PSS R4 Firecracker, Lancair and Tucano and Vortec's Zero Build-a-thon, - RC Groups
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Dec 06, 2009, 06:03 PM
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gavoss's Avatar
Build Log

PSS R4 Firecracker, Lancair and Tucano and Vortec's Zero Build-a-thon,

Actually it's going to be a Major How-to!

Props first: Carl Maas Sr did the Firecracker, TFLG (That Freeking Laird Guy, Brian Laird) and Carl Maas Jr did the Tucano. The Lancair is a product done by ISRDAN himself. Dan is currently making the kits and can be reached at

I've been asked by several to do a build thread. It's usually not my thing to do build threads because I'm a slow builder but many people over the past year have asked me how do I get things like a "short kit" built with little or no instructions. Since our slope season is pretty much over, I've decided to go ahead and build a couple, 4 actually, PSS models over the winter and document them here on RCG. I find it easier to build things as groups and think it saves time overall. That said, I'll build all of the tail feathers first, fill in the fuses with filler and spray them in primer and sheet all of the wings together. This means I only have to clean the spray gun once, pull out the vacuum bag stuff once etc.

There are others that have gone before me and done an outstanding job and in no way will this thread take away anything they've done. I don't claim to know everything. Maybe I can add something to the knowledge base.

First a bit of history about me: I've been modeling since 1969. I was 8 at the time and got involved in competitive Free Flight. Since there were a limited number of competitive kits available I learned to scratch build, or as some people call it, build by plans. At the age of 13 I took up RC soaring and with the help of the "Silent Few Soaring Society" I became competitive enough to place in every contest I flew with them, though that wasn't many contests. I pretty much gave up sports by the time I was 15 as I'd pretty much reached my max height and weight for the time and I was just too small for football. Instead, I devoted my time to building FF airplanes.

I worked at the local hobby shop, "Tips Hobby Shop" in Whittier CA. I actually had a sponsorship with them. We got all of our wood from Sig and I got first pick of everything that came in the door. I can tell "C" grain from "A" grain and know where to use which piece in construction and more importantly where not to use a piece. I guess I've built well over 200 models in the span of 40+ years. I turned 50 this year and enjoy modeling just as much as I did as a kid. I've flown just about every type of model from CL to tether cars, rockets, helicopters and more. I've built planes for customers as a form of minor income to help me sustain my addiction to flying but mostly I just build for myself because I enjoy the process.

Enough about me. Let's get on with building. The planes we'll be assembling are the Tucano 54, Firecracker, and Lancair from Dan at Flybyu and the Vortec model Zero. The kits from Dan include a fabulous fiberglass fuselage that can be laid up to meet your flying conditions. I always get the "standard" build which uses about 18 ounces worth of cloth total. Also, you get a set of blue foam cores. Again you can get non-stock airfoils but my slope is pretty small so I stick with the standard cores. The Vortec Zero fuse comes from Jeff Fukushima and it's a site to behold. Both of these men make great looking fuses. The Zero doesn't include cores.

The kits include a set of general instructions and printouts to make up the tail feathers. The Zero fuse comes w/o instructions but does include templates to make the tail feathers and no cores are included. We'll proceed like we don't have any information about any of these kits so you can see how we build when you've basically got nothing to start with. Here we go!

I always start on the tail feathers. I usually get my wood from Lone Star and order a bunch of it at once. It takes a fair number of sheets to make the tail feathers so plan on at least one sheet per tail feather. I usually order 10 each of the 3 and 4" wood. I've found through experience that Bass wood makes good LE's for wings and stabs. Instead of breaking, the Bass just dents. All of the kits use 3/16" balsa and bass in their make up. Notice in the photo that there is only 1/2 of a template for the stabs. I don't trust hand made drawings (in CAD you can just mirror an object and then it's exactly like the mirrored object) to be accurate. I use a machinests square to mark the center line and everything now is measured from the center line (CL). It's important that mirrored objects are exactly the same. When you make up the bass tips, make a pair and sand them together until they are exactly the same, then glue them in place.

First we'll draw out all of the tail pieces onto the balsa, cut them with a sharp razor blade, true them up with a sanding block and glue the parts together. I use both 3 and 4" wood, using the one that best fits the situation. For example the Tucano's tail is the largest so it was it was better to use 2 sections of 3" wide wood. If you can, make the stab and elevator one piece. This allows you to install the elevator joiner while the elevators are one piece and then you KNOW your elevator LE will be straight and align perfectly. The Lancair and R4 are done that way. To true up cut edges, place the part on top of another piece of wood or a wide ruler and allow 1/4" to overhang. Then use a 90 degree sanding block to sand the cut edge perfectly square.

I always cut the tail feathers full size out of balsa and then trim off the sections that the Bass will replace. This allows you the ability to use the balsa as the template for the Bass wood.

Finally, you'll notice the R4 fin is larger than the template. I went back through the archives of RCG and read Bill O's account of building the R4. In the final analysis Bill made the fin 1/2" longer in back. TFLG, one of slope soaring elite, recommended even a larger fin. I'm not a purest when it comes to PSS planes. The fuses aren't 100% scale to begin with so making the fin bigger in this case is only going to make it track better, so for flying's sake, I made the fin 1" wider than the original template showed.

The Lancair uses what is known as a "balanced elevator." That's what the small pieces of Bass are next to the stab. Balanced surfaces are used on full scale planes to make the stick have a lighter feel. Think of it as power steering for airplanes. For RC it's not needed but it does add to the scale appearance of the plane. Those of you who have thought ahead realize that there has to be some space between the stab and elevator to allow the balanced portion to function. That's why they aren't glued on yet. For spacing we'll use 1/64" shims to make sure there is a large enough gap. You can use 1/32" shims too but the closer the better.

From here, it's time to sand the parts level and smooth and sand the leading and trailing edges. I'll be back when I have more to write.

Last edited by gavoss; Feb 24, 2012 at 12:42 PM.
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Dec 06, 2009, 07:08 PM
BillO's Avatar
Hey George, nice thread! I always learn something from a new build, even if others have done it before. No tip is too small to pass on!

As for the Firecracker fin, you don't need to go any bigger than the extra 1/2" I put on there. In fact, after a crash, I cut off 1/4" so now my fin is only 1/4" wider than the plan. It still flies great, it's one of my favorite planes even after 2 years of flying and fixing it. It does great halfpipes and makes a beautiful, hands-off turn at the top...
Dec 06, 2009, 08:27 PM
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Joe Pierson's Avatar

Firecracker Build

Hi Guys
I like Yellow Airplanes So this will be a very good thread
Dec 06, 2009, 08:34 PM
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gavoss's Avatar
Thanks for the input Bill. I'll take a look at it when it's time to glue it on. If it looks too big I may cut it back. George
Dec 07, 2009, 10:37 AM
Mechanical gypsy
Good timing! Im just starting on the Vortech Corsair now, in fact I just bought the balsa to sheet the wings today.

Dec 07, 2009, 11:17 AM
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gavoss's Avatar
Last night after Bill made his comment I thought about about tail sizes. This would be something a novice with no instructions would have difficulty deciding on if he only had a full size 3-view. Typically PSS models have tails that are 10 and 15% the size of the wings. The fin is 10% and the stab is 15% of the wing area. There are a series of fairly technical calculations that go into those numbers, but they are general for PSS models. FF models, DLG and Thermal planes won't have those same percentages because of their fuse length. Basically, the longer the distance from the wing to the stab, the smaller the stab can be.

Bill, please remind us of your flying weight and wing span so I can make some comments about how mine will (possibly) be different.

Chris, I have a Vortec Corsair ready to 'glass, so I'm with ya! I'll take some photos.

Last edited by gavoss; Dec 07, 2009 at 11:33 AM.
Dec 07, 2009, 12:07 PM
BillO's Avatar
Mine weighs in at 49 oz and has a span of 48"...
Dec 07, 2009, 02:14 PM
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gavoss's Avatar
Thanks Bill. I'm guessing mine will have the same span give or take 2" and will be a little lighter due to the wing construction of 1/16" balsa over foam, then light fiberglass and Klass Kote paint. As of right now I'd expect my weight to be around 40 ounces with ballast capability. My slope isn't very big so we really have to watch wing loadings. Since Soar Utah only happens every other year it's not worth it to me to build a boomer.

More photos later today I hope. George
Dec 08, 2009, 09:48 PM
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gavoss's Avatar
After writing yesterdays bit my wife asked me to put a 6 plug outlet into one of the wall plugs. In an effort to try to screw a #8 bolt into a #6 hole, the plug came apart and I had to shut down the electricity in that part of the house so I could change the plug.

After changing the plug and installing the 6 outlet adapter we turned on the power and started working on the Christmas tree lights. I came back to my computer and my screen is black! Not black as in it's in hybernation, but black as in it ain't gonna work any more! So I got stuck having to spend $168 on a new monitor, which I like very much, but I didn't want to have to pay for at this time of the year! Needless to say, yesterday and even today ended up quite busy and I didn't get the photos I wanted. Hopefully I'll have them and some additional text tomorrow. George
Dec 09, 2009, 05:55 AM
Taranis Tyro...
MattyB's Avatar
Originally Posted by gavoss
Last night after Bill made his comment I thought about about tail sizes. This would be something a novice with no instructions would have difficulty deciding on if he only had a full size 3-view. Typically PSS models have tails that are 10 and 15% the size of the wings. The fin is 10% and the stab is 15% of the wing area. There are a series of fairly technical calculations that go into those numbers, but they are general for PSS models. FF models, DLG and Thermal planes won't have those same percentages because of their fuse length. Basically, the longer the distance from the wing to the stab, the smaller the stab can be.

From what I can gather tail volumes are a relatively complex subject, but this page has boiled the formulae down to some pretty simple approximations...

I'm not sure about the origin or validity of their "magic numbers" though!
Dec 09, 2009, 12:48 PM
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gavoss's Avatar
Thanks MattyB. The calculations I referred to are part of that web site.

I haven't brought this up yet but planned to, and that's the TLAR factor. TLAR stands for: That Looks About Right! The premise is if it looks right, it probably is. When DLG's became the norm, fuses got really long and tails got small. Through the help of some PhD.'s, the calculations for optimum tail sizes came about. Since we are talking about PSS models though, 3 views and plastic models are available to see what the full size model had.

One item the full size plane has that we don't is an internal combustion or jet engine to provide thrust. We use airspeed alone. We also fly much slower scale speed at times so having a slightly larger tail helps with directional stability. A 100% scale PSS model will fly, just not a well as one "optimised for the slope." Of course optimised for the slope means non-scale, but who called out the scale police anyway?

Thanks for bringing the approximation to our attention. George
Last edited by gavoss; Dec 15, 2009 at 09:44 AM.
Dec 09, 2009, 03:32 PM
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gavoss's Avatar
Sticks vs. sheets

You have a choice of buying sticks or sheet wood for things like LE and sub-trailing edges. All of my PSS planes us a bass wood LE on the wings and stabs for the reasons explained in the first post.

I know what you are thinking; after 40 years of modeling George has every tool on the market, including a table saw. That's true, I do have a table saw, a 10" Sears model. The problem with full size table saws is the blade kerf and the opening for the blade. Kerf is the portion of wood the blade removes to allow you to push the sheet forward. On a full size table saw the kerf is usually 1/8" or larger. There are special blades you can buy with smaller kerfs but they are expensive. I also have a Dremel Table saw but these are really difficult to find and cost as much or more than they did new. MicroMark sells a really nice one but it'll set you back three bills and then some!

After saying all of that, I usually cut my bass wood with a simple wood stripper. Bass wood is fairly soft actually and cutting it with the stripper is pretty easy. I cut about 1/2 way through on the first pass, reset the blade and complete the cut. This will save you money in the long run. I usually cut one sheet of 3/16" and strip the entire sheet for stab LE's

I only use 2 sizes of bass wood, 3/16" and 1/4". The 3/16" is obviously for the stabs and the 1/4" is for other uses like leading edges. If I need a 1" LE I use multiple sheets glued together. This cuts down on the amount of wood you need to have on hand.
Last edited by gavoss; Jan 03, 2010 at 09:28 PM.
Dec 10, 2009, 02:40 PM
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The attached photo shows 3 different airplanes and 3 different thoughts on tail size. The plane on the left is the Alfa FW190. The plane in the center is a TA152 which was a modified FW190. The one on the right is a PSS Hellcat that Carl Maas Jr. built and finished. As you can see, the Hellcat actually has the largest tail but it also has the shorest tail moment. Tail moment is the distance from the wing to tail. Like we said earlier, the longer the tail moment, the smaller the tail can be.

All of these planes fly well in their proper environment. Both the TA and Hellcat have thin airfoils and aren't exactly light for their size. You have to keep them moving or they will tip stall.

Even if I never fly the Hellcat again, I keep it as inspiration in finishing technique. Carl did an awesome detailing job on the plane. It's no hangar queen either. It was well used when I got it and I fly it fairly regularly myself.
Last edited by gavoss; Jan 03, 2010 at 09:37 PM.
Dec 14, 2009, 11:22 AM
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Not much has transpired in the last week obviously due to the Christmas Holiday. I hope you get what you want for Christmas. Now onto something soaring related!

I've read virtually every RC how-to book produced, mainly so I can become a better modeler. But the guys I really envy are guys like Dave Platt, Richard Jarel, and Jeff Foley to name a few. These gentlemen have or still do produce models for the movies. There is little room for mistakes and they must be fairly quick to get projects done in time.

For those that don't know me, I'm a disabled vet with a seriously bad back. This affords me lots of drugs for free. Unfortunately, all the medicine I take only dulls the pain and the morphine clouds my head. I'm not looking for sympathy here, just letting you know why it takes me so long to build. But by reading the how-to's, (I’ve even had some of my ideas in print) I learn to build faster w/o reducing quality. I’ve had 2 what I call “break-throughs” in my modeling life. One was at age 15 and the other about 20 years ago. In the simplest terms, I wouldn’t accept what I previously accepted as ‘good’. If a balsa piece wasn’t sanded to the exact angle, instead of using it and filling the gap with glue, I would simply correct the original piece or make another one. I realized that balsa wasn’t that expensive and it didn’t take that long to make a new piece and it looks so much better when all the parts fit perfectly!

Photo one shows a sanding tool I made out of hardwood. There used to be a similar one available on the market, but it would only handle 4” wide wood. Mine will handle 6” wide wood. The fence on the left hand side is 90’ to the sanding block and the slot the sanding block slides in. The sanding block is made in an “H” so you can use 2 different grits, one on each side, and I have a second block for 2 more grits. The open portion of the “H” in the sanding block is slightly wider than the center portion of the track it slides in. If you look really closely at the second photo, you’ll see the sandpaper can’t touch the base the wood sits on. This is what allows the sanding block to move freely and sand the material off. If the sanding block touches the base the wood is sitting on, it will sand the base along with the wood and you’ll eventually end up with the gap you should have started with. When you make the gap, consider the thickest piece of sandpaper you’ll use. 60 grit sandpaper is much thicker than 220 or 1200!

Next, you’ll see the triangle. It’s made out of bass wood, but plywood would work just as well. The screw holding it in place isn’t tight, allowing the triangle to rotate 360’. This will allow you to sand any angle you need and is what you use for non-90’ cuts.

Why am I telling you all of this? So you can make one of your own of course! I made mine with a table saw and dado blades but you can use piece wood if you don’t have access to a saw. I’ve made a couple of these for my friends and they love them. There are only a couple of critical dimensions. The fence has to be 90’ to the sanding block slot and the face of the sanding block needs to be vertical to the base. The amount of gap between the sander and the base can vary but should be about 1/16-3/32” wide. I chose hardwood so it would be stable. I didn’t seal the wood. I use 3M 77 to glue the sandpaper to the sanding block. The reason I made it to handle 6” wide wood is that’s what I use on all my PSS models. The roots of most PSS models is 9" but the foam is roughly 7" wide. This leaves me with one small triangle of sheeting at the root that I have to sand. Not having 3-4 joints saves about 2 hours worth of sanding on the wings overall!

Fuses next!
Last edited by gavoss; Dec 14, 2009 at 07:52 PM.
Dec 14, 2009, 12:13 PM
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Fuses and cores

Here are the fuses we'll be working with. The first photo is a full on shot of the Firecracker. You can see the excellent molding of the louvers at the front of the fuse. Of course these will make getting the appropriate lettering on, uh, interesting at least.

The second photo shows all 3 fuses together and their relative size to each other. It's easy to see why the Tucano (the one on the bottom) will be 54-60" wing span. I can honestly say that Dan does excellent glass work. Again, these are 'standard' builds with nothing special added or taken away. Dan will make them to your specs so if you want a heavy one he'll add cloth or if you want a real light one, leave some out or use lighter cloth. My conditions are rocky and the slope is fairly small so the standard build works for me. Most of the builds here on RCG for PSS models have used external linkage for the elevator and there just isn't much info out there on how to install internal linkages. That said, I'll use internal linkages where I can and explain how to do it.

Step #1 when dealing with any fiberglass product is to wash it inside and out with detergent and at least a rag, but preferrably a scotchbrite pad. Many fuse makers use PVA, (polyvinylalcohol) as part of the manufacturing process. It's light green in color and you can tell you have it on the fuse as soon as you put the fuse in water and start to run your hand over it because it feels slimy! This material helps the fuse to come out of the mold cleanly. In the mold, the PVA is over wax, so we need to clean any wax or PVA off of the fuse before we start doing anything else. Once the fuse has been washed and dried, I like to hit the inside with 80 grit sandpaper where anything will be mounted. This provides 'tooth' and allows better adhesion of the part to the fuse. Also, just before assembly, wipe the surface with Acetone to help adhesion. Arguably the best glue for things like servo trays is Zap-A-Dap-A-Goo or something similar. CA and Epoxy are brittle and the Zap-A-Dap-A-Goo will outlast them 100 to 1.

I'll cover this in more detail when we get to radio installation, but if possible, I try to install my elevator servo on its side so the motion of the servo is forward and backward and not side to side. This isn't always possible of course but it helps keep the linkage setup as free as possible without any binding. I also like to use captured ball links to keep friction down. The Pattern guys are serious about this stuff and they use ball bearing control horns and links! Next, I try to put the aileron servo in the center of the fuse so there isn't any offset on aileron control. I know what you are thinking, now we have 2 servos that have to be on the centerline of the fuse and you are right. This is why I said it can't be done on every plane. Just try to make your linkages as true as possible and as smooth as possible.

Most of the PSS planes use either Dow blue foam or Owens Corning pink foam. This foam is used moslty in housing construction as insulation. It's easy to cut your own but I just get mine as part of the short kit. I have a couple of fuses coming that won't have wings and maybe we can do a quick how-to on cutting foam wings. Anyway, the Lancair cores are in the middle and are the only ones of this batch that are 2 piece. You have a choice when ordering the kit of getting one piece or two piece cores and you can have the two piece cores with a straight trailing edge or a tapered. I got kit #3 and ordered the tapered TE. After looking at it I decided that it would be much easier to set up the ailerons if the TE was straight, so the next photos show how much I trimmed off of the core. This required me to sand the cores so the TE was all the same thickness.

The final photo shows the stock RG14 airfoil in the beds. This airfoil has proven to be one of the best for overall slope flying. Sometimes it's been modified so the last 2/3rds of the bottom are a straight line, or they've been thinned for really fast planes and large hills, but overall, the stock airfoil works great.

That's it for now. Hopfully what I've written so far has been of help to someone. If so, please let me know as it's what keeps me going! Happy holidays. George
Last edited by gavoss; Dec 14, 2009 at 12:21 PM.

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