light weight project - Page 7 - RC Groups
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Sep 19, 2012, 12:54 PM
Hope to get out of life alive
kenh3497's Avatar
Originally Posted by quincross
Today I finished the wing/boom mount and learn an important addition to the axiom “Measure twice, cut once” – it will now be “Measure twice with 2 different tools, cut once”.

You've got it all wrong.... My motto has always been and seems it always will be.... "Measure twice, cut three times"

Good looking build you've got going there!!

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Sep 19, 2012, 02:07 PM
Ride, Surf, Fly, Sleep
Originally Posted by The_Builder
Very Clean Mate!!

I am building one so I have something to fly in an upcoming event but I cannot find the camera battery charger so I am thrilled you are doing such a great job detailing the build. You are indeed a master builder.

No worries a pleasure - it's been a great build and I'm really critical about these kind of things. Cheers for the big up mate - but undeserved especially as I still can't believe I set the mounts too far back.....(bangs head on table)

Originally Posted by kenh3497
You've got it all wrong.... "Measure twice, cut three times"
Luv it - fits with my TLAR principle for fun-flys - "Don't measure, just cut and cut and cut - the airframe work out lighter"
Sep 19, 2012, 03:12 PM
ground penetration specialist
Nathan Schmoekel's Avatar
That half an inch error will not hurt you at all, infact it may save you needing a few grams of nose weight to balance her out.
Sep 19, 2012, 04:36 PM
God Created me to Create
The_Builder's Avatar
Since I put the servos in the wings on the one I am doing now I had to add .5oz to the nose which brought the AUW to 7.8oz. I think I could do 7oz and still have a conservative CG with a careful build.

Sep 19, 2012, 04:43 PM
Ride, Surf, Fly, Sleep
Let's hope mate - I'm certain you're right....but I could still kick myself!

Still I'll be using stripped down gear and if the CF rods prove too short now it gives me an excuse to use my CF micro tubing on something that isn't a indoor flyer.

I tend to use 0.7mm and 1.5mm OD tubing so have some lying about. I doubt I'll use the 0.7mm tube (inner dia is 0.25mm ), but the 1.5mm I have is perfect with an internal diameter of 0.7mm (bang on the wire Paul supplied). You can then get away with tiny wire ends so using tubes usual cut 60-70% off the push rod weight in total and still work out stiffer as they come in at about 60% unidirectional fibre. A bit of a waste of material on the FF as I doubt 1-2g will count much but....if there's an excuse!
Sep 19, 2012, 05:02 PM
God Created me to Create
The_Builder's Avatar
I just did my shorties with .030 wire ends and hypo tubing connecting them.

Sep 19, 2012, 05:23 PM
Ride, Surf, Fly, Sleep
Yeah mate - it's a cracking system for smart rods! Presume you're talking about steel hypodermic tubing? I used to use that too, until a mate shoved me in this direction (I think they have outlets for this stuff States side too).

Everything from a 0.030" OD tube (0.0098" inner) upwards at reasonable prices (~$6) for 1m lengths. Not sure there's much of a significant weight saving over hypo tubing, but hey it looks cool

Both hypo and micro tube beat the pants of "rod and shrink" push rods for looks, stiffness and weight
Last edited by quincross; Sep 19, 2012 at 05:40 PM.
Sep 20, 2012, 01:19 AM
God Created me to Create
The_Builder's Avatar
I will have to look into the carbon stuff. I had the Hypo stuff from when I was doing some RDS stuff.
Sep 21, 2012, 04:13 AM
Ride, Surf, Fly, Sleep
Last night I set the stab - I'll post the photos tonight - and then I noticed something very odd, the wing appears to be set at a negative AoA to the stab. I've double checked the rear incidence block, everything has the correct dimensions (, and mounting the posts further back won't have caused this as the boom has constant taper - so it must be an optical illusion or part of the design.

I'll check the AoA on a meter later on to be sure this is not an optical effect, but I think the wing is either set very slightly negative or at 0* - is this something specific to DLGs and camber needs to be added in the set up or have I missed something?

BTW stab is on the bottom of the boom as per design, so that's not caused it.
Sep 21, 2012, 06:50 AM
a.k.a. Bob Parks
Remember that the wing's incidence is from the very front of the leading edge through to the trailing edge, not just along the bottom as it would sit on a table.

Sep 21, 2012, 07:23 AM
Ride, Surf, Fly, Sleep
Originally Posted by bbbp
Remember that the wing's incidence is from the very front of the leading edge through to the trailing edge, not just along the bottom as it would sit on a table.

Yeah, thanks - that's caught me out before as some airfoils gives an "optical illusion" even when you are sighting down the correct line.....until you get the meter on it and everything measures out OK. I suspect, this is probably the case this time around, but I'm used to that illusion now and my eyes are still telling me this wing is small -ve or 0* - very weird. Must be my eyes' lack of experience with DLG airfoils

I'll get the meter on when I get home and that'll give me a definitive answer.
Sep 21, 2012, 08:57 AM
I'm slow but I'm expensive
Ken Lilja's Avatar
Most airfoils don't go to zero lift until they reach an AOA of -1 to maybe -3 degrees to the chord line. And the chord line is not the bottom surface of the wing. So yes visual sighting could look screwy.

Soon to receive most of a kit.
Sep 21, 2012, 09:38 AM
Ride, Surf, Fly, Sleep
Originally Posted by Ken Lilja
Most airfoils don't go to zero lift until they reach an AOA of -1 to maybe -3 degrees to the chord line. And the chord line is not the bottom surface of the wing. So yes visual sighting could look screwy.
Strange you should say that - I've been fitting the Vert, and that is cambered and needs to be set at the zero lift line.

Sighting up only approximates zero lift and I know I have issues here already given my take on the wing

So I grabbed a fag break (that's a 'smoke' to you guys across the pond not something on the wild side ) and pondered that what I needed was a portable wind tunnel.....mmmm......

So behold....drum roll....
"the ACME Portable Wind Tunnel"

3 mins later I had a Vert at zero lift AoA. Sighting up as a secondary check confirmed that it wasn't just some fluke. So it seems to work great and only took 1 min to make - if you have a try you want to do it in the centre of the room though to minimise wall cyclic effects. The straws should ensure that airflow is linear out of the cup, it's the same principle that I use on my big DIY tunnel in 'Shed No. 2'

Beep! Beep!
Sep 21, 2012, 01:07 PM
Ride, Surf, Fly, Sleep
Woohoo - finally it looks like a plane! And it looks great - the stab and vert are on but I've yet to patch the vert across the boom - I'll think on that tonight as I've half a mind to tie it to the vert's main spar as the boom ends 1/4" in front of it...but don't want to add unnecessary weight....dunno really

The wing's AoA is probably OK at very slightly above 0* - hard to know for sure as my DIY meter doesn't fit exactly because of the longer boom to root chord ratio than a standard thermaller.
Last edited by quincross; Sep 21, 2012 at 04:58 PM.
Sep 21, 2012, 05:12 PM
God Created me to Create
The_Builder's Avatar
OKay a Conformation and an admission of how wild this week has been. I finished up a plane for the Wilson event. Somehow I had it in my head the rear wing spacer needed to be 6mm/.25" and that is what I put on there. The plane flew fine, it took more tuning than I am accustomed to and it dragged it's butt a little.

I read James' posts earlier today while chatting with Nathan and I went hey that spacer should be 6mm not 3. Nate says no, you had settled on 3mm....HHMMMM

I pop the 6mm spacer off and replace it with a 3mm. I can now have my stab almost perfectly flat across the top and I gained 15-20' in launch. The plane is much faster on launch, will seriously move across the sky and will slow way down without stalling. On top of all that I am not dragon azz anynore.

James I will take a look at her later and post some camber settings and where my CG is so you can at least have a base line.

This plane is what I have dreamed of building for years. I may just take this one to a whole new level.

Seperate subject but realated to the FireFly;

There have been some occasions when I ended up with flat spots on the leading edges of my wings and tails. All this time I presumed it was my lack of skill. Here lately it has been happening a great deal. I have thrown out three wings this week.
The flat spots may or may not show up, when and where they show up is completely random.
The last one that went bad I had really taken my time on. I even used a magifier light to work on the leading edge. I had much more glass on the leading edge than needed and I still got a nasty flat spot.
Yesterday I decided to do some experiments. I cut a wing core with the intention of sealing the leading edge with foam safe CA or epoxy. It soaked up the foam safe like a sponge and formed a really nice leading edge.....except for a 6" section that swelled a lot. I tried sanding it back down but that was a no go.
Nathan and I were on the phone very late kicking around ideas on how to resolve this. It would be easy to just go back to standard blue or pink foam but that would be admitting defeat. I really like all the atributes of the white foam. It bonds to the skins really well and is super hard in thickness direction.
lying in bed I had an idea.....make the leading edge out of 60psi foam. This morning I ran to the shop and I found an old piece of HiLoad 60. I had just enough to try something. I blocked out a wing but left it so I could add 1" of HL-60 to the lading edge. What a pain in so many ways but what a beautiful wing. The HL-60 sand differently so I could get one of the nicest leading edges I have seen.
It is cooking right now and I cannot wait to open the mylars in the morning. If this works like I believe it will this will be the finest bagged wing I have ever done and the way the FireFly wings are done in the future.

Luap.....What a week !!!

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