Positioning the leading edge wing skins: In positioning the leading edge wing skins, I found it easier to start by clamping one edge in position along the line on the forward spar, then pulling the rest of the skin into position with 3 cargo straps over a 1X4 board on the other side of the wing.
New wing skin sequence: Hang the lower wing skins, beginning with the outboard skin. Note that the center and inboard lower skins will require a cutout to accommodate the flap track. Therefore only hang the skins by the forward edge with a few clecos to facilitate easy removal. Mark the exact centerline of the flap tracks and the aft edge of the aft spar line on the skin. Remove, and measure out from the center line on each side, drawing the outlines of the cut out. Caution: avoid getting too close to the rear spar. Measure the amount of clearance needed for the flap track and designate that amount as the line for the forward edge of the cut out. Round the forward inboard corners by drilling out with a 1/2″ drill. Mark & center-punch those holes accordingly.
Rivet the leading edge section of the lower skins on to the fwd spar, EXCEPT THE LOWER INBOARD SECTION, which will be riveted with the lower inboard skin, which is placed under the inboard leading edge skin. Note: It is much easier to buck these rivets before hanging any skins, except for the inboard lower leading edge skin. Then proceed with the balance of step 62, EXCEPT: If you plan to install the long range tanks (in the outboard wing section) Do not rivet the outboard rib (6) to the skins and spar at this time. Cleco and/or clamp it in for security and rivet after final assembly. Rivets can be squeezed on this outboard rib.
Nose ribs: Trim inner curves of tip flanges of wing nose ribs back about ¼” to avoid dimples in skin exterior.
Tie-down attachments: I had some tie-down rings custom welded and attached to the upper ends of the wing struts to avoid damage from some of the tie-down chains at airports.
Skin doubler installation: Don’t install skin doublers around the inspection plates until you have closed out the wing. The space isn’t big enough to get your hand through to hold a bucking bar if you do.
Spar root rivets: On the spar root rib attachment points, use AN3 bolts instead of -5 rivets as you can’t get in to buck the rivets.
Nav light wiring: Prior to close-out, run your nav light wiring in a conduit tie wrapped through the wing. Leave a string installed to fish any wiring you may want to add later.
Shaping the forward spar cap strip reinforcement strips: To fit the inside radius of the spar, use the cut-off end piece of the spar as a gauge to shape the radius.
Leading edge assembly placement: When placing the leading edge assembly over the front spar, the manual calls for taping the cap strip pieces in place. It is better to cleco them from the inside of the spar, and the leading edge skin easily slips over the slightly protruding clecos, which can be re-inserted through the back surface of the skin.
Flap track reinforcements: Leave the flap track reinforcements that you make a little wide and custom fit each one to pick up the required number of rivets.
Flap track reinforcements: Incidentally, I agree with the comment on the flap track reenforcement angles. The factory dimension of .75 inch width compromises the edge distance on the rivets, and these should be left at full 1 inch width until the required width is determined.
Fitting the root ribs: I had difficulty properly fitting the wing root rib ( #1). After checking with S/H I found that the root rib was too big to fit between the forward and aft spar by .040 to .060. I fabricated a former to fit behind the forward flange and spaced it back .060 and bumped the flange against the former. By following the procedures in the manual, my root rib assembly was too wide to fit between the forward and aft spar flanges. After a lengthy discussion with S/H the realization was made that the root rib is slightly too thick. My suggestion is to assemble the root rib and the angle reinforcements in place between the flanges with approximately .0005 shim between the flanges drilling and riveting at least 2 holes in each of the corners before removing the root rib for final assembly
–Danny – GlaStar Component Services
Root rib: There is a lot of labor in the root ribs, and you have to be very careful with them to get them built right. In addition they will be out where everybody can check your work and snicker every time you fold the wings. It is almost essential to have a set of Scotchbrite wheels (7A & XL-WL) on a good buffer (I have a Baldor) to get the tool marks out of the doublers. I have seen several sets and all were really a mess. Plan on spending most of a day cleaning them up.
Save yourself some grief and make a template with the web locations and rivet pattern. It is important to the strength of the structure to get as much offset between the rows of #40 rivets along the doubler as you can. But, you have to insure that you leave enough room to get a rivet set on the rivets close to the rib flange and to leave enough material between the rivet holes and the edge of the doubler to get a proper set!
Don’t cut the web doubler angles too long. No dimensions are shown but, there are several places where they will interfere with your ability to use a bucking bar when you rivet the skins. Leave yourself some room and cut the web flanges at an angle.
Danny is right on with his idea for fitting the root ribs between the spar flanges. I have seen three of them fitted (one of which was made on the latest redesigned tooling) and none of them would fit between the spar flanges. Do not even drill the holes for the rivets that are located inside the flanges until you have the rib in place with some kind of shim between the rib and the spar flanges. I used aluminum tape and it worked fine. Drill and rivet these holes with the root ribs in place between the flanges.
As an aside, all of the rivets in the root rib except the ones in the very center of the Web Doublers can be squeezed if you have a longeron yoke for your squeezer! . Both Avery and Cleaveland sell one. A very useful tool. It can be used in a lot of other locations where you otherwise would have to use your hammer.
Fitting the Main, Nose and Cove Ribs: The manual instructs you to insure that all ribs are installed so that the top and bottom flanges are aligned with the spars. They tell you to make any adjustments necessary and to split the difference if you cannot quite get them to line up. This will require you to move some of the pre-drilled pilot holes in the ribs. Be sure and get them aligned to the best of your ability because if you don¹t you won¹t know it until you rivet the skins in place and they are pushed or pulled out of alignment. Any misalignment will be most apparent on the cove ribs, because the upper skins are out there all by themselves.
The instructions tell you to drill up all the #40 holes in the ribs and spars to #30 at the end of Step 19, but there is no real reason to do it this early. Wait until the skins have been fitted and you have checked the alignment of each rib by at least temporarily putting a cleco in every hole to insure that there is no deformation. If you do not take these precautions the first time you will find out that something is out of whack is while you are riveting the skins. Any problem you discover then will be very hard to correct. If you have not drilled them out to final size and find a misalignment with a cleco it will be very easy to move the holes slightly when you drill them up to take a #3 rivet.
Ribs to spar alignment: As mentioned in the manual, check alignment on the main ribs, nose ribs, cove ribs for fairness where they intersect the flanges of the spar. This can be accomplished easily with 2 battens (strip of wood approximately 5/16″x1/2″x40″) spring clamped to top and bottom of ribs and cove at the same time and pulling clecos out and viewing any changes in position of the assembly. This will enable you to make minor adjustments to the assemblies before drilling the pilot holes from #40 to #30. I think more emphasis should be given to this procedure in the manual as it will make a substantial difference in appearance.
-Danny – GlaStar Component Services
Main Rib #3: Main rib #3 is installed in the center of the wing where the spars have doublers. It has to be cut and a new flange has to be fabricated out of the 1/4″x1/4″ material left over from the root rib webs.
Don’t be in a big rush to fabricate and install this modified rib. If you just cannot resist trying to fit this rib at now, do the best job you can but just attach it to the rib with clecos. Do not rivet the new flange to the rib unless you need to practice drilling out rivets.
No matter how careful you are and how sure you are that it is correct, you really won¹t be able to establish the proper length of this rib until the Strut Beam Assembly is installed. The strut beam pulls the spars together just enough that the newly modified rib #3 will not fit properly. If you had not been able to resist trying and have already drilled and clecoed the new flange to the rib remove it at this time and trash it. Find another piece of stock and use the holes in the rib to locate and drill the newly fabricated flange with the rib properly located in the wing. Rivet it and install it. (I just described the procedure I followed. Avoid the temptation. Wait until the Strut Beam is in place.)
Trimming the Skins: Not a big deal if you are careful. I did not try a cabinet plane but was able to remove as much material as was needed using a “panzer” file. I had two of them, a big 12″ file that was imported from England and an 8″ Vixen (brand name). The little Vixen cut twice as fast as the larger import (which I later returned). Stick with the Vixen and get the biggest one you can find. A longer file is easier to cut a straight line with.
What ever you use, file or plane, you will have to support the edge of the skin while you are working on it. The best solution is to temporarily attach a piece of 1×4 as long as the longest wing skin to the edge of your bench so that it sticks up about an inch above the top of the table. Then you can use another 1×4 to clamp the skin along its entire length with the material that you want to remove protruding slightly above the edge of the two boards. Sit down so you can see your line and whack away. You will have a nice firm edge to work on and all you have to do is take everything off that shouldn’t be there.
Nose Ribs: A little extra, easy to make tooling, will really simplify drilling and fitting the nose ribs to accept the nose skins. To drill a proper hole in the flanges of the nose ribs they should be supported from underneath. You cannot get a hand in to support them in most places and if you could you stand a pretty good chance of drilling a pinky. We made supports from 1/2″ 20 lb. foam that were cut to fit nicely inside the flanges. You will need to cut a hole where the lightening hole is to be able to reach in and adjust them as is discussed in the manual. We used a hole saw to cut a hole the same size as the lightening hole which worked fine but I think that you might be better off with a smaller hole. (See below)
The ribs must be adjusted to locate the centerline on the flanges when you initially drill the holes using the pre-punched holes in the skins as guides. The foam will support the flanges and allow you to drill a good hole. This is just the first time that you will be required to align the nose ribs. The skins must be removed and reinstalled several times in the process of fitting the wing skins. Every time you reinstall them you are faced with the same problem, adjusting their location until the holes line up. Very frustrating and time consuming. I think that you will save yourself a lot of time and temper by installing a fairly simple jig to hold these ribs in the proper location. A length of PVC tubing inserted through the holes that you cut in the foam can be used to hold the ribs in their proper location. There are several ways to temporarily attach the ribs to the tube. The simplest would be a little dab of hot glue, but collars, pins and several other methods have been suggested.
The reason I will probably use a smaller hole through the foam than the lightening holes is that a lighter schedule of PVC tubing is available in the smaller sizes which I have not seen in the larger ones.
Fitting the Nose Skins: The nose skins are a barrel of laughs to install. Don¹t even attempt to fit them until you have deburred the skins and nose ribs and removed the deformation at corners of the tip flanges per Jim Londo’s suggestion. You do not need to remove as much material as he recommends but you do have to cut out the deformation caused when the flange was formed. You don¹t need to worry about taking too much though as long as you stay far enough from the edge to set a proper rivet. The Scotchbrite wheels work great for this job too.
The outboard skin is the lightest of the bunch and the simplest to fit. They get heavier and tougher to fit as you move inboard and you have to deal with the overlap on the previous skin. Whatever you do, do not be tempted to use web straps to pull them in place. I watched in horror as my associates used them on the other wing at Ottumwa. They apply way too much pressure. If your spars, skins and ribs weren’t deformed when you started; they will be by the time you have finished with the straps.
You will need some help to install these skins properly, but, with each skin clamped initially to the spar on the top side, two or three troops can pull the skin in place using the heels of their hands. If you don’t quite reach your line on the first attempt (you probably won¹t on the inboard skin) you may have to adjust the clamps and try again, splitting the difference.
As you get each skin fitted you have to remove, deburr and reinstall it before you can fit the next one. When you finish you will probably have a skin line that has a few dog legs in it at each overlap. These will be taken out when you fit the main skins. Done properly you will end up with a single perfectly straight line defining the rear edge of the nose skins along the entire length of the wing. You will have each one off and back on several times before you get the main skins fitted. That is why it would be nice to have the nose rib alignment fixed so the holes line up when you reinstall the skins.
Transferring rivet line: When the Manual calls for transferring the rivet line to the lower inboard skin if you have an angle drill simply back drill through the spar cap the 3 or four holes you drilled to hold the leading edge skin in place. Then it’s a no brainer fitting the LE skin over the lower inboard wing skin and drilling out the remaining holes.
More on nose skin: I started putting on the leading edge skins yesterday and found a couple things that help. Firstly, large clothespin type clamps have helped me throughout the project. They come in at least three sizes and a half-dozen each won’t set you back too many $$$. Secondly, tarp-straps ( elastic straps with hooks at each end) wrapped around the skin next to a rib and hooks under the spar works well for conforming the skin to the nose ribs. Lastly cellophane (clear) tape anchored at each end with a clamp or your jig-post will hold your ribs perpendicular to the spar. If the rib center line doesn’t line up just make a mark on the rib or tape and take that side of the skin loose and move the rib under the tape. I’m working mostly by myself so I need some extra “hands.”
Wing root ribs: After working around this item as much as I could, I finally had to face the music today. After a little head scratching I came up with a different way of getting it all to work. The rest of the ribs have been installed. I placed and clamped the doublers inside the spars very near their permanent location. Squared them across the spars and placed additional clamps behind them so that they wouldn’t move. I then removed the aft spar jig pin and squeezed the rib in between the doublers. Snapped in snuggly like it belonged there. (I had previously cut it out to the template*) I then removed it, cut the template inside the lines a hair and glued it to the inside of the rib. Placed the rib back in the spars, adjusted it a bit then drilled and Cleco’d it in about 4 different places. I then removed it and drilled all holes. Put it back in the spars and it fit perfectly. Didn’t have to trim the doublers a bit. Beats trying to put it all together then making it fit between the spars. * The template is very close on the aft end of the rib and may show a little more material to be removed than necessary. Fitting it as above will allow you to see exactly what needs to be taken off. Even as it is, the holes came out within acceptable limits to the edges.
This worked out to be far easier than I thought. I don’t know how the interference with the skin rivets is going to work out yet but probably won’t completely rivet the assembly together until I find out.
Still don’t know if I HAVE to trim the doublers as shown in the manual or if I can just leave them alone. If it’s a matter of weight, they’ll not be trimmed.
Adhesive bonding: from my first thought on building the GlaStar I wondered about the possibility of using adhesives to attach the skins and other parts in addition to rivets. I have my airframe almost done now and used a 3M product called epoxy adhesive 2216. I called 3M in Minneapolis and talked to their technical department and was given 2216 as the thing to be used. I found a distributor in Phoenix – R.S. Hughes & Co.: 602-268-4800 and was reassured when i found out that they have been supplying this product to Learjet in Tucson for years for their repair work. The product is applied not to bare metal but to epoxy undercoating so it is paint to paint bonding-after acid wash & Alodine treating the metal. It is a 2-part epoxy-ratio 1:2/3 mix that takes about 7 days to cure and never becomes totally brittle. I will have used up 1-2/3 kits worth on the whole plane – about 10 lb.worth (a guess on the weight). I wasn’t sure about the water soluble primer from SH so I used Aztar that the military used for their anti corrosion. I found it useful to bond my trailing edges, let them cure, while clamped to a straight edge, then drill and rivet – I feel my trailing edges are straighter because of this. However, it was messy and many times i wondered if it was worth the extra trouble. I feel that i have a stronger wing and that with time it will remain strong. I thought I would at least toss out this idea to you early builders in case you hadn’t considered it.
Wing Skin Drilling: When drilling the inboard lower skin for the first time, the plans have you establishing the forward line of rivets by transferring the rivet line to the main skin, presumably from the ends and drawing a line then clecoing the inboard nose skin on the other side and then drawing it down and aligning the holes with that line. The potential for a mis measurement here is terrible. The easy way to do this is when the lower inboard main skin has been positioned with a few clecos in the correct spot and prior to clecoing the inboard nose skin in place, drill two holes (any two holes that are easy to get to) along the forward rivet line FROM THE BACK SIDE. I used that little angle drill that you purchased. and selected a couple of holes that were easy to get to through the lightening holes in the spar. Once you have two holes drilled through that inner lower main wing skin along the forward rivet line, It is simple to cleco the inboard nose skin in place, and then cleco the rest of the nose skin in place, and then complete the drilling of the holes as described in the plans. this eliminates the possibility of lining up those rivet holes with a possibly poorly drawn line while you are trying to bend that stiff nose skin back down where you think it was. When I read the instructions in the plans, my reaction was “What! Are they nuts?!”
John Steichen #5467
Aileron pushrod installation: If you want to save yourself some GRIEF, install the aileron pushrods with cotter, to the wing, not the aileron, before riveting the upper skins.
Riveting the nose skins: We were having a problem with the flush rivets on our leading edges. We could not get them to buck straight and finally had the opportunity to talk to a USAir sheet metal mechanic. He took one look and said “Your cones don’t match up!”. (I wish I could get the proper southern accent here – it adds quite a bit)
What he was saying is that we had dimpled the skins and the ribs separately, and that when we then stretched the skins around the ribs there was a slight mis-alignment between the dimples. This would cause the rivet to sit on a slight angle and make bucking it a realy iffy project. What we did is this.
We clecoed up the entire section of leading edge. Then took out one row of clecos. Using a female die on a handheld weight (Get it from Avery Tool) and a male die in our rivet gun (Again – Avery sells the proper 401 tool to hold the male die) we dimpled the row. By doing this we were assured that the dimples in both sheets matched perfectly.
We then riveted this row and proceeded to do another row in just the same way. This produced a very acceptable job.
Be careful you don’t use too much pressure on the rivet gun. It does not take more than 20-25 lbs. and a very short burst. Also make sure that you are well coordinated with the person on the bucking bar. If he/she lets off the pressure before you let off the trigger it will look poor to say the least.
By the way – Mike Allardyce has one of the nicest jobs I have seen on his leading edge rivets. He might have a better idea!
Leading edge skin tips: The manual’s directions are good but maybe we can add some ideas that we found helpful to make the job even easier. Perhaps the “easy word” should not be used. They do not just fall in place, especially the nose skins. We were fortunate in that our nose skins were well shaped and fit well. I have noted a few builders that had problem nose skins. The inner ones are thicker and resist being wrapped around the nose ribs. Luckily they are shorter lengthwise. Our nose skins were not overly long (over the rib direction) so we did not trim them. No use double trimming if you do not need to.
The overlying measurement to address in making a decision on trimming the nose skin, is the amount of edge distance that will be left from the main skins rivet line to the rear edges of the nose skin. If you cannot measure at least 2-1/2 rivet diameters from the hole centers of the lower and upper main skins, to the rear edges of the nose skin, you will have to trim the nose skin until that much distance will be available. (The rivet size we are considering is the final size of 1/8″ dia.).
What to use to trim the skin edge to size? We tried several different tools , including a die grinder with a rotary file, metal shears and a Vixen file. The rotary worked ok for large (marked) edges but had to be very careful it didn’t cut below the marked line. That file really moves out. Metal shears work fine on the larger width of cuts. Didn’t like the fact that each new bite produced a tiny kink in the thin metal. Finally we come to the vixen file. These have two depths of razor sharp curved teeth. Strangely, I could not find one locally, though they must have been around as they are used in auto body work. I finally ordered one from Avery tools of Fort Worth Texas. Pretty hard to go wrong with this type of cutter, except you hate to try filing off an eighth of an inch.
If your leading edge skins are not nicked and measure out per the above edge distance information, all they will need is an edge clean up with the Vixen file. Note: Be sure the edge distance from the punched pilot holes, to the edge of the metal, is the same over the length of the skin.
Using the vixen file with the handle that it comes with it, does not allow a really long flat cut. It must be held at a slant so the handle and tang will clear the edge of the metal. This gives you a very (short) flat edge. For a flat true cut, the whole length is desirable but the handle and a tang raised above the height of the cutting teeth, prevent that type of cut. After some agonizing about ruining a $21 file, I clamped it into the jaws of my steel chop saw and pulled the handle. Now all of the offending area was gone. Next, I ground all the sharp edges round, including the corners of the teeth. Now I could hold it in my hand.(comfortably) and use the full length of the file to make a long true cut and it was so easy compared to holding the file slanted with a short cutting surface. If you desire to try this configuration and do not have a chop saw, you could get it cut at any steel sales or welding shop. It is too hard to cut in any other manner, except breaking and it might break where you did not want it to.
Cleaning up or trimming the skin edges with the above modified file (with the skin clamped to your table top)
Things go much better if you “PULL” the file instead of “PUSHING” it, the full length of the edge with one walking stroke. When you have removed all the material you wish from the edge, take the sharp corners off the edges by drawing the file the full length of the skin with the blade held at 45 degrees. Use the fine teeth and VERY VERY LIGHT PRESSURE. You are working very thin skin and you don’t want it pointed. Finally, a stroke or two with a pad of fine emery paper and the edge will be clean, straight and deburred.
Orville Eliason, 5298