light weight project - Page 4 - RC Groups
Thread Tools
Aug 29, 2012, 01:31 AM
God Created me to Create
The_Builder's Avatar
I would worry about tearing up the foam trying to get a tube of that diameter into the FireFly's thin tails. The other thing that really helps is to make the intertable portion at least an inch or 25mm so the load is distributed over a larger area. In the case of the FireFly horizontal the spring reached the spar area on one side and runs with the control horn on the other. Running the spring along the horn helps make it more solid but it also keeps the tension where it should be. The horn is basically pulling on the spring with the surface along for the ride.

This is also a good time for an update. I have been working on a new pod mold because the one I have been using has taken some abuse in the shop lately. I did one I really like but the issue is servos and fitting them in there. The other issue is push rod exits if the servos did fit. I think i have a design I will really like so tomm I can hopefully turn a new plug and then do the extra shaping right on the lathe. The lathe has indexing on the head so it shoulkd make the needed machining a little simpler.

Why all this effort, I really believe putting all the servos in the pod is a great way to go. The weight advantage is obvious but along with that I am discovering all over again how much I hate dealing with wing plugs. A bagged wing with no cutouts will be stronger than one with cutouts. Finally, I would rather replace a bad servo in a pod than in a wing. These are just my opinions but they are why I am designing this plane the way I am. This new pod will have room for 285's !!!!!

Sign up now
to remove ads between posts
Aug 30, 2012, 11:56 AM
Will fly for food
davidjensen's Avatar
4 of them?
Aug 30, 2012, 12:22 PM
God Created me to Create
The_Builder's Avatar
Probably 4 but def 3. Some work may need to be done to the spline and horn to get all 4 in there but it should be possible.

The intent is to run 285's for the flaperons and a 188 or similar for the tail. With four 285's in the nose there is a good chance the plane will be nose heavy. A great deal of planning has gone into what gear to run and where to place it so no nose weight is needed. There is a bit of leway as to where the wing gets mounted so it might work out.

I have beefed a few things up just to add some weight as the Firefly seems to fly really well right at 8-8.5oz. The ones I have built for other people and mine have all come in at 7.6 with no nose weight and the CG is right on the dot.

I increased the area of the doublers on the wing and added more carbon to the back of the pod. The wings are still coming in at 108-110 grams.

Due to the afore mentioned pod I had to put the servos in the wing and add .75oz to the nose. This put the CG right on point and put the AUW at 8.4oz.
Sep 07, 2012, 03:55 PM
Ride, Surf, Fly, Sleep

Started the FireFly build...finally

Well, finally this week I got back from my work trip away and started the FireFly build - let's hope the kids give me some time this weekend.

Here's some pics of the build so far - I'll try and do a build thread but basically the pics tell the story of the last 48hrs - why so long to get this far? Well I've run out of 30min accelerated hardener and so am left with the 60 min stuff. Still I prefer slow cure for lamming and patching anyway as it can be thinned well by heating without you having to get wired on caffeine to beat the pot life clock

1. Checked wing dihedral fillet angle - spot on! That's a first, nice one Paul!
2. Filled wing hard points to within a gnat's salami of the joint line with epoxy/balloons mix - I've not done things this way before as I usually do the joint, then drill a skin hole and inject the resin mix into the hard point void so I don't get slump away from the skin as it sets.....but it seemed to work!
3. Sorted a few minor pinholes from the mold in the pod - usual sand & buff - not necessary and adds weight I know....
4. Cut the biggest access hole I could safely get away with in the pod - cut edges wetted and wiped with non fuming CA to take care of any stray crack starters!
4. Jigged up and did the first fix joint on the wings - really impressed here with the precision in Paul's layup, the spars were absolutely spot on.

That's it - I'll probably lay the second fix lam joint this weekend. I've not used CA as a matrix for a joint like this before, so I'll probably go with heated 60min epoxy.

So far - a nice build and great to be finally started after weeks of having to sit on my hands due to work!
Sep 07, 2012, 04:13 PM
God Created me to Create
The_Builder's Avatar
Nicely Done !!!
Sep 07, 2012, 04:55 PM
Ride, Surf, Fly, Sleep
Cheers, nice of you to say but so far it's a dead easy build, as everything lines up first time...... kudos to your skills mate, not mine!

It's building to a great looking plane - I'm trying hard not to get out the airbrush and start on the front end of that pod with a design .....must.....resist....adding.....weighty....blin g........nnnnnnggggghhh...
Sep 07, 2012, 07:40 PM
Dub Cult.
Your going to absolutely LOVE the firefly, just wait till you get it in the air.

I love mine so much, it takes ballast so nicely and just flies so damn nice.
Sep 07, 2012, 09:17 PM
God Created me to Create
The_Builder's Avatar
I know that white nose is screaming for some design. I doubt the weight would hurt you. I have yet to have someone buikld one over 8oz unless they ignored me completely.

CR, if you saw the one I have been flying in my yard you would laugh. I have beat up the vertical so much it almost looks like a V-tail, the horizontal is crooked, the pod has 6 holes in it (from trying stuff) the wing has a chunk out of the leading edge, the servos are just taped in so it flutters on hard launches, and she still flies amazinly well. These things are so forgiving....

I have a new one started and I will be trying some new servos that have me hopefu. If the numbers are even close folks will be able to do a whole plane for less than $30. They will only work with all servos in the pod, they are too fat to go in the wings.
Sep 09, 2012, 06:19 PM
Ride, Surf, Fly, Sleep
Well the weather broke and so the harvest had to be started meaning I didn't get any further with the FF this weekend - but a lucky break really as it gave me time to look at the tail feathers...

Both vert and stab seem to be cambered.....although it could be my cider addled brain after today. I'm presuming this is for either a reg/goofy setup as the vert has a symmetrical planform so could just be flipped over. But I'm a DLG newbie and a search of t'internet revealed nothing conclusive.

So which way round does the vert airfoil go for a reg/righty like me? I'm guessing camber line is towards me (i.e curved side facing me and the flat side away)?

Also before I make a stupid assumption based on previous non-DLG experience - the stab is reverse camber (flat side up) not positive camber (i.e. curved side up) - there's not a lifting tail requirement on DLGs or anything? Can't think why there would be - but I know too well what 'assume' makes.....especially having seen that cambered stab!

Wow - love this DLG thing - don't get me wrong I love my simple Alula, but this is a new level, it's like when I moved to building and racing crunchies on the slopes - so many in's and out's to learn
Last edited by quincross; Sep 09, 2012 at 06:44 PM.
Sep 09, 2012, 09:54 PM
Registered User
The cambered vertical helps keep it from stalling on the initial yaw from launch and the result is higher launches. You've got it right. The curved side should be facing the throwing peg and the flat side away. You want it at a negative angle of attack, too, so it doesn't create lift in level flight (thus causing a turn). In most cases, the way to do that is to close one eye and look at it from the back. When looking straight down the boom you should see an equal amount of the vertical on either side of its trailing edge. I'll let Phil answer on the horizontal's orientation.
Sep 09, 2012, 10:45 PM
ground penetration specialist
Nathan Schmoekel's Avatar
Rudder, yes mount it exactly as stated above.

Why it's 'weird' : The rudder is hot wire cut with one side flat and airfoil on the other. Paul's bagging method lets the flat side curve a little bit, but you can still tell which is which.

The horizontal is cut via the same method, but bagged on a flat surface. The flat side must be mounted up in flight. And the horizontal shall be mounted under the boom.

The airframe is set such that the flat top of the horzontal will end up parallell to the bottom of the boom. The boom is set (with the little wing shim) to the main wings incidence angle.
In other words, the kit pretty much falls together without any need of fancy angle measuerment equipment!
Sep 10, 2012, 05:11 AM
Ride, Surf, Fly, Sleep
Cheers guys - that makes sense, but I didn't want to guess just in case! Just to clarify "negative angle of attack" means something different to me, but I get what you're saying - you set it at the zero lift axis for the vert (in my job that'd be 0 AoA but would give a -ve AoA if you instead used the chord as the reference datum).

Nate - where did you mount the pylon in relation to the LE of the stab? All my designs put the pylon across the CF spar (as a sadwich i.e. without cutting it) for strength, but this seems a little far back on the FF to do this. That said most of mine are free-flying stabs, so they have to be mounted at the AC well forward of the CL. I've already PM'd paul about this but the poor guy must be getting a bit weiry of all the newbie questions from me by now, so hope you don't mind me asking you!

As to the stab profile - nice idea and I'll put away the incidence meter now! I wouldn't dream of mounting the stab above the boom - apart from having to use pull-for-down (wouldn't want that torsion spring holding "up" on a DLG launch!), surely the stab would sit in the T-flow if it was on top which would negatively affect your glide efficiency? On an aside, an interesting thing on reverse camber beyond the building advantages: I use it on some of my designs as there are some slight drag advantages shown in CFD when trimmed out on some of my big thermal ships. I can't say it's "all that" as it doesn't seem to make a whole heap of difference in *real life* flight; a little, I guess, but sometimes any edge will do
Last edited by quincross; Sep 10, 2012 at 06:33 AM.
Sep 10, 2012, 11:35 AM
God Created me to Create
The_Builder's Avatar
My blog has a bunch of info but I am by no means tired of questions. The fuse should finish out at 36" or the equivelent metric number so you may want to trim the TAIL of ther boom. The horizontal stab is set so the trailing edge is just clear fo the vertical. I have been playing with 570-560mm between the leading edge of the wing and the leading edge of the horizontal. My blog does have info on how I suggest you mount the pylon but it should be just in front of the spar.

Cheers, Mate.....LOL I have been practicing my English
Sep 10, 2012, 11:38 AM
ground penetration specialist
Nathan Schmoekel's Avatar
Pylon....Since the spar is rear shifted, you must mount the pylon forward of the spar. I like my rear bolt hole right in front of the spar. I even dig some foam out from beneath the leading edge of the spar, so the hard point pours 2 or 3mm under the spar's leading edge.

"surely the stab would sit in the T-flow if it was on top which would negatively affect your glide efficiency?"

Round here in DLG land most people seem convinced that the tail must mount above the boom in order to avoid the down wash of the wing..... we prefer to surf it!!! Also for launch rotation the elevator below is in clean air, which we think helps it's inverted foil lift down and rotate the plane with less preset drag.
Sep 10, 2012, 12:21 PM
Ride, Surf, Fly, Sleep
Originally Posted by The_Builder
My blog has a bunch of info ....snip....
Cheers, Mate.....LOL I have been practicing my English
Thanks Paul, yup your blog has been invaluable along with all your PM/email help - I've printed it all off and am using it as a reference point for the build. I just couldn't find stuff about which way round to mount the cambered vert and stab or where to whack the stab pylon in relation to the spar. My apologies, I know it's probably in there, but I'd spent all day picking and scratting apples so was not 100% with it and couldn't see the info anywhere! On the other hand in a few months I'll have replenished my cider stocks (or 'hard cider' as you guys call it) so not all bad.....mmmmmm.....cider....

BTW - good skills with the use of "mate" - try it for a while and you won't know how you did without it - "dude" just isn't the same

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Mini-Review HD Wing Cam - A 120 light weight 1280x720p cam Dreamcatcher Aerial Photography 11 Oct 17, 2012 06:00 AM
Discussion Lights go dim on yet another Obama energy project P-51C Life, The Universe, and Politics 31 Jul 06, 2012 02:52 PM
Sold Light weight alloy spinners ArtJ Aircraft - General - Miscellaneous (FS/W) 2 Apr 13, 2012 08:01 AM
Sold Spinners...light weight alloy ArtJ Aircraft - General - Miscellaneous (FS/W) 0 Mar 25, 2012 06:31 PM
Found 30 inch light weight V hull for project LarryFlew Boats (FS/W) 3 Jul 22, 2008 12:25 PM