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Fuselage

  • When the tail brace wires are brought up to app. 250# of tension the elevator starts to bind up. How are builders tensioning the tail brace wires and to what tension? I have the 3/16" wires and have used a Pitts factory tensiometer.  Hale Wallace with Steen Areo recommends 300# for the 3/16" wires (this falls into the spec called for by the Pitts factory for this size wire).  I found that the upper wires were always 100# above the lower wires.  I expect this is due to the legth of the wire and geometry.  With the upper wires at 300# and the lower at 200#, the wires felt, and sounded good.  However, the elevator movement is pretty stiff.  I reduced the tension to 200# on the top wires and 100# on the lower wires and the elevator traved "freed" up.   I would appreciate any comments builders might have.

From: Fritz Gunther

Here is some information that may help the elevator binding problem on some of  the 1D's.   I have spent the last 2 weeks trying to understand what is happening with the tail.  I completely disassembled the tail feathers and checked the following:  Trim tabs were free with no binding.  I then checked the elevator strap hinges for freedom of movement, I found that the LH outer hinge was rough, I soaked and worked the hinge with Free-All until smooth.  The elevator was then attached to the stab on the bench and checked for freedom of movement, no problems noted. I removed the standard KP-4 pivot bearings and installed KPS-4 bearings, these are a self aligning bearing that will accommodate up to 10' of misalignment (if the wires are in fact pulling the stab and elevator rearward).  They have the same radial load capacity with a lower axial capacity.  The stab. and elevators were installed with the push-pull tube and spacer block removed from between the horn. The brace wires were slowly and evenly brought up to tension (aft wires first) with the stab checked for level.  The aft  wires are at 250# and the front wires at 200# (Pitts gauge) with no binding of the elevators.  The spacer block was then installed and the elevators started to bind.  The spacer was to wide and pushing the elevators outboard hard against the hinge collars.  The block was removed, the elevators centered in the hinge collars and the spacer milled to fit the spacing between the elevator horn.  The control tube was then connected and the elevators are free, and smooth.  When the stick is let go, it moves to the full forward position on it's own. I feel the self aligning bearings and checking the whole system for rubs/binding and eliminating them solved the "sticky" elevator.

 

  • I can't make geometry work out for the fuselage bottom on drawing DR7-1-112. If I believe TRUE measurements at FS 83-76, FS 108-101, and FS 134-127.25 are correct then the W.L. @ FS 76 should be 20.104 instead of 21.104. Also, W.L. @ FS 101 should be 17.46 and W.L. @ 127.25 should be 14.90. (They are all off by about 1.0 inches.). And, if the bottom is truly in a single plane then the W.L. @ FS 76 should be 19.91 and the TRUE should be 21.129. Anyone else agree or confused??
From: Clearprop
I pulled out my plans and ran the numbers. You guessed it I came up with the same problem that you did. I ran these numbers every different way I could think. I recalculated the fs's so that I can build the sides flat and even that didn't help. Lets just hope that someone else here can give us some insight.
From: SKYBOLT55
We re-caculated the fuse. dim. to build flat sides and they came out right on the money when we joined the fuse. halves. The fuse. is now on the gear and we're installing tail surfaces. I've also just finished building the spar over the weekend. Next time I go to the hangar I'll bring the fuse. dim. home that we used.
 
 
From: Bill1533R
Well, I am committed to the dimensions that I previously calculated. I am not building it to straight sides, but rather to "canted" plans definition with dimensions that are suspect. The dimensions that I used make it a flat plane (geometric plane and not airplane) bottom from station 52 to 134. But, it sure would be easier to build it with straight sides. I am building it from top down to bottom up and the jigging is much more difficult than laying it out for both straight sides and joining it later. It is progressing nicely, but sure wish I had more confidence in plans dimensions and my approach.
  • Question for those who are welding...how much do you think a weld your self fues. will ultimately cost...ex. equipment.???
From: SKYBOLT55
$600 max I have receipts
From: Bill1533R
For you weld your own folks in the Rocky Mountain area, there is a supplier of 4130 tubing that has a reputation of being good, but I only know second hand, because haven't ordered from him yet.
He is:
Steel AirCraft
923 Weld County Road #7
Erie, Colorado
80516
(303) 665-5817
I called him and he sent out his catalog (small, but it's all there)
For costs, I ordered fuselage kit from Aircraft Spruce ($359). Shipping to ABQ, NM was $87. I can't complain about them because it was delivered in 4 days and there was no proplems or shortages. I have just under $1000 invested so far. This includes, plans, Smith Welder (Oshkosh Special), Tanks, welding table/ jigs, and misc. Incidently, the fuselage kit had enough to complete the fuselage without having to scrimp. I'm down to the 5 engine mount bushings and last 4 pieces of .75" diagonal bracing at FS 00. There are definitely dimensional errors in the plans. (see earlier messages). This weekend it is off the welding table and on the fuselage roticery (who can spell) for start of final welding. Did anyone else small holes at every weld junction. What I thought was a neat suggestion, was made in Ultimate 100 plans. They seal the fuselage tubing, fill it with nitrogen (no rusting), and pressurize, add a small pressure gauge to determine if fuselage integrety has been corrupted. What the heck, I'llgive it a try.
From: ClearProp
I have about the same money invested in my fuse. I don't figure that it is fair to include the tools (since I wanted them anyway). I stopped trying to use my homemade fixture on my drill press and ordered a "joint jigger" (gee I hope I dont have problems with the DEA ...) I had tried end mills with a MT #2 taper, but my drill press table won't put up with it although they worked great in the Bridgeport milling machine. There is too much cutting area with end mills.
As far as drilling holes for weld relief and oil.... I am going to drill my holes "inside" the tubing to connect the diagonals with the longerons. I figure that that should help reduce blowholes in my welds, and if I want to pressurize the fuse it should be possible. If I want to oil it I wont have all those holes to fill later.... just a thought...
  • Well I should get most of the fuse finish welded up this next week. I am tempted to leave the gussets and engine mount tubes off until I get the engine mount ( I will buy the engine mount ). I figure then I can make sure that the engine mount tubes match up straight. What do you guys think?
From: SKYBOLT55
I did exactly what you described with the engine mount and it worked great.
  • I'm basically done with the truss finish welding and eventhough I have not spent a great deal of time with the plans yet can anyone that welded the spar saddles already, walk me thru their process and throw in any helpful hints.
From: ACRO240Y
Build up your spar mounts on the bench, do not use a square reinforcing plate that the drawing shows use a round washer. Make the hole in the triangler mounts over size to the OD of the bushing. weld the plates on the bench you'll need a spacer between them to hold them square.Then put the bushing in place and weld the washers to the bushing, do not weld the washers to the plate yet. Jig the assemblies into the truss and weld the plates into the truss. With the plates totally welded jig your bushings paralel to the upper longerons, we use drill rod as as a locater pin for this. Now weld the outer edge of the washer to your plate. This will minimize any mis-alignment .
From: JAWS1D
I have my spar saddles welded up in my truss and this is what I did and where i am at. First I purchased the wing bolts and bushings from Acro Specialties. Along with these Items Doug Dodge sent me 2 flanged (or tee bushings) and 2 washers which mount onto the saddles to hold the bolts (these replace the square doublers shown on the plans at the bolt hole location). I feel that these items have a closer fit with the bolt than using steel tubing as a bushing, which is shown on the plans. The saddles were welded up on the bench without the flanged bushing installed (just an oversized hole to accept the bushings) and cut/ground to fit on the fuse at the proper locations. I used a piece of lumber clamped across the fuse at the fwd saddle location and clamped it to the saddles in order to hold the left and right fwd saddles in relative postion to each other. These were tack welded in place. The same was done for the aft two saddles except that i installed the bushings and a 5/8 steel rod ( in place of the bolt) i place between the fwd and aft saddles (done one at a time). The oversized holes in the saddles allowed me to move the bushings and rod around until i had it level. I then clapped the bushings and aft saddles in place and tack welded, then finish welded all four of them. To date I have not welded in the flanged bushing/washer doublers in place due to a cold!!! garage. Please note that all this was done after i had built and welded the drop links in place which were also bolted together, just to eliminate possible alignment problems latter on.
From: SKYBOLT55
I tacked the saddles on the bench then bought drill rod to align them to the fuse. and used the longerons..mainly top ...as reference the only problem was that I had to gingerly drive the alignment rods out with a rivet gun after all the welding was done. They seem to align with very little distortion.
  • I was looking at a friends Extra 230 and the entire turtle deck removes allowing for excellent inspection. The build process seems simple enough. Has anyone thought of doing this or is it going to cause problems I'm not considering.
From: ACRO240Y
I personaly don't see the need for a removable turtle deck . The removable tail fairing allows easy access to the rear idler arm and makes it very easy to remove any foriegn objects from the tail of the airplane. You must remember weight and attention to details is very important in keeping the weight down. Think twice about adding anything that isn't really needed.
From: RIHNAIRCO
Other options are to mount the removable panel on the belly and to have the turtuledeck fixed on one side and Dzu fastened on the other so that it springs up out of the way when opened and doesn't end up being blown around on the ramp.
  • The fuselage drawings call out a couple of feet of 1/2 x .035 dia in the tail area, has anyone used .625 x .035 instead?
From: RIHNAIRCO
Dan is not on the net, but I will answer as best I can and forward your question to Dan by 'phone to see if he has a better answer. First of all regarding the tubes in the fuselage. This structure has been thoroughly evaluated by stress analysis. Changing any part of it or its materials moves the stress someplace else which may lead to a failure that wouldn't otherwise have happened. If you change anything be prepared to do a complete stress analysis of the entire truss. This takes days even with a computer. Otherwise build it like it is.
From: RIHNAIRCO
I spoke with Dan this evening. The reasoning I gave you on the tubing changes is valid. The rear fuselage is so lightly loaded it isn't a big problem anyhow.
 
  • I am wondering about prepping my fuselage and tail section for priming, any suggestions ? There seem to be some tough spots like the welds on the tail section. Do I need to get it sand blasted, or is there a different way to go ?
From: RIHNAIRCO
Most people get the tubular steel framework sand blasted by someone familiar with thin walled chrome-moly tubing (it can get blasted to death). Very shortly thereafter it needs to be primed to prevent rust. There are three choices of which I am aware for priming, Zinc Chromate, Epoxy Primer or Powder Coating. They are all good and all have advantages and disadvantages. Generally accessability to one or the other source determines the choice, unless you live in a major airplane manufacturing region. Your nearest chapter of EAA can probably give you some good direction to proper sources.
From: Wilyum
Sandblast with walut shells or glass beads and prime with 2 part epoxy in a light colour .
lt grey or white.
  • I just finished tacking my two sides together and was wondering ; a-How long should a tack be? b-Should I tack on both sides of the tube? c-Is tacking on one side enough? Any info is helpful to this beginning welder.
From: PMorgan
You should make you tacks as small as you can and still keep them strong, you must weld through them (ie completely melt) when finish welding, this is because tacks are extremely brittle because they cool to fast due to cold surrounding metal. I keep the torch on them a bit to let them cool slower to keep them tough. I suggest you use FOUR tacks on each end of the tube. I know this seems like a lot, but it ensures that the fuse does not warp to badly, if you just use one tack you will end up with a hell of a mess when you finish weld it, you will be using the rubber hammer until you arm hurts trying to straighten it out!
From: SKYBOLT
Remember when you're making your tacks that you'll want them to blend into your finish weld. Could save you some time in finish welding.
  • Just a few questions about these plans for the Fuse. I've tacked my cross pieces from F.S.0.0 to F.S. 52.00 and I'm about to tack at F.S.76.00. The print says this bottom cross piece, from longeron to longeron is 15.03, and F.S.101.00 is 8.55.It seems that my longerons are going to meet to early at the tail post. Is this a problem that everybody else had.(I hope). And is there a fix on an plan update?
From: PMorgan001
I hope you have your problem resolved by now, I have been on vacation with the family and have not been online in ages (or worked on the plane !). I had the same variation in dimensions that you have noticed on the lower longeron cross members, but it did not cause any problem because I jigged up my fuse upside down on a table and located the longerons, tailpost and firewall tubes first and then filled in the rest. I still have a couple more to go. It is also a good idea to locate most tubes before tacking any because it makes putting them in easier.
  • I spent the night cutting out my firewall.... that 301 stainless is hard stuff! I wore out my pneumatic snips and had to finish by hand. I am trying to "picture" the bottom of the firewall where it wraps around the bottom tube. Doesn't that make it a little hard to remove? How far does the aluminum angle go?
From: Dan Rihn
The firewall wraps around the bottom cross member to help form a transistion to the exhaust tunnel. This helps engine cooling by creating an easier trnsition for the cooling outlet. It also reduces drag by tucking the exhaust pipes closer to the belly and in a more streamline position. It will be more clear when you get into all the sheet metal and especially the belly sheet metal.
As for removing the firewall---I have never found a reason to remove my firewall on my Pitts which I have been flying for 19 years. This should not be a problem.
  • Just recieved my plans and noticed that tere are no details for a swing over canopy as was on the prototype.Any idea's??
From: Dan Rihn
Canopy preference is a very personal thing. I received comments from pilots that flew the prototype which ran both ways. Since canopy types are such a personal thing I decided to draw only a slider. I did this knowing that each builder will change things to suit him/her self. Doug Dodge at Acro Specialties has a very nice side opening canopy system.
Roger Rourke has a nice slider. Take you pick.
 
Hints and Tips
Re: Roll over bar
From: SKYBOLT55
Fuselage Drawing : roll over bar on drawing DR7-1-117 it calls for .095 tubing this should be .035 It also shows this tube at a weird angle on the fuse. it should aline with the fuse. side member beneath it. or your turtle deck will not fit properly. Also the diaganals that go the the fuse. longeron should intersect infront of the cluster so the second turtle deck former will fit properly.
Re: Firewall
From: ClearProp
Well I finished up the firewall tonite...it looks great! I used a shrinker on the 3/4 X 3/4 X 1/16" aluminum angle and polished off the teeth marks. Make sure you use a slow drill speed and cutting oil to drill the 60+ holes in the stainless steel firewall. Have plenty of #31 drills on hand and watch where you put your fingers because you may break one or two of them... be sure to debur all the holes before you rivet, stainless steel burrs will win over aluminum rivets every time.
Todd W. Ashcraft
To the guy who is waiting until he gets the engine mount (bought) to weld in the bushings/gussets...That is also what I did. The Rourke engine mount worked great BUT I had a heck of a time getting the bolts out of the bushings after gas welding them to the longerons/diagonals. If you plan to use 3/8" bolts to hold the bushings in alignment while you weld, definitely machine down as much of the shank of the bolts as possible (Roger Rourke's idea, too late for me) before starting welding. This keeps the engine mount and bushings aligned, but allows you to get the bolts unstuck without dynamite.
I had a bad time gas-welding the bushings in. I strongly suggest a good TIG for this part (and I've got the Dillon/Heinrob AND a Smith Torch).