![\"strutside\"](\"http:\/\/www.balsaworkbench.com\/wp-content\/uploads\/2018\/03\/strutside.jpg\")
<\/p>\nBiplanes are a lot of fun to fly, and they look great. \u00a0But sometimes it seems like a lot of work to build the struts for the top wing.<\/p>\n
There is an easy way and a hard way to do just about any job, and building wire struts is no exception. \u00a0If you look at enough plans you will see lots of different ways to do it, but eventually you will settle on your favorite methods.<\/p>\n
Consider the plan for the Sporty Ace biplane from RCM, designed by Chuck Cunningham. \u00a0Here are the struts from the side, top and front.<\/p>\n
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I’m currently building a Sporty Ace biplane. \u00a0Just like all of my other building projects, before I did anything I figured out which details I wanted to change to suit my preferences. \u00a0I decided I wanted bolt-on wings rather than rubber bands, so I ditched the plywood rails on top of the cabane struts. \u00a0These will be replaced by wire terminals\u00a0like this one.<\/p>\n One of these will be\u00a0soldered to the top of each strut. (Take the insulator off first. \u00a0Burning plastic smells terrible!) \u00a0 Then the ring is bent horizontal, and a bolt goes through it into a threaded hole in the top wing.<\/p>\n I also figured that I don’t need the horizontal wire shown in the front view because after the wing is bolted in place it serves the same purpose. \u00a0I’m thinking about replacing it with an X brace from lower right to upper left, and vice versa, in the front and the back. \u00a0This will give it four X braces, one on each side, and at the front and rear.<\/p>\n The next little detail that I addressed was the attachment inside the fuselage. \u00a0As you can see on the plan, old Chuck wanted me to clamp the strut wire to the bottom of a hard beam using a J-bolt. \u00a0Notice that the nut is on top of the beam. \u00a0That doesn’t seem right. \u00a0What if the nut comes loose? \u00a0I can’t get in there to fix it. \u00a0So I decided that instead of a quarter inch beam I would install a 1\/2″ thick beam made of four layers of 1\/8″ ply laminated with Titebond.<\/p>\n Then I drilled a hole into the middle of each end of the beam.<\/p>\n Each strut is a simple L shaped wire, which is very easy to make.<\/p>\n The little end goes into the hole and will be retained with epoxy. \u00a0If they ever come out, I can put more epoxy in the hole and shove them back in.<\/p>\n Next, the X braces are formed, put in place and wrapped with copper wire for soldering.<\/p>\n Now you’re probably wondering how all four struts are held in place during this operation. \u00a0Good question. \u00a0This is the part that drives a lot of people crazy. \u00a0Here’s a photo of what usually happens to your struts when you’re trying to install cross bracing.<\/p>\n Clearly the best solution is to build a jig to tie the tops of the struts together so they don’t move. \u00a0Referring to the plan, I discovered that the tops of the wires are 4.75″ apart from one side of the plane to the other. \u00a0The front struts are 5″ in front of the rear ones. \u00a0So I made a jig with the holes spaced correctly to hold the wires in place while I add the bracing wires. \u00a0It’s a piece of lite ply with four holes in it.<\/p>\n As you can imagine, when the wires are inserted in the holes they want to point straight up. \u00a0When the jig is pushed forward to give the struts the forward rake shown on the plan, the struts will elongate the holes slightly, and the whole thing wants to spring back to vertical. \u00a0So I glued a balsa stick to the back of the jig and braced it against the back of the cockpit to hold the struts at the correct angle.<\/p>\n Now the cross braces are measured, bent and cut. \u00a0Don’t worry too much if the cross braces are a tiny bit too long or too short. \u00a0They can be slid up or down a bit\u00a0as long as you\u00a0make sure that the main struts are in the correct position.<\/p>\n Your steel music wire should be wrapped with soft copper wire at the solder joints. \u00a0Make sure that your copper wire is not coated with lacquer. \u00a0Lacquered wire can be called bell wire, transformer wire, etc. \u00a0It’s intended for winding coils. \u00a0What you want is plain, uncoated copper wire. \u00a0I have a big roll of it that I found somewhere 25 years ago. \u00a0I cut off little pieces as I need them. \u00a0The packaging has been gone for years, but I measured the diameter at .025″, or .63mm.<\/p>\n The first thing to do is to clean all of your copper wire and music wire with alcohol or acetone. \u00a0Trust me, your solder won’t stick until you do this. \u00a0Steel wire always has oil on it when you buy it, and copper wire has tarnish on it.<\/p>\n Next, wrap the joints so they look like the photos below.<\/p>\n If you’re thinking ahead, you may observe that it is easy to hold the front strut and the cross brace with one hand while winding the binding coil with the other hand, but it’s hard to perform the same operation on the rear strut because you have to pass the copper wire through the hole every time. \u00a0Here’s the easy way to do it. \u00a0Wrap the easy coil first, then remove it and slide it onto the rear strut. \u00a0Then stick the end of the cross brace into the coil. \u00a0Now wrap the other coil in the easy position on the front strut.<\/p>\n At this point the jig is put back in place to make sure that the struts are in the correct position.<\/p>\n I always solder my landing gear and cabane struts while they are attached to the plane. \u00a0This leads to a greater likelihood that they will be straight. \u00a0I always position the plane so the joint being soldered is hanging over the edge of the table with a trash can below for catching drips. \u00a0The wires being soldered should be horizontal or close to it. \u00a0I always use paste flux and 60\/40 solder, but a lot of guys swear by silver solder because it’s stronger. \u00a0It’s harder to make silver solder stick, but if you can hack it, take a whack at it.<\/p>\n I do the outermost joints first to give strength to the structure so it can withstand handling. \u00a0It’s a little bit ugly, but the brown and black garbage can be removed with acetone.<\/p>\n The joints at the rear struts create the risk of setting the plane on fire with the propane torch.<\/p>\n I use aluminum foil to prevent scorching. \u00a0I folded a piece of foil in half to make a double layer, then I cut a slit in it, placed the slit around the strut, and overlapped the sides to close the slit. \u00a0I suppose you could do it with a single layer, but I feel more comfortable with two. \u00a0Now it’s ready for soldering.<\/p>\n After soldering, the wood isn’t scorched, and due to proper positioning, there is no flux on the wood, either.<\/p>\n Next, the other braces are wrapped\u00a0and soldered in the same way, forming an X on each side. \u00a0I like to make a soldered joint where the two cross braces form an X, to prevent chattering.<\/p>\n Now it just needs the bolt lugs on top of the struts. \u00a0These are crammed into place and soldered.<\/p>\n Each eyelet is bent 90 degrees to accommodate a vertical wing bolt. \u00a0The top wing is laid on the table, the fuselage is placed upside down in the correct position on top of the top wing, and the four bolt locations are marked with an ink pen. \u00a0Holes are drilled and tapped for nylon bolts. \u00a0The bolts are trimmed to about half an inch in length, and are screwed in from the bottom at the flying field.<\/p>\n Here’s a photo of what it looks like with the with the wing bolted into place, and one with the bolt out of the hole. \u00a0These photos are both taken from the bottom, looking up at the top wing.<\/p>\n Biplanes are a lot of fun to fly, and they look great. \u00a0But sometimes it seems like a lot of work to build the struts for the top wing. There is an easy way and a hard way to do … Continue reading ![\"struttop\"](\"http:\/\/www.balsaworkbench.com\/wp-content\/uploads\/2018\/03\/struttop.jpg\")
<\/a> ![\"strutfront\"](\"http:\/\/www.balsaworkbench.com\/wp-content\/uploads\/2018\/03\/strutfront.jpg\")
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