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Oct 21, 2019, 04:38 PM
Retired CAD guy
birdofplay's Avatar
Um ???

FYI - I discovered a much higher rez plan on Outerzone.

I have added it to this post for anyone with AIE issues - Age Induce Eyesight
Even Whiskers can see this one ;^}

Regardless, El Gringo is a SNORKY looking AC ;^}
Last edited by birdofplay; Oct 21, 2019 at 06:19 PM.
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Oct 21, 2019, 07:53 PM
Retired CAD guy
birdofplay's Avatar
So I'm sitting here in front of the PC,
listening to the whine of yet another 3DPrint ,
and I thought , what the heck ,
I'll see about tracing this El Gringo plan.

Most of the time I find that plans have been distorted or some how skewed.
It happens over the years to paper plans and even during Scanning.

I attempted to trace the ribs but ... Wheew !
They just did not match up,
given the alignment holes and other "Tells" .

So, I took the root rib and ...
1. placed it on the Plan view
2. Squared it with the center line
3. Copied it to each rib location
4. Then did a 2D scale of ea ch as they were "In Place"

As for alignment holes and spar notches ... you're on your own.

As for the Fuse, it too was not all squared up and aligned any more.
So I simply did a symmetrical trace of the top view and Mirror copied it on the CL.
Side view is a simple trace.
My presumption is that this was a fully symmetrical wing with no washout.

This PDF has Vector and is importable .

Scale to suit your tastes.

After al this IS a SCRATCH builders forum

Bob @ Hoosier Cutout Service
Oct 24, 2019, 12:43 AM
Foam is where the heart is
brett.c's Avatar
Thread OP
Interesting take on the plans. The best plans I found for the El Gringo and El Gringito were in this very site

I only use plans to give me some guidelines and proportions. I just print them in A4 and use my desired wingspan as scale factor. In this case it was 4.14. I then measure every thing up with a digital vernier and draw up my own full scale drawing.

Update: The fuse is now covered with brown paper and a 50/50 mix of PVA /water. Started out at 158 grams and ended up at 169 grams.
Not too shabby all things considered. And the overall gain in strength and rigidity is many multiples that of the modest weight gain.
Oct 24, 2019, 01:37 AM
Build straight - Fly twisty
Whiskers's Avatar
Oct 28, 2019, 12:12 AM
Foam is where the heart is
brett.c's Avatar
Thread OP
The fuse and tail feathers are now covered and ready for undercoating with sealer.
With my previous paper covered plane (see below) I applied the sealer straight over the paper, which caused the paper to lift and bubble is some areas.
This time I thought I would play smart and add a coat of wbpu first. Result, lifting and bubbling , easily rectified with a bit of applied heat and pressure from a credit card. But something I could have done without.
Next time I will use a waterproof or exterior grade PVA to begin with.
Also, the paper I am using isn't the best quality because it does tend to tear easily if soaked for too long. It is cheap recycled stuff so I will have to hunt around for something better.

Thus far the bare airframe weighs 265 grams and the cg is 20mm behind the LE (target 65mm), so she may end up a little nose heavy. That is ok because there is plenty of room to move the battery and ESC further back if need be.
Last edited by brett.c; Oct 28, 2019 at 12:20 AM.
Oct 28, 2019, 03:17 PM
Build straight - Fly twisty
Whiskers's Avatar
Looking very sharp indeed. Well done re the CG. It's in a good place now because it tends to move back due to weight being added to the tail, like push-rods and paint and (maybe) a tail wheel.
Oct 30, 2019, 12:23 PM
Electric Coolhunter
Thomas B's Avatar
Nice job converting the El Gringo to foam construction. Ted White, the original designer of the El Gringo series, was a good friend and flying buddy for many years. He was the best RC pilot around in the days of pre-computer radio systems.

I flew his El Gringo, El Gringito, El Bandito and La Fletcha models from time to time from the mid 70s until the mid 90s.

Ted passed on a few years ago. He is missed.
Latest blog entry: RC events for 2019!
Oct 30, 2019, 10:40 PM
Foam is where the heart is
brett.c's Avatar
Thread OP
Cheers all,

On researching this plane I came across an few threads about Ted on RCG and RCU.
Seems like he was quite a guy.
I hope I can do the El Gringo some justice even though my flying abilities are well below par.

The fuse is now primed and sanded down. There is still a lot of brown paper showing through and I will touch that up with some white undercoat.
This stuff is real heavy, 1.8kg for a 1L can , but once sanded down it doesn't add all that much weight. 15grams in this case.
I usually use a wbpu and talc mix but this stuff is way better IMO. Easy to apply, adheres well and is very easy to sand.
A bit like you always wanted lightweight spackfiller to be but never really was.

I've also added a tailwheel assembly made up from a stainless steel wingspar from a defunked glider.
Nov 01, 2019, 03:03 AM
Foam is where the heart is
brett.c's Avatar
Thread OP
After much cursing and swearing I was finally able to produce two salvageable wing cores out of five attempts.
This is only my second attempt at hotwire cutting wings and my first with a tapered cord.
There is a bit of clean up and fill required to the LEs but they are usable.
Next time I will start from the LEs first. Tried it that way once but the wire got hung up and over cooked the goose.
Last edited by brett.c; Nov 04, 2019 at 03:55 AM.
Nov 01, 2019, 06:05 AM
I Look, Listen, and Learn
Timbo383's Avatar
Ohhh the joys of trying something new, still looks better than anything I can do. Been following this and do like what I'm seeing, excellent work in progress.
Nov 04, 2019, 03:50 AM
Foam is where the heart is
brett.c's Avatar
Thread OP
Now we come to the "boring" part of the build.
The plan is to end up with 16mm of dihedral at each wing tip.
Spar is 11mm OD carbon which is 750mm long, just long enough to span the servo and aileron cut outs (handy for cartwheeling ).
The jig is just some old scrap from a desk top, aluminium angle and 1/4 nuts and screws.

I bore out the holes slowly by hand and only rotate the tube 90 degrees back and forth. Any faster, say with a battery drill, and you risk tearing up the foam.
Nov 05, 2019, 09:09 AM
Registered User
Bsouthwell's Avatar
I have had very good results using Forstner bits in foam. They were used to cut wing tube holes as you are doing. The Forstner bits leave a clean, smooth and accurate hole.

Your El Gringo looks great. It is one of my all time favorite pattern type planes. In post #20 the first picture is twin that you built. Is that your design? It looks like it is a real hoot!
Last edited by Bsouthwell; Nov 05, 2019 at 09:20 AM.
Nov 05, 2019, 03:32 PM
Foam is where the heart is
brett.c's Avatar
Thread OP
I have some forstner bits but they are very savage on foam. They must be the the wrong type. The good thing about using the carbon tube is that you just leave it in the wing when you are done.
The twin is called the Bucko. It was just something I designed as I went along. Flies really nice. It is loosely based on a Bronco, which I also have. See my blog for details.
Nov 08, 2019, 04:40 AM
Foam is where the heart is
brett.c's Avatar
Thread OP
Ok, some more progress on the El Gringo.

This time I switched to Gorilla wood glue instead of PVA. The reason being is that is water resistant.
Problem is that it is also very fast drying and rather sticky. Great for doing small curves and folds etc but not so good for large areas.
Anyway, I persisted with it and the results turned out quite good. I just had to work rather quickly (not something I like to do in my retirement).
It dried tight as a drum with no bubbles and only a couple of minor wrinkles.

Prior to covering, the wing weighed 242 grams, and after, 295 grams. The increase in torsional rigidity is amazing.
So far there just under 600 of those little gramlins hiding in that airframe. This will easily double once complete.

Problem I have with this foam is that it is so soft that you'd swear that if a fly landed on it he'd leave his footprints behind. So you end up with a lot of dings and scratches just handling the stuff. But on the plus side. These dings virtually disappear with the application of boiling water, and unlike EPO it can be straight out the kettle.
Nov 08, 2019, 07:47 AM
Build straight - Fly twisty
Whiskers's Avatar
So nice...

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