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Old Dec 03, 2010, 06:58 AM
Fly fast, Dont crash.
Thepasty's Avatar
Cornwall, UK
Joined Sep 2006
2,459 Posts
Quote:
Originally Posted by IBCrazy View Post
So I think I can find lamfilm at an office supply place. I guess 1.5mil is thick enough. How do I apply it? Iron it on? 3M 90 spray adhesive? Heat gun and a sock over my hand? This is new to me, but I'm ready to try it. The crossweave worked great. If this is better, I'm going to do it.

-Alex
It comes in a couple of different types, softer more flexible stuff as well as harder and more rigid. You can have the same thickness but different properties.

I use 125micron CP (I think CP is the soft stuff) for the top wing surface so that I can get around the curves and I use 250micron DI (DI being the stiffer stuff I think) for the lower wing surface as it adds alot more puncture resistance.

You want to either buy a roll or two of the stuff or find someone whos got a roll and is selling is by the metre. From the roll is the way to do it as you can cover an entire wing or wing half in one.

Its best you do some reading on here before you go out and buy a load, you want to make sure you're getting the right stuff and experience it in its best form.
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Old Dec 03, 2010, 07:00 AM
Fly fast, Dont crash.
Thepasty's Avatar
Cornwall, UK
Joined Sep 2006
2,459 Posts
1.5 mil = 38.1 micron

You want to be looking at atleast 100micron.
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Old Dec 03, 2010, 07:01 AM
Post # 20 million
Kev.au's Avatar
Joined Aug 2009
2,636 Posts
I love a good scratch build, i'll be following along.



Cheers, Kev.
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Old Dec 03, 2010, 07:16 AM
USA: LakeGeorge, New York
USA
Joined May 2010
4,523 Posts
I like it Alex!
keep it up....one day people will start buying
these a lot from you..... "I will", once you
workout the Kinks for me ;-)

great job!
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Old Dec 03, 2010, 08:35 AM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,403 Posts
Man the "New Stuff" is expensive. $73 per roll with a 2 roll minimum I guess I'll go with the CP for $20/roll. If I have to deal with a little flexibility, so be it. in the mecahnical enigneering world (which I know little about, mind you) flexibility reduces stress.

So building strictly to the equation:

Force = change in velocity/time^2

Any way I can increase the time reduces the force the plane feels on impact. So more flexible stuff might be the key to having the whole airplane survive rather than just the wing. IT should be light anyway and the arrow is already glued int. I'm sure it will be fine. I really like the fact that it isn't as messy as the Henry's cloth. That 3M adhesive gets everywhere!

-Alex
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Old Dec 03, 2010, 08:47 AM
Fly fast, Dont crash.
Thepasty's Avatar
Cornwall, UK
Joined Sep 2006
2,459 Posts
that $73 roll is 50 or 100m long tho isnt it? which per metre makes it really cheap compared to your usual hobby coverings etc.

Some slope soaring outlets (it was originally pioneered for slope soaring use)sell it per metre so you dont have to outlay large wods of cash.

The CP will be fine for your needs, the DI is used more by the slope soaring guys as their planes dont have the luxury of soft landing areas... bin them in the nearest bush or least rocky area can be the softest choice
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Old Dec 03, 2010, 09:01 AM
Crashomatic
CrashMeUp's Avatar
United States, CA, SF
Joined May 2010
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Pure laminate is too flexible for the EPP where the plane can take really strong shocks.
Talking 80km/h meets a tree here... That's where I have fiber. Actually the wing I think about has 2 small spars with additional fiber on the tip (nose), rest is laminate, but fiber only is already great. (the fiber strengthens is enough so that the spars don't break, only flex even on big impacts - this is a special case as the batteries are right behind the spars (and pop out on crash (the EPP is thin here) ) - otherwise there would be no spars)

I tested it on scratch before doing that and I cannot break the fiber part of the EPP even hitting with all my (shameless) strength against a brick wall corner. Doing the same with laminate breaks the EPP. Of course thats not your regular crash, but I wanted it really strong.

If you think laminate is stronger for such impacts, then please elaborate.
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Old Dec 03, 2010, 09:25 AM
Fly fast, Dont crash.
Thepasty's Avatar
Cornwall, UK
Joined Sep 2006
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define stronger... lamfilm doesnt just give the epp more impact resistance it also adds a huge amount of structural strength and rigidity to a wing, cross weave tape doesnt compare.

the fact that slope soarers are moving away from lagging their planes in cross weave tape in favour of using lamfilm is proof enough.

Slope soaring planes take more of a beating than your average powered plane, an impact of 80km/h into rock let alone tree isnt classed as a hard impact for these guys.

I'm a slope soarer and I've moved away from crossweave tape in favour of lamfilm on all my epp models, so I am talking from experience also.

Of course you still need the normal spars etc in a wing that you would have with any wing construction, lamfilm does add alot to this tho, its not simply about making it impact resistant like tape is.

Maybe you havent been using it correctly or you've got the wrong type/thickness.
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Old Dec 03, 2010, 10:09 AM
KB3VOJ
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USA
Joined Sep 2007
2,591 Posts
Check out the grim reaper thread. It is a combat wing designed to crash every flight and hold up. They are using 3M bi-di tape on the leading and trailing edges as well as reinforcement areas. They then cover the entire wing in laminate. It is an EPP plane with shock corded fiberglass spars top and bottom in an A pattern. This is my next fpv plane that is already headed my way as we speak.
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Old Dec 03, 2010, 10:10 AM
Crashomatic
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United States, CA, SF
Joined May 2010
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Laminate gives a much better finish (=aerodynamics) and is lighter, yet pretty strong, that's why it's used as far as my knowledge goes.

Note that I'm not talking about crossweave tape, but fiber weave with 3M90, where the 3M90 is at least half the strength/flex, i'm not sure if we talk about the same thing.

I have a couple of plane with real fiber tape (and some regular EPP glue cause the tape doesn't stick that well) and these aren't strong at all in comparison.

I'm not sure of the thickness of my laminated film as Chris provided it for me, but i think (?) it's 10mil.

Another note, my fiber section is also covered by laminate
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Old Dec 03, 2010, 02:21 PM
I LIKE WAFFLES....
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Powder Springs, GA
Joined Sep 2010
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http://www.rcgroups.com/forums/showp...7&postcount=90

/thread jack
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Old Dec 03, 2010, 06:13 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
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Covering

I cut grooves in the top of the wing for my two half arrow shaft booms. I used Welder adhesive to glue them in. Once glued, it was time for covering.

Since patience is not a virtue I am blessed with, I decided to go to the hardware store to buy some of the Henry's roofing patch. As luck would not have it, they were out. So I opted for plastic mesh material called "silt fence fabric". It seemed very light, tear resistant, and cheap ($20 for 50 feet). Granted it's not stiff, but I'm looking for deflection. It apparently has a tensile strength of 124 lbs, which is plenty.

To apply it, I sprayed both the wing and the mesh with 3M 90 adhesive and let it get a little tacky. While it still was a bit wet, I put the mesh over the foam and pressed it in with a hotel room key card (I could have used a putty knife, but this was convenient). The mesh is porous, so the glue made it's way through in some spots, but adhered rather quickly. I then flipped it over and repeated the process.

What came out was a fairly stiff wing. However the surface was a bit rough, but there's no doubt it will not tear... at least not easily. Aircraft weight is now up to 6.6 oz.

I wanted a bit of color and a smooth non grabbing surface, so I chose to cover the wing with Econocote. I used a light coat of 3M 90 adhesive this time (rather than the heavy coat I used on the mesh. I waited until the glue was aggressively tacky and wrapped the wing. Once wrapped and dry, I used a heat gun to smooth out the wrinkles. This smoothed out the surface significantly.

-Alex
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Old Dec 03, 2010, 08:22 PM
Engineer for Christ
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Amherst, VA
Joined Jun 2006
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Airframe complete

The airframe is now completed. All I need to do is drop in the electronics and FPV gear then fly it.

The tail was made out of 4mm coroplast and glued with Welder adhesive. I already tested it's strength out by slamming the back of the plane into the ground. It just bounced

The fuselage is perhaps the most durable part of the plane, which is good because it will inevitably be getting slammed the hardest. I sheeted 2" EPP with 2mm coroplast. I could use this for a bumper. It takes the hardest wrecks with little to no deformation.

The wing and fuselage are joined by my 'breakaway method". Velcro straps hold the fuselage to the main wing. In the event of an impact, the straps will release distributing the stress throughout the airframe rather than on the joints only.

The weight with battery is up to 20 oz. I still need a motor, ESC, propeller, aileron servos, and FPV gear. All that will add about 9-10oz weight which will hit the target weight of 30 fairly closely.

-Alex
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Old Dec 03, 2010, 08:55 PM
I LIKE WAFFLES....
SENTRY 62's Avatar
Powder Springs, GA
Joined Sep 2010
2,452 Posts
Take a pic of it beside a common-sized object so I can imagine the scale size.
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Old Dec 04, 2010, 11:25 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,403 Posts
Airplane completed!

I finished the Wraith this morning and already got the maiden flight out of the way. This thing flies faster than I thought. It goes 55 mph yet has a flight time of 8 minutes at wide open throttle and can sustain flight for 30 minutes with good throttle management.

I have not crash tested it yet, nor have I flown it under the hood. My BoB transmitter died on me just before the flight, so I never got to pull the hood down

I also will be flying this one on my old JR XP6102 radio. It appears I somehow lost my 9CAP

-Alex
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