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Golden Oldie Scratch Build

#21
I was wondering how Oratex compared to Sig Koverall, which is a plain woven polyester cloth that would probably distort or crush this wing during shrinking. Moneykote would be fine, but...I need a Saito engine mount and some Williams Bros Vintage Wheels, so that’s why I’m thinking laminating film on this one.

Anybody ordered any wood lately? I just realized I have no 3/16 square spruce/bass and no 1/16” ply. Figured I’d restock the balsa while I was at it, so I’m looking for a vendor.
 

speedbirdted

Legendary member
#22
I was wondering how Oratex compared to Sig Koverall, which is a plain woven polyester cloth that would probably distort or crush this wing during shrinking. Moneykote would be fine, but...I need a Saito engine mount and some Williams Bros Vintage Wheels, so that’s why I’m thinking laminating film on this one.

Anybody ordered any wood lately? I just realized I have no 3/16 square spruce/bass and no 1/16” ply. Figured I’d restock the balsa while I was at it, so I’m looking for a vendor.
I doubt this wing would have much of a problem with the shrinkage of fabric. I've seen lighter wings covered in it. Just be careful of how much shrinkage you're putting into each area of the wing; try to keep it consistent without adding too much. I've heard the shrinkage of fabrics is less than that of plastic films, but my level of expertise in the realm of fabric materials is not exceedingly extensive. My main concern would be the additional weight, but I wouldn't worry about it too much.

Sig Koverall is similar to Oratex, except it comes with no adhesive and is invariably unpainted while Oratex can be had pre-painted. The adhesive is brushed on separately; you can use something like Polytak, or the stuff Sig themselves sell. This is advantageous as you can very easily control when the covering will stick down. A lot of the time with stuff like Monokote, if you have to shrink down areas of the covering in an open fuselage bay with an iron, you can end up sticking the covering down where it shouldn't be stuck to anything by accident.

I buy from here a lot. It's expensive but nice because you can specify whether you want A, B or C grain and density. A lot of the time with other companies it's a crap shoot.
 

speedbirdted

Legendary member
#23
Something I neglected to mention; Concerning motor mounts. 4 strokes love to vibrate! Enough so that electronics can be damaged and screws can start to work themselves loose from all parts of the airframe if no measure is taken to counteract it. It'll also make your reciever batteries last a surprising amount longer - each pulse of vibration getting to the servo means the servo has to work that little bit harder to maintain the position the reciever tells it to be in. Something like this may seem pricey, but it is worth every cent. Personally I don't even like the radial-type mounts - I much prefer the ones with separate halves as in the event that they need to be adjusted in width there's no need to buy a whole other mount.

If you use plastic mounts, you can actually sometimes get away with no extra insulation. Some naturally have enough flexibility in them to absorb a suitable degree of engine vibration. An example of this is the setup I have on my Senior Kadet. It has a Saito 91 which provides an irresponsible amount of power and it actually has enough torque that I can see the mount flexing a little bit when it's throttled up. That's a good thing though, as these are vibrations that don't get to the airframe. It passes my lipstick tube test with flying colors (take a tube of lipstick or chapstick or whatever, set it so it stands upright on the cap because it's usually a little rounded, put it on some area of the airplane that's not in the prop wash, then throttle the engine through its entire RPM range, and if the tube doesn't fall over that's a pass)

Another thing to note, is lock washers and locknuts exist, and you should use them! Some people will drill through the mounts that come solid and then tap them without adding any other nuts or washers and this is such a stupid idea on so many levels I don't know why anyone does this. Here I actually have both locknuts and lock washers installed, just to be extra safe I guess...

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#24
I've covered a few planes in Koverall, one of them back when I was a kid which was a 1/2A design that had no business with such a heavy covering on it...I don't think the wing distorted when I was heat shrinking the cloth, but after a few weeks the butyrate dope had its way and turned it into a pretzel! These wings really remind me of that. I think you'd have to be a little more careful than normal, but it would probably work out. No matter, I found the Oratex on Balsa USA and it looks a lot like a prepregnated Koverall. In fact, their Planetex is probably very similar to Koverall, or even the "non-certified" <3 oz/yard polyester/dacron cloth covering materials available from Wick's or Aircraft Spruce. At $65 for a 15 foot roll for the Oratex, it's actually priced very attractively for what it is, especially if I'm correct in understanding that the weave is already sealed. (That sounds like what Speedbird is saying.) Very interesting! I might actually keep that option in my mental list of possibilities for this project, even though it's not a scale model of anything and won't necessarily benefit from having a "scale" textile finish.

Speedbird, I'll take your comments regarding engine mounts under advisement. The Saito 50 on my Cloud Dancer seems like a smooth running little unit, and I really like the metal Saito mount. It is bolted to the firewall via blind T-nuts and lock washers and then thinned epoxy was brushed into the fuel tank compartment, which seeped into the threads. I actually tried to remove the mount after a dozen flights and that was *not* happening. The bolts that secure the engine to the mount, on the other hand, I check frequently, and are often found to be a half turn loose or more! Do you recommend any particular 2-piece nylon mount? I was thinking of the Great Planes adjustable mounts I used to get for 2-strokes but that doesn't look like what's in your picture.

I don't know how I got this far in life without discovering Specialized Balsa. I think I'm going to be putting in a large order with them.

I appreciate the comments! I've moved on to framing up the fuselage, and will be performing a photo dump this upcoming weekend.
 
#25
Build Update

Both wings have quite a bit left to do before they’re ready for cover. I still need to rig up the lower wing’s aileron pushrods and bellcranks, install the cabane and strut attach points, and finish sanding and shaping. Here’s a picture of them sitting one on top of the other to assure me that things will be lining up okay:
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I printed the fuselage formers full-size on cardstock and spliced together a part of the fuselage to get a template for the sides and doublers:
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I cut out the 3/16” balsa fuselage sides, and then trimmed the template to the markers indicating the 1/16” plywood doubler, and cut those out. To laminate the doublers to the balsa sides, I elected to squeegee on a *very thin* layer of 30 minute epoxy. During the same operation, I attached the top 3/16” square longerons. I cleaned up any squeeze-out with a rag soaked in denatured alcohol. In this picture, the doublers are on the bottom, out of sight:
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Then, I assigned the subject some heavy reading and left it for the epoxy to cure: (A sheet of wax paper, topped with a piece of glass, is used to spread the load.)
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Fred Reese calls for 3/16” square spruce for the fuselage sticks, and suggests 1/4” square balsa as an alternative. I remember when spruce was readily available, but it seems bass wood has become the commonly accepted alternative. I was fresh out of 3/16 bass, and Hobby Lobby wanted $5 for 5 sticks that were 24” long. I noticed they had a 4”x24” sheet of it for the same price, so I bought it with a 40% off coupon and ripped more than enough sticks on the bandsaw, and scarfed the two pieces I needed that were 32” long. Anyway, I framed up one side:
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And then I built the other side right on top of the first one:
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The designer’s build article instructed me to glue the cowl cheeks on next, shimming the nose end off the bench 3/4” to account for the specified 2” spinner. I was sure I could come up with a better way, but in the end I went along with it. I decided to use epoxy because this area will undoubtedly be subjected to a lot of glow fuel and exhaust. First, I cut and shaped the cheeks. I gave the firewall edge a 10° bevel for a halfway decent joint. (I came up with that angle by test fitting the butt-joint and using a protractor.)

Then, I applied a piece of cellophane tape along the butt joint:
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I folded the tape back along the joint’s edge, lined up the cheek, and pressed it on:
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Then, I attacked it as if I were edge-gluing sheet balsa, which I guess I was. The tape held the joints together tightly while preventing squeeze-out onto the bench top, while I lightly weighted the sides and shimmed up the nose ends. I wiped away excess epoxy because this is where the firewall is going, and sanding epoxy off in this area later would be a real chore.
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I epoxied the rear bulkhead to one side:
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I was preparing to glue the firewall on when I realized I would rather have the engine mount attached now, or at least have all the necessary holes drilled for the mount, fuel lines, and throttle cable. So, I stopped there until I round up an engine mount and a fuel tank. It’s just going to be too tricky to drill those holes with those cowl cheeks already glued on.
 
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speedbirdted

Legendary member
#26
Wings are looking good. About covering again, if you want to use something to be finished with dope, use nitrate rather than butyrate. Butyrate shrinks very slowly over a long period of time; nitrate will stop shrinking after a day or two. Just make sure to not light it on fire before it dries, but this goes for everything. I'm not sure if Oratex is sealed against fuel from the get go - I know the natural stuff isn't but I'm not sure about the pre-painted stuff. Most guys I know that use it end up sealing it with something anyway, regardless if it's pre-painted or not, and I would recommend doing this, as fuel and exhaust goop can sometimes creep under the seams in the covering which a sealant will stop.

True, it's not a scale airplane, so a fabric covering isn't really required. But it's definitely got that old rag-and-tube look to it from the plans at least. This is just me but I also much prefer a slightly more matte fabric-like texture and appearance to airplanes (and it's somewhat functional too - less shine means less sunlight glare!)

I don't remember exactly who made the mounts the Kadet has. I bought them many years ago at a swap meet, they came in a Sullivan box but as far as I know they don't make that kind of mount so it must be someone else. Great Planes used to make a really nice sliding two-piece mount that I have used on probably 6 or 7 airplanes, the nice part about it being it was made from two interlocking halves which meant that each half of the mount was secured at four points instead of just the two normally. I have a sub-hobby of hoarding them because they're no longer made. Some people sell clones of them on ebay, which seem okay material wise but the fit isn't as nice.
 
#27
I have a GP adjustable mount here, but it’s too bulky to fit. A Saito mount ought to fit, but I agree a glass/nylon mount would be ideal. I found a Dave Brown 4045L mount at Grave’s RC, so I ordered it. Hopefully it will have a similar footprint.
 
#28
it’s been several months now, but a recent catastrophe has left me without a glow-powered sport plane. My Cloud Dancer was obliterated when the receiver battery became faulty:
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So now I’m motivated to finish this project and get her flying before this season ends.

When I last posted, I was waiting on a nylon mount for the Saito from Graves RC, but it did not fit. So, I resorted to fabricating one from hardwood blocks and ply:
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I tacked the nose ring on to help me position the engine and mount:
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Then, I screwed and glued the mount to the firewall. I gave the whole thing a coat of epoxy thinned with denatured alcohol, and glued the firewall into the fuselage.
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I don’t think that last picture actually shows the mount/firewall/fuse fully assembled. It looks like a tentative mock-up. But you get the idea.

I’m actually much farther along than this. It would appear that most of the sanding on the wings is complete, and the fuselage framing is finished except for the sheeting on the nose and cowl. I will check back later this week with more pictures. I’m hoping to have it on its gear and ready for “bare bones” pictures within 14 days.
Edit: it’s to its
 
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#29
Okay, fourteen days came and went more than twice. From here on out, I’m not printing my time goals.

I wanted to get the landing gear mounted, but before I could glue on the chin plate, I had to drill and mount the lower wing. Here I have a couple of yardsticks clipped to the top longeron, and a fairly straight dowel clipped to the wing. I’m trying to get the flat bottom of the wing somewhere close to 0° incidence to the longeron.
A5103369-BE0C-44E9-9863-DD5ACD54B205.jpeg


It bears mentioning that before I took the above picture, I had progressed quite a bit in aligning and drilling the top wing to be mounted where the lower wing is supposed to go! Future pictures may betray the now cut-off front dowels in the leading edge. Anyway, here’s a shot of the lower wing in place:
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Then, I glued in the ply landing gear doublers, the chin-plate, and started mocking up the wire landing gear. There’s one of my 3D-printed wheels. I’m still in development on that. I’ve succeeded in achieving the same weight as the Williams Bros wheels of the same diameter, but I’m still working on getting the TPU tire a little squishier:
F49241E3-BA53-49B5-8E10-6A46678AF245.jpeg



I forgot to take any photos of fabricating the upper wing cabanes. Hopefully when I make the struts I’ll remember, but I’m basically following the designer’s plan, except the “clips” shown on the plan are .030 brass instead of aluminum, because that’s what I had on hand. Once I had the cabanes made, I installed the wings on the fuselage, clamping the cabanes so I could make adjustments:
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Once I was satisfied the wings were parallel, I penciled around them for reference marks, drilled through the fuselage and cabanes, and jammed kabob skewers through the holes:
BA7FDF4B-B745-4D5C-BE31-DEDED46EDE7C.jpeg


Then, I disassembled everything. I finished shaping the front cabanes, and epoxied them in, using the kabob skewers and reference marks to hopefully put them in the same position as when I was eyeballing the wing alignment:
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Once the epoxy set, I cut the skewers off flush with the sides of the fuselage.
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Before I mount the rear cabanes, I’d like to add the sheeting that goes from F-7 to F-4. Then I can cut the slots for them and glue them in. Currently, I have edge-glued some 3/32”, wet it, and wrapped it around a round container so it will be somewhat pre-formed. Hopefully soon I can show you some more progress.

Until then!
 
#30
This one brought back some fond memories. Many years ago I built a Golden Oldie from plans. Coverite made one version called Antique; it was somewhat see through. William Brothers Vintage Wheels. And I believe that it was a Saito 4 stroke. Wonderful flying model and not hard to look at. At one point several years ago I went from balsa models to foam board. See tips and resources for the foam board RC modelers on my blog at: https://foamboardflyers.com/ Thanks so much for posting these pics!

golden oldie - 1.jpeg
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#32
Wow, I don’t think mine is going to turn out that nice! Thanks for the pics, they are inspirational and will help me immensely as I continue with the build.
The pictures show that you are doing an excellent job of building; looks like you are keeping things square. Just curious, where did you get those orange screw clamps? They look like a perfect solution to some clamping problems. I'm looking forward to seeing the model covered and trimmed. I bet it will be a beauty!