Peter Sripol is at it again...

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

Michael Silvius

Well-Known Member
Joined
Jan 26, 2020
Messages
90
Location
Maine USA
No diagonal/drag strength. Take every other rib and add some angle inside of the spar box to prevent the structure from paralleling.
You can use paper over the solid foam but it dents easy. Works fine tho and paints with latex well.
The Tailwind has no diagonal bracing, the plywood sheathing carries the torsional load. Same with the Pik 26 wing in the two photos I posted.
In the case of the sketch none is needed as the solid foam caries the torsional load. Peter used no diagonal bracing on his and it was not even solid foam.
 

Protech Racing

Well-Known Member
Joined
Jul 10, 2020
Messages
417
I'm doing the same. Sheet the flat bottom between the spars. Set the upper ribs on the sheet. Stiff and drag controlled.
My spars are at 28% and 90% tho.
 

karmarepair

Well-Known Member
HBA Supporter
Joined
Jan 13, 2011
Messages
356
Location
United States
All tails "shake" from prop blast. It isn't "flutter".
All tails "shake" from prop blast. It isn't "flutter".
There are TWO videos on this plane. The first is about the fuselage and the empennage, and he taxis around with the Vitorazzi running.
He hadn't built the wings yet. The first video shows the steel tube forward fuselage, and the poplar "stick built" warren truss aft fuselage and empennage, which is fabric covered (I'm betting Oratex). Put another way, the controversial Vinyl Wrap over Foam construction is NOT used on the horizontal stabilizer. Initially, the brace wire (singular, per side) for the horizontal stabilizer ran from the rudder post to the AFT spar of the H.S. And in the FIRST flight in the SECOND video, it pretty clearly flutters. About 8 minutes into the SECOND video you can see where he added another brace wire to each side, from the LE of the rudder to the FWD spar of the H.S.
 

karmarepair

Well-Known Member
HBA Supporter
Joined
Jan 13, 2011
Messages
356
Location
United States

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
14,740
Location
Port Townsend WA
Ah, ok, he said it fluttered. The video I saw must have been a shorter video without that segment or I didn't notice.
 
Last edited:

Michael Silvius

Well-Known Member
Joined
Jan 26, 2020
Messages
90
Location
Maine USA
Marvin is using EXTRUDED Polystyrene foam here. Higher mechanical properties than EXPANDED Polystyrene foam for the same density.
Yea but the point that Protech Racing raised was about the need for diagonal bracing.
I contend that no diagonal bracing is required in Peter's plane, the PIK 26, Tailwind or the Flying Squirrel. Torsional loads are carried bythe solid blocks in case of that sketch I posted, and similarly by cored foam in the case of Peter's plane. And in the case of the PIK, TW and FS by the skin.
 

karmarepair

Well-Known Member
HBA Supporter
Joined
Jan 13, 2011
Messages
356
Location
United States
Yea but the point that Protech Racing raised was about the need for diagonal bracing.
I contend that no diagonal bracing is required in Peter's plane, the PIK 26, Tailwind or the Flying Squirrel. Torsional loads are carried bythe solid blocks in case of that sketch I posted, and similarly by cored foam in the case of Peter's plane. And in the case of the PIK, TW and FS by the skin.
You and I are in complete agreement on these points.

The only questions in my mind are 1) IF Peter used EXPANDED PolyStyrene, if it's strong enough to take the Drag and Torsion loads, and 2) how long the vinyl will last.
 

Michael Silvius

Well-Known Member
Joined
Jan 26, 2020
Messages
90
Location
Maine USA
You and I are in complete agreement on these points.

The only questions in my mind are 1) IF Peter used EXPANDED PolyStyrene, if it's strong enough to take the Drag and Torsion loads, and 2) how long the vinyl will last.
I am sure that for his application Peter did the math and concluded expanded polystyrene it was strong enough.
How long will it last? well, I think someone here recently mentioned that Peter builds disposable airplanes. He is really experimenting to see what can be done.
That said I know the guys in Argentina building the Facil are using expanded polystyrene (something they call Tergopol down there) for their ribs and it appears to be holding up well.
1.jpg2.jpg3.jpg
4.jpg
5.jpg6.jpg
 
Last edited:

stanislavz

Well-Known Member
HBA Supporter
Joined
Aug 21, 2016
Messages
945
Location
Lt
That said I know the guys in Argentina building the Facil are using expanded polystyrene (something they call Tergopol down there) for their ribs and it appears to be holding up well.
Write him to add layer of fiberglass on each side of his foam, it will add only 500-800 grams per wing, will give structural ribs.. By testing it with sandbags - eps works only in compression, but in real life - you have load on top skin only, and eps works on tension.. Eps and tension are not friends.
 

Michael Silvius

Well-Known Member
Joined
Jan 26, 2020
Messages
90
Location
Maine USA
Write him to add layer of fiberglass on each side of his foam, it will add only 500-800 grams per wing, will give structural ribs.. By testing it with sandbags - eps works only in compression, but in real life - you have load on top skin only, and eps works on tension.. Eps and tension are not friends.
So far there are about two dozen of these MS FACIL aircraft. None has fallen out of the sky yet. Due to the limited supply of materials and punitive import costs they are built entirely out of locally sourced materials. MIG welded 1025 tube. Agricultural irrigation pipe spars. Tergopol ribs. Greenhouse plastic sheeting for covering. Fiat or Renault engines for power. Leading edge cuff is quite large as you see and made out of fiberglass and polyester resin over a mold and then glued onto the wing. I am fairly certain Miguel Scheinin did the math and knows the numbers.1.jpg
 

stanislavz

Well-Known Member
HBA Supporter
Joined
Aug 21, 2016
Messages
945
Location
Lt
So far there are about two dozen of these MS FACIL aircraft. None has fallen out of the sky yet.
Better late than sorry. I would still insist on it. This kind of load on eps - tension is not being tested with sandbags.
 

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
14,740
Location
Port Townsend WA
Sandbags do load the inner face of the foam in tension. Kind of hard to simulate flight loads exactly with sand bags. Any testing is more than most do.
 

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
6,040
Location
US
That study is a good find, thanks for posting it. It contains info on EPS that is hard to find. I've been thinking about lightweight under-seat energy absorption using EPS, and the crush data in their graphs is perfect.

I'm a bit surprised that the tensile strength of EPS is as high as they show. If someone is using the very low density EPS sheets from the hardware store (approx 1.8 lbs per cu ft = approx 30g/L), the tensile strength of .45 MPa (65 psi) is higher than I would have guessed. I wonder how a real EPS rib in a real airplane subject to vibration, flexing, heat, lots of repeated load cycles, etc would perform. XPS would seem less prone to brittle fracture and resultant tensile failure over time, but that's just a guess and not real data.
 

Aviator168

Well-Known Member
Joined
Sep 21, 2012
Messages
2,272
Location
Brookville, NY. USA
I am sure that for his application Peter did the math and concluded expanded polystyrene it was strong enough.
How long will it last? well, I think someone here recently mentioned that Peter builds disposable airplanes. He is really experimenting to see what can be done.
Of cause. Polystyrene foam has a tensile strength of 10 psi which is much higher than the wing load (4 lb/square ft) of an UL. At full UL speed, the drag on wing is less than 50#. Say his wing is 8" by 25'. That's only 0.02psi.
Will his plane last? Hell no. I would never fly a plane with a wing built like that. The wing can't take any torsion load. Put either ailerons or flaps on, someone is going to die. I am saying a foam wing is not good. The LongEZ has foam wings and it goes 200mph. He should have at least connect front and back spars, take advantage the struts so the wing can take on torsion loads and it is easy to do.
 

Protech Racing

Well-Known Member
Joined
Jul 10, 2020
Messages
417
Treated how? Latex paint with slow the gassing off. ? I may paint the foam and the GG glue . The glue needs it to last and stops the hardening/ browning of the GG.
 
Top