Scale Build-Off Sig Quarter Scale Piper Cub

[ScottyWarpNine]

I'm just gonna put this here. I'm about half way done building a Sig quarter scale cub. I have built up the fuselage and most of one wing panel so far.

The fuselage and tail s just about ready for covering. I will be using Dacron to give the finish a more realistic cloth texture.

Power system is very similar to what I am using in the C-47. I do not recall the motor dimensions off the top of my head, but it is the same size as on the C-47, different KV. 100A ESC, 10,000mAh 6S.

I have half built floats too

You may be thinking, Scotty, you're absolutely nuts. Surely you can't expect to finish your 1:8 scale C-47 and this 1:4 scale cub in time for the end of the contest.

I do intend to, and don't call me Shirley.

 

[ScottyWarpNine]

Well, this build log begins with applying covering on the fuselage.





I've found that the only really difficult part about building a cub is this complex little "fin fillet" curve between the front of the vertical stabilizer and the fuselage. As you can see by the fragments of yellow film, I attempted it with Monokote, but I couldn't get it right. I decided to drop film altogether and use fabric, which is where I am at now.

I am using the thinnest Dacron cloth available from aircraftspruce.com, and I am using an adhesive called Poly-Tak to stick it to the balsa frame. Poly-Tak gets brushed onto the wood and is allowed to dry. Then the fabric is draped over the frame and a covering iron activates the adhesive and bonds the cloth to the wood.

As you can see, I think I got the fillet pretty good. The cloth, being able to flex and twist easier than film, fits right around and conforms to the shape I want it to. The cloth also provides a much more realistic look, since real Cubs aren't shiny like a covering film.

I have one wing almost built up, so once that is done I will post up some more pictures. Just thought I should probably make an update.

 

[ScottyWarpNine]

Well, this build log begins with applying covering on the fuselage.

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I've found that the only really difficult part about building a cub is this complex little "fin fillet" curve between the front of the vertical stabilizer and the fuselage. As you can see by the fragments of yellow film, I attempted it with Monokote, but I couldn't get it right. I decided to drop film altogether and use fabric, which is where I am at now.

I am using the thinnest Dacron cloth available from aircraftspruce.com, and I am using an adhesive called Poly-Tak to stick it to the balsa frame. Poly-Tak gets brushed onto the wood and is allowed to dry. Then the fabric is draped over the frame and a covering iron activates the adhesive and bonds the cloth to the wood.

As you can see, I think I got the fillet pretty good. The cloth, being able to flex and twist easier than film, fits right around and conforms to the shape I want it to. The cloth also provides a much more realistic look, since real Cubs aren't shiny like a covering film.

I have one wing almost built up, so once that is done I will post up some more pictures. Just thought I should probably make an update.

 

[Tench745]

Dunno if you've come across it before, but Bob Benjamin has a blog of all the how-to articles he's written for Fly RC. He's got a whole build of a Stinson SR-9 he covered in polyfiber. It's got a few tips, covering starts here:

http://rcmodel.com/2013/07/building-the-stinson-sr-9-21/

 

[earthsciteach]

The fabric will definitely look better than monokote. I had to build a new vert stab for my E-flite Super Cub (bought it new, but damaged). that fillet was tricky for sure! I ironed the Ultracoat down to the areas on the fuse and the vert stab where it contacts the structure. Then, I shrunk the heck out of the slack with a heat gun. It tightened up nicely, but was really a pain!

 

[The-One-Who-Never-Crashes]

Wow! That's so beautiful! Be sure to keep us posted as you get closer to finishing it

 

[Joker 53150]

I'm looking forward to seeing this come together. I just got a similar Cub, the SIG 1/4 scale J-3 with floats from a swap meet. The covering is dated and will eventually be replaced after I fly it for a while.

 

[ScottyWarpNine]

I'm looking forward to seeing this come together. I just got a similar Cub, the SIG 1/4 scale J-3 with floats from a swap meet. The covering is dated and will eventually be replaced after I fly it for a while.

I have the floats as well. The floats were sold as a separate kit. I have my floats already built up and ready for finishing. I'll take some more pictures this evening.

 

[PeterGregory]

You may be thinking, Scotty, you're absolutely nuts. Surely you can't expect to finish your 1:8 scale C-47 and this 1:4 scale cub in time for the end of the contest.

I do intend to, and don't call me Shirley.

What contest?

 

[willsonman]

The FT Forum build-off.

 

[dwight]

Wow - that brings back memories for me!

The Sig 1/4 scale Cub was the first (and only) 1/4 scale plane I built - 15+ years ago. I powered it with a Zenoa G-23 gasoline engine, and that plane just flew beautifully. I flew it quite a bit until the day of the "incident" -- I took a radio hit (back in the 72 mhz radio days) on my landing approach, and by the time I got control back she was heading into the woods. I had just enough time to line up the fuse between two big tree trunks and watch the wings get sheared off. I was close enough to the ground that I was able to recover the engine and radio bits without any damage, but the plane was pretty bashed up and I just didn't have the heart to rebuild it.

Dwight

 

[ScottyWarpNine]

I'll post some photos tonight, but I'm almost done with construction of the right wing. I stumbled in a few areas and had to do some "fixing" where I screwed up or mis read the instructions. Hopefully this wing isn't too much heavier (or less perfect) than the second one...

 

[Joker 53150]

How is the covering working out? I'm starting to look at options for covering my 1/4 scale Cub and the regular iron-on fabric coverings are super expensive. Considering how much a plane this size would take, fabric covering put on like you did would potentially save a ton of money!

 

[ScottyWarpNine]

How is the covering working out? I'm starting to look at options for covering my 1/4 scale Cub and the regular iron-on fabric coverings are super expensive. Considering how much a plane this size would take, fabric covering put on like you did would potentially save a ton of money!

Cost is exactly the reason I went with full scale covering fabric. Dacron is significantly cheaper than any of the hobby alternatives. Of coarse you need to use an adhesive and paint it afterwards.

I am very happy with the fabric. It is much easier to apply than the film I originally tried. The adhesive dries almost instantly after brushing it onto the wood, and the covering iron makes quick work of applying the fabric. I have also found that dacron is much less picky about temperature than the film.

Dacron is harder to cut neatly though. Having good, sharp scissors helps.

 

[Joker 53150]

On areas where you overlap the fabric do you paint the adhesive on top of the first fabric layer, just like you did with the balsa? THe more I look at it, the more I like this solution.

 

[ScottyWarpNine]

On areas where you overlap the fabric do you paint the adhesive on top of the first fabric layer, just like you did with the balsa? THe more I look at it, the more I like this solution.

Yup, that's what I did.

Here is a little bit of progress.

Right wing is almost done. Still some sheeting I need to do on the leading edge, and the tips need to be added.

I've learned a lot on that wing...

I also made a wall hanger for the fuselage so nobody trips over it and smashes it to bits

 

[ScottyWarpNine]

Here is a good tip, when you're setting a weight on top of a wing to hold something down, hold the weight with both hands so it doesn't slip and fall. The crunch is soul crushing.

 

[Joker 53150]

Oops! It's better than having it happen after the wing is covered, at least...

I did some more reading from various sources on the covering, and a lot of people were recommending 100% polyester dress lining for the covering. It's super cheap ($5.00/yard) and durable. To stick it down, Polycrylic is often used. Since I'm a pretty cheap person I'm trying it out, and got 6 yards of fabric yesterday for about half the cost of one regular roll of the fabric iron on covering! Now I just need the Polycrylic and I can do some test pieces. This stuff is supposed to shrink very well and conform to the curves/contours, so this should be a fun test.

 

[ScottyWarpNine]

Oops! It's better than having it happen after the wing is covered, at least...

I did some more reading from various sources on the covering, and a lot of people were recommending 100% polyester dress lining for the covering. It's super cheap ($5.00/yard) and durable. To stick it down, Polycrylic is often used. Since I'm a pretty cheap person I'm trying it out, and got 6 yards of fabric yesterday for about half the cost of one regular roll of the fabric iron on covering! Now I just need the Polycrylic and I can do some test pieces. This stuff is supposed to shrink very well and conform to the curves/contours, so this should be a fun test.

Damage wasn't too bad, I glued it back together last night and this morning I didn't even notice it as I unpinned some parts.

I look forward to hearing about your dress liner results. I read about that method as well, but I went with Dacron just because I wanted something tried and true. I didn't want to buy a bunch of fabric that potentially wouldn't work. If it turns out well, I keep that in mind for future builds.

 

[Joker 53150]

I saw the recommendation from a number of people flying 1/4 scale planes. Fingers are crossed!