abufletcher

BTW, interesting point about how to lay down the first layer of veneer! Since I had always just imagined gluing it right onto the frame I never though about this. I would be a rolal PITA to try to clamp each bit in place and then expect the second layer to make it all hold it's shape. I don't imagine that these shell was all that rigid before it was nailed to the fuse frame.

lazyace

My Feedback: (126)

just a fast ? i'm haveing a kit cut for the d111a from polapink plans by a club member , just need a source for colours & markings would like photos of diff. scemes. any one know where i can get them thanks in advance charlie

abufletcher

Charlie, not that many Pfatz color schemes out there on the web. I suggest you pick up the Datafile (#21) or any of the other references mentioned at the beginning of this thread.

OK, everyone here's a couple of Pfalz tidbits. First, the new Pfalz DIII datafile (#107) includes in the 1/72 and 1/48 scale drawings a detailed structural drawing of the wing and the fuse. The DIIIa plans don't include these -- just standard external three views! So I can over to Kinko and made some REALLY BIG copies! These drawings appear to be based on the Flugsport drawings but are actually a little more accurately drawn.

Second, here's a little design insight into the classic Pfalz tail. I've always been curious about why these old planes ended up looking the way they do. You might imagine that the shape of the tail was just some desginer's flight of fancy or based on some half-baked ideas about aerodynamics. The answer is simpler. According to the author (and the factory drawings included) the original Pfalz prototype and a very angular rudder which required four sharp bends in the corners. To be able to accomplish this the workmen had to fill the tubing with a scarce wax substance to keep the tubing from kinking when bent. This was hard work and required a hard to come by material. The solution? Make rounder bends! And Voila there's that Pfalz tail roughly within the boundaries of the old squarish rudder!

Now I need to find out if the wing on the DIIIa was actually the same as the DIII and if now how was it different. More ribs? Same number of ribs spaced differently?

abufletcher

Well, I've pretty much collected all the available plan materials on the Pfalz and I think I would rank them in this order in terms of authenticity and quality:

1. Simkin drawings in newest Pfalz DIII datafile (#107)
2. Drawings from 1919 Flight/Flugsport -- very detailed but look a bit like sketches
3. Wylam drawings in MAN Scale Drawings

In terms of model plans I'd rank the Spievack plans above the Polapink plans. Wing construction on the Speivack plans is much more in keeping with scale construction.

Personally, I've decided to use 1/6 scale enlargements of the Simkin drawings as the primary building plans. I will then suppliment with information from the Flugsport drawings and/or Wylam drawings. I'll only bne using the two model plans as "reality checks" for my construction techniques. At this point I'd like to experiment with making and honest-to-god wickelrumpf fuse. This will invovle the construction of a dummy fuse (in halves) that will form the master mold. I'm assuming that this shell was probably quite flexible until nailed to the fuse formers and longerons. Initially I plan to try to use two layers of 1/64 ply with either epoxy or maybe Gorilla glue. If this proves impossible I'll try traditional sheeting or maybe planking with balsa. I'm also planning to use fully scale wing airfoils rather than the non-scale wing airfoils shown on both model plans.

It's going to be paramount that I keep the weight of the fuse behind the cockpit really light. The use of scale constructin might actually help here.

abufletcher

BTW, is anyone aware of any original photos that show the actual process of doing Wickelrumpf construction? The the folks at Pfalz learned how to do this from Roland maybe photos of the Roland factory would show something.

abufletcher

Since the Roland aircraft used the same "wickelrumpf fuse construction (the Pfalz people learned it from them while licence building Roland DII's) I thought I'd look around for photos fo the Roland Walfisch. I've been wondering to what extent you could actually SEE this construction technique and I think I have my answer here. I've also noticed vague diagonal lines on a number of the photos in the datafiles.

BTW, another detail I love in one of the datafile photos is the scuff marks from boots all around the step below the cockpit. I can almost hear the sound of the boot tapping the side trying to find the foothold as the pilot climbs out after combat!

zoomzoooie

What are the references used for the Simkin drawings in the Datafile that make you prefer them? What year were those drawings done? I don't have a copy yet.

I want to do the Pfalz DIII so I will modify my plans, but the DIIIa would be a better flying model with more area in the tail.

Nice shot of the Roland. I can clearly see the ply lines.

I took out a 12" x 48"sheet of 1/64 ply to look at the grain because I was thinking of using that to cover the 1/4 scale Alb DVa I have plans for. The plans call for 5/32" balsa sheet so I thought 1/8" balsa and the 1/64" ply would give a good scale appearance, since it will have a varnished look. I don't like the grain pattern. It's too big, even for a 1/4 scale model but the wickelrumpf construction would be ok an a 1/4 scale model. I might try it when I get to do a 1/4 scale Pfalz... that is if it works out well for you. I still think it would be easier to do, laying the ply directly on the fuselage frame, even if it isn't an authentic technique, the result will be the same.

Anyway, what I want to get at with the 1/64" ply, is that it seemed pretty heavy at 4oz. I don't know how much you will need, but I would think one 12"x 48" sheet might be enough for one laminate. So now you're looking at 8oz(2 sheets) plus the added weight of the glue and the glass or doped finish. For a 1/6 scale model I think you will end up being little heavy but maybe manageable. It will fly faster than you might want.

In comparison 6 sheets of 4"x 36" (should be enough) 3/32" balsa is 4oz. You would be doubling the fuselage weight using ply. The AUW for the 1/6 scale Pfalz should normally be around 5-6 lbs, 7lbs at the most. Don't forget undercamber airfoils are better at light wingloading.

What do you plan to use for power? I think one of those RCV 90-4c linear engines would be nice. You could swing a scale diameter prop that should hall the extra weight as well as hide the engine in the cowl and need less balance weight in the nose.

You are planning on using all scale pull-pull controls, even for the ailerons?

ZZ

abufletcher

The copyright on the Simkin drawings is 2004. Basically, I think there are copied from the details of the Flight /Flugsport drawings but while those are clearly "sketches" the Simkin drawings have the sharp, straight look of technical drawings. The outlines look exactly the same.

The thing I don't like about the DIII is the embedded guns but I still haven't completely made up my mind. If I feel I have every documentation fo the DIII vs. DIIIa or prefer one of the DIII color schemes I might go that way.

I agree with you about the size of real grain -- way too large for our models. In fact, i once posted a question on that subject but didn't get any completely satisfying responses. The "mock" grain usually used is just straight streaks. I started wondering if I could make some wood grain decals in PS and apply to panels. Just a thought.

I'm going to have to do some materials testing before I can decide of the fuse construction method. The real question is whether a ply shell will be strong enough to allow me to use scale internal formers. Balsa formers would need to be much bigger. Personally I don't see how I could possibly make a scaled out Pfalz or any fully scale WWI biplane come out at 5 lbs. My eindecker was almost 9lbs. And yes that is a bit heavy. I'd be shooting more for about 9lbs on the Pfalz. I think laying the ply directly on the frame might have some serious problems. A scale frame is very light and would twist. The whole point is the the shell provides the bulk of the stregth and that relies of the strength of the individual halves. Anyway, that's what I'll try first even if it doesn't work out.


Haven't got as far as thinking about an engine. I would like to own one of the RCV 90s. But I might have to settle for something cheaper like an OS 70FS.

I'd like to go totally scale on the controls. I'll definitely use pull-pull on the rudder and elevator as I did on my EIII. I might just create the apperance of cable controls on the ailerons.

zoomzoooie

I've always liked the looks of the DIII with it's sharp point tail and lower wing. I think it is because it was my first plastic model I got for christmas when I was a kid. I like seeing the guns exposed to but you only notice that close up. It's just like the Alb DII with guns buried and only a tube extending out beside the engine. Looks strange.

Wow! 9 lbs for a 1/6 scale EIII? That is very heavy. Was it built from a kit or a
2x4? [X(] I had a sport biplane with a ply sided fuselage, heavy construction and an OS 61 FX in the nose and I had to add 8oz of lead to the tail and it came in at 8lbs. A 1/6 scale fabric covered WWI plane shouldn't come in at much more than 6 lbs even with a 4C engine. A Pfalz or Albatros with a sheeted fuselage will of course be a bit heavier. I have a VK 1/6 scale Fokker Dr1 and Nieuport 17 that are less than 6 lbs. Have you seen the way they are built. Very light but still strong construction that closely follows scale construction.

I think once you have your shells glued to the frame it will become very strong. I don't think you will need much for frame work. Maybe use light ply formers if your are leery. Once the flex factor is eliminated, the shell will become rigid.
Yes you're right it would be hard to lay up directly on the frame without setting it in a jig. But even then in a jig it wouldn't be easy since the plys spiral around. The molded shell method would be a better way to go then.

The Spievack plans show false aileron cables but I will use functional ones. I don't like seeing servo arms and push rods coming out even if they are under the wing. My 1/4 scale Halb and Alb DVa plans show scale aileron cable set ups. It's actually easy to do. The cable attaches/detaches at the servo in the fuselage and from the aileron control arms. They run thru small pulleys before they exit the lower wing to go to the aileron. IMO, I think if you spend all that time with scale details everything should be as scale as you can, or at least have the appearance.

ZZ

abufletcher

Since there'd be no room for a servo in a scale airfoil I guess I'll have to be using a cable system for the ailerons anyway. I haven't even begun to think that far ahead on this project! I built my EIII based of the "figure it out as you go" system.

In terms of weights, I'm not a very experienced builder and the EIII was definitely heavier than it should have been. On the plus side I was careful abuot where the weight was added and didn't have to add any weight at all to the nose for a proper balance.

I'm not overly obsessed with the DIIIa vs. DIII external guns thing but I do prefer the rounded lower-wing tips. It may just come down to preferred color scheme.

Trev

Don,
I think it would be possible to do up a light and scale frame of using 2mm ply formers and thin hardwood stringers. To get it strait and true you could align each former buy incoporating 'feet' that are fastened onto a base and later sawed off (prior to sheeting). Even with very thin stingers (providing there are enough) I think you'd see that such a construction would already be quite rigid.
As for the sheeting, I think I'd go about it by first sheeting with thin balsa strips (which minimize the danger of warping the structure) and then applying the ply layer in counter-diagonal fashion, similar to what Laaars and his dad did on their cosmic wind.
This would have the added advantage that you could sand small irregularities out of the balsa layer prior to laying on the 1/64th ply strips. Strength-wise this should hardly be inferior to a moulded 'double-ply' shell.....the production of which seems a daunting task to me! I'd imagine it could be a problem to get both halves completely identical, could result in a visible seam..

Btw, if I had a choice between the DIII and DIIIa, I'd probably go for the latter.....the larger tail surface should provide better in-flight stability

abufletcher

Here's a shot of the tail assembly on the Blue Max Pfalz DIII replica. A friend in NZ is taking photos of the Omaka Aerodrome airshow this week. It's the equivalent of Ol Rheinbeck.

Trev, I'd rather do the DIIIa but I need to find out if the drawings of the wings I have (DIII) are the same in terms of rib count and span. Ultimately I'll do the version that I can find the best info on. As purely a matter of preference, I'd rather do the DIIIa.

I'll have to think about the fuse construction. If I think of this more as a historical project I'll go with the authentic Wickelrumpf method. On the other hand, it might be more practical in terms of a flying model to sheet with balsa and then fake the wickelrumpf effect (which IS visible). As far as having a visible seam where the halves join, I imagine that this might also be visible on the original.

abufletcher

Note the laminations in the tail skid! I had been wondering how to get that shape out of a single piece of wood and no end up with weakness at the grain.

zoomzoooie

Trev, the "feet" you are talking about. Are they attached to the bottom of a full former? If so you will not be able to wrap the skin properly. They would work on half formers though.

So here's a way to go about doing it using tabs (feet) without using a mold and still making it in halves. Make your formers in vertical halves with about a 1/2" tab where the formers would join together. Mirror the other side so they are identical. The tabs will be used to fix the formers 90 degrees to a flat surface board marked with your former positions to keep everything from moving and keep it straight. On each side of the former tabs, put 1/2" square piece of scrap spruce, or other, to sandwich the formers. It would be best to place them on a block a few inches off the surface board to give you room to attach the plies to the ends. When they are all aligned and all is tacked firmly you can put the scale and/or added stringers in. Now you can start wrapping your skin. When your done, remove the tabs and glue the halves together. Now you have a scale warp free fuselage.

I was thinking about the balsa/ply combo too. You won't loose too much strength compared to ply/ply if you glass it. Since it sounds like you want the plies to show thru you won't be able to glass it. You will have to dope your covering on so you will loose strength there, so ply/ply would be best in this case. You could use balsa/balsa for the skin and glass the inside of each half before you glue them together and use doped fabric on the outside to give you the scale look and give you strength. The balsa will have to be thinker, maybe 1/16". Use ply in the cockpit area where you can see it. You can either lay on as a first layer in the cockpit area or add it to the inside after.

I'd like to see more pics if you get them.
I think I'll want a copy of your plans when they are done too.

ZZ

abufletcher

I'll need to decide what my primary goal is with the model. Am I'm doing a miniature replica which will "sorta" fly. Or making a good flying model that is as scale as first criterion (flying) will allow. The practical side of me says fake the ply. Just sheet the fuse with balsa and then fake the ply around the cockpit area. Heck I'm pretty sure I could even figure out a way to fake the apparance of the ply strips. Maybe "fake" is too strong a word. After al the real essence of a scale RC model is "smoke and mirrors." This is a long an honorable tradition.

The the dreamer in me wants to try something new -- maybe something no one has tried before. I sure won't be the first or last person to model a Pfalz DIII.

I'm think of building a solid male mold of the fuse using fuse former halves and maybe also sheeting and glassing it. BTW, I've never done either of these things before. Then I'll try my hand at doing a Wickelrumpf.

BTW, I have to say that I hate the idea of glassing the outside of a WWI model. Just doesn't seem right. I might go for glassing an inside surface but it seems like that would be really heavy. Mostly I suppose I'm just letting myself be guided by the idea that if it worked on the actual aircraft it ought to sorta work on a model. I know that's naive but...

abufletcher

Hmmm...here's an idea. What if I built a fuse (no scale interior at all just ply formers for strength) then sheeted with balsa and glassed. Here's the radical part. When I'm done I'd cut the thing in half to get my two R and L male molds for the Wickelrumpf! Sound crazy?

abufletcher

Just a little philosophizing...

For me the whole point of building WWI era aircraft models is that we can actually make them with something like the same construction techniques as the originals. And even use somewhat comparable materials. All that changes once aircraft moved to all metal construction. I love the looks of quite a few of the WWII birds but I just don't have a burning desire to model any of them. The detailing is all on the outside.

I guess I just prefer to do scale detailing from the inside out rather than the outside in.

lazyace

My Feedback: (126)

that sounds a little to much work for not you can't see it after it's coverd & painted don't you think ?

zoomzoooie

No one really know's what your airframe looks like but you. Making a good flying model can be done and still give the outer appearance of a truly scale airframe. Since the Pfalz fuselage was covered in silver dope and fabric, there is no reason not to be able to make a light functional structure that still shows scale details. Use balsa skins and don't glass at all. Instead use few more spruce stringers. The glue between the skins and the skins cross pattern will add a lot of strength. As well the doped fabric will tie it all together. Myself, I would follow the idea I said above to build the fuselage for a good flying model.

And on the other hand you want a true scale build... no reason not to do both

I was thinking about engine cooling for the RCV engine in the Plalz. There isn't much air flow into the cowl area. I looked at the isometric drawings and it shows the firewall as a half solid former. If this is accurate I wonder why it is like that. The ammo box covers the open area in front of the former but doesn't seal it. Maybe this was for warm airflow into the cockpit for heating, less the chance of fuel,oil and fire? This scale setup could be used to vent the air from your cowl for cooling airflow. You would need a filter screen, like a furnace filter or something, to keep the fuel and oil out of the cockpit. Place baffles on the sides below the dummy engine to direct airflow from the cowl engine opening over the RCV engine and out to the firewall opening.

ZZ

tommyp

My Feedback: (1)

Hi,
I just recently spotted this thread and thought I’d join in. I’ve been a fan of the Pfalz D.III & D.IIIa for many years and am happy to see it is getting some attention as a model subject. It seems to have been neglected all along for the most part.

I drew up plans for the 1/5 scale version, which appeared in the Feb. 1994 issue of Scale R/C Modeler. It was inspired by Alan Spievak’s 1/6 scale version which I’d seen in Flying Models magazine years earlier as a kid. My model was based on the Wylam drawings, with a correction made to the nose, as it was well-known by then that the shape was somewhat off. I use the Wylam drawings for documentation, combined with photographs of actual aircraft to show the shape of the nose and other deviations from the drawings. The model was originally built around 1991 and was finished in von der Marwitz colors (I used the Profile Publication on the Pfalz to document those colors). It was repainted a couple of years ago in Max Holtzem’s colors, and it is still flying.

Weight was originally around 13 lbs, and it flew great with an early OS 120 FS, (when the engine wasn’t throwing props). I added a pound or so refinishing and fixing things. A friend suggested adding a muffler and running pressure to the tank to get it to run more reliably, and that worked very well. Unfortunately, I lost some power in doing so. That, coupled with the extra weight has made the performance suffer somewhat. On a cool day it seems to be okay, but when it is hot, it isn’t as much fun to fly. I should probably pick up a new OS 120 Surpass, but it isn’t in the budget right now. The model might be considered a little heavy for its size. The fuselage is fully sheeted and I’ll be the first to admit that I used a lot of filler to make the lower wing fillets, which I thought were kind of tricky to make. It also has quite a bit of nose weight to compensate for the sheeted fuselage and fin.

It doesn’t utilize scale construction. I did that to make it easier to build. I also knew that if I went through all the extra effort to make the insides scale that the next time I would get to see all of that work would be seconds after the first major crash! I admire the guys who do all of the internal scale detail work, but for me, I prefer to use simplified construction and just get it to look fairly accurate on the outside wherever possible.

The airfoil shown on the plans was actually borrowed from Dave Platt’s Top-Flite S.E.5a. It was an undercambered airfoil and I had seen how well the T.F. S.E.5a flew, so in my mind at the time it was a safe bet. I’ve since taken the 1/5 scale plans and blown them up on a digital copy machine to ¼ scale. I switched to the scale airfoil, and the model is a great flier (I just need more practice with it). If anyone here builds the 1/5 scale version, you might consider blowing up a drawing of the scale airfoil to the same chords as shown on the plans, to replace the non-scale airfoil. That’s what I would do if I ever built another 1/5 scale version.

I also left out the washout…if I ever need to rebuild my lower wings, I’ll be sure to add that in, because it adds to the gracefulness of the design, and probably helps it to fly better too.

The ¼ scale version weighs around 22 pounds as I recall, and has a Moki 1.8 for power. The trickiest thing about the Pfalz is hiding the muffler. Again I opted to leave the muffler off, and wow…that Moki sounds awful without it! I plan to make a custom muffler for it this spring. It is finished in Berthold’s colors. I flew it at Top Gun one year with a heavy crosswind and it really performed well. It was rock steady in fly-bys, which surprised me. I think this one has the right combination of weight vs. power to fly in both calm and windy conditions.

One problem I had was that I made the model too nose heavy. If I got it going just a little too slow on my landing approach, I wasn’t able to flare it properly. I thought the nose heavy condition would just make it more stable, but I didn’t make the connection about the flaring problem until I flipped it over a dozen or so times. At least I proved it was a sturdy design! It seems to be better now that some of the weight has been removed.

The bigger model also has plug-in upper wing panels, which makes it easier to transport. Some of the construction was changed a little here and there, but overall, it is very similar to the 1/5 scale version. The center-section is sheeted and the aileron servo is hidden in the radiator on both models. I guess the cockpit cutout may well be the wrong shape, but it was done from the Wylam drawings and comes close to matching them.

I know that Arizona sells plans based on my 1/5 scale version, enlarged and reduced to ¼ scale and 1/6 scale respectively, but I don’t know if they have changed the construction at all. I haven’t seen the drawings.

Here are a few pictures if anyone is interested:
http://www.wwi-models.org/Images/Polapink/CP/index.html

Good Luck!
Tom P.

abufletcher

Tom, it's really great tohave a Pfalz expert like yourself could join us on this thread! I now have both your plans as well as the Spievak plans (and also the Wylam drawings). The photos of your gorgeous models on the WWI-models site are what first inspired me to try my hand at a Pfalz DIII. For the most part I'll be working off drawings (rather than plans) in the datafiles and just looking to the plans for practical ideas for solving construction problems.

I'm glad to hear that your model weighed in at 13lbs. Zoomzooie's estimate of 6-7 pounds was a bit frightening. I'm not sure I could ever built a totally scaled out 1/6 scale model for anywhere close to that. I'd be happy to come in at about 10-11lbs.

In so many ways I prefer the earlier WWI "bag-o-wires" aircraft where what you put inside really shows on the outside. With the Pfalz and Albatros (and any of the other semi-monocoque aircraft) we could probably mold the fuse out of fiberglass and no one would know the difference. But I'd know. I probably won't end up going with full scale construction on the fuse, but I'd like to try something that at least approximates the original construction techniques.

What is your experience flying the Pfalz? How does it compare with other WWI models you've flown? I was thinking of getting one of the Funaero DIII as a kind of "practice plane."

tommyp

My Feedback: (1)

Hi Abufletcher, and thanks very much for the kind words. I was very happy with the flying characteristics of both Pfalz models. Other than the nose heavy condition (caused simply by adding too much nose weight to the model), and unreliable engine runs (due to everything from using old fuel to not running back pressure to the tank) I've had no other problems. Now that my 1/5 scale version is a little heavier than it was when it was first built, and the engine is now muffled, its performance has suffered. Just keep it as light as you can and make sure you have power to spare when flying it and you will enjoy it.

I remember seeing a Special Models issue of WWI Aero many years ago where a 1/4 Scale Pfalz DIII or DIIIa was being built with what I believe was scale construction (I think Wally Batter was the builder)...I'm not sure if that was already mentioned here or not. In any case, the basic framework was built using formers and stringers. Small foam blocks were placed between each opening between the stringers and the formers and they were then carved to shape to give the fuselage its form. Strips of plywood were then applied first diagonally in one direction, and then a second layer of strips were applied in the opposing direction. I assume he did something to remove the foam afterwards, but I'd have to go dig out the article to find out for sure. It looked like a very nice job, but I don't know what became of the model. Let me know if you'd like a photocopy of the article.

It's funny you mentioned the fiberglass fuselage thought. I've been thinking about doing that for a few years now. I think it would be a good way for guys who don't want to go through the trouble of building an Albatros or Pfalz fuselage to have the chance to own and fly one (or the other...or both).

Happy Flying!

abufletcher

Tom, that's the first I've heard of the Wally Batter model. Sounds like an interesting approach to the fuse construction. I had even been thinking about carving a fuse out of foam and then glassing it and then using that as a mold for the Wickelrumph construction.

I'm sure there are a lot of Sunday flyers out there who would love to have a well-done fiberglass fuse for a Pfalz or Albatros. Personally, I'd hate the idea. The whole reason I model WWI stuff is that I like the fact that the materials we use are similar to the materials the original builders used. On the other hand, if fiberglass were around during WWI I'm pretty sure the folk at Pfalz would have experimented with its use! So maybe it's still in keeping with the spirit of the builders. WWII warbirds all about gluing stuff to an exterior. That's not nearly as much fun as "building a miniature aircraft."

What size engine would you recommend for a heavy-ish 1/6 scale model? I've thought about one of the RCV 90's but will probably end up with a regular 4-stroke. Would .71 be enough for a 10 lbs plane?

Also we'd love it if you could post some photos of your DIII(a)'s here! Construction photos would also be very welcome.

tommyp

My Feedback: (1)

I have a Sterling Fokker D.VII which is a little on the heavy side. It is 1/6 scale and is powered with an OS .90 FS engine. It seemed to be a pretty good combination. I'd always suggest going with more power than you think you'll need...you can always throttle back, but at least you'll have that reserve power in case you get into trouble and need it.

I'll try to post some pictures at some point. I just joined RC Universe so I haven't looked at how to post pictures yet and I need to scan some pictures too. Are there any construction pictures in particular that you are interested in?

Tom

zoomzoooie

I've been buzy with my website and haven't checked in for a while.
But Welcome aboard TommyP. Nice to have a veteran here.

It's funny that you posted a link for those pics. I was just thinking about them the other day and was wondering about who's kit or plans they were and how accurate they are. I planned on drawing up 1/4 scale plans, most likely based on Abufletcher 1/6 scale plans when they are done. He doesn't know that yet, hehe.
Right now I am slowly working on my Halb DII but when it's done I want to start on the Pfalz DIII or DIIIa in a smaller scale. I need to get a 1/4 scale plane done quickly by summer to display my rib stitch tape for various shows and meets I will be attending, so I think I will do a DH60 Gypsy Moth.

You mentioned 13lbs for a 1/5 scale Pfalz. I agree that is a bit heavy, but 1/5 scale plane is noticeably larger plane than 1/6 scale. I just read over Spievack's article and he states the prototype was 8lbs including 8oz of lead in the nose. He states that it should come in as light as 6,1/2lbs if you place your gear appropriately. I don't see any reference to glassing. He only states painting, so glassing would bring the weight back up but not that much, maybe back up to 8lbs. Use the lightles cloth. If you used doped fabric instead you should keep the strength up and the weight down.

I'd love to see any construction photos of your Plalz projects too

ZZ