece, so i figured what the heck.....and it worked like a hot damn! i didnt have the exact right size endmill, so 30 seconds of filing after notching and i had a perfect fit

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Jigging it up on the budget princess auto table

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welding turned out decent
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i climbed under the airplane, and tack welded the tube to the two side plates with the mig, removed, and welded on the bench, completed piece....
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I will powder coat it at a later date when i am powder coating some of the other steel pieces
 
Nice welds. Now do you have to heat stabilize these joints because its 'just' a throttle rod, or is it good to go?
 
Sorry, it wasn't intended to be a debate, just a question

Its such a contentious topic in the homebuilt community i dont really want to comment to much on it

all of the professional sources say no (lincoln electric, awws), PWHT (stress relief) is not required on thin wall 4130.....yet all the guys who have built 1 or 2 tube aircraft say that yes you do have to....by heating it with a torch and letting it cool :rolleyes:

i do know that proper PWHT of any kind really requires an oven, pre-set cooling rates, jigging to control warpage, etc. is a guy making it better or worse by heating it to some random temperature with a torch and letting it cool and at uncontrolled rate ? maybe some have less stress, maybe some have more, maybe they just moved the haz to another spot in the tube, there is no way to know for sure
 
Thanks, that's exactly why I was asking. Nothing nefarious. I occasionally lurk on other forums & exactly as you say. My welding experience thus far is limited to a couple of SAIT evening courses (knowledge level = squat). TIG is slowly percolating up my long acquisition list. Anyway it came up in discussion at the TIG course & that's exactly what ensued - a lively discussion amongst individuals who came from different backgrounds & experience including the instructor. I was just a bystander but I recall the 2 most vocal, hotrodder was pro-post heat & the aircraft guy was not, go figure. And post heat is apparently yet another topic as you say. Both were involved in unrelated crashes & they mentioned their welds were 100% intact but the frame was a mangled heap. So there was agreement there LOL.
 
back to it, a trip to hawaii and a different weekend project held me up from making any progress

Started work on the heat muff's, the right heat muff will provide carb heat, and the left is for cabin heat. i used 20g 304 where the muff actually touches the header pipes, and 18g 5052 for the remaining. Intake air will come in at the front via a scat tub i intend to route into the air intakes, the heated air will exit at the back inwards through more scat tube and into the air box and cabin heat diverter.

still need to make/weld the inlet and outlet pipes wich the scat tube will connect, deburr, and decide how many egt's i plan to run before riveting the whole shebang together.

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Few things today, designed and formed up the cabin air diverter box that will rivet to the firewall, just need a hinge for the flap and the 2" tube to connect the scat hose to. used the printNC to cut the pieces out.....made a bit of a mess, but i was able to salvage the parts, 20g 5052
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Ive been racking my brain trying to figure out a simple solution to the filtered air/carb heat airbox dilemma, i was going to make a whole new airbox with flaps and bla bla. After staring at it for a while more, and looking at the carb heat diverter that came with the carb, i figured out i could just turn it sideways, put a 90deg elbow on it, and run my air intake piping into that....a quick sandblast, some paint, and then added a mount point for the control cable....done....for now

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Im waiting on some materials to finish these few bits off, i will have to find something else to work on for the next week....or do my taxes...hmm
 
back to it, a trip to hawaii and a different weekend project held me up from making any progress

Started work on the heat muff's, the right heat muff will provide carb heat, and the left is for cabin heat. i used 20g 304 where the muff actually touches the header pipes, and 18g 5052 for the remaining. Intake air will come in at the front via a scat tub i intend to route into the air intakes, the heated air will exit at the back inwards through more scat tube and into the air box and cabin heat diverter.

still need to make/weld the inlet and outlet pipes wich the scat tube will connect, deburr, and decide how many egt's i plan to run before riveting the whole shebang together.

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Hmnn you might be the guy I have to hire to make me some new manifolds for my bird.
 
Nice work. So I'm seeing glimpses of hardcopy 2D drawings/plans in the background. Does the kit include corresponding 2D/DXF type files you can load into your CNC cutter to save some work, or are you having to transcribe into your own CAD system in order to cut? Did your kit-in-progress acquisition include the bulk of remaining materials to complete the structure, or only as far as the last guys got? Is Aircraft Spruce kind of the go-to place for this kind of stuff?
 
Its such a contentious topic in the homebuilt community i dont really want to comment to much on it

all of the professional sources say no (lincoln electric, awws), PWHT (stress relief) is not required on thin wall 4130.....yet all the guys who have built 1 or 2 tube aircraft say that yes you do have to....by heating it with a torch and letting it cool :rolleyes:

i do know that proper PWHT of any kind really requires an oven, pre-set cooling rates, jigging to control warpage, etc. is a guy making it better or worse by heating it to some random temperature with a torch and letting it cool and at uncontrolled rate ? maybe some have less stress, maybe some have more, maybe they just moved the haz to another spot in the tube, there is no way to know for sure

My impression, from friends who have built several aircraft with different methods.
If MIG welding, then post heat (normalizing) is pretty much a given (necessary) due to the speed of the weld (no inherent preheating in the process).
If gas welding, then slowly removing heat takes care of the normalizing and none further is required.
With TIG welding, as much as it is an almost instant start, the process of the weld is slower so normalizing is taken care of as well.

@phaxtris would know more than me, but that is/was my impression on the subject. It seemed to make sense to me.
 
Nice work. So I'm seeing glimpses of hardcopy 2D drawings/plans in the background. Does the kit include corresponding 2D/DXF type files you can load into your CNC cutter to save some work, or are you having to transcribe into your own CAD system in order to cut? Did your kit-in-progress acquisition include the bulk of remaining materials to complete the structure, or only as far as the last guys got? Is Aircraft Spruce kind of the go-to place for this kind of stuff?

No digital content, all just paper copies, and the plans really only cover the airframe. There are a few bits in the plans regarding the firewall forward, but really not much, I have to come up with most of that stuff by looking at the web.

I did get a few extras from the previous owners, they had bought a few parts from zenith (new gear, the forward hinging canopy stuff), some tools (several rivet guns, manual and air, solid rivet gun/bar), a pile of solid rivets from there last project and a few avionic and instrument related items (some of wich i will use, some will collect dust). It didnt come with any raw material unfortunately.

Im getting things from a mix of places, some things i can source locally, some stuff amazon, used stuff (instruments etc) ebay, and yea, Aircraft Spruce. I try to get from places other than AS when i can, they are quite expensive, but unfortunately some things are just to specialty.

The only raw material i have had to buy from a/s so far has been the chromoly tube for the step and Y stick (not shown), if i need some thin 6061 sheet i dont think i would need much and would probably buy it from a/s. If i were to build another aluminum plane or rag and tube plane after this i would search out better sources for material, a/s has a huge markup (i paid 95$ for a 20g 4x8 of 5052, a/s wants 391$ for that same sheet), but for what i need to finish this thing it wouldn't be worth it, if i could even find someone to bring in the small quantity's i would need (6061, chromoly, etc).
 
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