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"I haven't flown any of my other planes since I built this stupid thing.
What's wrong with me?"


Depron Substitute - Foamboard

Foamboard seems to be the most easily obtainable substitute for Depron.

Bob Harold writes:

I first scratched the shiny cardboard with 80 grit sandpaper to break any water seal. I took foamboard and soaked it in water overnight in a plastic garbage can liner.

This morning I just rubbed the cardboard right off the foam. Now I have clean foam sheet 1/8" thick. I cannot tell any grain direction so I will not be able to have the grain of the foam run spanwise.

One piece 1250 mm by 800 mm is what is called out in the drawing - that is 31.5" by 49.2"

Further Notes: My stripped foamboard did not want to bend very easily to form the leading edge. I added some thumbnail creases to help it bend. This caused a small problem since the material bent too much at the creases causing me to work hard to get it to come out right.

Bob Botha writes:

I was initially concerned about obtaining Depron or a substitute, but it is no longer a problem. Foamboard is easily obtainable anywhere in the USA and removing the cardboard skin is a simple procedure.

I first cut out all the parts, then sanded them, as suggested by Bob Harold, but then, instead of putting them in a plastic bag, I put them in my bathtub and covered them with water, weighing them down with various heavy objects.

I wasn't as patient as Bob, so after a couple of hours I removed the pieces and peeled off the cardboard. Most of it peeled off easily, the remainder I rolled off using the heel of my hand. The whole process took about 15 minutes, no trouble at all, really.

I also chose not to use spray type adhesives, opting instead for my favourite contact adhesive for foam - Dave Brown's Sorghum. This looks like pure liquid latex rubber and provided it's used correctly is the best adhesive for gluing foam. Simply apply it evenly and thinly with a sponge to both surfaces, then let it dry thoroughly, before joining the parts. writes

I trashed the first effort when I had trouble making the LE bends. I was using 3/16th foamboard. I went to another store and found 1/8th inch foamboard ($4.57 for a 3'x4' piece) and it bent rather easily

I had no problem removing the cardboard using the two Bob's methods of soaking for a couple of hours, and then removing the cardboard and rubbing the glue off.

My Pibros came in at 8 ozs ready to fly. I used 270 mah pack and FMA S-80 servos with a FMA Micro Rx. If it flies as well as everyone says they fly, I'll be really happy.

Jim.Keller writes

My 125% stock foamboard Pibros had trouble staying up with the lower than normal winds. I decided to make a lightweight Pibros, incorporating some survivability measures that worked on its predecessor.

I soaked and peeled the paper off the foamboard and found that 60% of the weight is in the thick paper "skin".

I planed a 3/16" dowel into a "D" and stuck it on the L.E. to protect from the rocks, then covered with clear packing tape, using a minimal overlap. Final weight of the new airframe was 3.5 ounces, 8.5 ounces with radio gear for a wing loading of 3.8 oz/sq ft

I went up to our slope last nite and the wind was about double what it has been. I tossed the little Pibros off, expecting it to get blown around like a potato chip. What resulted was about the most
fun a body can have for only $3!!!

With the elevon rate set to an obscene level, it would do three consecutive rolls with only a few feet of altitude loss. Inverted flight was almost effortless. The vertical acceleration was amazing. Trying tight loops into the wind from a low airspeed resulted in a funny slow motion manoeuvre that
made me chuckle. Despite the wind speed, this thing tracked rock stable, except for a little humpty-bump now and then as it hit some shear or a gust. I attribute this behaviour to its low drag
compared to conventional planes.

I admit now, that my doubts about this thing being able to perform in strong wind were unfounded, based on my experience with a lots of conventional slopers!

Chris Handley writes
Here is something I learnt whilst contemplating building a Pibros.

Why waste good flying time waiting for the foam board to delaminate in the bath. The card lamination can simply and quickly removed using lighter fuel (liquid form) by pouring a small amount onto the card surface which is quickly rubbed in. Then give one corner a good squirt and pick up the edge with a finger nail and use the fuel again to work between the foam and card. The card can them be peeled off in one piece and repeat on the other side. To do this, a 100ml can of fuel will be required and about 15 minutes of time!

Mike Bailey writes
I used 3/16" foamboard striped of its paper for the top and bottom. I did not have enough for the bottom so I used blue foam for the middle. It came out at 6.8 oz.

I had a cheap 3 channel radio so set it up with separate elevator and ailerons.

I would use shoe-goo to mount a tow hook. Apparently the foamboard doesn't like it as it melted promptly. Not bad enough to really hurt it because it stopped at the blue foam.

Now if someone would plant some mountains in Kansas...

Depron Substitute - EPP

Mark Mech (Tempe, Arizona) writes:

I have been flying my epp version of a Pibros. It has a nose so it looks like an Avro Vulcan bomber.

It is heavy because I installed 6 LEDs and wiring for night flying and some spars for bungeeing.

It is also 36", 4.8oz wingloading and it flies great. Thermals like a handlaunch. Without the extra stuff I could get the loading down to about 3.8oz. [Loading for standard Pibros ~ 3.7 oz/ft2].

The whole idea behind epp is durability and you need the covering for that.

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Depron Substitute - Dow "Bluecor"

Al Mangani (USA) writes:

The material is Dow Bluecor P/P Extruded Polystyrene Sheet.

Dimensions: 4 feet wide x 50 feet long x 1/4" thick folded into 2 foot x 4 foot panels.

Density: 2.2 lbs per cubic foot.

[Editor's note: Depron is about 4.5 lb per cubic ft.]

For Bluecor in the UK, Graham Woods (UK) recommends trying
Sheffield Insulations,
West London

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Depron Substitute - "Coroplast"

Tord writes:
Sitting idle waiting for some varnish to dry I sat fumbling a piece of coroplast ... An idea struck me, that I want to test with you all (the idea is mine, but if you build one for me it's all yours!):

Have any of you tried building a Pibros from thin coroplast?

Take two squares of thin Coroplast with DIAGONAL WEBBING or wells or channels - you know what I mean!

Tape them side by side with strapping tape or any other heavy duty tape. Now follow regular pilbro practice using scrap pieces to fill the innards.I don't think you can buy squares with diagonal channels, so You will have a lot of scrap - remember to place the channels on the inner pieces spanwise, if possible!

Use three leftovers as fin and tailerons!

Tord writes (6 Oct 97) :

...When I did a density comparison, I was shocked to find that my "standard" (?) coroplast weighs 5 times what the foam core does.

In view of the fact that the Pibros is so much fun because it's light, so I've benched the idea for now. Maybe a part coroplast part foam construction? My coroplast is about 3mm thick, maybe you have a thinner variety?

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VH-grade polystyrene writes:

Before I found a handy source of foamboard, my first Pibros was constructed from a denser form of polystyrene foam known here as VH Grade polystyrene. It's appears almost the same density as Blue foam, but is much lighter.. I skimmed a few 3mm sheets off a block using 5mm piano wire either side to run the wire across. The wire of course melts a little more foam so you end up with an approximate 3mm sheet..

When sprayed with 3M adhesive it becomes remarkably flexible,and construction is much the same as normal,but use a little more care to avoid dinging the foam. Sand the leading edge with a fine sanding block to complete it... A thin piece of coroplast from a real estate advertising sign make a sturdy yet light vertical stab...

I also covered mine with a very light transparent packing tape similar to that used on the Zagi (mainly so I could see it) and it has proved just as agile and resistant to damage as the foamboard one!

Using this method,I guess normal polystyrene may work,no harm in trying if you have a few bit's lying around (doesn't everyone?) Go to it!

Tim Wood writes:

My method using 20mm polystyrene is not really cutting - more like melting :)  Lay the basic 800x400 triangle flat.  Then get a piece of greaseproof paper and lay it over the triangle. Using a hot iron you can melt the polystyrene into shape (the paper protects the iron - as wife wouldn't be too happy). Start at the middle (roughly) and work back to the TL applying more pressure here will melt a curve - and so on. It really works try it - it make making these sorts of wing simple - you need to sand it all down after but its neat ! and it makes the foam stronger as you are melting and compressing it together. I am going to try this method for making a proper electric trainer next.

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Depron Substitute - "Amocor"

R Mertins (Pensacola, FL) writes:

Re Depron, I have found a source for this material under the name of AMOCOR P14 FANFOLD it comes in a 4 X 50 foot bundle, and in the Lowes hardware store here in Pensacola, FL, costs $33.85. The company's address is

Tenneco Building Products
2907 Log Cabin Dr.
GA 30080-7013.

Anyone local interested in splitting up a bundle email me.

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Installing a Towhook

Bob Harold writes:

The Pibros flew well from a Zip start. I taped on a hook mounted to a 2'"by 1" piece of 1/16" plywood, located 1/2" ahead of the C.G.

I let two of my soaring buddies fly it so they now have the Pibros fever!

Bob Botha writes:
The short highstart that I have been using was originally intended for launching HLGs and comprises of 10 feet of 1/8" ID 1/16" wall thickness surgical tubing, joined to 18 feet of 20lb fishing line.

With the towhook located about 1/2" in front of the CG it shoots off at about a 45 deg. angle and continues to about 200-300 ft. - a whole lot higher than any HLG would go!

To attach the towhook, I recessed a 2"x1/2"x1/4" piece of hardwood into the foam just ahead of the CG. A modified cup hook was screwed into this. I made the fin out of solid foamboard (the cardboard left on) and epoxied it into a slot. This was just as well because the fin is the only "handle" to hang onto when pulling it back on the zipstart. I had visions of being left with the fin in my hand while the glider took off without it, but so far it has held on!

Possibly making a fin that extends through the wing to make a small sub fin would enable one to grip it there for a more normal above the shoulder launch.

Mark Mech writes:
Since finishing the proto Avro/Pibros I've flown it more in a month than I've flown anything the last year. I can get 150ft. off of my 20ft. bungee and even though the flights are only a couple minutes. I don't have to walk far to re launch, so I get a lot of flights in short session.

Jim Keller writes:
I tried launching my Pibros using my light Highstart. I taped a hook about an inch ahead of the c.g., and gave a 30% pull on the line for a test hop and away she went. Straight into the ground.

...I then tried releasing it with about a 30 degree angle of attack. This proved to be the thing, as it climbed out and reached about 80 feet or so and popped off, giving me about a 20 second flight - enough for a quick victory roll and a loop, then a gentle glide for a landing at my feet. Variations on this theme resulted in flights of higher launch altitude but about the same duration

On one launch, I added more than obscene amount of tension. I must have not added the angle of attack part. It left my hand like a Sidewinder off an F-16's wingtip, struck the ground about 20 feet away, then cartwheeled seemingly forever. The only damage was a slightly rumbled beak and the battery pack fell out. I replace the battery and flew again without touching a thing.

Observations: Pibros is quick on a highstart. The elevon trim has to be dead neutral, or you'll instantly have foamboard all over the place.

Pibros is a great little sloper, but definitely not a thermal duration competitor.

Chris Erikson writes:
Boy I'll bet some folks are getting sick of these endless Pibros posts.... But what the heck, it's just so darned fun!

...I realized I'd never tried the cat launches everybody's been raving about. We dug in my field box and came up with 20 1/2" x 3" rubber bands. We daisychained them together, then tied the last one on the end of a stout stick. I used a piece of music wire for a towhook about 2" in front of the CG.

My friend held the stick up at shoulder height, and I held the Pib by it's well anchored coroplast tail. I stretched back about 10 feet, lowered it till we had about 45 degrees of launch angle, and let fly. Unreal. The rubber bands have plenty of kick to accelerate this light plane, it would make this great "whoosh" noise and knife up into the sky to about 75-100 feet, I'd guess.

The sight of this tiny delta screaming up into the sky and not slowing down much had us both practically rolling on the dirt, I almost crashed on the first flight cause I was laughing so hard I couldn't see straight. If you can't get any tubing just try some hefty rubber bands, it works great!

...I haven't flown any of my other planes since I built this stupid thing. What's wrong with me?

:^0 DOH!

Bob Douglas writes:

Geez, we finally got the Pibros to hi-start. Gawd almighty !!. Used a 6 foot length of 3/16 surgical tubing, 20 feet of line with a couple of streamers attached about 18 inches below the tow ring to help pull off the ring (TOTALLY unnecessary - trust me).

6 backward steps for tension and pointed it at about 30 degrees. Did I mention that this is a two man operation ? The launcher needs to hold the plane with both hands by the LE and the Pilot needs to stand behind the launcher to tell him either more up or more down. About 30 degrees seems to be cool.

One final waggle to be sure that you remembered to plug in the battery and tell the launcher "anytime" (I assume this is similar to a carrier pilot saluting the catapult officer when everything is green - there ain't much left to do except hang on and pray fervently).

HOLY MOLY what a launch !!! The darn thing accelerates to about mach 4.5 (I exaggerate - but not much) in three and a half feet and ROCKETS up the line. It was shedding the tow ring at about 15 feet but that didn't seem to slow her down much. Launches were phenomenal !!! She just kept climbing to around 100 to 125 feet.

After the peak, it was just float around in a big circle, right or left or loop right at the top and land at your feet.

Next time I'm going to try a roll or two on the way up the zoom and I've also got some longer rubber and line. I'd like to try to keep her on the line a little longer. The streamers were not needed at all. The line pulled off with no problems but they might be needed with the longer line.

BTW: NO up or control inputs are needed at launch. Just make sure that the Pibros glides straight and level BEFORE you try the hi-start.

This darn Pibros is just getting funnier and funnier !!!

Chuck Hough writes

Have been launching it with a 25 foot piece of surgical tubing and a 30' piece of 50 LB. string with a welded metal ring. I tie it to a park bench and have at it 150 feet may be an exaggeration but not that much. The fun begins 50 feet after release. The rolls and the loops, both inside and outside are incredible. I launched this last weekend over fifty times, rolling out inverted, then giving full down elevator doing an inverted inside loop, then circle around and play with the light air and a landing. Hook it up and go at it again!.

I too built a larger version, 40 inches, to use standard gear. It flies equally as well. I flew it last week at the beach in cold winds and blowing sand. Great in medium wind off the cliffs.

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Euro-Pibros from NSP

Al Mangani (USA) writes:

The Euro-Pibros from NSP weighs 7.3 ounces all up with a 250 mah square pack and 2 S-133 Futaba micro servos and a Hitec 535 receiver.

Elevon pushrods are 1/16" music wire about 7 inches on each with a brass coupler and brass Sullivan clevis at the servo end and a Z-bend at the elevon horn which is a Goldberg large nylon horn which I mounted to the elevon with hot melt glue.

On my next ship I plan to use 1/16" homemade elevon horns epoxied into the elevons with 5 minute epoxy in a hacksawed slot. I think this will provide a more durable horn setup. make sure both horns have identical holes and are located in EXACTLY the same position relative to the hinge centerline, both in the vertical and horizontal planes.

Battery pack, receiver and servos are held in with Scotch 2" wide filament packing tape that I picked up at Office Max. I traced the servo, battery and receiver locations on the top surface once I had everything in position to balance the ship at 208 mm from the apex. Then I routed out the "pockets" with my Dremel tool with the router attachment set at about 1/2" deep and carefully opened up the pockets till the respective components fit with a somewhat tight fit. It is not real hard, in fact I did mine at the motel room during the Nats..... ;-))

I expect this one to come close to the 7.3 ounce finished weight. Balance is critical. I balanced mine at 208 mm from the apex of the delta. The plans call for 210 mm. There is not much latitude here. Stick to what Marcel says.

Initial flying setup should be CONSERVATIVE. I really bashed mine, thinking I could handle the 45 degree elevon throws. This thing is a handful with 45 degree throws. Start with 20 degrees and go from there. Hand toss it a few times, dialing in some up trim. Mine took about 1/8" of up to give a reasonable glide. Zip starts are flat and fast. Keep the stick inputs minimal till you get the hang of it. A 20 pace zip start will launch it at a 10 degree up angle at 40 mph. Keep the speed up for 250 feet or so and make a GENTLE 180 degree turn back to you, KEEPING THE SPEED UP!!! If you give it too much up, it simply raises its nose and stops flying! It will then mush to the ground. I am not anywhere near an expert pilot, but I got the hang of it quickly.

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Trimming and Flying

Bob Botha writes:

[My Pibros] weighs 9oz and flies beautifully, except it won't loop! One thing I discovered, though, was that it is not that touchy about CG position. I experimented by moving it back and forth and other than having to adjust the elevator neutral position, it remained quite stable throughout the range, but still wouldn't loop! Possibly if it were heavier it would have the necessary momentum to carry it through, but then its light wind attributes would be lost. Oh, well, you can't have everything, I guess! All I can say is that I've had a lot of fun with that $5 glider.

Happy flying - Bob

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Adjustable Ballast

Rick Swancott writes:

I am experimenting with a light balsa keel together with squeeze-it-on lead ballast for instant C of G adjustment. I am finding it very helpful for both launching and C of G adjustment.

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Bamboo strengtheners

Rick Swancott (Sydney Australia) writes:

Just completed two pibroses.

Try strengthening the leading edge by taping bamboo meat skewers from the front to about 10 cm back. bamboo is very hard and yet exceptionally light ( a natural composite material) and can be found in any supermarket. This stiffens up the front end and helps to stop the crumple problem.

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Richard Frawley writes:


I have just build the worlds first ultra-light weight Pibros...4oz..

1. Use 50mah batteries (gives me 30mins)
2. Use those tiny FMA direct Servos
4. Use a de-skinned 4 channel ultra-micro rx
5. Use 2mm carbon pushrods
6. No tape anywhere
7. Carve out the centre of the internal triangles

I think I could increase the wing area to get a lower wing loading, I am going to try a 25% increase, when I get some building time in the next week or so. I have not flown this one yet, but I have flown the 5.5oz one I build with 100mah batteries and wire rods. Penetrates and flies in as normal, incredibly fast elevator response, flying to 20+mph winds no issues.

Richard Frawley writes:

The best Pibros I have is my 5oz one..the message, the lighter the better. Any talk of anything over 9oz, is silliness.

The agility of the 5oz one is amazing, much more responsive than the standard 8oz one. Also much, much harder to damage..

Penetration is just as good, I thought it may be a problem, but it isn't.

Bernhard A Goetz writes:

Having always being interested in the Pibros I built a 1 meter span version to take standard radio gear.

I got some company in Cape Town to cut me 4 mm thick foam sheets and away I when as per the normal instructions.

I added a bit of strapping tape in a X shape to the bottom of the Pibros (just to put my mind at ease).

Flying the Pibros was great, its easy , very stable yet has a very impressive roll rate - not bad for about R10-50 and some change!!!! Hovers are nice and easy - inverted or 'normal' flying. Maybe the tail should be made of coroplast for that occasional combat hit!

I did find that the 'elevator' trim seem to change through the flight with more up trim being required as the flight progresses - any comments from experienced Pibros flyers would be welcome to remedy this one and only problem. Well that it - just had to let any doubters know - standard gear in a 1m PIBROS , no problem.

Amish Desai writes:

I built my Pibro 50% larger with foam board found in the US in craft shops. Total weight was 21 oz which comes to 5 oz/sq. ft wing loading. I had an old radio so I had divided the elevons into ailerons (outboard) and an elevator (centre).

First couple flights were not too good because of pilot error but after a couple minor dents the plane flew great. Next time a little more wind up the slope is needed; I only had 5 mph puffs.

In scaling up I added TWO more layers of triangular foam sheets so that the delta wing thickness was scaled 50% more also. Great site....creative design - Thanks to the inventor Marcel!

Mike "Inspector Gadget" writes:

The only foam I could find locally (and quickly) was 6mm (1/4") Dow Corning pink fan-fold insulation (25 2' x 4' sheets). So, I upscaled the Pibros 50% and used 3 sheets. I used my standard RX and a 650 mAh flat pack with 2 micro servos (HS-80's).

Comes in at 22oz with a 1.2m wingspan. Since I was using twice the normal thickness of foam, I took Richard Frawleys advice and cut sections out. But, I didn't think to do this until the airframe was done and I discovered it weighed in at over 16oz. So I cut triangular sections out of the finished frame. Cut all the way thru and then cover the holes with ordinary packing tape (like some use to cover EPP models). Then I heat shrunk (?) the tape to get it nice and smooth.

Final frame weight, 14 oz. Looks similar to a "built-up" covered stab. Only had 5 mph breeze to try it out. No long slope flights today. Also gave the histart a whirl. 33' of 1/8" ID tubing, 60' of cord. Off like a rocket to 150 - 200 ft. Not too bad. I think it's too heavy for its scale.

I've got a ton of this "pink foam" left, so the next project is to up-scale the Pibros to 2 meters! This should be ample surface area for my standard gear, plus I want to thermal this puppy! Should help sloping on those slow wind days, too. ;-)

Many thanks to Marcel for sharing this with us all! :-)

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Last updated June 06, 2002