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Stuart Chale 02-08-2018 03:29 PM

Alchemy Electric Build (CK Aero)
 
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I always like to read build threads. I have learned much of my building techniques from them and by writing my own hopefully I am sharing what I have found to work well. Putting what I found works best all in one place. Best as in straight, adequately strong and light at the same time. Also allows others to chime in with their ideas of what works best for them and we all keep learning. Then there is the selfish part of making these threads. They become a record for me to go back to, to see how I did something and if I was not happy with something what was different on the build before :) My last build was my Allure. I modified the battery tray somewhat (maybe forgot to add the blind nut ply supports is a better way to put it) and I lost a new battery and canopy because of it. Luckily I did not lose the plane. Reviewing my Mythos build showed that I had the additional ply support under the blind nuts. In my Allure the blind nut holding the battery hold down pulled through the tray launching the battery and canopy into the brush or trees never to be seen again.

I have been very happy with the flying characteristics of the Allure especially with the Contra in it. No need for excess vertical fin add-ons to stabilize it. I have had the Contra in 3 planes before the Allure and all three required additional vertical fin side area although I have to say that the Mythos flew very well with it once added.
So the natural stable mate for my Allure had to be Bryan's next design the Alchemy. Looks a little different with a different canopy placement smaller thinner horizontal stabs different shape to the vertical fin/rudder and a chin cowl which was not on the Allure electric version. Landing gear attachment has also changed.
Took me a while to get used to the looks of the Allure and not sure I think the Alchemy looks any better. There are "sexier" planes out there but of course all that matters is how it flies and looks in the air.
When I purchased the Allure I had it painted in a custom scheme in yellow based on Bryan's Shinden color scheme with the bottom painted like his USA team plane. The straighter lines and yellow base work better for my "getting older" eyes :)
So the Alchemy was painted in essentially the same pattern. I even have my pattern plane that I use in Real Flight with the same color scheme.

Hopefully this will be of some interest.
Stuart Chale
D1 pilot

As it comes out of the box:

Stuart Chale 02-08-2018 05:07 PM

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The Alchemy comes in a sturdy box 78 x 22 x 13.5" It is pretty strong cardboard with extra material wrapped around it. In contrast the Allure came in a less sturdy box but was packed in a second heavy cardboard box. Next to the wood boxes used by Oxai pretty indestructible. No issues with the Alchemy packaging though everything arrived intact.

Stuart Chale 02-08-2018 05:30 PM

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The Alchemy fuse comes with a chin cowl like the glow version of the Allure. I like the looks of it but would prefer it not be removable and may end up gluing it in place. Either way it is already installed with alignment pins and just needs 2 socket head screws 3mm I think to hold it in place. (funny, screws not provided)
The canopy is held in place with a spring latch and is a little shorter in the front compared to the Allure. It is also already installed so no real work there. There is a Depron brace that runs down the center of the fuse. Pictures of the inside rear of the fuse above and below are attached. The 2 holes on the right below the Depron brace are for a paper tube for the servo wires. It was lose so I removed it for now. Probably will not use it.
The Rudder is center hinged with a "live" hinge. There should be a hard point in the rudder for the horns.
The gear attachment plate is different. The Allure used a more conventional flat ply plate that you attached the gear leg tabs to. The Alchemy has a Carbon Fiber molded section that holds the end of the gear legs with 1 screw each. The attachment portion of the gear legs are flat with the rest of the leg. (Easier to describe with a picture.) The wheel pants are a bit smaller that the ones included with the Allure

Stuart Chale 02-08-2018 07:04 PM

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The wing has center hinged ailerons. Again live hinges. A recessed area for the servo on the bottom. The wing root is flush unlike the Allure where the root rib was recessed a bit and a spacer is required around the wing bolt to avoid deforming the fuse when the wing nut was tightened. There are no incidence adjusters. Hopefully none will be needed. The Allure was fine as built. Several previous planes I built required them after wards for fine adjustments.

Stuart Chale 02-08-2018 08:43 PM

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The stab is smaller and thinner than the original on the Allure. It is top hinged instead as well. Adjusters are built into the stabs.

Stuart Chale 02-08-2018 09:05 PM

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The accessory pack includes a tail wheel bracket (without wheel), It is light and worked fine on the Allure. The metal gear wire did break where it enters the bracket during its second season but I have had almost all brands fail at one point or another. Wire and connectors for the pull pull rudder are included. Cap screws with nuts for axels. There is a ply battery tray and rudder servo tray. The rudder tray is a bit flimsy and would definitely need some added structure. I usually use 1/8" end grain balsa fiberglass composite for these although this has been harder to find in the last few years and the quality has not been the same as it used to be :) The included ply can at least be used as a template if you want to replace it. Battery straps are included and new with the Alchemy is a 1.5 mm carbon fiber plate cut into servo arms and horns. I believe these might be made by Jason Arnold of Australia. At least they match what he has on his site as being produced there. There are 2 rudder servo arms, one for pull pull and one if you mount the rudder servo in the back of the fuse. There are 2 arms to attach to the aileron servos and 6 control horns. 3 different sizes. The smallest 2 go to the rudder. Not sure if the larger 2 are for the elevators or ailerons. Perhaps Bryan or Jason will chime in :) There are also additional reinforcement for the servo cutouts on the rudder tray and for the elevator servos.

Stuart Chale 02-08-2018 09:12 PM

My field is closed till April so I will not be in a rush to finish the build. First steps will be to get the plane on its wheels. Hopefully to be done in the next couple of days :)
Stuart Chale
D1 pilot

Stuart Chale 02-10-2018 01:54 PM

2 Attachment(s)
I did hear from the designer, Bryan Hebert, the Larger carbon Fiber horns are meant for the elevator, the medium ones for the ailerons and the smallest for the rudder.

Stuart Chale 02-10-2018 03:20 PM

Main Gear
 
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Throughout the build process one has to keep the weight of everything added in mind. With my flying style and perhaps the elevation/air density in my area, I find I use High 3's to 4000 mAH per masters flight. I prefer the extra overhead that I get with the 6000 mAH packs over the 5000's. But this also means extra weight that needs to be accounted for. So careful selection of components and use of glues etc. must be kept in mind at all times. Just because Epoxy will work in one area it doesn't mean that you can't get away with a lighter substitute. For a lot of the construction you are gluing parts to somewhat weak materials so you can easily get away with lightening the epoxy being used by adding micro balloons. Choosing between different materials for servo and battery trays can help. Choosing one tail wheel assembly over another, using aluminum screws etc. On servo extensions I usually use the lighter gauge wire. Especially in electrics where we use under 80 mAH per flight it is hard to believe that we need heavy gauge servo wire. That can be a bunch of grams going to the tail servos.

I always start out putting the plane on it's wheels. This allows me to have it on the bench without a big cradle and I also hang my pattern planes by their main gear against the wall vertically for storage. So I can get it out of the way if I need my work bench for I don't know lets say a house project that my better half wants done :)

Choice of wheels, axles and mounting method can provide weight savings. Generally as far as axles and wheels the lighter you go the more they will wear and need replacing. We could use much heavier real rubber wheels and buy 1 set for the life of the plane, steel axles will hold up much better as well. Most of us chose the foam rubber tire wheels that may need to be replaced once or more during the season based on how much you fly and from what surface. I only get out once a week or so during the flyable months but fly off asphalt and go through 2 or 3 sets of main wheels per season.

My preference for axles is to use NMP aluminum axles which I have been using for quite some time. They are the lightest wheel mount I have found although being aluminum they will wear and may need to be replaced , so keep an eye on them if you use them. They use an E-clip for wheel retention which is also about as light as you can get. A pair complete only weighs about 5 gms.

I use the Axel and a second 2 - 56 cap screw with blind nut to hold the wheel pant to the leg. The axel retention screw goes through a piece of 1/8" lite ply glued to the inside of the wheel pant. Center this at the wheel well opening. I use blue painters tape and mark this position extending a line vertically on the gear leg side. Make sure both pants match and that you are making a left and a right :)
Using 2 1/2" wheels means that the wheel center will be fairly low in the wheel pant. They pants are fairly small. I chose a spot 8 mm above the bottom on the center line. This allows the wheel to move freely and hopefully provides enough material to support the axle. The axles have to be shortened a little to fit inside the wheel pant. Cutting through the second clip recess makes them the right size. I center the wheel in the wheel pant by using the plastic prop adapters from APC props and aluminum washers on the axle. The smaller opening prop adapters can be drilled to match your axle. I also cut a new groove for the E-clip closer to the wheel as I use the thin wheels from Maxx Products. The outer portion of the axle sits in a little ply donut glued to the other inner side of the wheel pant. I have done this before but not recently. It should help prevent any side to side movement of the wheel pant on the landing gear leg.


Stuart Chale 02-10-2018 03:47 PM

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The gear legs as mentioned are unusual being flat on the fuse side with a single attachment screw. The end slips into a Carbon Fiber pocket and is retained with a single cap head screw. The Allure used a standard landing gear attachment plate sitting flat across the fuse. I ended up switching to the longer Falcon Carbon fiber gear and wheel pants on my Allure and except for being a little bouncy on hard surfaces they fit and worked out just fine. I do not believe that there are after market gear of the design used on the Alchemy available at least not yet.

Stuart Chale 02-10-2018 08:06 PM

10 Attachment(s)
The final step is to align the wheel pants and fix them in place with a second screw. I use a 2-56 cap screw into a blind nut glued into the piece of lite ply attached earlier. The exact angle of the wheel pants are not critical but I really want each of them to be exactly the same. I set them to what looks to be level with the plane in a flying attitude. To do this set the flat portion under the canopy to 0 degrees. This area is the reference line for this design. Once I am happy with the angle of the wheel pant and I will often use straight edges on the table of different heights to make sure I think the wheel pant looks level I drill the second hole. You want this second screw to be as far away from the axle as possible while obviously still being through the flat portion of the gear leg that abuts the wheel pant. In fact the hole in the leg should be drilled before making final position adjustments. , I cut a piece of Depron to match the angle. This piece of Depron can then be used to match the angle of the second wheel pant. Once you are happy with the angle drill through the wheel pant and lite ply, then just open up the hole in the pant to accept a blind nut. Glue in place and you should be done.

The tail wheel is next.

flywilly 02-11-2018 06:16 AM

Very nice project. Thanks for taking the time to share the build process. A LOT different than your Brushfire review in Flying Models back in the '80s!

Stuart Chale 02-11-2018 07:56 AM

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Except for the few real kits available, today's pattern planes are like instant gratification. Open a box slide the wings and stabs on their tubes and voila: pattern plane :)
And thanks flywilly at least I now know that one person has read my thread :) And I really wish the Brushfire was one of the planes I kept from the 80's. I still have my 60 sized Atlanta but I would rather have the Brushfire for the occasional classic pattern event.

Stuart Chale 02-11-2018 09:55 AM

Tail wheel
 
6 Attachment(s)
Tail wheel assembly selection is another place where you might save a few grams. The assembly that comes with the Alchemy is pretty light 11 grams with a foam tail wheel and collar (although an e-clip may find its way there) The kit does not come with the wheel. The Allure came with the same bracket with a nylon bushing to insert into the fuse first which was a nice touch. The wheel is turned by a spring that is stretched and attached to the rudder. See below I found the bushing it is included :)

F3A Unlimited has a nice similar setup with aluminum bushing and music wire to fit under the rudder. Needs to be able to slide through a bracket. It also comes in at 11 grams. Just needs a piece on the rudder to allow the music wire to slide through.

F3A Unlimited also sells an MK clone as they are no longer available. (they weighed 12 grams with the supplied tail wheel. ) I have not seen it in person but appears to be 3D printed from the pictures and listed at 10 grams.

I bought a few MK look a-likes from one of the China websites Bangood I think) under $3 each but they are a little bigger and weigh 18 grams. The wheels are good to use though :)

ltc 02-11-2018 10:47 AM

Hi,
Have you seen or tried this lightweight tailwheel assembly from Mike? It says 9 grams
https://www.gator-rc.com/f3aunlimite...-part-f3atwalw

I have swapped out all the stock BJCraft tailwheel assemblies with these on my planes. Much better ground handling in grass IMHO.

Stuart Chale 02-11-2018 11:30 AM


Originally Posted by ltc (Post 12405339)
Hi,
Have you seen or tried this lightweight tailwheel assembly from Mike? It says 9 grams
https://www.gator-rc.com/f3aunlimite...-part-f3atwalw

I have swapped out all the stock BJCraft tailwheel assemblies with these on my planes. Much better ground handling in grass IMHO.

No I haven't tried that one. The one I have from him also lists 9 gms but I measure at 11. Website specs could be without the wheel?

And I lied the gear included with the Achemy does have a nylon bushing. It was sitting on the table.

One thing to keep in mind that no matter which you use make sure you can get spares especially the wire part. It will likely break at some point generally right below the bracket. And it will only happen at a contest!

Stuart Chale 02-12-2018 06:37 AM

12 Attachment(s)
I choose to use the tail wheel bracket that came with the kit. Installation is simple. The bushing takes a 5 mm hole and 3 holes for the attachment screws. 2 in the fuse and one on the bottom of the rudder for the spring. There is some additional material to screw into at the rear of the fuse but I found it too soft and the screws stripped it. Where I choose to drill into the rudder I did not find anything significant to screw into. I used one of my old tricks and glued pieces of yellow Nyrod into the fuse and rudder to retain the screws. I usually do this when using composite servo trays for the servo screws. I want the glue (30 minute epoxy with micro balloons) to still be viscous so not a lot of micro balloons. Put some in the hole and piece of Nyrod then place the fuse right side up after inserting the Nyrod. This way the glue runs down to the entry joint and hopefully holds it in place. On the Allure I glued a blind nut to the bottom of the rudder for the spring attachment. Both methods worked fine.

Interestingly there is a plate in the rudder to screw to, I just didn't pick the right spot. If I stretched the spring a little further I would have found it. You can't feel or see the plate. So how do I know it is there :) There was a loud rattle in the rudder. Something loose floating around inside. I cut away the piece of filler foam on the top of the rudder under the vertical fin extension to get it out. Just a broken off piece of glue. You would be amazed how light that chunk of glue was. Lots of micro balloons or similar filler. Looking down into the rudder I can see both the rudder horn wood block and a small piece of ply at the bottom.

Just an FYI in weight savings. The 3 steel screws weigh 1.5 grams. Steel is 2.5 times as dense as aluminum so 3 aluminum screws would save almost a gram.

DRC1 02-12-2018 04:01 PM


Originally Posted by sc204 (Post 12405547)
Interestingly there is a plate in the rudder to screw to, I just didn't pick the right spot. If I stretched the spring a little further I would have found it. You can't feel or see the plate. So how do I know it is there :) There was a loud rattle in the rudder. Something loose floating around inside. I cut away the piece of filler foam on the top of the rudder under the vertical fin extension to get it out. Just a broken off piece of glue. You would be amazed how light that chunk of glue was. Lots of micro balloons or similar filler. Looking down into the rudder I can see both the rudder horn wood block and a small piece of ply at the bottom.

sc204, Were you able to determine the distance from the hing line to the plate for the rudder pin?

Stuart Chale 02-13-2018 12:50 PM


Originally Posted by DRC1 (Post 12405666)
sc204, Were you able to determine the distance from the hing line to the plate for the rudder pin?

I should be able to give that to you. As soon as the fire wall glue hardens I can try to get a measurement.

Stuart Chale 02-13-2018 01:06 PM

Firewall
 
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Decided to handle the motor mount next. Not a difficult procedure but I don't enjoy working with Carbon Fiber :) In the past I have just trimmed the edges of the firewall by sanding them down bit by bit. This time I decided to make a template out of lite ply first to limit the CF sanding.

I am using a Contra Drive V4 which I was lucky enough to win on the NSRCA USA team Auction. Mike G recommended the new 10 pole Pyro 600 that they are offering. Lighter than the 650 but able to use a greater variety of speed controllers than the original 600 which had more poles. I have been happy with the Castle HV Lite ESC's so I will continue to use one with this motor.

The V4 Contra is a little easier to install than the V3 as the motor shaft simply slips into a collet on the drive unit. It is much easier to dry fit. First step is to mount the motor to its CF plate and mount that with the included soft mounts to the CF firewall. After tack gluing my 3mm ply spacer to the back of the drive backplate using Foam-Tac, I tape it into the nose of the airplane. Keep it flush with the nose ring and centered as best you can. The nose ring of the plane is a couple of mm larger than the rear cone of the Contra. Once taped in place you can trial fit the motor/firewall into the plane. The firewall will need to be trimmed. The idea is to get the motor shaft to freely slide into the drive collet all the way until it bottoms out and still have a slight bit of play in the firewall. I do mean slight but I do not want the firewall pushing out on any portion of the nose. The glue I use will take care of filling the slight gap. The Foam-Tac glue can be easily peeled off of the backplate of the drive once done.

Stuart Chale 02-13-2018 01:31 PM

12 Attachment(s)
I would prefer not to have the removable chin cowl but it does make it much easier to fit the motor :)
As I mentioned I hate sanding Carbon Fiber so I made a copy of the CF firewall out of 1/8" Lite Ply only took about 5 minutes with a scroll saw and drill. Mount this to your motor instead of the CF firewall and start fitting the unit into the plane. Line up the shaft to the drive collet and keep removing material until it bottoms out inside the collet. I use a bench top sander with vacuum attachment. Fitting the lite ply is a whole lot easier than the CF firewall :) Remember to tape up the openings in the motor not to get anything inside it.

Once satisfied, I traced the ply template over the CF firewall and cut to size. A table type scroll saw worked well. The carbon fiber firewall needed just minimal sanding to fit. All in all a better way to do this.
As mentioned I want the firewall to fit in but not push out on the nose of the plane. I recommend using Hysol 9462 (Aeropoxy) as the adhesive for the firewall as it is thixotropic and stays where you put it. The CF firewall is only 1.5mm thick so a small filet of glue on each side increases the contact area and strength. The only downside is that it takes a while for the epoxy to harden. Mounting the motor is the only place that I do not lighten whatever epoxy I am using with micro balloons. Generally I need 2 applications to properly glue in the firewall. Before gluing I clean and lightly sand the area in the fuse to be glued to. Then mark the firewall position with a pencil from the rear. A small bead of Hysol is placed in front of this line and the firewall is slipped into place. Then another bead is placed on the rear of the firewall and smoothed with a moistened finger. Once hardened I will remove the drive and the motor and add some Hysol to the front of the firewall and fill in any voids from the rear.
Often i hang the plane from the tail while this is hardening but everything seems to be sitting well as it is.

Stuart Chale 02-13-2018 02:14 PM

2 Attachment(s)
On second thought why risk the motor weight twisting anything before the epoxy sets, so hung next to the Allure by its tail.

Stuart Chale 02-14-2018 07:08 AM


Originally Posted by DRC1 (Post 12405666)
sc204, Were you able to determine the distance from the hing line to the plate for the rudder pin?

Looks like the middle of the ply should be about 85 mm back from the hinge line.

DRC1 02-14-2018 04:30 PM


Originally Posted by sc204 (Post 12406018)
Looks like the middle of the ply should be about 85 mm back from the hinge line.

Thank you...

Jason Arnold 02-15-2018 01:02 PM

1 Attachment(s)

Originally Posted by sc204 (Post 12404748)
The accessory pack includes a tail wheel bracket (without wheel), It is light and worked fine on the Allure. The metal gear wire did break where it enters the bracket during its second season but I have had almost all brands fail at one point or another. Wire and connectors for the pull pull rudder are included. Cap screws with nuts for axels. There is a ply battery tray and rudder servo tray. The rudder tray is a bit flimsy and would definitely need some added structure. I usually use 1/8" end grain balsa fiberglass composite for these although this has been harder to find in the last few years and the quality has not been the same as it used to be :) The included ply can at least be used as a template if you want to replace it. Battery straps are included and new with the Alchemy is a 1.5 mm carbon fiber plate cut into servo arms and horns. I believe these might be made by Jason Arnold of Australia. At least they match what he has on his site as being produced there. There are 2 rudder servo arms, one for pull pull and one if you mount the rudder servo in the back of the fuse. There are 2 arms to attach to the aileron servos and 6 control horns. 3 different sizes. The smallest 2 go to the rudder. Not sure if the larger 2 are for the elevators or ailerons. Perhaps Bryan or Jason will chime in :) There are also additional reinforcement for the servo cutouts on the rudder tray and for the elevator servos.

Yes Stuart, the Carbon Control horn set is made downunder. :-) The longer Control horns with three holes are for the elevators. Bryan wanted an extra hole for use with the Futaba BLS 173 servos which are a little higher in profile. There is also a longer servo horn which is an option for those choosing to mount the rudder servo down the back with direct linkage to the rudder. In this case you would use just one of the included rudder horns. There an instruction for these horns on my website here: Attachment 2254791

Cheers,
Jason.


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