Erich_Prinz

Looks like some sort of medieval torture chamber for an airplane.

As always, super work - inspiring and depressing at the same time!

Are you targeting next spring or summer for it's roll out? Really seems to be coming along quite fast compared to the DIII.

Sethhunter

Thanks Erich - yes it has that "stockade" look to it! Hopefully the Spring. It does seem to be rolling together faster than the DIIIa. Probably because I spent more time up front on the plans. (I designed the DIIIa a bit on the fly.)

Here are a few pictures of the struts. Each strut will secure to the wings with 10-32 threaded rod going into the wing, and a nut inside the wing to hold it in place. I'll have some little doors of some sort to access/install the nuts. Both the top and bottom center sections will be quasi-permanently installed, so I wont need frequent access to the nuts. The threaded rod (made from a 10-32 bolt with the head cut off) butts to 3/16 steel rod with two layers of brass tubing spanning the joint. (I'd like to thank Dan Schmidt for the idea of joining the wires this way - with all the attachment points and different planes, making the struts in one piece would be a nightmare). The joint will also be reinforced by the diagonal strut wire, but I haven't gotten that far yet. Where the bolt enters the wing, I slipped on a washer, backed it with a wrapping of .010 s.steel wire, and soldered the whole shooting match. Of course, the wires will be covered with fairings. On the fuselage end, the wires plug into hardwood blocks, and will be retained either with collars (with a good size notch to hold the screw) or I might thread the ends and put nuts inside the fuse too.

(PS - it always gives me pause when I light a torch near my latest creation - wondering if I'm going to make the pages of the safety column in Model Aviation!!!)

destrat

Seth:

Thank you for the credit on soldering the brass and bolts, you're work is superb! Haven't maidened the D-XII, the weather is turning on me. There is still hope though!

Dan

Sethhunter

Strut wires are coming along! First pic shows lower assembly including LG wires; they are connected to the lower cabanes by a short strut. Like the upper assembly, the assembly plugs in as a unit. Collars keep retain it inside. Any ideas for a something like a s,all bellville washer (wire is 3/16) on the inside to take play out of it? I didn't leave room for a spring, and it might not need anything but I was thinking of just using some santoprene sheet as a washer between the collars and the blocks. Second pic shows upper assembly going together (plane is upside down). Next three show "J" piece that wraps around the center cabane and plugs into the fuse - at the bottom-middle of the "W". I wrapped it with wire and soldered. Purpose was to keep the anchor point at the center of the bend. Probably better ways to do this but it seemed logical at the time. Last too pictures show the upper and lower assemblies installed on the fuse. Note - the LG goes through the LE of the lower wing. I plan on notching the LE and putting a somewhat "floating" fairing on it to cover the notch and absorb movement so it doesn't apply load to the wing. Ideas welcome! Next step is to get some wood fairings on all this wire...

Sethhunter

Question about the plane itself - There appear to be air scoops at the pilot's feet on both sides. Any idea what that's for? I can imagine that getting suited-up in the artic flight suit (esp. boots) for cruising at 18,000 feet would make one pretty warm at low altitude - but I've never heard of open cockpit planes having pilot air vents. Am I way off? Is it for something else?

Also - anyone know if there are differences between the Mercedes 180 top half and the BMW IIIa 185? The DXV was outfitted with the latter.

Thanks!!

Erich_Prinz

Anything to allow movement to dissipate the energy load will be a bonus.

The workmanship looks more like artwork than struts. The downside is all that wire is it's STIFF and unforgiving.

Some sort of stepped receiver in the upper and lower wings where the first step is larger to accept a soft bushing (rubber or some synthetic material) and the second step a brass bushing to allow the rod to 'float' 1/16 or so of travel. With the soldered base on, the platform is ready to ride against the energy absorbing material. Seems to me the inner diameter of the first step needs to be slightly larger than the material to allow for the expansion under load.

You may not need the same setup for the upper wing.

There's plenty of material at the ends to fashion a retainer. Something adjustable from access ports in the wing would be pretty helpful I'd think. Maybe a threaded end on the struts themselves where you can adjust the travel from the access ports on the far side of the top and bottom wings by turning a nut. You only need about 1/8" travel tops and with all that material, you've got plenty of room on the plane to create a setup like this ... not something for small R/C or Free Flight scale!

abufletcher

I don't get it. There seem to be WAY too many struts on that thing! [sm=50_50.gif] As always your workmanship is superb.

Sethhunter

Thanks for the comments guys. It's really a big help to have "real time design reviews"!! Erich, I think you proposed a solution to a problem I hadn't thought about, but will. Attached is a sketch of the design. I was planning to hard mount the wings to the 10-32 threaded ends of the struts. I haven't had problems before with wire struts being too stiff, but maybe I was lucky (and I haven't used 3/16 before). I'm a bit concerned if I soften the mount, I'll introduce low frequency movement of the wing. I'm generally concerned about the overall flexibility of the design because neither of the wings is tied directly into the fuselage. Everything's kind of floating, and there's no rigging wires. Just hugely thick cantilever wings, 1 bay N struts, and yes Don, more struts than I can keep straight around the fuselage! On the plus side, the wing panels will be attached to the center sections with tubes, which I learned with my Junkers J10 are VERY forgiving when the air gets hard quick! I was, however, thinking of putting some soft washer between the collar and blocks inside the fuselage, to keep the struts pulled-in tight agains the fuse. I also like your idea because I could open up the holes in the wing plate, use a soft pad between the strut and plate, and use the play to fine tune wing position before locking down the nuts.

abufletcher

I don't see a need to build "flexibility" into the wing mounting. The whole point of the biplane wing system is for the both wings to function as a single unit. On earlier thin airfoil designs this necessitated lots of wires to form a rigid unit. With the later (German) thick airfoil cantilever designs the wings were self-sustaining and inter-wing struts were only there to reduce the possibility of flutter.

To think of it from a different perspective, the cabane struts are really only there on the DXV to "suspend" the fuse between the wings. It's easy to fall into the trap of thinking that the struts "hold up" the wings. They might on the ground, but once the machine is flying, the fuse is literally hanging from the wing (and lifted up by a bottom wing).

The only problematic bit is the UC leg butting against the lower wing LE. But as long as there's enough spring in the sprung UC design, that shouldn't be a problem.

Erich_Prinz

I was thinking of the airplane loads while on the ground and on landing.

Very good point that the fuse is suspended between the wings - that seems to me (intuitively) that any low frequency modulations wouldn't be introduced while in flight.

Erich

cocobear

My Feedback: (2)

I concur with Abu that I strive very hard to avoid flexibillity. You can't plan for every accident but I have seen many problems caused by trying. Unfortunatly, I know that 3/16 wire will bend:-)

Sethhunter

I agree. The strut system here takes a little thought as there are 10 on each side, including UC, and there are no landing, lift or drag wires so the loads all come through the struts. I like the idea of a spring behind the collars to take out any axial play where the struts plug in. But I agree the wing attachments should be solid.

Thanks for the input!

PS - Abu - car tire works the same way: Pressure (like lift) holds up the tire, and the car hangs from the tire. Tension in the upper sidewalls is like the tension in the cabane struts!

geezeraviation

My Feedback: (3)

Seth, awe inspiring work as always, I've been following along to see how things progress. This is a very challenging subject you've chosen with all the struts, interplane, cabane sub cabane and landing. Didnt take me long looking at your progress to figure out that if the lower wing isnt fixed to the bottom of the fuselage I dont want to mess with it. More to the point I just recieved some Data-files from the folks I order from and in the title "WWI Warplanes Vol II there are some good pics of the Pfalz DXV, along with three views ( sure you dont need those) and some text, unread as yet. You may already have this material but just thought I'd let you know. I order all my Windsock Data-file books from the printers in England as they are the best source for all the books that have been published. Just got an issue of the 2nd printing of #12 on the Dupont Hanriot HD1 from them that has been out of print for 10 years or nearly so, I've got a Glen Torrance kit of it that will be my first serious scale build and am trying to get all the info possible on it . If you dont have thier website just Google windsock datafiles ond you'll find it. Doc.

Sethhunter

Hi Doc - looking forward to seeing how your Hanriot comes together - It's a great looking airplane, reminds me a bit of the Pup. And as you know, lots of pictures on the web of examples in various museums. Thanks for the comments - the struts have definitely been the challenge of this airplane! Here's the latest pics of my progress. To get the best fit for the fairings, I traced the wires, in position, onto cardboard templates, transferred to tracing paper, then tacked the paper to ply and cut. The trial fit of the fairings required lots of trimming and adjusting of the 100 or so wooden pieces. Using the fixture to hold the wires in exact location, I glued them all up. Nice part about having the struts removable, is you can then take them off to sand and shape. Now that they're in four groups, they're a whole lot easier to handle! Last pic shows the paper template of the as-built bolt locations to transfer to the wing (not built yet).

I've only used the Herris Pfalz book for reference. Will check the source you mentioned - thanks again!

Next steps are to fill/prime the fuselage and start the wings.

Erich_Prinz

Interesting technique - haven't seen that method before. Very clever.

It's really coming along nicely.

It looks like you've glassed the fuse since the prior photos or is that just the lighting in the photo?

Erich

Sethhunter

Thanks Erich - actually the fuse was already glassed. It's just is a bit more visible in that picture. I should probably elaborate on the paper template, since you might ask why it's necessary to make a template for the actual bolt positions when a fixture was used to locate the bolts on the struts to begin with. I found that SLIGHT misalignments between the some of the strut wires caused built-in stress when they were wrapped and soldered, so when the fixture was removed, the struts "sprung" slightly, a couple of millimeters or so. I figured it's better to allow the shift, drilling the wing to match, than force the struts into the exact original position and have that stress permanently in the structure. There may be a better way to do this, but it seems to be working out as well as I hoped.

Sethhunter

Hey all - been lost in the details for a few weeks but finally have some progress that's maybe worth posting. This plane has quite a few air scoops and leuvers. Following pictures show details of making them from cardboard and ply, and construction of the subplane/stretcher on the LG, before sheeting. The subplane has threaded rod that passes through the LG struts to secure it in place.

Sethhunter

and a few pictures of the fuselage/struts/LG primed and assembled. Time to start seriously thinking about wings!

JohnF

Hi Seth, Awsome work! How much does that puppy weigh?

Erich_Prinz

.

1. I'm very curious about the process of building the tooling and jigs. There has to be a fair amount of math involved.

How did you come up with the scoop shape, taper on the jig, and the outline for cutting out the correct shapes?


2. Already primed and waiting on paint!! Looks fantastic. Can't wait to see the wing buildout.

Erich

abufletcher

Wow, Seth, all of that great work just sort of crept up on me! Wow!

Erich_Prinz

Seth,

I was just looking at the exploded view of the strut design. The only time I see date stamps in the format of 18 OCT 08 are from active duty or retired military. Do you fall into one of those categories?

Erich

Sethhunter

Thanks guys!

John - funny you asked about the weight - I just finished checking it. Current weight is a bit shy of 7 lbs. I'm still hoping for under 20 ready to fly. The DXV has narrow rib spacing which I plan to replicate, although I could save some weight by thinning those down. With all those struts, there's a fair bit of steel (3/16) on board. Fortunately, there's no rigging (well, a bit in the LG but that's all). Outter wing panels will slide in place on aluminum tubes.

Erich, unfortunately I didn't do any fancy math with the scoops. I never understood why the DIII/a had those funny spherical scoops; perhaps the Eversbrush brothers figured conical (straight tapered) scoops were a whole lot easier to fabricate; thats what they look like to me in the photos. So I just layed out the plan view, which sets the radius of the front of the scoop (I took it to be exactly semicircular). Then straight sides back to a small radius short of the vertex of the cone. The rest was alittle trial and error: I made the flanges out of plywood (stacked and temporarily glued together with contact cement) and pressed a paper template into the inside of the flange, and marked it with a pencil. Then cut it out, layed the template on the cardboard tube and traced it. I washed the cardboard in CA to stiffen it, and cut it out, then again fit it to the flange and marked it, then sanded it on a bench sander while holding it in roughly the right shape. I glued the flanges to the fuselage, then cut the fuselage away from the inside, leaving a lip for the cardboard scoop to butt against, while "sprung" against the inside of the flange. Glued the cardboard in place, faired with thickened epoxy. I put a few strips of fiberglass inside to reinforce the cardboard. Last step will be drill some small holes for 00 countersunk machine screws. Alternatively, laying out the scoop "exactly" isn't all that hard - since a cone is a deployable (flattenable) surface. I would use graphical techniques to do the flattening (rather than math). It just didn't seem worth the effort here.

I'm still not sure what the aft scoops are for; pilot cooling for the lowers, gun cooling for the upper? I do realize the photos show different scoop configurations and sizes, and I think the upper aft scoop on 8364/17 looks a little smaller than the other scoops, but I made mine the same size.

While I was waiting for the day to warm up to go flying, I made a few flanges for the struts - they dress it up a bit and are easily made from thin alumimum.

PS - no, I have not served in the Military. I do design medical devices for a living, and since that's a regulated business, we have procedures on everything including how to sign and date documents. This is the preferred "unambiguous" format I've just gotten used to from work!

destrat

Seth:

Wow! You have made some real nice progress on the Pfalz, getting anxious to see the wings! Everything looks great, as complex as a machine as it is, things seem to be moving faster than the D-IIIa. I'm plugging along with the Halberstadt DV, finished framing the wings today, now on to the fuse. I'll try to post pic's of my progress.

Sethhunter

Thanks Dan - yes indeed I'm moving this along a lot faster than the DIII/a - I think mostly because I'm using more conventional model building approaches - to make it easier to build and fly. The DIII/a was my longest build at a couple thousand hours. While definitely fun to get into one project like that, there are just way too many planes (and other things) I'd like to build, so I'm going to try and keep them under a year (about 700 hours). We'll see. Looking forward to seeing your DV.