Building Tips and technical articles. > Building techniques
Skyray 35 Triplets
realSteveSmith:
FAIR WARNING: This first post has little to no building related content. It's more of an intro to my project, and for whatever reason, I wanted to explain why I was endeavoring to build 3 Skyrays. Most of you will probably want to skip right to my 2nd post where I start making some parts. But, if you like reading....there's lots of words down there, so have at it.
I noticed there wasn't an active Skyray 35 build thread. I'm just getting started on a build of my own and I thought it might be fun to keep track of it here. I know this is the 'building techniques' section but I don't expect I'll be teaching anything to anyone. These are simple airplanes and I can't imagine I'll be using any tricks that most of the old hands around here haven't already pulled off dozens of times. The main reason I'm posting here is to help hold myself accountable for finishing these airplanes. I've found that professing my desire to complete a task, in front of everyone on the internet, tends to motivate me to follow through. So....why am I building 3 Skyray 35s anyway?
A bit of background is in order. I got interested in C/L stunt late last summer ('23). I was mainly attracted to the idea of contest flying as I'm the type that has always enjoyed organized competition. I found this site and after some research, I elected to start with a Ringmaster 576 kit from Pat Johnston. As I was building on that, one of my fellow club members (Dan McEntee) was kind enough to connect me with someone leaving the hobby and I ended up with a turnkey Brodak P-40 with an OS LA46. Dan suggested that I buy several of the airplanes that this guy was selling, but I was only interested in the P-40 so I passed on the others. As it turns out, ignoring this piece of advice was not a wise move. LOL
On my first trip to the field with the P-40, Dan got that airplane trimmed/tuned for me and I made 3 fairly successful flights with it. However, when taking off for flight number 4, I managed to hook the up line on a clump of tall grass, and as you all know, things got ugly. The airplane was damaged to the degree that I was unwilling to repair it. Since I wasn't smart enough to heed Dan's advice, 1 airplane had become NO airplanes and I was dead in the water. As mentioned, this was late in the season so I just kind of reconciled myself to finishing that RM576 before I flew again.
Over the Winter, I kept working on the RM576 and got the airplane to about 90% complete. But when Spring rolled around, I found myself pulled in another direction and I put my C/L stunt aspirations aside for other hobbies. I kept reading here on Stunthangar.....I enjoyed seeing Stunt News when it came each quarter.....I watched some of the hangouts....but there was no further building and no flying at all this Spring/Summer. I had fun over the Summer but part of me regretted the fact that I was no closer to flying in a Stunt contest. Now that building season is back, I'm determined to do what I can to change that.
While reading Stunthangar this past Summer, I started to encounter threads about the Skyray 35/OS 25LA combo, popularized by Brett Buck. I like the idea that this combination is reported to be easy to build/trim/tune. I REALLY like that idea that if 'the formula' is followed, the combination will perform in a manor that lets someone learn the pattern without learning any bad habits to compensate for the airplane or engine. I noticed another recurring theme in what Brett suggests when it comes to learning with the Skyray..... don't show up with just 1....build several. Seems like I've heard that type of advice somewhere before.
I've decided to save the RM576 for a time when I can competently fly the pattern. For now, I think my progress will be best served with a fleet of Skyrays.
Time to get to work...
realSteveSmith:
Since I wasn't able to buy an authentic Sig Skyray 35 kit, I'm building from plans. I'm choosing to forego 'easy to repair' in exchange for 'easy to replace'. In that vane, I'm spending some time now making a few jigs/fixtures that let me make parts more quickly. I'm also going to be building a D-tube style wing instead of Sig's open framework.
I like the Brodak/Pat Johnston style of wing jig. I decided to incorporate the wing rod holes into a jig that lets me make consistent/symmetrical ribs. The jig pictured below uses short sections of 2016 arrow shaft (5/16" OD) to locate the rib stock while the shape is cut, lead out clearance slots located and spar notch cut. Sharpened brass tubing is used to make clean holes in the balsa.
I use the upper jig plate as a template to cut holes in the rib stock. In this case, I'm using 5/16" OD brass tubing in my hand drill.
Then, the rib stock is placed on the locating pins of the lower jig plate.
I then slide the upper plate on the locating pins, cut half of the rib outline, cut the spar notch and use the larger brass tube (3/8" OD) to cut the ends of the lead out clearance slots. In the photo, I've completed this and have removed the upper plate to show the completed cuts/holes. At this point, I remove the stock, flip it over, and repeat for the other side of the rib outline. In theory, you could leave the stock in place and simply flip the upper plate, but being right handed, I prefer making all the cuts from the same side and in the same direction on the template.
All that's left at this point is to use a straight edge and xacto to complete the lead out clearance slots.
There are 19 ribs per wing. Here are 3 full sets...ready to go. My template leaves the spar notch slightly undersized. Before building I will stack them on the jig rods and use a piece of spar material with adhesive sandpaper on the bottom only to bring the notches to final size.
I made a jig just for the Skyray wing. I used a $12 piece of Melamine shelf board (surprisingly flat) for the base, 1/8" ply for the rod holding stations. I've transferred the rib locations from the plans on to the Melamine base to help with rib alignment during the build. As mentioned above, the rods are Easton 2016 Aluminum arrow shafts. In order to build a full span wing, each rod is comprised of 2 arrow shafts, joined in the center with appropriately sized brass tube and hot-melt glue.
The jig rod holding stations allow clearance for the spars and leading edge sheeting (slot to the lower left side). On this jig, I install ribs, spars, leading edge and sheeting, then flip the wing and install the sheeting on the other side along with shear webs. I've had good luck with wings remaining warp free when removed from the jig after this process.
That's all for now.
Colin McRae:
Looks to be a great project.
I recently built one Skyray 35 from a SIG kit, but I did incorporate most of Brett's suggested design mods, with a few of my own (wing tip adjustable weight box and adjustable lead outs added).
I run mine with an OS 25LA and APC 9-4 prop and also started with Brett's basic trim suggestions. CG and lead-out locations, etc.
I can't do the full pattern as yet but an experienced friend of mine flew it and did the full pattern. It pretty much flew quite well right out of the box.
Good luck on your project!
john e. holliday:
The old DOC here really likes what you are doing. I will be watching this as you go along. Also if you see Dan again tell him the old DOC says hi. D>K
realSteveSmith:
--- Quote from: Colin McRae on October 17, 2024, 08:25:17 AM ---Looks to be a great project.
I recently built one Skyray 35 from a SIG kit, but I did incorporate most of Brett's suggested design mods, with a few of my own (wing tip adjustable weight box and adjustable lead outs added).
I run mine with an OS 25LA and APC 9-4 prop and also started with Brett's basic trim suggestions. CG and lead-out locations, etc.
I can't do the full pattern as yet but an experienced friend of mine flew it and did the full pattern. It pretty much flew quite well right out of the box.
Good luck on your project!
--- End quote ---
Hi Colin,
I saw your build thread on here. Seems like yours turned out nicely.
I'm using a tip weight box and adjustable lead out guides on mine too.....both are laser cut setups from Pat Johnston.
Thanks for the well wishes -SS
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