• If You Are Having Trouble Logging In with Your Old Username and Password, Please use this Forgot Your Password link to get re-established.
  • Hey! Be sure to login or register!

Therapy Project

Well, that sets the wheels turning. I guess I'm going to dig in a bit more on flap design and wing "beefing up."

One idea I've seen is to have compression members bracing top and bottom of spars instead of just the middle.

Correct, similar to the N brace at the lift struts but primarily you need to transfer the upper and lower flap attachment loads forward to the front spar. If the flap has a greater cord the mounting loads are actually reduced at the spar since they have a shorter moment arm back from the structure. Higher loads yet less moment arm.

A year ago my project was to use a wood structured wing. I was going to use Vee braces to carry to control loads forward though the structure. I have evolved from there to achieve my design goal but am still not fully locked down on details yet. I do not need to be yet.

You are scratch building so you are open to many options to achieve your desired goals. As with me on my project, you are building the fuselage structure first. This is very good since once the main fuselage is built there is still a massive amount to do to build out the systems prior to covering.
It is during the main structural work on the fuselage that you do your final design and planning for the wings. There is no need to be stuck with what was provided 70+ years ago when you can benefit from the decades of what has been learned since.
 
primarily you need to transfer the upper and lower flap attachment loads forward to the front spar.

I think triangulation, like with the N-strut you mentioned or another method such as with the ribs, also matters in order to prevent twisting the spars.
 
RV

FWIW, if you look at Pipers design flaps and aileron hinge points are mounted to the spars but fairly lightly. The "false spars" are closest to the hinge points and carry most of the loads thru the false spars into the ribs...... that spreads the loads. If there were no false spars there would be greater need to stabilize the spars.
 
Materials arrived

So I finally got my fuselage materials. Had the 24 foot long box delivered to the local depot to save shipping costs.

But the driver called me and said I ought to check it over for damage:

as dropped off.jpg

I talked to Wicks and was told to accept and inventory the damage. They'll make it right. Happily, when I got it home, I found only 1 six foot section of 1" X .035 and 3 six foot channels damaged beyond usability. Everything else looks sound.

I've got my jig table set up and a bunch of steel. The only thing I don't have at the moment is time. But I hope to be scratching some of that up shortly.
 

Attachments

  • as dropped off b.jpg
    as dropped off b.jpg
    126.6 KB · Views: 181
  • as dropped off.jpg
    as dropped off.jpg
    152.5 KB · Views: 229
Damage sucks, luckily they are just shorts which are easy to ship the replacements.
 
Yesterday I had a pleasant enough time cutting up tubes, profiling ends by grinder, file, and snips, and laying things out for the upper section of the fuselage.

Of course, once it was there, I had to tack it. I love the new Smith AW1A torch, but didn't think to take pictures of it.

20180210_163937948550406.jpg


Over on CharlieN's thread I mentioned the Vagabond. The responses there almost had me switching to building a Wagabond (I have the plans in the shop). I was thinking of lengthening it and putting on bigger wings, etc.

Then I remembered I went through all this before. I'm sticking with the original plan unless I get persuasively derailed. I'm looking forward to fitting the lower fuselage section together this week and then jigging the frame for joining. It really is nice to spend some time just working with material.
 
It's a good feeling when each sub-assembly comes together.

My gas rig that has been my mainstay has been a Purox 200 which I believe is the same size torch your Smith's is. Great size to work with.
If you get tired fingers or hand cramps you might consider some friction tape or similar on the body of the torch so it will stay in your hand without gripping it. This will allow more finesse while working.

My father gave me the Purox torch I have back in the late '60s, it was a used hand me down and has seen allot of use over the decades. That was the first "real" tool I had.
 
RV. save the Doug Fir for your boating hobby. Weight of it will be more than the aircraft standard Sitka Spruce.

As to transferring flap loads to the tear spar and beyond. Doubling the ribs at the flap hangers or making a truss rib with an additional plywood web will transfer the loads to the front spar an ameliorate rear spar twisting more elegantly than doubling compression members or having "N" struts.

imho
 
RV. save the Doug Fir for your boating hobby. Weight of it will be more than the aircraft standard Sitka Spruce.

As to transferring flap loads to the tear spar and beyond. Doubling the ribs at the flap hangers or making a truss rib with an additional plywood web will transfer the loads to the front spar an ameliorate rear spar twisting more elegantly than doubling compression members or having "N" struts.

imho

Good points. I did check out the fir more closely. It's really solid, hard, old-growth stuff from the Blue Mountains of WA/OR. Really tight rings and really dense. I weighed a rough cut 2X6X16 and it came out to 48 pounds or so. That's more than 36 pounds per cubic feet. In boatbuilding we always rule-of-thumbed doug fir at 34 pounds/cu ft. Just now I see them using 32-33 pounds, but that must be the lighter new-growth stuff.

I'm pretty much sold on some kind of truss rib instead of additional compression members. Mike MCS mentioned something like that in an older thread and that started the gears moving.
 
My gas rig that has been my mainstay has been a Purox 200 which I believe is the same size torch your Smith's is. Great size to work with.
If you get tired fingers or hand cramps you might consider some friction tape or similar on the body of the torch so it will stay in your hand without gripping it. This will allow more finesse while working.


My father gave me the Purox torch I have back in the late '60s, it was a used hand me down and has seen allot of use over the decades. That was the first "real" tool I had.


I passed on a Purox torch in an auction 2 decades ago because I didn't know anything about them. I think it was a "Presto" model. I now wish I had grabbed it.


So far the grip feels pretty nice. I don't grip it very hard. The next improvement will be to get some lightweight hoses.
 
I'm pretty much sold on some kind of truss rib instead of additional compression members.

Yes. You'll be resisting moments with the truss rather than torsional stiffness of the spars.
 
Another week, and most of that week was spent doodling and planning. I spent a lot of time laying out the jig for the lower fuselage frame. I didn't like how the plans depicted the jig.


The lower fuselage bends up at the rear gear attach point. The jig drawing is set up to more or less accomodate it, but I wanted a precise X-Y-Z coordinate for each station. That is not in any one place on the plans.


Bouncing among various drawings, I was able to finally locate all the points I wanted. It turns out that the plans for the jig look to be fairly accurate, but I wanted to see for myself.


Last Friday, I visited the new Harbor Freight that opened in Lewiston, ID, last month. Before that, the nearest one was 135 miles north. I saw an "open-box-scratch-and dent" mini-lathe for $350. I looked it over and it followed me home. I actually had been scouring the local Craigslist for something I could use to turn down liner tubes. This ended up being a decent enough solution.


20180217_1616001279210822.jpg



On the lower fuselage frame, there are two splices at the gear attach points, just as there are on the super cub. The plans have 3/4" .035 longerons joined by 5/8" liner tubes. I didn't like that much gap--the longerons' ID is around .680 and the 5/8 OD is, of course, .625. The standards apparently allow that much gap with several rosette welds, but I wanted tighter. I had ordered a length of 11/16 X .090 from Univair and had it ready. It just needed to be made a little smaller.


20180219_134124.jpg



20180217_1615441073715542.jpg



My first try on the lathe was a little rough. After shimming the tool height and getting familiar with its operation, I ended up with some decent pieces.


Prebent the liners and dry-fitted joints.


20180219_143401.jpg


20180219_143342.jpg



Then I started tacking tubes.

20180219_155136980522897.jpg


20180219_155152.jpg



I mentioned doodling and planning. I've spent a surprising amount of time reading aerodynamic books and articles. The focus has been trying to calculate flap and aileron forces on a spar, of all things. So far, I think I have a handle on it using the drag and lift equations and estimating various coefficients. I'm surprised there doesn't seem to be a lot of information on such things. I know people put big slotted flaps and move ailerons outboard, but I've never actually seen any calculations to support it. I'm sort of obsessed with seeing the numbers.

Anyway, another thrill-filled day and a half in the shop. A cold front and strong winds kept outdoor activity at a minimum--and made me appreciate the heater I put in the shop last year. Plugging along.
 
Small update. I'm closing in on tacking up the lower section of the fuselage.

20180224_144853507738580.jpg


I picked up a laser level before putting in the heavier tubes in the front. I was surprised at how square things remained. One of the issues I had is my floor settled slightly a year after it was poured. There is a fairly consistent 1/4" in 10 feet slope in one of the quarters of the floor. I tried to account for that with shims under those 1X4s. Even with my table on casters, it remains true when I put it in the same spot.

The other thing I learned today is not to let your Harbor Freight lathe's lead screw run to the end of its travel on its own. Instead of it running out of thread, it reaches a stop, and the drive screw seizes.

It was not a hard fix, what with plastic gears. I was able to take off the gears and back it off. The plastic gear had its key-way stripped, but it was still a fairly snug fit. I was able to cut another key-way with a small wood chisel. It now works just like it did before. Live and learn. I was used to an Atlas lathe from long ago that had a little interrupter on the half-nut to disengage it.

I've got one question for now: Is it OK to heat bend .090 sheet 4130? So far my attempts at a homemade press brake are falling short.
 
You can heat bend .090 but don't allow any air movement while your material cools. Don't even walk by while it cools. Piper didn't use 4130 for their heavy brackets in the 40's.
 
You can heat bend .090 but don't allow any air movement while your material cools. Don't even walk by while it cools. Piper didn't use 4130 for their heavy brackets in the 40's.

I saw someone mention covering it with fiberglass insulation before it cools. Would that be a good idea?
 
Covering it with fiberglass will reduce it's mechanical properties. It wiil tend toward being annealed. You want normalized, which is cooled in still air. I'm assuming it is normalized sheet, which would be marked as condition "N".
 
Covering it with fiberglass will reduce it's mechanical properties. It wiil tend toward being annealed. You want normalized, which is cooled in still air. I'm assuming it is normalized sheet, which would be marked as condition "N".

That's what it is. Thanks for the head's up.
 
I've made Piper replica fittings with heat bend. I've also made redneck style press dies and bent the .090 cold. Had equal success with each. Too late for you but anybody building a Wag aero airplane would be way ahead buying their fuselage material kit. They supply all those hard to make fittings ready to weld on. Its actually a real good buy considering.
 
I've made Piper replica fittings with heat bend. I've also made redneck style press dies and bent the .090 cold. Had equal success with each. Too late for you but anybody building a Wag aero airplane would be way ahead buying their fuselage material kit. They supply all those hard to make fittings ready to weld on. Its actually a real good buy considering.

Right, too late for me--except that they told me it would be two-three months to get it. That was a month ago and I was impatient!
 
A few weeks went by, and I had more therapy than apparent progress. But I was plodding along.

The main time-consumer was getting the top and bottom assemblies lined up. As far as I could tell, the jig dimensions on the plans would not do it. The dimensions would place the upper assembly askew compared to the frame drawing referencing a datum line.

So, I abandoned the pre-fabbed jig approach, ran a datum reference string fore and aft, and shored up the frame piece by piece. It ended up being sort of tedious.

20180303_161336418344132.jpg


Every adjustment changed something else. I'd take a break, come back, fiddle with it again, and finally got everything aligned pretty close to the specs.

Today I tacked a few tubes:

tube-fwd.jpg


2018.03.17-tube.jpg


In the mean time, I had a side project. The $350 scratch-and-dent 7X10 mini lathe from Harbor Freight is now a 7X16 mini- lathe.

As it was:

20180217_1616001279210822.jpg


As it is now:

20180317_154949.jpg


The extension kit came from Little Machine Shop and added $180 to the machine. It took several hours to put it together, but now I can turn down some of those 11/16 liner tubes in the rear fuselage frame.
 
Here I am sitting at the end of the day with a smirk on my face and a little bit of a chuckle. Thinking back to how many times a structure just will not take a set, it can get frustrating, angering at times. Then all of a sudden, it is just right. But I am too damn worn out to start fitting tubes and weld. Will it still be in alignment in the morning.
But when it is right, it is just that, it is right and that is such a damn good feeling. It is so nice to be moving along.

Nice find on the lathe, Out of curiosity what diameter tube will pass through the headstock and chuck?
 
Here I am sitting at the end of the day with a smirk on my face and a little bit of a chuckle. Thinking back to how many times a structure just will not take a set, it can get frustrating, angering at times. Then all of a sudden, it is just right. But I am too damn worn out to start fitting tubes and weld. Will it still be in alignment in the morning.
But when it is right, it is just that, it is right and that is such a damn good feeling. It is so nice to be moving along.

Nice find on the lathe, Out of curiosity what diameter tube will pass through the headstock and chuck?

Right now the limiting size is the chuck. 5/8 passes through, but 11/16 does not. If you take the chuck off, there is .80 inch diameter clearance. I'd think I could bore the chuck enough to pass a 3/4 tube easily.

Vic
 
I have never liked how the jig is depicted on the wag aero plans for the 2+2. I got lucky when I helped build a 2+2 fuselage. I had a bare PA12 sitting net to my jig work off of. I set the PA12 on the jig table and built the jig to the bottom of the PA12. Then it was easy to build the wider top, affix it in place and fill in. I'm a crap carpenter and I felt like there was too much carpenter work involved with the wag aero jig. Glad to see your progress.
 
Last edited:
I have never liked how the jig is depicted on the wag aero plans for the 2+2. I got lucky when I helped build a 2+2 fuselage. I had a bare PA12 sitting net to my jig work off of. I set the PA12 on the jig table and built the jig to the bottom of the PA12. Then it was easy to build the wider top, affix it in place and fill in. I'm a crap carpenter and I felt like there was too much carpenter work involved with the wag aero jig. Glad to see your progress.

A spare PA 12 would have been nice to have. That sounds like a good way to get it done.

I'm quite used to working in wood, but in this case I think the dimensions are wrong. For instance, a jig is laid out for a certain height and set a certain number of inches from a station. Cut a 3/4 notch for the longerons, and you end up with a longeron a couple of inches out of position in reference to the datum line. I couldn't make it work, even assuming for logical typos.

I remember reading Marty's website how he mentioned some problem with the jig so he worked around it. I think everyone has to do it, apparently.

But that's the fun of scratch building. I ran into the same sort of thing on the last dory I built, too.
 
Right now the limiting size is the chuck. 5/8 passes through, but 11/16 does not. If you take the chuck off, there is .80 inch diameter clearance. I'd think I could bore the chuck enough to pass a 3/4 tube easily.

Vic
As long as the jaws have the travel you should be able to use a boring bar and open the body of the chuck up to the .80, Take a look at the backside of the chuck, you might consider splitting the body and look at the scroll to make sure there is room for the cut, I expect there is but best to check. Bad enough to scrap material but aggravating when one scraps tools.
That was you can work longer pieces with stability.
 
That sounds very frustrating about the plans being off, hopefully it is just an error in the tooling and not so much in the structure.
I just got to realizing I have some Wag plans here that I purchased back in the '80s that I never worked with. Truly forgot I have them.
One would think the errors would have been corrected by now.
I have worked with a number of Rutan influenced planes, Quickies and and EZs and such and when you find a template for cutting out the foam wings is wrong it is really aggravating to find how much scrap you have from errors that should never have made it to print. That was one of the big drives for me to draw all my own projects be it to redraw an airfoil if not just to see if the shape I draw from the ordinates is the same as they drew. Many times it is not as was the case for the plans we had from the later '70s era.
Those problems should not have made it to print and truly should not still be in print 30-40 years later.
 
So I started this thread high on hope I'd find maybe 20 hrs a week. Past 3 weeks I've gotten 7 hours in. Best laid plans; surprise twists and turns in my caseloads, etc.

But, reporting now just bit more progress.

I finally lined up the tailpost and confirmed the fuselage was square overall before tacking it.

20180407_140754473973110.jpg


BTW, I do have a good quality level in addition to that Harbor Freight one in the picture. But that came with a laser function, which was fun to play with for a while, before I went back to strings for a datum.

I wanted to see how things fit with the stabilizer:

20180407_141326.jpg


I turned out that the tail post angle is slightly off. Everything back there is still tweakable as it is only lightly tacked.

Slow, but perceptible progress:

20180407_151732.jpg


I keep telling myself, "I just need to get through this month...and then...."

Heh. Still having fun, though.
 
Did you remember to put doublers in the longerons in front of the tailpost?

Err, Umm. Funny you should mention that.

Before I saw your post, I walked out to the shop to get some chicken feed and I looked on the table by my lathe. Lying there were the two doublers I turned down from 11/16 tubing 3 weeks ago, waiting for installation....

Good thing those tail post tacks are light.

Of course, the doublers are not shown on the Wag Aero plans, and I had forgotten to note them on the plans.

Two steps forward, etc.

Thanks for keeping an eye on me, Jimbo.
 
Back
Top