Hello All.  I would like to build a Sig 1/2a Skyray kit and I'm looking for some tips.  It doesn't seem super complicated.  There are only three sheets of balsa in the entire kit.  But it did not go well when I tried to build a Sig Buster when I was 14.  I'm hoping for better results this time.

I was inspired by spectating at the Brodak Fly-In this year.  That was really amazing.  I had a Cox RTF P-51 when I was a kid, and I have a box of old Cox engines that I'm exited to get running.

I've been looking through many of these 1/2a building threads (there are so many) and I haven't found the specific answers I'm looking for so I figured I'd start my own thread.

1) The kit instructions (copyright 1977) recommend sig-ment for glue.  Is this still the preferred option?  It seems like most RC planes use CA and epoxy these days.  If sig-ment is still preferred, is there a hardware store equivalent?

2) The instructions also recommend dope for paint. What is dope?  What's the preferred finishing method these days?  I've used heat-shrink covering for RC models (eg Monokote), but maybe that's too heavy for the little Skyray?

3) The leadouts are plain wire twisted at the ends and sealed with epoxy.  Is this still the best way to make the end loops?

4) Fabric hinges?  Anything better?

5) Any areas where the kit could use improvement or modifications?  I've found references to the fuselage easily snapping ahead of the wing.  Also complaints about the bell crank and control horn.

6) How about lines and line length?  I have leftover Cox dacron line, but it seems like maybe steel lines are preferred?

7) How about trim and setup?  Here is the area where I truly have no idea what I'm doing.  I've seen many references to lead out angle, weight distribution, thrust angle, rudder position, etc and it all seems very complicated.  I figure I'll just follow the plans and hope for the best, but any tips would be appreciated.

And other advice for a beginner?

Axle,

Hope you have a good time with your 1/2A Skyray. I have one I use for a beginner's trainer and it works great. Set up right, you shouldn't have any problem.

1. You can use Titebond or Elmers for most everything. Epoxy would be fine, too, especially around the firewall. But, in general the nose pieces have plenty of gluing area. Personally, I wouldn't mess with SigMent for this application.

2. You can always use dope, which is a traditional aircraft lacquer paint, but it isn't particularly fuel proof with glow fuel, and especially 1/2A glow fuel with 25-35% nitromethane. Some quick and easy--but not as long-lasting methods include painting with Rustoleum automotive primer and then a solid color. These are fairly fuel-proof for a while. But refueling a 1/2A is generally pretty sloppy, so....   An epoxy finish such as KlassKote is very fuel-proof, but unless you already have it on hand, it's not going to be worth it. You will only need a tiny amount and it won't be inexpensive.  Go read the many reports on Rustoleum and it will help you decide. On my current Skyray, I used MonoKote on the wings and KlassKote on the fuselage and tail.

3. The pull on a 1/2A plane is miniscule. The pull test is only five pounds, meaning that each leadout has to withstand without yielding a whopping 2-1/2 pounds. Twisting works. A cleaner method that works for larger planes is to form a teardrop loop in the end and then wrap with very fine copper wire and then solder it. You can go quick and easy, or you can use the Skyray to practice for building larger planes. See the attached picture of one of my 1/2A leadout terminations.

4. Fabric hinges are traditional, and work, but are part of a system. Typically a paint system to get them fuel-proofed. If you use them, do not use cotton fabric. Use dacron or some type of synthetic. You can also use sewn Spectra hinges if you put a spruce or basswood strip along the hinge joint. You can look up some prior threads that had pictures posted. I use these on 1/2As all the time. The Skyray trainer I am using now has a clear adhesive tape hinge. Works fine. The Blenderm tape is probably the best overall, but others work well enough. And if you MonoKote the surfaces, then a MonoKote hinge is easy.
https://stunthanger.com/smf/open-forum/thread-hinge-variations/msg638289/#msg638289

5. Everyone has mods for everything. I've even seen pictures of a Lamborgini that was "modified" into a rat rod. I guess you'll have to wade thru the "improvements" and use your best judgment. On my trainers, I put in a balsa triangle fillet under the stabilizer and beside the wing joints to increase the gluing area and to spread out the stresses from mishaps. I have not snapped the fuselage in front of the wing (yet). As long as you get some decently firm wood for the fuselage, you shouldn't have trouble. That said, you can keep "beefing up" areas that people have found broke in a crash. Pretty soon, though, you will have a very heavy plane that is good at crashing but not flying. I added a landing gear using a 1/16" plywood spacer to capture it. There should be pictures of that here as well. I fly from asphalt, so it helps keep things from grinding away, and lets pilots practice real takeoffs and landings. I haven't had any issues with the standard bellcrank or horn. These are very well proven parts, used on a lot of different 1/2A airplanes.
https://stunthanger.com/smf/12-a-building/sig-12-a-skyray/msg635133/#msg635133

6. Don't use the old Dacron lines. They are way too draggy and stretchy. I'd use 20 or 30 lb test Spectra at 42'. You can use the .008 stranded cable lines but most guys complain that they are too hard to handle without damaging them. And you need a handle for a 1/2A. That means no Hot Rocks or similar. You want the spacing at the handle to be around 1-1/2". The RSM-Renger handle is good.

7. Build it like the plan and it will work. I like to use packing tape to attach a big fender washer under the outboard wingtip on the fore/aft CG. This is great for training and for windy weather. It limits maneuvers, but if you are not doing loops, then it helps a lot. This is especially good for first flights.

8. Hopefully, you will be able to get a good, reliable (ie. clean, and not previously mangled or worn out) engine. Be sure to screw it to a block of wood and test it out before you ever put it on the plane. Get used to starting it. Two keys are using clean fuel with at least 25% nitro (that makes them easier to start) and a good battery system to light the plug. Expect to prime the engine before each flip. A spring started saves you from engines that want to run backwards. If you have trouble with the engines, send more questions. The most important tip of all: have fun!

One thing you will find:  there are a lot of guys who don't like 1/2A planes. They will tell you that they don't fly well, that they won't fly in a breeze, that the Cox motors won't start and are a PITA, and on and on. That bellcranks don't work because they aren't five-inchers. Etc. The fact is that if you can work on smaller parts and don't expect to get a $1,000 dollar plane that will "get you thru Advanced," a 1/2A plane can do a lot of initial training with low investment and low intimidation factor. If you have cubic dollars and only the best will do, then hire some guys to rebuild the larger ones for you....and you can still have a ball.

Here we go again a newbie with no reference of where he is located.   You may have people close to you that could give a lot of personal help.  I was at Brodaks spectating also as the family won't let me drive and physical I'm still on the mens from problems.  As you can see at the end of this post is where I live.  Been flying and building planes since the 50's.   Ahy way a lot of good advice has been given already.  I too had to learn control line way back then by reading books, magazines and any other lirutature I could get until I found the Flying Eagles of Kansas City Ks.   Also after all these years I am still learning.  Remember to have fun.

I’ve used lots of kinds of glue over the years and am back to simple wood glue like tight bond for most wood to wood connections. I agree with Dan on epoxy for the engine and bell crank mounts.

What Dan said about rubber band mount for engine is spot on if flying over pavement or short grass. I did a lot of 1/2a flying in a hay meadow were it was less important.

I also agree with braided spectra flying lines. Not monofilament. Not braided nylon. (I don’t know if braided nylon fishing line is even available anymore but just in case some is still laying around somewhere, it is springy like a rubber band.)

I also recommend sewn hinges. I’ve used the same kind of fishing line for hinges that I use for the flying lines.

I’ve had good success with rustoleum paint if I let it dry a couple of weeks before getting fuel on it. It may not hold up as well as some other finishes but it’s easy to use and readily available.

Go have fun.

Axle,
I'm painfully cheap. I discovered that Deft Clear Sanding Sealer smells.and behaves like Nitrate dope. It is a great balsa filler,.and topcoats with just about anything just fine. Deal with Deft, then spary with a (barely) colorcoat with just about anything, and then a quick, light spray of clear poly-utethane for fuel proofing.

Don't make a mistake and call this one your "forever" plane. That is, regard this one is a trainer, and don't spend too much time making it perfect. Trace all your parts so you can replicate at will (or crash). The idea is to be able to build/fly often as you settle into Roundie-Roundie flying.

Sewn hinges: I love them. Regarding the option to strengthen the hinge line...it isn't needed on these puny planes. I do "Frankenstein" hinges with the penetrations about 3/16" from the hinge line. I do drop a drop of CA at the start hole with a knot that gets clipped short just after the glue sets. I also try to use a non-conflicting color so I don't feel the need to paint the hinge. If the line feels a bit loose, then I CA each hole, and then the last hole (hardest to get a know tied right at the hole). Between the "far-from-hinge" holes and the CA, I haven't had hinges tear out in crashes. My favorite hinge alternative (though harder to implement) is floppy disk mylar cut into narrow strips that get CAd into hinge slots. Making the slots is a bit of work.

I like old butyrate dope...but I do mist the nose of the plane with poly-u spray just to make the finish last long enough to survive a few crashes. Once crash and fix has happened, the plane starts to look pretty rough...remember those templates and build another!

I prefer side tanks rather than Cox Babe Bees...just easier to troubleshoot if the engine fails to draw fuel.

Most importantly, don't get too hung up on your first few planes. Remember this IS supposed to be fun.

1/2A profile planes are a hoot! Jump over to CoxEngineForum for the comraderie of like-minded fellows enjoying their childhood again.

If you really want to do built-up wings and things, there are several 1/2A kitters in the cottage industry with kits that will you your building game. No financial interest, but I'm fond of Dave Cowell kits aka DPCModels/Aerowerkes. He has reproductions of Scientific and Sterling (and more) kits, and they are quite remarkable in that he reverse engineers the original issues/concerns out of the kit. There are others...Stan Fronenberger (Vintage Performance), and really good looking kits from one of the SH guys, Pat King (PDK LLC).