Aiden,
Thanks for the heads up! (now I know) I guess I'll try both methods out and find how clumsy I am with my F3P planes I planned on trying very light weight Spectra thread and small (.375" dia. x .014 thick) carbon disks to keep the thread from ripping the foam. I'm pretty sure what ever I use for an adhesive for the disks with will let go long before the Spectra or the disks break.

I’m going to try an Index 2.2, a Cirrus and a Bling Bling V3 with 9/64” hotwired foam sheet since I can't find "Climapor" anywhere, and my Depron stock is non-existant. I’ll put the sheets in an oven between two sheets of glass to remove any warps and give the foam a slight ‘skin’. In the past this has worked very well for 1mm foam sheet, so why not a little thicker.

I’ve seen a few planes that have ‘skeletonized’ airframes, done with a CNC router or by hand with a Dremal and a jig. Does anyone know what sort of weight savings this yields? I realize if you rout 10% of the plane away, you save 10%, but does anyone know what Depron or Climapor weighs either by square foot or square meter at 3mm thick? (lol, no I don’t even have 1 square foot left of Depron to weigh) I’d also be curious how much more fragile this ‘skeletonizing’ makes the aircraft since places will be ½ the thickness or less. My guess is it’s not worth the effort unless I somehow manage to make it to the F3P TOC (if there is such a thing) or just think it looks cool and fly well enough that it is not an issue.

Matt

Here's a dutch guy who did this.

more in this topic (dutch)
http://www.modelbouwforum.nl/forums/...k-elipsia.html

Savings on his model elipsia: 43.57 before and 36.34 after = 7,2 gram with depron sheet.

I used small pieces of plastic tube (control snake inners) to reinforce the anchor points when I used thread bracing. Each piece of tube was about 4mm diameter ands 3mm long. This was plenty to deal with flight loads but could still start tearing in a crash or rough handling. Your disks should do a better job spreading the load. Are you sure thin carbon disks won't cut through the spectra over time?
Tim Hart's guide to kevlar thread bracing for monoplanes is attached to the plan posting for my original Index design here. You may have seen this guide before but if not it's worth a look.

Depron weighs about 120 grams per square metre.
I think Extrupor is about 15% to 20% lighter but I'm not certain.

Aidan

Aio 1, I've seen the plastic tube used in a few places, but considering the stress the foam and thread will be subjected to, I figured the small carbon disks would distribute the load better. I'm not concerned about the Spectra thread being cut by the carbon for 2 reasons. 1. I plan to chamfer the hole with a tiny countersink while in the process of drilling the holds and while it is still in sheet form, and 2. because once the thread is glued into the foam/carbon disk, it shouldn't move or chafe at all. I could be totally off base since this will be my first scratch F3P build, but I'm going to give it a shot. (then I'll try the carbon rods)

Turbocingy, thanks for that link! After running it through Bablefish, I managed to glean quite a bit of useful info out of it. I don't remember who the person was, but it looked like they built a skeleton frame and covered it with Solite film. 107gr! Now that is a light plane! I also imagine the film covering added massive amounts of strength to the sub-structure it was 'laminated' to.

Slightly off topic, but does anyone make a light weight carbon prop for these planes? It seems to me that if everyone is trying to shave weight off their plane, the thick plastic prop would be a good place to start. Perhaps if everyone sent GWS or APC an e-mail or letter, they would build some F3P props out of carbon or just redesign the prop entirely to be lighter and made from a stronger material. I mean they are making props already, it is not a big stretch for them I had considered making a mold to build a few super light carbon props, but then again, I hardly have time to work on the projects I already have

Matt (who's always willing to learn)

Matt,

Wes-technik make suitable carbon props - they're mighty expensive though so try not to crash!

Aidan

I picked the Cirrus as my first 3D foamy

Hopefully I will finish it later this week.

I scaled it to 60cm wingspan. I'm going to use the HobbyCity 10gram motor.

Thanks for designing a great looking plane.
I've just built this Micro Cirrus 16" span.
Weighs 26g excluding the battery. All constructed from 2mm Depron except the lower fus half which is 3mm. U/C and pushrods are 1mm x 0.5mm carbon tube, struts are 0.8mm carbon rod.
Radio is modified PZ board with TOKI for rudder, AP03 for motor and a 1g 3A esc.

I've got a choice of batteries all 1S, 100mAh, 180mAh and 240mAh.

I plan to test fly it at Rochdale this Sunday.

PS the plane coffin is 6mm Depron !!!

Very nice Shaun! Be sure to post it in the "Micro and Indoor" forum as well.

Flew great...rolls about 2 per sec only change was to prop...now a 4.5 X 3 gws...Extra thrust made a difference.

I have a short vid...

http://www.rcgroups.com/forums/showthread.php?t=1018147

Shaun

Nice design!!!

I just downloaded the plans for this little baby. It's going to be my fist F3P plane. I can't wait to get it together. It'll be made out of stripped down foamcore (3.75mm thick) and powered by a cdrom motor.

Here's what I've done with the DFX file... it's much easier now to adjust to any thickness of material!

Marco

I am building one. What kind of pushrods would you reccomend?

I was playing with my 3D cad software and noticed that the rudder has a very limited throw due to interference with the elevator. Why is it that way? Is it because you don't need to use the rudder that much? I would be tempter to modify the elevator to allow more throw...

Heres my first Cirrus. Already am building another.....

Ok.. i have finnaly flown it and it does really well. Slow and has a fast roll rate. No coupling. The airbrakes really make it slow... all out weight with battery is 5.5 ounces

Nice. What size prop? And 2mm foam?