I've recently finished a Stafford Birddog (72") and having seen Marutaka and Vailly Birddogs I've come to the conclusion nobody makes true scale Birddog kits or plans. The 3 view drawings that are prevalent in my research are wrong which is why, probably, all the models/plans available aren't true to the full scale aircraft's lines. Is anyone else out there wishing there was a truly scale Birddog, of any size, that could be competitve at the Master's level?

What do you see in the various kits and plans that is so far out of scale? I ask this because I have Vailly's plans for the 1/4 scale, and the kit cut by Precision; can't seem to get started on it for one reason or another, but it WILL get built.

I have about 150 detail photos of two extremely nice, recent restorations of L-19/0-1's, and I also have Minard Thompson's most excellent resource book, "The Lovable One-Niner" which has about 99.5% of everything you need in order to build a master scale model of this aircraft. After comparing the pictures and plans to the drawings and info in the book, I can't find anything so out of scale that a bit of the normal desire that a builder has to change things can't fix. There is a very nice version of the Vailly 'Dog in this month's MAN. Not enough pics of it to suit me, I'd like to see a complete article on just that plane.

Exterior: If you scan a good side view photo (full scale) and scan in Vailly's plans you'll see the tail isn't high enough relative to the main cabin and it's too thick throughout the fuselage cross sections. The Vailly flaps don't have the right angle at the fuse and there's too much wing dihedral. If you look at the fuselage where it transitions from the aft spar pickup bulkhead to the main tail cone, nobody's hit it right. They're not straight lines on the full scale Birddog so straight longerons aren't going to give you the true contours.

Interior: As previously mentioned, the fuse longerons are incorrectly placed and the cockpit kit can't hide that fact.

Okay, I'm picky but to be truly scale, an aircraft should look right from every angle, inside and out. Vailly's is nice but one couldn't take a photo of the best rendition and pass it off as the real deal because it's not "right". The best efforts of a scale modeler are for naught if the basic airframe doesn't have the correct lines and contours.

Here's what I'm talking about, re: longerons.

I pulled out my plans (Vailly) and compared the cross-sectional data in the book I have, plus compared with the view you posted, plus compared with the many photos I have and what's in the book. There does seem to be a difference, but nothing that can't be reworked if one really wanted. The straight longerons in the plans I'm sure are just considerations to structural integrity. After all, this is stick-and-glue, not aluminum-and rivet/weld. I can't find a specific dihedral angle given on the plans, although the plans are incorrect where they state the dihedral starts (a rib about 1/4 span out from the root). The full scale's dihedral starts at the wing root. I can't imagine dihedral being more than the full-scale, it's got a ton (2-1/2 degrees in the BirdDog book, 3 degrees in some Cessna references). Considerably more than most GA high wing planes. Mine will be honest to the full-scale, though, and I plan on some mods to the fuse anyway, so bringing the cross sections into line will naturally follow. Most of the models of the L-19 I've seen, including the Stafford kit, and probably all the ARF's, are built with too little dihedral.

The short blurb about the L-19 in this month's MAN mentioned that the builder had to relocate a former in order to make the scale door work correctly, so there are other differences as well as the longerons. I, too, like scale fidelity, but some considerations have to be made by the engineers/designers of these model plans to make them buildable by the majority of modellers. It's up to the true purist to change what they don't like, or just design their own.

You're starting to see the light. You can't make a silk purse from a sow's ear...it's easier to start with the right basic airframe to begin with. Some of the other items you'll have to change to bring the Vailly Birddog up to snuff are the landing gear. They look like football players legs on a ballerina. The Birddog has very elegant, slim legs, thank you. And the cowl...it ain't right. Your photos will tell you that. The full scale cowl only has a nose bowl. That's because the rest of the cowl is flat sheet, bent to shape. It's not like a 150 or 172 cowling at all.

And then there's the weight...unless you change you basic thought process from boatbuilding to airplane making...you'll always be building something that's heavy like a boat. In my book, 27 lbs. for a 8' wingspan aircraft is way over the limit for scale flying of this particular aircraft. As an officianado, (Which I appreciate you for), you know the Birddog is nothing short of spectacular in a high performance, STOL takeoff or landing. That's because it's a stressed skin airplane that weighs far less than any other Cessna with little cross section drag and lots of wing/power.

Why not build a truly, stressed skinned aircraft that's got similar weight/wing/power/drag ratios. My 5th scale Birddog will weigh in around 8 lbs. finished. 1/4 scale should come in around 12-15 lbs. Yeah! put a 120 nitro or 26cc gasser in the 1/5th scale and a 35-42cc gasser in the 1/4 scale for almost vertical performance. (Geee, like the "real" one!)

For stand-off scale, Vailly's and Ikon N'west are okay. (Ikon's are even worse when it comes to flying weight...kind of like old Nosen kits...glue all the blocks together and carve off what you don't want.) Marutaka's got a great kit but...it's stand-off scale, not a Master Modeler's foundation.

As I said, I consider you a comrade because we share a love for this airplane and I'm trying to help other modelers move into the next generation of truly scale airplanes that aren't like the loveable F-4's...rocks with big motors that CAN and DO fly.

I'll be doing a construction article for MAN so you'll see the proof of the pudding in progress.

Later

I'll look forward to the MAN build. The landing gear is another "compromise". Unless you want to have a custom made carbon fiber or spring steel landing gear, the chunkier aluminum is all that will stand up to any sort of decent life-span; I have considered it, but not beyond the initial thought that it might be a possibility. As far as the cowl goes, I have the fiberglass cowl sold by Vaillancourt, and except for the rounded front edge, there's not a compound curve anywhere on it. I was fairly impressed by the thickness and overall quality and scale fidelity. Of course, it doesn't have any "wavy" spots like all the full-scales I've seen, where "flat" just isn't, really; so I guess it's too good, especially for what I plan to build mine as, a Vietnam-era "Dog that's seen some action.

The span on the 1/4 scale is actually 9 feet (108 inches), and I fully expect mine to weigh in the 25 pound range. I'm putting a ZDZ-50NG in mine, to turn a scale 22" prop. Should fly fine, and with the flaps it has, STOL won't be any problem at that weight. I have an old Nosen trainer, very similar basic form, 96" wing and 22 pounds, with a US-41 and 20" prop on it. No flaps, but takeoff takes about 75 feet and it will climb at a 60 degree angle. I'm thinking my 'Dog will be at least that good, with another 20% wing area and 5 pounds heavier, but almost twice the power.

The full scale, depending on the model (A,B, or E) weighs a little more or a little less than a basic 170B, has the same wing and flaps; the gross weights are within a couple hundred pounds of each other, also dependent on model, and performance is also similar. So it isn't all that far ahead of some other GA craft, and the 170 will do it with 4 people in it. What gives the BirdDog more oomph is the extra 55 hp. Dang, I'm gettin' all pumped up to build this thing, all over again. Guess I'll have to clean up the shop[:@]

Not having ever had a Vailly cowl in my hands, I'll take your word for it concerning the compound curves. The cowling still isn't right, however. (see attachments) A picture's worth a thousand words...yes, that's a Vailly Birddog, right off their website. Notice how much it resembles the full scale aircraft - NOT! The model's tail cone upsweep is too little, the fin/rudder's is too big, the rear windows are too big, the fuse is too thick...picture tells the story.

The overweight problem...think about it...if the aircraft only weighed 12-15 lbs. the wing/power loading ratios would be around half of what a 27 lbs. airplane has (Basic Physics/Aeronautical Design 101). Sure, it'll fly but at what speed? A Birddog zipping around at twice it's scale speed doesn't look very scale and it's going to have twice the landing loads imposed on the mains, wing struts and engine mnts. Hence, they've got to be twice as stout, the support structure has to be twice as stout, etc. (Read: HEAVY!)

Your comments on the "real" aircraft's weights and performance...you may want to re-read that section. One thing that's clear to anyone with eyes, the L-19 has near 1/2 the fuselage cross section as the 170 and, on it's best day, right out of the shop, a 170 will never be considered a STOL aircraft. Not because of the power difference but, moreso, because of the lift/drag ratios. (An L-5 has far better STOL performance than a 170 because of the lift/drag ratio of the aircraft, not horsepower.)

As to the landing gear, one could easily fabricate the mains from double, soldered together, music wire (old school) and have main struts that actually do have spring. Aluminum, especially your higher grades, have a terrible memory modulus! Anyone who's had to rebend their aluminum gear after a hard landing knows that! After a number of "Ooops!" landings it bends on every landing unless you take it off and re-temper the aluminum. How many modelers know how to do that? It's a band-aid fix, at best.

Why compromise on looks when you're compromising on performance as well?

Picky, yes I am but if you're going to put the word "Scale" and not "Stand-off Scale" or "Almost Scale" in the description, it had better be that...a scale representation with which, from any angle, a photo could easily be mistaken for the "real" airplane. I think Vailly makes a fine kit which is easily built and satisfies most modelers' desires for a giant, almost scale, Birddog that you can run into a garage door with little fear of dinging it. Just don't try foisting it off as a "Scale" aircraft and telling me minor detail changes will make it so. A major redesign and rekitting, maybe, but no band-aids are going to make the Vailly Birddog a truly, scale aircraft.

If you're going to do it, do it right...do your best!

Hmmm...the more I look at them...doesn't this thread belong in Giant Scale where Monokote's cool?

Hey guys! I am getting one of the older (circa 2003) JSM L-19 kits and am not sure what engine to put in it. I do not want electric, but would like a nice, scale-like sound. Any suggestions? Thanks.

While you're correct that the 170 can not be considered a STOL, it's not due to the lift/drag ratio that the L-19 has an advantage. Cessna's own literature regarding the Model 305 speaks of the takeoff power available from the 0-470-11 or 0-470-15 engine, which is capable of 213 hp for takeoff, to quote: "This 213 hp available for takeoff provides unusually good short field performance under adverse conditions", meaning usually, max gross weight and a rough field with near obstacles at the departure end. When you compare the wing loading and power loading figures for the L-19 and 170, you'll see that the wing loading figures are virtually the same (within 0.5 lb), where the power loading is grossly in favor of the BirdDog, with over 3 lb/hp. advantage. Add the larger diameter prop (90 inches for the L-19 vs 72 for the 170) plus the fact that the fixed pitch props on the 'Dog were lower pitch than the 170's and that later models even had constant speed props, their acceleration and pulling power on takeoff gave them the distinct advantage to get off the ground and climb out more quickly. Drag difference between the models at speeds of 50-60 mph would have to be considered negligible, IMO.


If you want to compare the L-5, it has a max gross wt almost the same as the 170 (2250 vs 2200 lb) with less wing area and a better power loading by 1 lb/hp. but the airfoil of the L-5 was a flat-bottom NACA 4412 with leading edge slats. It could out-lift the semisymmetric wing of the 170/L-19 (NACA 2412), which gave it its STOL capability, which is not quite as good as the L-19's; again, I believe, due to the superior power-to-weight of the BirdDog.

It's really all academic; I haven't yet been able to con myself a ride in the closest local BirdDog, but I have seen him put it through its paces, and it is a sight.

A 91 four stroke is what you want. If you mount it inverted you can hide most of it but you'd be well advised to put an on-board glow lighter for flame-out insurance. 4 strokes are more reliable but they still quit. The model comes out quite tail heavy. My first suggestion to you would be to redesign all the tail surfaces. Stick and sheet would be substantially lighter than the solid surfaces indicated. Also, plan on putting your rudder/elev. servos under where the pilot would sit. Adding weight to an airplane to balance it is a sin...I had to put a Harry Higley Heavy Hub on mine to get it balanced, without said servos installed. I'll send you some drawings if you'd like.

Thought I'd attach some pics of JSM Birddog finished.

I have an OS 70 4 stroke on my Stafford L-19. It is a perfect combination for the plane. I fly it around at about 1/3rd power. I am scratch building a second one as we speak. I was wondering where themadmax got his documentation for his color scheme on his plane? Thanks Dave

Max-- That's a very nice lookin' 'Dog. I like the camo scheme, the one thing I hated about most of the scale paint jobs is how blah they are, dirty ol' O.D., or the AF gray. I'm not sure how I want to do mine yet. I want it to be historically accurate, and competing dictates doing a specific bird, but on a couple of other scale builds I did, I incorporated features of several different planes, sort of made the model representative of the type, rather than a specific plane. I don't think I'm all that interested in scale competition, but a couple of my flying buddies want me to at least try fun scale, or even try the beginner level, whatever it's called, at Mint Julep one year. It sure won't be done by the next one, though.

I have pictures of a couple of L-19's in a sort of tiger stripe camo, they look pretty cool. Camo patterns were not very common, and were unofficial. USAF tried a camo pattern for a very short while, but abandoned it because the fast-movers couldn't see the FAC down in the treetops. They painted a bright orange stripe from wingtip to wingtip on top of the wing,and one on the top of the fuse behind the cabin. It didn't help, and the camo was eventually abandoned altogether. I still like it though, and ought to make it easier to see (the model, that is)

OK you scale buffs, need some help here. The leading edge of the stabilizer, fin, and rudder have, full scale, has some sort of aluminum wrap around it and extending several inches toward the center of the flying surface. How would you simulate this on a 1/4 scale Vailley Birddog. Mine is ready for primer, wish I had seen this thread soon enough to help myself with a truer scale model. Hey guys please help with my problem? Thanks. Chic

Hey,
Glad to see you're making the effort! "If you're going to do it, do it right, do your best!"

Preparation: The fin's leading edge at the dorsal is actually sharp up to where it meets the forward spar of the fin. From there up, it's rounded. Shape your leading edges accordingly. The outboard leading edges of the stab are round.

One could hammer a piece of aluminum to the shapes or use plastic. I've done both but for the uninitiated to metalsmithing, plastic's the easiest. Tape a piece of .010" ABS over the plan and draw a side view outline of the leading edge allowing a couple of inches past your desired part. You're going to be stretching the material from this direction so allow lots of gripping room. Determine where the material would come back to and draw a line there. Cut out the aft edge of your piece and tape it on the aircraft. Once you're happy with it, cut two just like this with scissors. (Bigger the Better) DO NOT cut the leading edge, yet.

Tape the piece along the aft edges and run a bead of Super Glue along that edge removing the tape as you go. Don't try to bend it over to the leading edge at this point. Now take out your heat gun and experiment on some of the excess to determine how much heat's enough.

You're working a compound curve wherein the material has to change shape and the more area of the material you heat, the more uniformly it will change shape. Apply the heat and, pulling you'll be able to get it to conform to the shape, to a point and it may be half-way, it may be less, but you're going to fill the difference with spot putty. Inside curves require shrinkage, outside curves require stretching. Plastic when heated naturally shrinks so you just need guide it. Once you've got it formed as far as possible take a very sharp exacto and carefully trim off the excess at the centerline of the leading edge or thereabouts. Be careful on this cut as it's a dangerous one...better way to cut this is with a Dremel tool. Tape it on the leading edge and wick Superglue into the joint.

Now turn the part over and glue the other side. Fill the very leading edge, 400 grit sand and you've got a leading edge that's as good as it gets.

With my 1/5th scale Birddog the plans include exactly scale panel lines, rivets/spacing/screws/Dzus fasteners, access panels, the whole enchilada! (Why Guess!?) I've got a 1/5th Scale Beaver that's ditto.

If anyone's interested in building a truly scale Birddog or Beaver contact me: [email protected]

I applaud your efforts. If you're trying you're doing a lot more than most.

Max - Thanks for the photos; What covering did you use on yours? It looks like probably coverite or solartex. And did you use latex paint for the camo design? Also, thanks for the CG info. I'll definitely try to get as much weight toward the front, as I am leaning toward using a Saito FA-72 in mine.

Cool, competition brings out the best in all of us.

Attached is my doc. pics for the JSM Birddog. It's flying today so, obviously, documentation score: "10".

This Birddog was never destined for scale competition...it's just an exercise in finishing so I took the liberty of leaving off the orange. It looks so much better without the "SEE ME" orange.

Please keep us posted on your 15lb 1/4 scale birddog . I would be very interested in the weight of just the airframe less all servos engine batterys etc..

Max - couple of questions. Do you what issue of MAN your article will be in? Also, do you have dimensions for the landing gear. I would like to model them in SolidWorks then do some FEA on them to determine best material to use for weight & proper spring.

Thanks

Hi all,

Here's mine I did a few years back. It is an ARF with extreme makeover. DP

http://www.rcuniverse.com/forum/m_25..._1/key_/tm.htm

Hi there,
Just reading the posts on the L19 and in particular the weight of the 1/4 scale one. I have the Vailly 1/4 scale Bird Dog and its weight came out at exactly 25 lbs.

I regard myself as a very light builder, but I just don't see where I could have saved 10lb ! .However the 'Dog , at this weight, is a great flying plane. A 15 lb, 1/4 scale, Bird Dog would be such a handfull in anything more than a very slight breeze due to it's very low wing loading. Don't know about you guys but all we seem to get here in the UK is wind, wind and more wind.

Most designers sacrifice true scale for everyday ease of assembly and flyability. But I will be following this with interest.


Good luck

I tend to agree. The weight of the wood alone in my 1/4 Vailly Dog is 10-1/2 pounds (I piled it all on a scale). So, add the engine, cowl, electrics, landing gear, glue, cover, paint and hardware and only gain 4-1/2 pounds? The covering and paint alone on my 1/5 WACO weighs 4-1/2 pounds.

What you said about sacrificing true scale for flyability is true; sometimes it makes for an easier build, but sometimes is critical for control. I had some questions regarding my plans, so I e-mailed Roy Vaillancourt the other day. I got a reply in less than 6 hours. One of my questions was what in particular had been modified from true scale on these plans; his reply was this:

1- the area at the rear portion of the cabin above the rear side windows, at the wing root. The full scale has a "jog", or angle, and this was changed to make a straight line wing root, easier for the average builder. He also commented that few people change it, and judges rarely catch it. I think it looks ....fat... and I have worked about half of today revising the plans and recutting fuse former #4 to bring it back to scale. I will modify the wing root to fit when I build the wings. It is a fairly simple fix.
2-Landing gear is thicker in material cross-section and wider in the side view. This is because of the material used and the strength needed. Full scale gear is spring steel, while the model gear is aluminum.
3-Horizontal stabilizer incidence is zero to +1 on the model "The scale angle just doesn't work for the model. Don't even think about fixing this one or you'll only fly it once" to put it in Roy's words. The scale incidence is about -2 degrees

He said that everything else was "good", meaning very scale.

Marcol, I'd like to see some pix of your BirdDog. What do you have pulling it around? I have a ZDZ-50NG thatI bought specifically to use, but after measuring, find that the spark plug cap will need a clearance hole in the cowl bottom, and I don't want to do it. I have found a 50cc twin that will fit in the cowl without cuts, thinking hard about getting it (LS50 twin, from LS Pro engines). It weighs only a couple of ounces more than the ZDZ single.

In answer to a few questions.

It's powered by a Roto 50 Twin gas engine

Weight is 25 lbs exactly.

It was finished in glass cloth and epoxy resin

Painted using cellulose paint mixed by my local car body repair centre.

Uses J.R. pcm radio with a mix of HiTec and Futaba digital servos.

The only modifications I made to the plan was to put the 2 elevator servos at the back, under the tail, rather than use push rods.

And I installed a working landing light in the wing leading edge.

Marcol--I'm such an idiot. I totally forgot you had posted these pics before, and I commented that I thought it looked like a Roto engine. Damn nice BirdDog, The "toothy grin" is a great touch. One of the planes I'm thinking of modeling has something similar.

The working landing light is another detail I'll build in. What did you use? While I was poring over the plans, I happened to think that the size of the lights looked close to the reflector of a AA size Mini Maglight flashlight. So..... I took one apart, and guess what? It is such a perfect fit you'd think it was made special for the plane. I also used one for the landing light on my Super Decathlon's cowl (goes just under the prop hub). It was one of the few salvageable pieces left of the cowl when I tried to take the shortcut to China

Notice that the BidDog pic is a mirror image (reversed) print. The landing light is on the wrong wing