• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

Scratch build Predator

lobstermash

Propaganda machine
Mentor
#1
I'm having a go at my first scratch build. Being a big fan of the predator, and not having a glider type plane yet, I decided to give this one a go:

http://rcfoamfighters.com/blog/?p=950

The plans recommend 3mm foamboard, but that would involve buying it, eh?

In my quest to find decent foam, I noticed the recycle bin at a local whitegoods store and asked if I could help myself. Unfortunately the only stuff they had was a few long, right angled pieces of EPS and a 90x90cm square of lower density crap (the kind you can't really take a sander to). A refrigeration mechanic friend had a solution for me however: a nice big piece of good quality EPS with just enough flat, straight foam for the wings and a thick part for shaping the nose. The wing foam is/was 16mm thick and the lower density stuff is about 19mm.

The wings took shape pretty easily after drawing where the thickest part would be with a marker. The good quality EPS was happy to be sanded and I also used a scalpel to help shape it. The fuse is going to be quite thick but easily replaced if it affects performance too much.

Instead of buying carbon rods for the wings and stabs, I cut down a bargain carbon fibre fishing rod. The thinnest pieces went into the stabs and the thicker parts went into the wings, interlocking in the middle to keep the dihedral. The wing rods extend just beyond the ailerons.

And that's about where I'm up to. I've been using HK 4-6 minute epoxy to put it together and have run out. I don't buy the stuff from the local stores anymore, as it's literally ten times the price... I have to order the servos, pushrods and horns anyway, so the project might be on hold for a bit.
 

ananas1301

Crazy flyer/crasher :D
#5
Hey nice build you got there.

That EPS looks kinda styrofoam like. How is that EPS as a working material? Do you think it is comparable with depron or blue/pink foam
 

lobstermash

Propaganda machine
Mentor
#6
The fuse is more that styrofoam-ish type stuff, which is flaky but very lightweight and hopefully bouncy ;). It was hard to work with but cuts OK with a razor sharp scalpal. Thankfully I've got a dissection kit full of them.

The EPS on the nose is much denser, more like depron. I've just got word from my mate that he has lots more good quality EPS and even some EPP (God bless refrigeration!). I may be replacing the fuse panels.
 

lobstermash

Propaganda machine
Mentor
#8
You could. It's quite floppy and hard to shape because it crumbles when sanded. But if you could get the shape OK, reinforcing with cf and covering with film would probably make it OK for wings and stabs (until you crashed...).
 

colorex

Rotor Riot!
Mentor
#9
You could. It's quite floppy and hard to shape because it crumbles when sanded. But if you could get the shape OK, reinforcing with cf and covering with film would probably make it OK for wings and stabs (until you crashed...).
Well, that's too bad. This is the only foam there is plenty of here.
 

lobstermash

Propaganda machine
Mentor
#10
Alrighty, the glue arrived yesterday, along with the control horns, rods, hinges and servos. The stabs and wings are attached to the frame, and I'm currently attaching control surfaces. This fella should be ready to fly tomorrow night. I'm thinking of strengthening using some contact or something though.
 

lobstermash

Propaganda machine
Mentor
#12
My camera's not good enough for night pics, but I'll post some tomorrow. The build is now 98% done. I have one more panel of foam to attach to the roof, and need to make a canopy of some sort for easy battery and receiver access. Oh, and need landing gear. I hate hand launching maidens, and the vertical stab would get damaged in a belly landing anyway, so need some wheels.

The sticking point tonight wasn't so much in the build, but in the programming. I've always used a Y cable for ailerons and a single servo for elevator, and I've not really gone that far on my new 9x before. In the end, not too difficult, but not exactly intuitive...

All control surfaces working as they should, and I've got the option of some other cool mixes by using the extra servos. The powerplant for this build is a KD A2210S 1200kv from HK, which coupled with a 9x4.7 prop should give me about 600-700g static thrust at 14A, though speed will probably only be around 40ish mph. Last weigh in was 468g, including 1600 battery. Final weight, with the last couple of foam panels on there, shouldn't be much over 500g.
 
#18
That's a Reaper not a Predator....but who cares? At least it's a plane! And a very nice one, especially for a first scratchbuild!
 
Last edited: