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Engine Mount, Gear Legs |
Aileron Rigging
I am getting the rigging triple checked on my ship and have a question for you guys, especially the ones that have got flying ships or have built RV's. As you know, there are two ailerons and four mounting points for these aileorns. I had Mark make a new aileron as one of them was too "high". I have also noticed that my left aileron is 1/8" shorter than my right aileron. Anyway... I am going to mill slots into my mounting brackets so I can get ALL the aileron mount points the same height to have a nicer flying/balanced plane. I made a jig with a dial indicator on the end of it to allow me to measure the height of the aileron spar relative to the wings spars. As expected, they are off a bit, but pretty close (all but one plus/minus .050"). I will need to lower the right hand inboard point by .070" to get into agreement with the others. The big dilema is... what is the correct reference height for these ailerons. They are all different so I must assume that none are correct.I can't tell if the top skin should be flush with the wing, or bottoms or what. It's nearly impossible to get an accurate measurement that can be reproduced from one plane to another. Anyone got any ideas "WHERE" the ailerons should be to minimize drag/flutter etc? Also, this bit of two different sized ailerons. big deal or don't worry about it? Thanks! Warmest regards, Bob Gross Bob, First thing you do is pin the aileron bellcranks in neutral position. You do this by drilling through the bellcrank and the upper and lower 1/8" support angles with a long #40 drill bit, and then use a long drill bit as the pin. If you can get a set of RV-4 prints the measurements are there for the neutral position on the bellcranks. Then with the wingtips off you take a long ruler and line the ailerons up through the 3/16" tooling holes so they are in line with the tooling holes in the wing ribs, they should be right on the chord line. Adjust the aileron pushrods as necessary, and if you need to adjust the height of the ailerons, you can slot the mounting holes (not the pivot holes.) This time around I'm going to use a rotary laser that you can rent from your local tool rental place. Then, stand directly in front of the airplane and eyeball the ailerons by sighting below the chord of the wings, you can tell if the nose of one alileron is higher or lower than the other. When you fly the airplane for the first time to correct a wing-heavy condition, you squeeze the trailing edge of the aileron on the "light" wing. You squeeze them with your fingers only, it doesn't take much to fix the heavy wing condition. As a side note I've found that a slight deployment of flaps in cruise doesn't do much to change pitch so all of the finaggling might be overkill. So I think it would be safe to say that you can screw around with the alignment and you might get things close, but the curvature of the trailing edges of the ailerons makes a bigger difference than the alignment probably does. Randy Pflanzer might want to chime in here; I recall him adjusting the ailerons on his RV-6 and if I remember correctly doing so didn't make as much of a difference as squeezing the trailing edges did. Also, if you pick up the "21 years of the RVator" book there's a few articles in there on the subject. If it flies hands-off the first time, all of the mistakes made during construction have cancelled each other out. Bob #80, RV-6 flying Bob This might be a bit crude for a man with a dial guage but it does work, or at least has for me in the past. Take two thin strips of wood fastened at one end with a clamp. slide them over the aileron, one on the top of the wings skin the other on the bottom of the wing skin. The strips should be a couple of feet long. What you are trying to see is what the air sees, a smooth flow from the skins to the aileron. Move the strips inboard and outboard to "see" if there is a difference, then try the other wing. This wing is very forgiving, there are thousands of them flying. I would say you are close enough now for first flight, fine tune the plane after you have flown, what you are measuring with your dial caliper may not tell the storey in flight. On my planes the old "squeeze the trailing edge" trick has worked fine. Tom Martin FWIW I used the stick and eyeball method on the Turbine Stewart 51 and it flies hands off and stalls straight in just kind of a mush at 50MPH. Don't underestimate the ability of your eyes and the (That looks about right) method. Bob W Totally agree Tom. The key word is "what the air sees". At the urging of some very early experienced builders I clamped the top skins of the ailerons/flaps to the respective outboard ribs. Using a long alum yard stick forced the surfaces into perfect trail. This has worked for many builders, many on their second try who first used those god-awful wood templates that came on the lid of the crates. Be sure to verify that the leading edge of the aileron is not sticking down into the slipstream. According to local speed guru, Rich Jankowsky, that is responsible for a huge drag penalty on many RV's. So the long and short is, smooth skin line on top, let the bottom take care of itself. Adjust out the difference by squeezing the trailing edge. Eric I wanted to add something to this post. I have kit number 71. I did not have to do any of the below because the wings on my F1 kit were exactly as I would have put them. It seems that they ironed out these details between Bob's kit and kit 71 somewhere. Newer builders should not have to worry about this. Eric Likewise with kit #74 Bob W I think I figured out this aileron thing. When I set up my ailerons originally, I used the old manual which had me using ALL the tooling holes in the tip rib to determine the aileron TE location. It turns out that the FWD holes in the tip rib are bad, so Mark had me recheck it all using only the holes in the main rib. This showed a discrepancy. I raised the left aileron .25" to bring it to its' new location. This made a world of difference. Suddenly, things made sense and the ailerons began to show some signs of symmetry. After jinking up the flap to match the aileron, all parts fell into to place. I need to redo the wing tip and root fairing, but hey...this thing will never be REALLY done will it? I attached a picture of my homemade tool. It is a scrap bar (closet shelf part) with the cheapo $20 dial indicator attached to it. The two machine screws are set so they will lay on top of the main spar and the rear spar of the wing. This leaves the dial indicator to rest on the aileron spar. Now all the parts agree with each other within .040" I used the same tool to compare the position of the aileron TE's and flap TE's. So far, the flaps match within .004" (scary eh) and the ailerons match within .030". I also found that laying a straight edge on the bottom of the wing so it spanned the aileron gap, showed about 3/16" of space below the aft wing spar and the straight edge. I see this on both sides now and seems to agree with what Mark told me he was seeing on his ships. Thanks for the help to all for you suggestions. All were very helpful. This is a far cry from the .100"+ I was seeing when the left aileron was in the wrong position. I helped Bobby Hester work thru the CG calcs on his bird -- he measured the wheel centerlines at sta. 77 3/4" (about 2 1/4" in front of the wing leading edge). Can you fellas confirm this data from your CG sheets please? thx Mark Mark, I measured my main wheel axle centerline 77.5'' aft of datum, which is 2 1/2'' in front of the leading edge. Pretty close, huh. Distance betweentailwheel and main wheel was 184''. Jim Cash Elevator - HS Leading Edge Clearance Anyone else have a very tight clearance between the leading edge of the > elevators and the HS trailing edge spar bars? Yes, the bearings are set > at exactly 13/16", and the elevator spar is within 1/32 of the hinge > cutouts. How did you solve it? > Thanks, > Scott Scott > The problem likely has to do with how you formed the leading edge of the > skins. If they are are completely round it could touch in places. You will > have to reform this leading edge. You may be able to reform it without > removing the rivets by applying pressure. Call me at 519-631-1369 if you > have problems, I know Mark is away for the week. > > Tom Martin The ideal curve on the top of the elevators, at the root end, would be somewhat flat where the rivets are and a tighter radius on either side. Thus the final product is not one bend but a combination of two bends, one on each skin. Ok, if you have done it the way I did, which was incorrect the first time!, you need to flatten the rivet line. To do this you can, with pressure and strong fingers push the curve down. In a couple of tough spots you will need to apply a little extra force. Get an extra pair of strong hands somewhere to hold things and lay a stout board against the rivet line. Now carefully, experiment here, tap the board with a heavy rubber mallet. This should do the trick but be careful. Another area that I noticed was the centre cutout was not quite wide enough to miss the rivets that hold the brackets on the horizontal spar. In this case simply trim the cutout away to miss the rivets. 1/8" per side should do the trick. The sides of the cutout will no longer be perpendicular to the spar but this is all hidden when assembled. Tom Hi, A little problem. After painting me elevators, the weight on the RH one was not heavy enuf. How does an experienced builder add more weight to an assembled elevator. My elev tips are very permanently installed. Warmest Regards, Bob Gross How about drilling a 1/4 inch hole in the elevator tip fiberglass section, pouring in some epoxy and shot, then seal it up with some micro and glass. Do it on the bottom since that would require some repainting. Greg Nelson Bob, I like Greg's method. I had the same problem on my -6 after painting. I might add a little deviation to Greg's suggestion that might work and also alleviate the need to repair/repaint the tip when done. What I did was put the elevator on the stab and then take a paper cup and tape it to the counter weight on the top and most forward part. I then added weight to it until I got the required balance. I then took a simple "teeter-totter" balance and mixed up enough epoxy in another paper cup to balance the weight in the first cup. I drilled a 3/16 inch hole through the web of the counter weight arm behind the weight on the inside. I heated up the epoxy ever so slightly in the microwave (five or ten seconds), and then used a paper funnel to pour it in the hole. I had the elevator positioned so the epoxy would run to the front of the fiberglass tip and harden in the fiberglass area. Only thing to watch for is excess heat or exotherm of the epoxy as it sets up. If it is a large pool, it could get hot enough to burn the paint. If it does get hot, just put water on a towel and hold it against the paint to cool the set. I didn't use any shot because I only needed about an ouuce of epoxy. You could sure add shot if necessary. The small hole doesn't affect the strength of the web at all and you don't need to fill it like cutting a hole in the fiberglass. Good luck, Jim Baker 101 How important is rudder balance? It seems that mine needs > another ton of lead to balance You are NOT trying to 100% balance the rudder! Use about 830-850G lead on this one.... The elevs ARE balanced 100%, after paint. Cheers Mark I am fitting the HS to the fuse. The plans call out for a 5/16" shim under the fwd HS spar. I can't get the HS to show level unless I reduce the shim to .250" Just wondering what you guys have needed (shim thickness) when mounting your Stabs. Regards, Bob Gross Bill You may encounter difficulties with getting the forward attach of the vertical stabilizer to fit as per plans and you are also lowering the elevators which might cause some linkage issues. If in the future you ever found that you needed to lower the front of horizontal stab for an alignment problem that option would not be available. In this critical area I would recommend building to plans. Tom Martin Bill, (I'm going on memory...) I think that the incidence angle is the most important relationship. That angle can be achieved (parallel planes, no pun) infinitely, depending on the rear attach height. If you only need a 1/16" shim, rather than a 1/4", AND the incidence is correct, then your rear attach (4 bolts) must be a tad low as well. I think that the lower HS won't make too big a difference in the connection to the VS; that (HS-15?) brkt attach point would just be higher. Due to "production variation", my HS and VS required a 3/16" plate (riveted to the HS-15) to maintain that relationship. The elevator linkage will be a tad lower, but I don't think that it would bind. Just my rookie opinion, but hope it helps. I have some pictures of my install if you think that it would help. Brian #28 Bill, Tom is correct in that having too much shim in the front is better than not enough. Also, borrow beg or steal a builders transit or rotary laser to establish level at the wing tips, and work from there. Move it off to the side and you can check incidence and control surface trail. Makes setting up the tail easier and more accurate too. A friend of mine does this and 4 out of the 5 RV-8's he's built fly hands off, no trim tabs, certainly not dumb luck. You will discover how inaccurate a level you think is 'on' isn't. I'd also check the engine for level and shim as required. Regards, Bob Absolutely. wptew@att.net wrote:Bob - are you recommending that the HS and VS not be bolted down intil the wings are mounted and one can set HS in relation to level wings? Thanks Bill Bill, to answer your question, I'd advise that you wait and do it all at once (wings, tail feathers, check engine for level, etc.) As far as the engine goes hopefully you are rigging before you installed the cowling (I think its often overlooked, and my experience with engine mounts is don't trust them to be right-on). I probably need to explain a bit better on how a transit or rotary laser works. A rotary laser is set up on a tripod somewhere behind the airplane, and high enough so the projected beam is above the canopy with the airplane level fore/aft using the longerons. So now you have this line projected over the airplane (you'll see it on every wall in the shop around you.) Then, you take a long ruler and go to the outboard point of the leading edge/main skin junction, stick it up in air, then you will see the beam of the laser on some point on the ruler. Write the distance down. Go to the other side, do the same thing. Then shim whatever is holding up the airplane (wheels, jacks, etc.) until you get the same measurement on both sides. OK, now you are wings level, you can set the incidence with a hand level per the manual (but don't drill yet.) After you do that, clamp the HS on using the distances in the manual as a starting point. Draw a centerline or whatever down the back of the HS spar. Use the ruler to measure from the centerline to the laser mark, and adjust the HS until the distance between the beam and the centerline is the same all across. Then set the HS incidence per the manual with your hand level, and if remember anything from your trig class in high school you can double check the incidence against the laser beam at the wingtip (if your mind isn't messed up like mine is this is optional). Of course this is all supplemental to the instructions in the manual. Walk away from everything for a few hours to clear your mind then come back and double check everything you did earlier and drill your bolt holes. Don't blindly make assumptions that your longerons are perfect from the factory, that your engine mount is right, that the firewall is square, that the aft deck is level, etc. The laser won't lie to you; if something is out of whack you will be able to see it and compensate for it before it is a real pain in the ass to change something. It is nice to have the tail on in the shop so it looks like an airplane but tie a big cinder block on the aft deck...I imagine your wanting to install your engine soon and that is why you probably want the tail on. Regards, Bob Bill, glad to help. Why use 1700's technology to rig your airplane when you can do it with 21st century stuff. If you ever want to get an accurate bubble level, get a Starrett machinist's level. There adjustable so you can calibrate them. I've seen smart levels that were calibrated but didn't read correctly. Regards, Bob GlacierHi Guys, I am doing my wing fairings and have a rigging question. What is the "correct" position of the flaps when properly retracted? It looks like the lower surface of the flaps trailing edge likes to be flush with the lower fuselage skin. Comments? Also...how many fasteners does it take to join the front and rear halves of the wheel pants to keep them from blowing off at 300 mph? Regards, Bob Gross If you have your wings set up as we call out, your flaps will be very close to flush. The TE radius might be 1/16"-1/8" up from flush. > > Comments? > > Also...how many fasteners does it take to join the front and rear halves of > the The aft sections will have fasteners in both the fuse and the wingwalk at the extreme fwd end. In addition, you can glue this area down with RTV or similiar substance (just cut it with a chip-chaser if you ever need to remove the fairings). If you haven't painted your ship yet, use a paintable adhesive. The front section does not actually attach to the aft section, thos if you were to install a small tab on the front section, you could install a nutplate & run a screw thru the aft section at that joint. You will need to install a bulkhead at the TE of the wing (inside the root fairing) to keep air from getting in there & blowing the AFT section off the ship. Again, you can use RTV to glue in a shaped & formed pc of .032 aluminum. I leaned this bulkhead fwd about 30 deg on my ship. It will need a small bend near the lower edge for flap clearance if you do this. Cheers Mark Fellow Builders, I've been working on rigging the empennage to my fuselage and found a "gotcha" that you might want to look out for. While drilling the mount for the tailspring in the last fuselage bulkhead, I decided to check the torque on the bolts that hold the tailspring to the second-to-the-last bulkhead. It sure looked like there were a lot of threads sticking out from the end of the nut. Sure enough, the nut was tight but the bolt was not tight in the mount. The nut had bottommed out on the bolt. I replaced the bolts with shorter ones and now things are much better. This area takes a pretty good beating (especially the way I land) so I'd hate to have the bolt holes wallow out over time. You might want to give this a quick look on your bird. Perhaps mine was just an exception. Also, my fuselage has a pretty good twist in it from the cockpit rails back to the empennage deck. It is twisted towards the left. The difference in H-stab spacers from the left to the right ones is about .130 in a span of only about 12 inches! In the end the twist won't make a difference in anything but it is something to watch for when fabricating the spacers. Randy #95 Randy We noticed the bolt thing on one plane but not the other, the bolts were in backwards as well. One of the F1s also had a twist in the rear deck and on the other one the rear bulkhead was not perfectly straight up and down. Generally the fuselages are very good, almost every flat surface in the cockpit area reads the same on my level. I did note that the skin on the turtle decks was not always parellel to the rivet line, which was not parrellel to the longeron. This means that you have to pick a particular spot on the fuse and mark it as the level spot for setting your tail and later your wing incidence. By doing this the tail and wing are fixed relative to each other which is really what you are after. Tom Randy Take this a step farther. The Horizontal stab has to be level span wise when the wing is level span wise. The wing is fixed so all span wise levels have to start with the wing. My wing was level with the longerons but this does not have to be the case. Blue skies Bob W Bob has a good point here. There is no guarantee that the longerons are the same distance above the spar; setting wings-level should be done from the spar bolted in, not the longeron, IMHO. A while back Van's put out some good directions on setting wing incidence on a RV, and all of it applies to our airplanes: http://www.metronet.com/~dreeves/pdf/WINGINCIDENCEDRILLINGSIMPLIFIED.pdf Regards, Bob
How far does the rudder cable/pedal move from neutral upon full rudder deflection? As I recall, full travel at the rudder horn is 3 3/4". This is for the F1 rudder; it is different from the Van's rudders (wider rudder horn). 30 deg L/R displacement is called out. User confirmations welcome! Mark How far should the stick be from the instrument panel at full down elevator? When you finally get your elevator rod connected, you will see that you will To the builders who have completed their project, I have a couple of questions about tailwheel weight. 1. How did you measure the weight that is on the tailwheel? Is it measured as the aircraft sits on the ground or with the tail raised in a level flight attitude. Does the different geometry change the tailwheel weight? 2. I assume the greater weight on the tailwheel makes ground handling more difficult. Is that correct? 3. What is the average tailwheel weight and empty weight of your individual airplanes?
1.The aircraft is to be in level flight attitude when weighing. 2. The more weight on the tail keeps you from getting the prop. But remember a rear seatpassenger is going to put a lot more weight on the tail wheel. 3. Can't find the exact number but it was around 50 lbs (47 I think) total weight 1287. Jack #70
Hello All: Weigh the a/c in level attitude, using the upper longer as the ref point. Look for 55lbs +/- as a target. Of course more weight will make ground handling more sensitive....but we're tryng to not imitate the HR2 fleet with it's prop strike syndrome. I think compromising towards a bit more weight on the tail is better than the alternative. Cheers Mark
1. I noticed that the Harmon Rocket and RV4 blueprints call for reaming the close tolerance bolt holes on the spar. There is no mention of this in our text and picture book or I overlooked it. Is this done already? If not how much reaming and are starndard high speed reamers the way to go? 2.Bob Japundza I believe uses a 2X or 3X turned way down to install oiled bolts, was this true? Any other clever tips. 3. RV flaps let the bottom flap skin overlap the bottom of the fuselage, my interpretation of the F1 is that you want the lower flap trimmed short of the fuselage Mark. True? Is the RV approach ever used? 4. The text and picture book make no mention of if the spar is bolted up when the incedence is drilled and set at the rear fitting. I bet it does need bolting up, is this true? If so see question 1 and 2. Best Regards Howard Rhodes
The steel splice plates are plated (generally) and thus might need reaming to remove the plating from the inside of the holes. Also, it might be necessary to ream some of the spar holes...so go ahead & get the correct reamers (.374 & .249) and have at it. Much easier to do off the plane
Howard, Some fit, some don't (early) depending on S/N. I had to ream mine to get the bolts in. Later ships, the bolts slide in easily. If you need it, I've got a .372" reamer that will fit a 1/4" threaded angle drill. .372" seems to small, but when you add in working on your knees and unavoidable tool wobble etc., the holes fit nearly perfectly. It was the only way I could see to ream the lower holes (you'll see what I mean when you get in there).Bolts tapped in easily with a small hammer after reaming. Using a rivet gun gun scares hell out of me as removing them will be a *REAL* nightmare. One can only imagine what it'll be like after an off field landing trying to find an air compressor to allow the wings bolts to be removed. An odd thing... I ended up ruining one of the steel doubler plates on the first attempt to push the reamer thru. The reason was because the spar stubs at the root end were a bit to long and prevented the holes from lining up. I sanded them down a few thousands and that fixed the problem. Mark gave me a new steel plate and the rest went pretty easy. It sounds difficult, But I think on early ships, it would be worth the effort to mate the wings in the hanger to confirm they will ideed fit. Sure beats hours on kness in the cockpit with mirrors and borescope trying to figure out why things won't fit. I experienced absolutley no detectable movment in the wing assemblies during flight test and subsequent attempts by "Redline" Reed Somberg to black me out. Thats what 56 bolts will do for you. Sheesh this thing is strong. Warmest Regards, Bob Gross
Howard, in the old days the RV-4 plans reflect the need to ream the holes as many spars were built from scratch. The spars on the F1 are anodized and because of the anodize thickness (which can vary depending on how much time the spars sat in the dip tank), I found it to be very difficult even with a hammer or rivet gun to get the bolts thru the spar; the holes are undersized. When I bolt the wings on for the final time, the only good way I can think of to get the task accomplised is to temporarily use some undersize bolts in the spar which I will make on my lathe by turning down some hardware store bolts. I'm going to put a few of those in to secure the wings and ream the open bolt holes (I think I measured the big bolts to be .372 or something like that, so you need to get a reamer that is .001 undersize for an interference fit), inserting the NAS bolts as you go along. To insure accuracy do this all in assembly. All reamer! s are not created equal, there are chucking reamers and hand reamers. You want the hand reamer, because it will guide itself through the hole where a chucking reamer is designed to be chucked in a mill or lathe which guides the reamer (the end is square). You can probably do as others have done and employ some different methods to achieve 'close enough' results but in my opinion this is the most accurate way to do it. Whatever you do once the bolt holes are the right size, use the rivet gun and a flush set to push the bolts in, don't force them in too hard as the threads can tear up the holes. The rivet gun makes the process go a whole hell of a lot faster. Regards, Bob Please don't re-design this important sub-structure; allowing some flex in the structure is as important to the design as sufficient strength. Cheers! Mark
Bolts tapped in easily with a small hammer after reaming. Using a rivet gun gun scares hell out of me as removing them will be a *REAL* nightmare. One can only imagine what it'll be like after an off field landing trying to find an air compressor to allow the wings bolts to be removed.
Something I came across that I think is a great product to use on bolts being permanently installed in the spar is a product used by Beechcraft when installing the spar bolts in their aircraft. It is made by Castrol and is called Brayco 137. It is MIL-C-16173E(2)GR.11 Military spec. number. Basically, it is an oil about the viscosity of 90 wt. gear lube but it "drys out" after applied and changes to a soft wax type compound. The material is listed as a long term corrosion inhibitor in assembles. I saw my local shop using it one time when they were changing the spar bolts on a Baron, looked into it, and then ordered a quart. I used about a half ounce putting my RV spar together and when I looked at the bolts last month during the conditional they still have a nice fillet of soft wax around the heads and washers. Seems to be a good product with more specific qualities than paint or straight oil. Just another pennies worth of information to process, Jim B |