Monday, October 26, 2015

DIY Canard Airframe 02

I was introduced to last week, and it's very eye opening to see how much can be done inside a browser! I'm really not sure how heavy they will weigh, and I haven't yet figured out how much offset I need to give the pieces to accommodate the laser's kerf.
I'll stew on this for a day or two, then hopefully I'll have some laser cut pieces later this week.

In other news, I have also been experimenting at making a strong fuselage out of DTF (Dollar Tree Foam/Readiboard). While Experimental Airlines has a great way of making a strong fuselage, I do not have the space nor tools to do what he does, so I've been trying out various ways to get a strong fuselage.

It seems like without cutting a hole in the fuselage (for putting in batteries etc), I could get a very very strong tube by leaving the paper on, and constructing a tube similar to the way Flitetest does their swappable power pods.

However, once a hole is cut, the structure weakens immensely, and you can see that it won't take torsional stress very well. For a canard planform that relies on a strong section connecting the front and back, I thought this would be a major weakpoint, something I had to figure out.

Experimental airlines deals with it using additional pieces of DTF to strengthen the walls, in additin to some bracing to keep the tube square, and this appears to work well. I tried this, and it didn't seem all that strong, when I realized... perhaps I was using the wrong kind of glue?

Being the need for strength, I pulled out Foam Tac as it's been very strong so far for bonding many many materials, and I really like that it's rather flexible after it's dried. It was this flexibility that I was concerned with, and did a quick test, gluing two pieces of DTF using Foam Tac and Gorilla Glue.

Gorilla Glue was the clear winner in this case, the material broke first before the joint - heck the joint is still there and everything around it is all broken up from my attempts to pull (shear) them apart.

Foam tac unfortunately didn't work as well in this test case; I pulled it apart really easily.

This further reinforces the need to test various adhesives in various contexts. Hot glue, for example, I haven't used much as it's so heavy, but perhaps it may prove to be an even stronger joint.

In addition, with wood-wood adhesive joints, there is still one glue type designed purely for wood that I haven't tested: Titebond III. This is supposed to be *the* ultimate wood-wood adhesive. Have to test this shortly.

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