Scale Build-Off – 140" C-47 Foamy

[willsonman]

I suspect not Scotty. The spackle dries very soft. Softer than the foam. It can fill dents and dings from working on it and even some bumps from wire cutting but I would not recommend it for your large cut where the wore sagged. It would be much more work than to cut new anyway.

For a harder, but also sandable, filler you can thin the spackle as suggested by Joker with WBPU. To make this softer after drying you can also add baby powder.

 

[Joker 53150]

I'd agree with Willsonman, large areas or thick coatings should be avoided with spackle. It's great for dings/dents and the occasional low area, but nothing is small on this plane!

 

[ScottyWarpNine]

I think you're right, I should cut a new center section in two pieces. I can make the bow smaller which should also help by increasing the temperature of the wire, so it should turn out pretty good. Not sure how I'm going to do the outer panels in small chunks. I'm going to have to split the wing up and align formers just right. I guess I'm lucky the DC3 has a straight trailing edge that I can use as a reference.

 

[ScottyWarpNine]

one half section done, one to go. I coated the edges of the balsa with epoxy. Not the best, but definitely better. The holes are still hard to do and kinda rough, but they will work. I'll keep working at it, but so far I have one center section half done.

Not perfect, but I can work with this.

 

[ScottyWarpNine]

Bought some more foam and a smaller pic pipe to use as the outer wing panel spar. Here's what I have:

Oh, and did you notice those two big beautiful props that came in today?

The little spar is going to overlap with the big spars by about 10", so things should stay pretty rigid. I have some layers drying right now so tommorow should be a pretty productive day. I want to get the center section totally done, as well as at least one engine nacelle and start to get the tail planned out.
I also want to start looking into fiberglassing my airfoils as soon as possible because I've noticed that the 77 adhesive isn't completely up to the task of holding my laminates together. I don't think it will be an issue when everything is held together with fiberglass, but it's a pain to have my wing sections delaminating as I mock them up.

 

[Kurt0326]

Scotty to answer the question... DTFB 140in Ziroli DC3 Do I dare? That would be a heck funk'n yeah!

watching!

 

[willsonman]

Need to see more DTFB

 

[ScottyWarpNine]

Need to see more DTFB

Maybe with some detail work...
Can I change the title? I'm gonna change the title

 

[earthsciteach]

Pfffftttt….. Build that thing as you will, ScottyW9! Don't limit yourself with DTFB.

Topic of convo when you are back in Lancaster, Joshua, "Merits and demerits of DTFB." ;-D

 

[ScottyWarpNine]

I didn't get as much done as I wanted today, but little steps I guess. Center section is done other than sanding, filling, and glassing. I made some new templates, ply this time, for the outer wing panels so hopefully I can get started on those these next few days.

My servos came aswell so I'm gonna try to print out my retracts and start figuring out rudder and elevator servo positions so I can start to wire up and skin the fuselage.

Oh, and I painted my prop tips

 

[airhawk]

im trying to build a mash up with nick ziroli's swoose his designs are interesting any way great job on the build and keep up the good work
-Airhawk

 

[ScottyWarpNine]

This makes me giggle uncontrollably.

 

[Bambua]

That's a monster

 

[ScottyWarpNine]

Here's a wing:

 

[ScottyWarpNine]

In the last couple days I've made a little progress:

Vertical stabilizer is pretty much done. I'm still thinking about how I'm going to make the hole for the hinge pin because it needs to be as perfectly straight as possible. One wing is cut out and I'm hoping to get the other cut out today. I got my dihedral sorted out and everything is looking quite nice. I tried to show the PVC joint. I made the hole in the outer panels that accepts the center section spar a little oversize because I'm going to add fiberglass inside the hole to create a stronger tube than just foam. I'm going to try wrapping the PVC in plastic wrap to keep the epoxy from bonding the PVC to the fiberglass. We'll see how that works out.

I'm about to make a big order from aircraft spruce for fiberglass cloth and epoxy resin. I can't decide if I want a quart or two, or a gallon. Shipping for a gallon is ridiculous, and slightly less ridiculous for two quarts. The problem is I don't really know exactly how much I will need for the whole thing. I'm planning on buying 8 yards of 3.74oz cloth. I think that should be more than plenty, considering it is 60" wide. How many layers should I use? 1? 2? More? I think one layer would require about 8 yards and 1/2 gallon of resin according to the online calculator.

I tried using Poly Urethane instead of resin on a test part and I wasn't happy with the strength, so I'll just use that and talc to fill in the weave afterwards as was suggested here. I'm going to try mixing epoxy and balsa dust to fill some of the larger gaps in my wings and other parts.

My buddy is making a wood form on his lathe for me to make fiberglass cowls. I still have to rebuild the nose to make a fiberglass part. I have no idea why I chopped it off in the first place...

I bought some white beaded foam to try to skin it with. It is much cheaper than the pink stuff. I'm sure it will be plenty strong with the glass. I might make another update tonight, depending on how much I get done on my day off.

 

[AkimboGlueGuns]

Looking good. The fiberglass cowls will make construction a bit easier.

 

[wilmracer]

Looking good! I'd call that a LOT of progress.

 

[Tench745]

A good how-to on fiberglassing models. This is written for built up balsa models, but the same techniques apply.

http://www.airfieldmodels.com/information_source/how_to_articles_for_model_builders/finishing_techniques/apply_fiberglass_finish/index.htm

 

[ScottyWarpNine]

A good how-to on fiberglassing models. This is written for built up balsa models, but the same techniques apply.

http://www.airfieldmodels.com/information_source/how_to_articles_for_model_builders/finishing_techniques/apply_fiberglass_finish/index.htm

Thanks for the link, that was very interesting. I think I'm going to revisit the polyurethane idea again. I applied another layer of fiberglass to my test piece so tomorrow morning I'll take a look at how it went. One layer added some strength to the part, but not as much as I wanted. I think 2 layers over the entire model would be beneficial since I am not just using it as a covering, but as a structural part of the fuselage. I'm hoping my test piece will be strong enough to be workable because epoxy resin is so expensive. Polyurethane is also so much easier to work with. It comes off my hands and tools with water and it doesn't need to be thinned. It wets the cloth so effortlessly and uniformly.

 

[willsonman]

True, WBPU is much easier to work with but I suspect in your case the strength will have to come elsewhere. There is no substitute for epoxy on glass to increase wing strength. It may seem strong but IMHO over many flights you may see the glass weaken and become brittle and you may not even be able to see it beneath paint. This could lead to a very large model completely failing in the air without warning. If you want a safe and reliable model, the price goes up the larger you go. In your case... much higher than I suspect many others here would consider a "toy."