destrat

Donairplane:

Hey, good to hear from you, maybe we have previously met and don't even know it with these forum's and all. I belong to the "Barnstormers" and fly out at the club field in Butteville. How about you?

Dan

geezeraviation

My Feedback: (3)

Seth, thanks for the input, Ill have him recheck the CG but it seemed to have plenty of "nose down" during the check I witnessed, the cables are tight at neutral , dont know if they loosen up as travel progersses or not. I'll definitely bring it up. Thanks, I'm a virgin to full flying stabs and I'm not sure Bobby is any more aware or not.
Doc

ARUP

I think it was Mick Mannock who stated 'I have never seen an airplane (the Halbi) dive so steeply and for so long'. Also, the Halbi was evidently a good 'spinner' for it was a common practice for the pilots to spin out of a tight spot, mimicking being shot down, only to recover and escape! It was, evidently, a well mannered aircraft to fly, too. This info might be a rehash from the same Profile Publication that you have and if it is- my apologies! What a cool build!

Donairplane

My Feedback: (3)

Hi, Dan, I fly at the Dusters. Maybe we have meet at the Dusters Big Bird. Don.

destrat

Don:

I was there last June with the 1/4 scale Pfalz D-XII.

Mein Duff

Seth, This project is looking awesome...I, like the others are in awe of your well thought out ideas and inventions in solving age old problems....
A few questions, I am thinking of building a 1/4 or 1/3 scale Rolland DVA ( never seen one done yet, with lapstrake planking) the tail section on this aircraft (and on the Pfalz III) has an inverted airfoil, meaning the curved side is on lower side..apparently as I read somewhere, to help assist in pulling out of a dive !?!?! maybe true, maybe it helped...I was wondering if your Pfalz had the same airfoil or if you even considered this in planning. I would like my Rolland to be as true to scale as possible but not sure if this might cause me more problems than I bargained for....maybe I should just go with a basic cross section?

Also wondering what design software you are using or what you would recommend I should use?

What airfoil you used on your Pfalz? Any suggestions for my Rolland?

What engine are you considering for your Halbi?

Keep up the great work, you are an inspiration to us all...also enjoyed your you tube on putting you Pfalz together and flying.

Sethhunter

Hi Mein Duff -

Sorry I didn't respond sooner. For some reason, RCU has been slow for the last few days. Were they doing something with it? I don't think I've seen the DVa - I have seen a lapstrake fuselage but don't recall the aircraft. Perhaps it is the same. Anyway it sounds like a great project. I'd love to see a thread on it. My Phalz DIIIa does have an inverted airfoil. The Phalz DXV does not. I don't think it makes a huge difference and I don't think you will get in trouble with it, so long as you don't get carried away with the camber. This subject of stab lift is really difficult to predict since it depends immensely on the angle of downwash behind the wings. Downwash will be greater, at the stab, on high wing an bipes. I'm guessing a couple of degrees, which makes the angle of attack of the stab more negative, producing downward force. I have downwash tables for full scale planes but don't know how they scale. And it varies depending on the position of the stab with respect to the wing. Downward lift of course is good - improves stall recovery, etc. I don't know about dive recovery.

I used zero stab-incidence on my DXV, and found I needed some down trim. So if I ever built another, a degree of positive incidence would be about right. That's with a symmetric stab section. If you compare lift characteristics between a symmetric and asymmetric foil, you'll find the asymmetric foil has a zero-lift angle of attack a few degrees less (negative) than the symmetric foil. (And of course the lift coefficient slope v. angle of attack is steeper). So if I used an asymmetrical foil on the DXV, proper trim would probably require another degree, say 2 total, of positive stab incidence. The DIIIa seems to support this. It also needed down trim - I think a bit more than the DXV.

I've been using CADKEY. It's an old 2D program. I don't think you can buy it anywhere, and it's a bit tedious to use. Professionally, I use Solid Edge and NX. Siemans PLM offers a free version of Solid Edge for home use, but it is a big program, and not the easiest to use so I would not recommend it to the faint of heart. This might be a good question for this forum, to find out what others are using. Let me know!!

I think I used a Gottingen 303 (1918) on both Pfalz and the Halberstadt. A friend also used it on a huge (20') Gotha with good results. If you PM your email I can send it to you. I've scaled the section up a little on some planes to get a bit more strength.

Engine for the Halbi will be a Fuji 64 EI. Just got it.

I started working on the top wing. Here's a few pictures. I tried something different with the main spar. Rather than a box, I built an "I" beam by splitting the spars and gluing to each side of the web. This guaranteed a really good bond between the web and spar (rather than the typical butt joint). But of course you need to build the spar first, then put the ribs on. I still used an aluminum box at the root, and an Alum root rib.

Getting there!

JohnF

Seth, I can see the web's are balsa but is that bass wood you are using for the spars? Maybe I missed something. Thought I was going to be asking you about coming out to the flying field in a week or two but Ron and I decided to do an engine swap on the Aviatik. The total weight is approx. 27lbs. so a G62 will now replace the 40cc, 4-stroke. Hope to be doing the maiden by the end of April If that is okay.

geezeraviation

My Feedback: (3)

Seth I think Mein Duff meant the Rol D VI or D VIa, it had a lap strake fuse and is an interesting not beat to death subject. I have drawings for it and have figured out how to duplicate the "ship lap" planking. Joe Huntly has just finished a set of drawings in 1/3 scale that will be available through AZM "if" I have my signals straight. Mine are at 1/5 scale and I sort of accidentally found them, they were done by Jim Kiger at Replicraft with credit given to Dan San Abbott but I dont believe they are available any longer.
Doc

Mein Duff

To Geezer:
I have never seen a Rolland D.V1 as a flying model i, thats why I am thinking it would be interesting build, I love wood working and I'm sure I wouldn't be disappointed if I chose to do this aircraft. I'm thinking now more probably in 1/4 scale due to space restrictions in my shop.
I would be very interested to see your plans somehow or to get a copy of them, no problem paying. If Jim Kiger had anything to do with them I am trusting they will be more accurate than scaling up my Windsock datafile outlines done my Ian Stair.

To Seth: Thanks so much for you great info. and the time you took..I am processing all that good stuff...never realized the wing down wash effect being a force to reckon with in models!...I wish I had built my 1/4 scale SE5 with adjustable tailplane to compensate this like the original now.....although I think it has a few degrees positive built in already.

I usually build engine side and down thrust in my models and this has served me well in general...offsetting the need to down trim somewhat.

Seth, If you don't mind me asking, are you employed the aeropace or the aircraft industry, your knowledge of aerodynamics is impressive, I'm learning a lot.

I used Cadkey a few years ago doing some temp work...wasn't to difficult to grasp. I will try the other design program you suggested also.

Sethhunter

Hi John - exciting to get that bird in the air! I'd like to be there - though I have to visit some colleges with my son in the next few weeks. Let me know when. Opening day at the field is May 2. It's also "builder's day" where all the new ships come out for their maidens. Yes, my spars are Bass.

Mien Duff - yes indeed down/right thrust also helps, although it tends to compensate for power changes, whereas the stab trim balances a bit more of the aerodynamic forces. No I don't work in aerospace - although I sometimes wish I did. My major in engineering was applied mechanics (especially elasticity, mechanics of continuous medium, and dynamics). I did manage to cram in few electives in subsonic and supersonic aerodynamics, and theory of airfoils - just for personal interest. But a lot of my practical understanding came from many years of reading about sail design and trim and racing sailboats, building models, and flying full scale. Professionally, I design medical devices with a specialty in precision mechanisms and numerical analysis. If you have any background in Solidworks, you'll find Solid Edge very similar.

JohnF

Oh boy , I remember those days of visiting colleges. My son is now in Drexel University's PA program. Is Drexel on your list? I will definitely let you know when the Aviatik is ready and hope to make it out there May 2nd. Should be a couple of weeks away. Good luck to your son.

Sethhunter

Hi John - Drexel is a great school. I know a few people who graduated from there and loved it.

Since you asked about "missing something" I thought maybe another comment is due on the spars. It's more common to set up the ribs and install the spars separately, with the rib running between the spars (i.e., notch top and bottom), and glue in shear webs after the spars are in, either on the sides of the spars (box) or between them (I). The latter is hard to do well, I think, because it's tough to cut the webs to fit well, and at best, the web-spar joint is a butt. I like the box for the reason the fit is less critical, and the glue joint to the sides of the spars makes for a great joint. But it is a bit heavier unless you have the foresight to use thinner webs for the box than for the I (I tend to forget to do that). It's perhaps worth mentioning there's no "engineering rule" that says the spars have to be symmetrical (i.e., I or box or whatever). So you could but webs on just one side (C shaped). But the spar will tend to warp out of the vertical plane when it bends. Not the best thing but on many designs it doesn't matter much. (D-tube leading edges are asymmetrical but the curved part of the D really keeps the whole thing from warping underload). Regardless, symmetrical beams are simpler and more common.

On this project, I made the main spars as a separate unit because the lower ones are curved, and so I just did the same for the uppers to make all the ribs the same. Making an I spar as a unit gives you the option to sandwich 4 spars to the sides of the webs (top and bottom spar are really 2 pieces), rather than butt join the webs to the inner sides of 1-piece spars. Actually as I think about it, you could use 2-piece spars with the typical wing construction too: Cut notches in the ribs wide enough for 2xspar + web thickness. Set ribs in place. Drop one spar into notch, top and bottom, and glue webs to the sides of the spars (i.e., full depth), then drop in the next set of spars (opposite side of webs) and glue those to the webs. I've never tried this (or seen it done) but it would work and produce a much stronger web joint. You do loose a little beam strength because of the balsa running up between the spars, but something like 1/64 ply web would make a really good strong light alternative, glued up this way.

Anyway, when you make the spars as a unit, the ribs either slide-on or drop on, but either way the ribs are generally weaker because you don't have that bit of rib running between the spars. To make up for that, I put little gluing pads spanning the spars at each rib location, to glue the ribs too. The cap strips also do a lot to lock together the front and back half of the ribs.

Sethhunter

Progress - progress. Time seems to be moving in slow motion, but at least the wings are pretty much done. Need some finishing work on the ailerons (horns and hinges), install the engine, cover, rig and paint. Build the faux engine, make a pilot, fly! Well, that's the plan anyway! The following pictures show the "mold" I made to laminate the tips, some simple fixtures (wedges) to set the washout, ailerons - which were built as part of the wing and then cut out, and finally the center wing joiners. The Joiners are laminated aluminum and ply beams that slide into the box spars and tie the wings together side-to-side. I'll use a bolt/pin down thru the spar and joiner to hold the panels in place. This is why I put the aluminum box around the spars at the root - to really hold that pin and spar together. The root ribs in the panels are aluminum to put some beef behind the flying and landing wires - carrying the load from the wires to the spar-pin. The top center ribs are aluminum to hand onto the top wing joiner, and transmit the load to the cabane struts.

Flew the Pfalz DXV today for the first time this year. Nice to be back in the air, but breezy here in NJ. The wind was backing in gusts (rotating counterclockwise) which was catching a few guys by surprise on their take-off runs. A few WWI birds got dinged. Ahh Spring!

Sethhunter

oops - forgot to upload this end view of the aileron, after cutting it free...and a shot down the bench showing the wingspan.

Sethhunter

Hardware week! Finished making the cable anchors. Steel for the lift and landing wires. Brass for the interplane braces and drag wires. Each plane, it seems, I try a whole new approach to strut anchors. Haven't found a favorite yet but I will say the cam-locks on the Pfalz DXV are holding up well and work nicely. For this plane, since the wing panels come off as a unit, I don't need quick release type mechanisms. Sooooo.... I'm bolting the anchor plates to the wings with 6-32 bolts. Each bolt has two brass tubes soldered to the head. I can still access the hex socket heads through the tubes. The struts will have holes in the ends that slip over the tubes. The outer tube will be cross drilled to receive a 2-56 cross bolt, through the strut, to hold the strut to the anchor bolt. I put 2 tubes on each bolt, cross drilling just the outer one (holes not drilled yet), so if I need to further tighten the bolt, I can heat and rotate the outer tube (with the cross hole) back into alignment with the strut hole - without overheating the works. That's the plan anyway!! Struts next, then covering. BTW - I find it MUCH easier to grind these things if you sandwich them between two pieces of alum or brass, clamp with a vice-grips, and hold to the grinder. Doesn't mar the steel and sinks the heat nicely.

JohnF

Nice work Seth, might have to try that myself.

Sethhunter

Starting to get big! I made the strut ends from plywood, drilled to receive the brass tubes on the wings. Slid them in place on the tubes, then set the wings in place. Fiddled for about 4 hours getting the wings aligned with weights, shims, and clamped "temporary struts" - constantly checking for equal gap (strut length) on both sides. This is tricky because each strut on a given side is a different length, due to the drooped lower wing. Well I got close enough that final rigging will pull it in, and glued ply to the connect the end blocks. Next step will be to take the struts off, put a balsa center, spruce LE/TE, and ply on the opposite side.

Sethhunter

Struts are coming along. Once the ply ends were bonded to one ply skin, I removed from airplane, added balsa core, hardwood LE/TE, then glued on opposite-side skin (stacking them all to use the weights once). After shaping, I cross drilled the struts and brass tubes to take a 2-56 bolt. The notch on the brass tube is a visual key to remember which side is forward, when screwing them back on after covering. I might use some heavy card stock to make faux brackets on each side, where the bolt passes through, to give a bit more "functional" look. Obviously these struts will be painted.

Sethhunter

Well, nothing too innovative to report.... Fuji 64 with Bisson inverted muffler fits snugly. Tail rigging is also done - thought for once I'd do that before covering. I'm also showing the cowl attachment method - dowels on the backside of the cowl go into holes in the front bulkhead. Screws enter the side, pass into the dowels and thread into nylock nuts set/glued into the dowels. The brass brackets anchor the drag wires. They pass through the ply sides and screw to blocks in the engine compartment. Ignition module sits snugly behind the firewall. And lastly, the servos are in. Next step is to cover, paint and assemble!!

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

JohnF

Hey Seth, looks great! Don't forget the rib stitching.

Airwarrior

I was impressed with your Pfalz build, and this very much lives up to that one. This is a very cool subject, and I'm really looking forward to seeing this one come together.

Sethhunter

Hey thanks! Funny you mention rib stitching John - I wasn't planning on stitching for times sake (still hoping to fly before our warbirds event in September). But you had a point so I tried simulated stitching. On the Pfalz DIII I found it easier and better looking (but not quicker) to use real stitching. This round I tried glue dots, covered by tapes. I think it looks pretty good, not quite as authentic looking as thread but passable. Included a photo of the eyelets behind the cockpit. Hopefully I can start painting this week.

JohnF

Hi Seth, Looks real good. BTW, do you know if the rib tapes were really stitched on or where they tacked like the Aviatik? Speaking of the Aviatik I am afraid I have very bad news. I lost her to a servo problem or electrical problem it seems at WOD. We tested the battery after the crash and it was still good. The last flight was really great. Finally got the balance right and Ron was getting ready to try some loops and stuff. On a low pass about 20-30ft off the ground she suddenly turned left which Ron corrected but in the next second she snapped right and went down. It all happened so quick and Ron didn't have a chance of saving her. Ron was very distraught but it wasn't his fault at all. Maybe down the road I'll build another since it really turned out to be a nice handling model all around. For now it's full speed ahead on the next project. Looking forward to seeing your Halb. finished.