brown bear
Registered User
emporia ks
GSMX440
It sounds like you are on top of it and will have a fun plane when done !
Doug
It sounds like you are on top of it and will have a fun plane when done !
Doug
I guess I missed this the first time around. Tell me more about this roller. Still like it, still recommend it? Looks like exactly what I'm looking for.
a cheap Harbor Freight roller to form the bend...I like the roller machine since it will not kink the tube like other methods and there is no need to fill with sand or other measures
I guess I missed this the first time around. Tell me more about this roller. Still like it, still recommend it? Looks like exactly what I'm looking for.
So continuing this build I have finished the flaps and ailerons to the point of inspection, meaning for the most part I pushed through the build of these four items and left the odd dodgy rivet and now will go over these with a fine tooth comb and mark anything that doesn't meet specs and will replace that item.
I built the flaps first with the thinking that my skill level would improve with each item and indeed that was the case. The first flap took a couple of weeks and the last aileron took two days. The first flap will require the most replacing of rivets and the last aileron will not require any corrections.
I have a question on the hinge rivets on the flaps and the outer hinges on the ailerons. I used AN455A - 4 rivets. These are the soft aluminum rivets. Should I change these for a harder alloy?? The center aileron rivets are the correct steel rivets so they are fine.
During this build I finally ponyed up for a hand powered rivet squeezer (159$ with sets and gauges). I should have bought that originally instead of the air powered equipment I got.
First picture shows one of the ailerons with center hinge and horn mounted. All parts were coated with primer (zinc chromate) before being riveted together.
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Here I am milling slots for the trailing edge to fit over the back of the ribs. Note: I used the D&E trailing edge material. I believe it to be a little heaver and not as good as the bent piece piper specs. It does work but has a little "bump" on both sides. I made some wood (3, one inside and two outside bevels) to keep the vice from collapsing material. A bit futsy so practice on some cutoff scrap before committing to the real piece
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Here the aileron horns and hinges riveted with the steel rivets that were so hard to do. I would recommend buying the spars from Javron with these already done to this point
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This is the D&E trailing edge with one slot machined.
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The next couple of pictures are of and aileron with the ribs attached. NOTE: do not do as I did but instead follow Mikes advice and attach the "end" bulkheads of each leading edge section at this point! I didn't and it caused way more work than should have been necessary. Another windmill 10 hours!
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Cleco'ed and taped together for now.
This all happened over weeks so I'll give this a minimum of 30 hours Mostly learning to rivet and remove bad rivets.
Spaincub that seems like a really good idea on the face of it. One thing that would concern me when using CF or even heavier walled metal parts in a wing is could you be introducing stress points the original designers didn't want. Is everything designed to bend and flex together with each part designed to do it's share of flexing in heavy turbulence? If one part winds up to stiff then another part has to flex more? I once flew through something that made my Cessna 172 fuselage "oil can". That was not a pretty sound! Smashed an expensive camera on the ceiling at the same time. Planes need to bend and not break. BUT CF struts would allow an encapsulated nut and a bonded foot on each end probably cutting the overall weight in half at least. My completed 14222 compression struts (the main ones with a foot on each end) using standard rivets and my own billet inserts weigh 8.68 oz. each. I have one that is using Dakota inserts and with I will have to assemble it with bolts and that one comes in at 11 oz. I ordered all my tubes precut from Dakota (beautiful by the way and perfectly cut) but one replacement they sent had the inserts already in it and they are "stuck" in the tube so I can't really see what the difference between theirs and mine is. They may be glued in somehow? I'll just use them as is. I didn't "lighten" my inserts as much as the Piper original cast ones so another ounce or two could probably be shaved using originals.
Do you have a picture of your compression struts with the foot on each end? Any new ideas on compression struts? Thank you.
I thought I had posted pictures before but I couldn't find them so I dug around and came up with these from 2010 or so:
First I used a block of wood to press with and my milling machine vice adjusted to press into. I didn't own a press back then so I used the machine quil to force the blank into the mold. Quick and dirty.Note extra pieces of stiff sheet metal on each side to help make the bend even.
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Various pieces finished and unfinished for compression strut builds. Miss my bird!
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Here is the completed bend. Note the bottom lands on a piece of steel to be bent back to flat at the end. Without that the bottom "bows". Also note soft jaws inserted at end of bend and that PVC covering is left on blank during the bend.
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Starting to put one of the "N" struts together:
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A foot starting to be riveted
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The slug has to be installed before the last rivet is put in.
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Here is the completed stack ready to build the wings.
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Hope this helps and I am sure I posted some of this a few years ago but I can't find it now. This was all scratch built except for the tube blanks which came from Dakota Cub. I was not able to source the correct tubing (size, corner radius, and thickness) anywhere else at that time.
Steve, I've been thinking about your post and I would imagine that some of the clipped wing T-Crafts have doubled up ribs for the very same reason. If I remember correctly the T-Cart has the same compression members, or at least very similar. I guess that would stand to reason since the same guy designed both airplanes. I also thought about your comment about running a compression strut at top and bottom of the spar. By doing that you're basically re-inventing a Stearman compression strut (without the cross bracing). I think what Chris and I may do is create something like what you're talking about for our ship. Rather than a single tube, we'll create a truss beam (there's that deeper web strength again) similar to a Stearman compression member or doubling up the stock Piper compression members.
Once again Steve, I owe ya'![]()
This thread is just another example of the knowledge in this group. Really interesting. As far as cable being used in "squaring" aircraft rigging, remember that most aircraft up into the thirties were braced with cable. The Jenny had flying and landing wires that were cable back woven and soldered. Once rigged, you usually don't have to touch it from then on. The trammeling cross braces on my Travel Air are made from rolls of "Hard wire", hence the term hard wire bracing. The wire is simply loped through a turnbuckle eye, bent back over and run through a wound ferule and bent back. The compression members are just ribs made out of 1/4" solid spruce rather than the normal 3/16" spruce. They also glue a diagonal piece of 1/2 or 3/4 (I can't remember) square spruce lengthwise to strengthen the rib and that's it. I guess what I'm trying to say is there are a lot of ways to skin a cat when it comes to maintaining wing squareness.
The compression members are only there to keep a preload off of the ribs. In other words, the two spars are two sides of a box. The trammel wires are there to square the box but in order to square the box you have to draw the wires in an appropriate way to produce that squareness. However, when you draw the wires in you put in inward pressure on the spars. The compression members are there to hold the spars apart, creating the final two sides of the box. Properly done, there should be no preload or compression of the ribs. Also, there really shouldn't be any "Shear" on the plug in the square aluminum Piper compression member. The bolt which goes through the spar is basically just a pin. Some Pipers didn't even use steel bolts. The plug is just there to hold the bolt (pin) in. Once the square tube is pressed against the spar web, there shouldn't be any shear load between the tube and the plug. The Stearman, for all its load carrying and G pulling capability has aluminum bolts holding the compression members in. A Pitts (I believe) has wood compression members and drills holes through the spars to run the trammel wires through and tightens the nut on the other side of the spar against an angled wood block. The Travel Air even has hard wire bracing in the fuselage bays as does a Jenny. Wires or cables or anything "crossed" in a trammel bay is not designed for compression in any way, only tension. The cross braces like Piper's tank bays are both compression and tension. You could build the entire wing with either. And if you have a stressed skin wing, wood or metal, you don't need internal trammeling or Vee wing struts at all (The Maule is a long story). Chris and I could build our wood SC wings (actually Wag 2+2) with wood compression members if we wanted.
Many different ways to do the same thing and they all work. Good discussion. Sharp group!
D.A.
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Thanks guys, great thread. Here is a photo of a Stearman compression strut.
I have always wished people would bring their unfinished planes to airshows. Not much to see or learn from all of those rows and rows of planes, once all of the glossy paint dries.
Well I have researched SC.org, google, etc. etc. and decided to start a light wing building thread to try and get some of my questions answered. Many of the threads I followed ended without conclusion. IE whatever happened to the carbon fiber wing build? Did it fly? How much did it weigh? I don't really need the answer to that, it was just an example of how some of the threads went along and then no "ribbons on it" so to speak.
I'm attempting a 1320# gross weight super cub build based on a 1977 totally bare fuse I have. I have built tail pieces (six) from scratch. I have a box of "schneider" stamped ribs (3 piece type for the main wings). Control surfaces will be scratch built. So my parameters are safety, and lite, lite, lite. At this point I'm mainly interested in conventional construction, not carbon fiber etc. I am of course planning the usual "lightning" methods. No electrical at all, 6" wheels (looking for cheap wheels), single puck (I have the cleaveland calipers), bungees, no interior, No rear seat (if thats what it takes), narrow deck o-320 (I have firewall forward <300# measured).
The wing: Like the tail this will have to be mostly scratch built. I want to base it on the PA-18 with flaps. I'm not interested in speed so minimal ribs would be fine. I'm think 13 ribs/wing. I have purchased D&E front and rear spar blanks.
Questions:
1. I would like to make the leading edge skins (other than tank area that would be .025) from .016 2024 T6. Dis regarding dents etc. would this be strong enough? .020 adds about 4# to leading edge. 8# if trailing edge requires thicker. This question comes because of a comment Mike made concernig 2024 being stronger than stock 3003.
2. How about .016 for the trailing edge? To weak for supporting flap hanger/hinges? If to weak maybe double up for a few inches in that area?
3. The D&E wing uses a heavy sheet of aluminum under the tank bay as a "drag strut?" to replace the tube going through the fuel tank. Actually in stock wing it's two tubes since there is the "welded to the tank" tube and the actual drag strut tube passing through it. What does everyone think about the concept both strength and weight wise of the torque plate vs drag strut tube? If it wasn't any heavier I would want to incorporate that "torque plate" idea and avoid the more complicated fuel tank construction.
4.Using the extruded compression (D&E) parts is tempting but it looks to me that the original type square tube compression struts would be lighter. Maybe not with all the extra little parts.
5. I am looking at Christian Sturms site for diagrams but find some are not there for the PA-18-150 as per the parts book. Does the Northlanmd CD have all those missing diagrams like 14387, 14389 concerning the LE skins?
Comments? Thanks
My super cub has wooden ribs and wooden wing spars. The total weight is 1108. It has 150 hp. I am not sure how many ribs are in the wings. But they are standard llength.
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Subject to the comments in post #233, yes you could reduce the stall speed by increasing the wing span. It would require increasing the tail volume (area) to maintain good stability. This can be accomplished by lengthening the fuselage (weight) or increasing the area of the tail surfaces (less additional weight). The added wing span would not need the same sized material as the inboard section of the wing as the loads carried would be less. This would help in keeping the added weight to a minimum.I want to build a STOL Wagabond, but have to keep it a LSA. Can I use a tripacer or colt fuselage if I manufacture all the other parts myself and get it approved. Would also like to get the stall speed down on it if possible. Should wings be made longer and extend fuselage? Open to all suggestions.
I may condense the whole thing for easier reading with less detail.