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1/3 Scale Halberstadt D.III

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1/3 Scale Halberstadt D.III

Old 07-11-2010, 12:15 PM
  #101  
BobH
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Default RE: 1/3 Scale Halberstadt D.III

John, I was REALLY bummed to see your plane smack the ground. I felt so bad for you. You did a superb job of buildint and finishing it.

Seth. when faking rib stitching with glue... next time try a tooth pick and make a line across with glue. It will look good too.
Old 07-11-2010, 02:09 PM
  #102  
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Default RE: 1/3 Scale Halberstadt D.III

Yeah Bob, sorry it ended that way. She was flying really well.
Old 07-11-2010, 05:49 PM
  #103  
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Default RE: 1/3 Scale Halberstadt D.III

John,
So sorry to hear you lost the ship. I'd be interested in learning what failed, if you ever find out. It was a beautiful plane - I'm glad I got to see it fly.

Hi Bob - Good tip. I'll try that next time. I think there must be a better glue. I was using Titebond, with a rectangular nozzle. If the nozzle touched, or I fussed with the glue, it would wet out into a circle. If I kept the volume down so it didn't wet, the % solvent (water) is so high there wouldn't be much left when it dried. I agree it came out a bit blobby. I should definitely play around with the technique some more.
Old 08-15-2010, 05:04 PM
  #104  
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Default RE: 1/3 Scale Halberstadt D.III

Hi guys - latest pics. The plane is painted. Hope to test fly in a few weeks. Still needs some details - Argus engine, hatch handles, radiator and gas tank, cockpit details and pilot. Haven't rigged the wings yet. That's next! The bottom surfaces are linen white. Round hole on the bottom wing is for the compass, borrowed from my Pfalz DIIIa. Wheels will get solartex covers and paint too. So far the weight is looking really good - the fuselage all-up ready to go is 10lbs. Wings will add at most another 10. Balance is very good. Shouldn't take much ballast to hit the cg. I think its going to be hard to reach 30 lbs!

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Old 08-15-2010, 05:25 PM
  #105  
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Default RE: 1/3 Scale Halberstadt D.III

Seth
I can't tell you enough how I have enjoyed watching you build this beautiful aircraft. Fantastic project. Good luck with the test flight.
Tom K.
1/2 Scale D-8 Build
Old 08-15-2010, 06:51 PM
  #106  
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Default RE: 1/3 Scale Halberstadt D.III

As always, another stellar WWI model! This one will be a joy to any and all who get to watch it fly!
Old 08-15-2010, 10:35 PM
  #107  
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Default RE: 1/3 Scale Halberstadt D.III

Very nice Seth, you're going to have fun with this one.
Old 08-25-2010, 06:21 PM
  #108  
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Default RE: 1/3 Scale Halberstadt D.III

Hey thanks - I appreciate the comments! Getting down to the wire (no pun intended!). I was pretty happy to see the incidence, rib-by-rib, is quite uniform side-to-side, i.e., within a few tenths of a degree (I was a bit worried with the droopy trailing edge). So I just put the wires on and tightened everything to about 1 octave above middle C! You'll notice on the landing and lift wires, I swaged the wires to threaded rod and used a steel clevis on the end. I couldn't find clevis turnbuckles big enough for the steel anchor plates, and since I was going to have to use dubro-type threaded clevis' anyway, couldn't see any good reason to spend a couple hundred extra $ for turnbuckles (i.e., just to hang the dubro clevis' on the end of, like I did for the running rigging). I've also included a few pics of the cockpit combing. The material is fake leather from a fabric store, and I found it was easiest to make the holes for the eyelets with a soldering iron. You can see this machine barely fits in my little shop. This is the first time I had to sit on the workbench next to the plane to work on it. A step-stool has come in handy too! At this point, really wishing I built a full scale!
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Old 08-25-2010, 06:50 PM
  #109  
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Default RE: 1/3 Scale Halberstadt D.III

Looks real good Seth! Next time you take a photo try and position yourself so it looks like you are actually in the cockpit. Would make for a good photo I think and maybe get those Full Scale juices flowing on overdrive in the process.

Ron
Old 08-26-2010, 03:17 PM
  #110  
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Default RE: 1/3 Scale Halberstadt D.III

"Looks real good Seth! Next time you take a photo try and position yourself so it looks like you are actually in the cockpit. Would make for a good photo I think and maybe get those Full Scale juices flowing on overdrive in the process."

Or better yet, just climb aboard, strap in, and take off! VERY impressive machine, when is the maiden?...................John
Old 09-04-2010, 11:25 AM
  #111  
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Default RE: 1/3 Scale Halberstadt D.III


ORIGINAL: Sethhunter

Hey thanks - I appreciate the comments! Getting down to the wire (no pun intended!). I was pretty happy to see the incidence, rib-by-rib, is quite uniform side-to-side, i.e., within a few tenths of a degree (I was a bit worried with the droopy trailing edge). So I just put the wires on and tightened everything to about 1 octave above middle C! You'll notice on the landing and lift wires, I swaged the wires to threaded rod and used a steel clevis on the end. I couldn't find clevis turnbuckles big enough for the steel anchor plates, and since I was going to have to use dubro-type threaded clevis' anyway, couldn't see any good reason to spend a couple hundred extra $ for turnbuckles (i.e., just to hang the dubro clevis' on the end of, like I did for the running rigging). I've also included a few pics of the cockpit combing. The material is fake leather from a fabric store, and I found it was easiest to make the holes for the eyelets with a soldering iron. You can see this machine barely fits in my little shop. This is the first time I had to sit on the workbench next to the plane to work on it. A step-stool has come in handy too! At this point, really wishing I built a full scale!

Beautiful model!

A question:
which incidence have top wing, lower wing and tailplane?

Thanks for the reply.

Ciao!

Enry
ITALY

Old 09-04-2010, 12:04 PM
  #112  
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Default RE: 1/3 Scale Halberstadt D.III


ORIGINAL: Sethhunter

Everything is covered. Decided to try the lacing technique published in MA a few months back (sorry I don't know who to credit). Easy and looks nice! Painting next
Hey Seth,

Was just rereading your thread and noticed you used the lacing technique I developed, great job! You are the second modeler I know of who used it and I'm glad it's working well. The SE5 that I worked out the technique on is finally done and ready for it's maiden. Now that Earl is out of the way it looks as if Monday morn. will be soonest.

Looking forward to seeing the Halbie fly it would be a great addition to the Rhinebeck line-up this coming weekend Sept 10-12. Would be great to see you there!

Ron
Old 09-04-2010, 08:54 PM
  #113  
John Cole
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Default RE: 1/3 Scale Halberstadt D.III

Seth, really, really nice!! Good luck to you on testing and trials.

Need an Argus engine?? Try these guys...

John
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Old 09-07-2010, 05:40 AM
  #114  
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Default RE: 1/3 Scale Halberstadt D.III

Hey folks -
I appreciate the input. John - is that an original poster/brochure for the engine? Very interesting. I don't know very much about Argus and the power plant. Probably time to google it!!
Sorry Ron I didn't know it was your technique for the lacing. It worked very well. I used separate strips on the sides, and turtledeck because I didn't think I could get one piece to lay properly all the way around. Next time, I'll just slit it at the transitions, rather than using separate pieces so the joint isn't as visible. I was also afraid I wouldn't be able to "lift" a tighter fitting piece to (get my thumbs in there and) pull the lace through, but found a looped wire a huge help in snagging the lace and pulling it through. I also didn't know how the Germans did the lacing, but I chose to position the first eyelet in the middle of the lace, and thread both ends through each eyelet, alternating top and bottom in kind of a figure 8.

Enry - good question about the incidence but a little hard to answer with the drooped wing but I'll try. With straight wings, it's often a good idea to have the top wing a degree or two negative relative to the bottom. Biplanes have interaction between the wings that results in the top wing having more lift than the lower, so negative incidence helps equalize the loading. I learned on my Pfalz DXV, which was aligned 2 degrees top and bottom, that it flew much better with both ailerons deflected upwards a bit, creating washout and a bit of negative incidence relative to the bottom wing. The problem wasn't stalling, but rather when I backed-off on power, the nose dropped a lot. The engine already had down thrust. I believe as the plane descended and the angle of attack increased, the center of pressure moved back abruptly, causing the nose to drop. This is a characteristic of under-cambered wings. Reducing incidence on the upper wing "softened" that response a lot. Because of the droop on the lower TE of this plane, I set both wings to same incidence, +2/+2 relative to the fuselage centerline, at the root. The engine has 2 downthrust. The stab is full-flying (not fixed) so I can trim it anywhere. On the first flight, I'll align it to the fuselage centerline and have lots of expo and travel. The top wing has 1.5 degrees of twist for washout. The bottom wing droops gradually as the TE curves downward to +2.5 incidence (relative to the root) at mid-span, and the trailing edge then curves up to a net -.5 washout at the tip (again, relative to the root). This creates, on average, a bit of positive incidence of the lower wing relative to the top. We'll see how it works!

I like the photo ideas - I'm still mulling over how to carve a pilot in my likeness! Failing that, there are all kinds of photoshop possibilities!!

I've attached a few pictures of the faux Argus engine under construction. Anyone have any good ideas how to simulate the asbestos wrapping on the exhaust and intake manifolds? Was the asbestos a woven fabric?
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Old 09-07-2010, 05:41 AM
  #115  
Sethhunter
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Default RE: 1/3 Scale Halberstadt D.III

A few more...
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Old 09-07-2010, 08:37 AM
  #116  
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Default RE: 1/3 Scale Halberstadt D.III

Your airplane is big enough that you could have an electric motor drive the valvetrain of your Argus while the engine is running! Just a simple set of cams on a shaft connected to a geared electric motor should do.
Old 09-07-2010, 10:51 AM
  #117  
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Default RE: 1/3 Scale Halberstadt D.III

Thanks for the reply!

Ciao.

Enry
Old 09-07-2010, 12:07 PM
  #118  
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Default RE: 1/3 Scale Halberstadt D.III

Seth, the dummy engine looks very good! Where do you order your casting materials and what all is needed?
Old 09-07-2010, 12:09 PM
  #119  
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Default RE: 1/3 Scale Halberstadt D.III

Nice work Seth...that was also my next question
Old 09-07-2010, 12:27 PM
  #120  
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Default RE: 1/3 Scale Halberstadt D.III

For a pilot in your image talk to Patti4 here in the scale aircraft forun under poseable scale pilots. A couple of photos and she can put you in the cockpit. She's not cheap she's an artist, follow the thread through and you will see.
Doc
Old 09-07-2010, 12:59 PM
  #121  
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Default RE: 1/3 Scale Halberstadt D.III

Or look into something like this!

http://www.youtube.com/watch?v=nM41ID9jLUE
Old 09-07-2010, 08:14 PM
  #122  
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Default RE: 1/3 Scale Halberstadt D.III

Thanks - I'll check out the links. I realized I didn't show a picture of the casting resin, only the molding silicon. See below.

I'm not an expert at all in molding, but I started with a kit from www.Aluminite.com. It came with Aluminite low-viscosity liquid casting plastic. The kit included a useful, albeit brief manual on techniques. I don’t recall what mold-making compound came with it. But when I used it up, I bought silicon RTV, type 1328 from www.Silpak.com. Various distributors also carry it, including Amazon and Kit Kraft Inc.

Things I’ve learned:

Make the plugs for the mold as nice as you can. Every detail, even wood grain, will show up.

Build a box for the mold pretty small around the part (but not closer than ¼ inch) to save material. RTV is expensive (I think mine is a pint for around $25)..

I like using shiny-paper-backed foam board to make molding boxes. I get lots of it from the garbage in our marketing department after every trade show. Graphic artists use it for rigid posters. Tape the box together and seal the seams with a glue gun. I CA the plug to the bottom of the box.

I use powder, sand, or even water (if the plug is waterproof) to check the volume of the mold material needed to cover the plug (again, at least ¼ inch over the top surface).

I measure the Silicone RTV on a postal scale. The mix is 10:1 (1 part catalyst) by weight. Tare the scale!! The shelf life of the silicon is about 45 minutes. You only need a few minutes to pour, so use the time to mix SLOWLY so you don’t get air bubbles. I sometimes tip the cup so the mixture is shallow, so bubbles reach the surface quickly. Tapping and can help bring bubbles up. Then pour slowly into the mold. Thin stream to prevent trapping bubbles. It takes overnight to cure.

I use water again to judge how much casting plastic I need to mix. For my flanges, I only needed about ½ oz each. I put ¼ oz of each part in separate measuring cups, and pour them at the same time into a 3rd “pouring” cup. Using 3 cups helps ensure the final mix ratio is right (versus pouring one into the other, which will never produce the right ratio because of the film left behind). I can then keep reusing the “measuring cups” and also the pouring cup, by pulling out the residue out when it hardens.

This stuff cures FAST so mix carefully for 15 seconds and pour into the mold. Maybe sooner for a bigger part. Try not to poor too quick, or directly into small features. Did I mention bubbles? It’s hard in about 1 minute. But I wait 30 minutes for it to cool so it won’t warp when I pull the part out of the mold.

I use Silpak mold release every couple of castings. But I’ve never cast enough parts to wear out the Silicone, so I’m not sure it’s needed. Parts seem to pop out easily either way. In a pinch I’ve used epoxy in the mold. That tended to stick and mold release helped.

It's pretty easy and kind of fun!

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Old 09-07-2010, 08:18 PM
  #123  
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Default RE: 1/3 Scale Halberstadt D.III

Oh I have to say - I really like the idea of moving valves. Kicked back and thought about it for awhile. Then an image came to me. Two guys walk up to the plane with the engine running, valves flying. One says "look at those valves go!" The other guy says "where?" The first guy says "there" and points his finger at 'em. Trip to the emergency room.[X(]
Old 09-07-2010, 09:29 PM
  #124  
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Default RE: 1/3 Scale Halberstadt D.III

Thanks for the concise mold info. this helps me a lot in norrowing down the types of products out there and the jargon used ...sooo many similar choices..
I spent an Hr. in TAP Plastics recently and walked out with my head spinning with the variety of possibilities and haven't had the time to read up on all the products.
My attempts at fiberglassing have been very succesful but of course time consuming..keeping in mind the lightest weight possible as the end game..
Just wondering if there are any additives ( balloons?) that would lighten up the epoxy part but still leave a smooth finish?
Your anecdote reminds me of our club president who lost two fingers last year at age 73 !! doesn't recall how his hand hit the propof that beast...probably pointing at something !!
Old 09-07-2010, 09:58 PM
  #125  
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Default RE: 1/3 Scale Halberstadt D.III


ORIGINAL: Sethhunter

Oh I have to say - I really like the idea of moving valves. Kicked back and thought about it for awhile. Then an image came to me. Two guys walk up to the plane with the engine running, valves flying. One says ''look at those valves go!'' The other guy says ''where?'' The first guy says ''there'' and points his finger at 'em. Trip to the emergency room.[X(]
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