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Old Nov 13, 2006, 12:22 PM
AKA Cactus
Phillybaby's Avatar
Cornwall UK
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Zipper mods?

about to sheet my wings ( epoxy/ply ) so while i ponder that i've had a few ideas and questions.

first up, should i glass the wing and then cut out the elevons.
reason being i think i can make a neater job of the glassing that way, and it leads on to idea two/three
or should the two really be seperate ( it would also make the following ideas much harder )

idea two. when glassing the rear of the elevons instead of cutting the glass flush with the ply carry it on a bit on the same line as the elevon using a flat shiny surface to carry that on by laying the peice on it.
then rub back on the unglassed side and glass that side so you end up with an epoxy glass TE for the last few mm.

this should give a super sharp and clean rear edge similar to a mouldie.
i think this would also be easier if the wing was still a whole rather than the elevons cut out.

idea three is the hinges.
it's top hinged with a flat and cut out leaving a V at all but full down deflection.
as the skins are ply and glassed i don't see why i can't cut back some foam in the wing at an angle going from the top and then cap that so i have a ledge at the bottom.
then do similar on the elevon again so it's like the Whisper's surfaces i have.

the idea of still having the cap and angle is to give a silicon hinge something to hold on to.
tho theres no reason i couldn't simply cut back both to this kinda shape wing[ ]elevon and then epoxy in a strip of fiber glass at the top on the inside as a hinge with nearly no visible hinge line, just a fraction to allow up movement.
maybe wipers at the bottom to keep the gap sealed.

i'll have to have a good look at my Whispers wing to see how it's done but thats the kind of set up i'm thinking about.
partly to loose the gap and keep the section clean, being a plank reflex section i guess thats more important than on a normal wing.
partly i hope, to get that nice scream you get when rolling a mouldie


last ideas for now are on the tail. rather than just round the front of the fin and maybe sharpen the rear a little should i give it a better section as you do with all sheet wings.
reason being Slopetrash's Wanabee review over here where he said the tail waggled because it was a flat sheet.
also thinking of swapping the wood at the bottom of the fin for carbon to make that rear a little stronger after reading here it can start to get weak.

any thoughts on all this??
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Old Nov 13, 2006, 01:41 PM
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I have a 60" Zipper, and while I dont fly it as much as I used to, I learned quite a bit (lots of it the hard way) while flying it.

Keep the tail light- It seems the lighter this plane is the better it flies. The fuse is sorta weak in the tailboom (?) dept, so a light tail is the hot setup. If you can bag a foam tail and glue it on, that sounds good. I would reinforce the tailboom with a carbon rod like they show with a spruce piece. Mine only seems to need more vertical if you mash the elevator or egg out a roll.

The huge hassle with this plane is: Any time you damage something, you have to take the wing off, which means getting the antenna out of the wing (at least on mine anyway) so come up with a way to unplug your antenna, i.e. those gold plated connectors. PLUS- disconnecting the clevises is a royal pain. I found a surgical instrument that works, but if I were to redesign this plane it would use f3f style ball links for the elevons, and I would make the fuse fatter back there to allow a tool or whatever to fit in there. A Bluto style tail setup with a hacked-off fuse and the tail on a carbon rod might be the way to go.

On the wings, hmm. This plane, for me anyway, go a lot of rough use. I flew it like a foamie, with the foamies, midaired foamis, etc. I think you would be better served getting it done and into the air than setting it up with wipers, etc. I do think that a stout sub-trailing edge made my wing survive some grinding midairs that would have broken it if it had been build stock. I tape hinged mine and its held up well. I think if youre going through all that trouble get a set of PW51 cores cut for it, as the stock ones balloon quite a bit at speed.

Radio setup: You need *tiny* elevator throws, like 1/8". It loops really well. You'll find mixing 5% elevator to throttle will give a throttle trim that will allow you to adjust the trim for the speed your flying. It DS's very naturally, and seems to seek its own orbit back there.

Overall, its a good, low tech slope screamer. I'll probably build another, but I'll make it a 48" so it fits in my trunk better.
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Old Nov 13, 2006, 01:58 PM
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it won't be combatting, and the LZ's are nice and smooth so no problems there.
i could make the carbon rod a tube, sure i'll loose 6" of aerial in it but the rest will be hanging out the back ok.
could also go with a plug in aerial but thats hassle and i don't like to mod my rx aerials.

no reason i couldn't have a tube above the carbon tube glassed into the fin.
bagged foam i can't do, no bags around here.
glassed balsa is the plan.

having it really nice is more important than on the slope repairs or airborne as quick as possible.
mouldie hingle will mean no gap on show giving that mouldie impression with a invisible paint line, and the bottom style may give that scream i've just brought a Whisper for.

i'm even thinking slightly translucent paint on the wing to give it the same look as the Whisper.
of course, it's not.

new cores isn't an option.
1 i brought this kit, and as 90% of it is the cores i won't be spending money on more.
2nd i'm in the UK, i doubt anyone would know what a pw51 core is. i don't.
does it have machine guns and a merlin up front?

the throttle trim was a given.
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Old Nov 13, 2006, 03:19 PM
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Phillybaby,

I put mylar wipers on my Zipper one day and it stopped rolling properly. Ripped them off and the roll rate came back... Not too sure why ???
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Old Nov 13, 2006, 03:36 PM
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were they acting like turbulators just behind that all important hump?

looking at the whisper the gap only closes at full down deflection.
not sure why mouldies use this open gap when you'd think the inverted V should be smoother.
the area around the hinge is also prettly flexiable with the aileron allowed to move up and down without deflection a fair bit.

are all moudlies like this?
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Old Nov 13, 2006, 03:39 PM
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Put something in the trailing edge in between the sheeting. I use .007 x 1/2 x the length of the trailing edge carbon. Then you can sand down to a knife edge and it will be stronger. If you don't have carbon, use a f/g strip. This will also keep the elevon nice and straight.
Terry
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Old Nov 13, 2006, 04:09 PM
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bit late, it's sat in the shed now under two 6" concrete blocks, gallon of glow fuel, two car batterys, tool box, vice drill case....

it is epoxy ( with thickener ) skinned tho not tape.
might have mixed up a bit too little tho, it certinaly won't fill the holes in the foam.
the two bits of ply were joined with tape at the TE and then folded over. this trapped a fair bit of epoxy so it should be strong there.
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Old Nov 13, 2006, 05:16 PM
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You don't want to use enough epoxy to fill the holes in the foam, so you're ok.
I do the same thing on the trailing edge. Tape them together, draw a line on the skin where the foam trailing edge goes, add epoxy, foam core, any re-inforcement, and fold the whole thing over.

Quote:
Originally Posted by Phillybaby
bit late, it's sat in the shed now under two 6" concrete blocks, gallon of glow fuel, two car batterys, tool box, vice drill case....

might have mixed up a bit too little tho, it certinaly won't fill the holes in the foam.
the two bits of ply were joined with tape at the TE and then folded over. this trapped a fair bit of epoxy so it should be strong there.
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Old Nov 13, 2006, 05:39 PM
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ang on.. draw a line where the foam TE goes...
I took 1/8th off the foam te as it says then my foam te went right to the fold, not that theres a gap where the foams pushed it out, at least, I hope there isn't once the tapes removed.

kinda ignored that bit about leaving the overlap because Iím not using the tape and figured the epoxy would glue that bit at the same time rather than go in later with the cyno.
also figured it's hard enough lining up all the foam bits without some being hidden away not actully on any line i can see.

ah well, just have to let my epoxy and glass TE take up the bit I left out.


anywhos, had another idea.
as a plank it needs a small amount of elevator with decent resolution, and still have a larger aileron throw.
hard task for two mini servos.

so hows about old school? one servo does ailerons, the other pushes the aileron servo on a little slider, you'd only need a small amount of slide and done with the full movement of the elevator servo you get great resolution.
depending on room I could either have the servos line astern and have the elevator move the aileron, or have them side by side ( as they would be ) and have the elevator move them both on the slider by having the other end of the arm fixed to a hard point.

only downside I see is the loss of differential, which could be set manually if you know the angles, or some elevator mixed in via the transmitter which is a bit of a bodge.
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Old Nov 13, 2006, 07:34 PM
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Message edited by user.
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Old Nov 14, 2006, 03:45 AM
Aeronut
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Phil - nice to see you've started - mine#s still in the box!
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Old Nov 14, 2006, 04:15 AM
by ZIPPER
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I found that the rear wing mounting would pull out if the landings were anything but perfect, so I reinforced it with an extra bulkhead, also mount the rear wing mount a little higher than the fuse, so the fuse dosent cut into the wing.

Glenn
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Old Nov 14, 2006, 11:56 AM
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No need to worry about servo resolution here Phil. Flying a zipper is a battle of elevator trim anyway. Some pilots mix trim in with the throttle stick. Sure the elevator movement is low but you constantly have to work the stick anyway.
If you trim for a slow pass, you'll need half down stick on a fast one and vice versa. Messing with the CG ain't gonna help much here either.
Think my servo are hs 81's.

Andy
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Old Nov 14, 2006, 01:53 PM
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Quote:
Phil - nice to see you've started - mine#s still in the box!
see where i go wrong than and don't make the same mistakes

biggest tip so far was to join both of the ply skins at the back with tape, turn over, apply epoxy and then fold it.
made things very easy.

i'd also reccomend numbering the core parts and laying them in the order required with all the weights and sheets of pressing wood to hand so you can pile them on top as quick as possible.
get your level sheet of wood on, jiggle the foam around till it all matches then pile it on making sure you don't twist anything as you go.

10g of epoxy wasn't quite enough for one wing half, go with 12-14 and then mix in the thickner till it's like vasaline.
mixing double that will allow you to do both at once and you have more than enough time for that.
cut a mini tile grouter ( did mine from a scrap of depron ) and key the epoxy before laying it all together.


i was pretty sure i'd be 4 axis flying, adjusting the mix% on the throttle till i found something good that still gave elevator on the right but flying trim on the left ( both sticks in the middle should give the cruise trim for that day using the elevator trim tab )
on the Wanabee it simply amounts to do i want to slow down and climb or go a bit faster, the effect on the elevons is hardly noticed.

the idea of the seperate servo was to up my elevator res from what, 2-300ish total points of elevator movement back to 1000 while the ailerons still had 1000 covering a far greater movement of the elevons in roll.
i figured it'd make this flying active trim more senstitve acurate and give full torque, your fault for writing about this stuff last month

DS.... i wish

andy, got any pics of your ballast and aerial installation
seen whats on your review, can make out the aerial hanging out the back but not how it got there.

whats your opinion on mouldie style hinges and the shaped fin?
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Old Nov 14, 2006, 02:26 PM
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Quote:
Originally Posted by Phillybaby
andy, got any pics of your ballast and aerial installation
seen whats on your review, can make out the aerial hanging out the back but not how it got there.

whats your opinion on mouldie style hinges and the shaped fin?
Aerial sticks out the back. Bit of tape then let it dangle.
Ballast goes under the wing!
Silicon hinge after paint and shape the fin.....
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