"SkyWing" hybrid wing body ultralight

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

Allen

Well-Known Member
Joined
Jun 3, 2010
Messages
51
Location
Key West
This wingless aircraft is an ultralight I'm designing to build with 2" blue styrofoam and 1 1/2" PVC pipe for wing spars. Power will be a 22hp Briggs 4-stroke gas engine. meeceblog.wordpress.com
 

Attachments

Allen

Well-Known Member
Joined
Jun 3, 2010
Messages
51
Location
Key West
Well now I know where 2JO is. [near the glittering metropolis of good old Sopchoppy, home of the internationally reknowned Worm Gruntin Festival] It'll be my first destination when the SkyWing flies. [which will be nice if it happens. I'll rejoin the EAA to use their talented builders' savvy. ;=]
 

pwood66889

Well-Known Member
Joined
Feb 10, 2007
Messages
1,834
Location
Sopchoppy, Florida, USA
Yeah, Allen, that Worm Fest is quite the event around here. Can attest there to as a proud resident of... :)
But do join the EAA if you can. Some chapters can be standoffish (If you ain't a pilot...). Even hanging out at the local flying field helps.
Hear Marathon Key has a museum and EAA Chapter.
 

Victor Bravo

Well-Known Member
HBA Supporter
Joined
Jul 30, 2014
Messages
8,622
Location
KWHP, Los Angeles CA, USA
With no disrespect meant at all, and saying this trying to HELP rather than insult, you might want to change the name of the project.

"Sky Wing" sounds just like one of those ridiculous "Chin-glish"names they have for low quality ARF model airplanes made in China. To an experienced airplane person, that name immediately costs you half or 2/3 of the credibility before the conversation even starts.

PVC tube is another huge credibility-killer when you are talking about it in front of anyone who is involved in aviation.

Once again I am NOT trying to make fun of what you are doing or discourage you. I am, however, pointing out things that are doing damage to how knowledgeable people are going to look at your project.
 

Aerowerx

Well-Known Member
Joined
Dec 1, 2011
Messages
5,712
Location
Marion, Ohio
I was going to say run as far and fast as you can from PVC pipes, but others beat me to it.

In general 'pipe' is a conduit---moves something from one place to another. But 'tube'' is structural.

Since you already mentioned using 2" foam, why not make a spar out of that with fiberglass cloth covered with epoxy, and maybe some carbon fiber rods?

As already mentioned, use the search function on here. All of this has been discussed ad nauseum.
 

Allen

Well-Known Member
Joined
Jun 3, 2010
Messages
51
Location
Key West
I figure that since PVC tubed furniture is made for heavy people to sit on that it should not break under the stress of 500 pounds of ultralight airplane and pilot distributed over seven wing spars of 14 feet long.
That's 75 pounds on each wire-braced spar. I'm searchin for total affordability. Maybe $6,000 with engine. Hirth F-33.
 

Victor Bravo

Well-Known Member
HBA Supporter
Joined
Jul 30, 2014
Messages
8,622
Location
KWHP, Los Angeles CA, USA
Multiply that 500 pound gross weight by 6, which will give you a conservative figure for flying through a strong and unexpected gust or turbulence.

Then decide if seven pieces of cheap plastic PVC will support 6 times 500 pounds, or 3,000 pounds (that's a small car) with your life at stake.

1) I am sorry to burst any bubble here, but PVC is not a strong enough material.
2) If you are honestly trying to save money, don't forget to add the cost of the hospital and the mortuary in with the cost of your PVC wings. The total cost of those three things (trust me, they all go together) will be higher than the cost of aluminum.
 

poormansairforce

Well-Known Member
Joined
Mar 28, 2017
Messages
1,106
Location
Just an Ohioan
Multiply that 500 pound gross weight by 6, which will give you a conservative figure for flying through a strong and unexpected gust or turbulence.

Then decide if seven pieces of cheap plastic PVC will support 6 times 500 pounds, or 3,000 pounds (that's a small car) with your life at stake.

1) I am sorry to burst any bubble here, but PVC is not a strong enough material.
2) If you are honestly trying to save money, don't forget to add the cost of the hospital and the mortuary in with the cost of your PVC wings. The total cost of those three things (trust me, they all go together) will be higher than the cost of aluminum.
3) Each of the wing panels on my Minimax weighed about 30 lbs ready to cover. 75 lbs for just the spars is crazy.
 

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
8,812
Location
North Carolina
6061 tubing is not horribly expensive.
If you can't do the required maths to design a plane, that won't work either. Either too heavy, too weak, or most likely, both. There is no room for TLAR engineering in an Ultralight

Buy some plans, follow them exactly.
Minimax and legal eagle are popular for good reason.
 

enderw88

Member
HBA Supporter
Joined
Jun 28, 2020
Messages
9
TLAR (That Looks About Right) should never be trusted.
TLW (That Looks Wrong) should never be ignored.

Strength-to-weight of the PVC is not high enough. By the time you get the structure stiff enough to be safe it will be too heavy to fly. So, in a sense this is a self-correcting problem.
 
  • Like
Reactions: BJC

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
8,812
Location
North Carolina
I'm not too worried about the OP. If he gets this up to flight speed, the wings will snap off at an altitude of 0 feet. The danger is that he make improvements that give a 1.3g ultimate failure strength.
 

cblink.007

Well-Known Member
Joined
Jul 7, 2014
Messages
632
Location
Maryland, USA
I'm not too worried about the OP. If he gets this up to flight speed, the wings will snap off at an altitude of 0 feet. The danger is that he make improvements that give a 1.3g ultimate failure strength.
Not defending the OP, but seriously, who would use PVC for a spar?

When I was a kid at the tender age of 9, inspired by an article I read in Boys Life, I made a rogallo wing hang glider, using bedsheets and PVC. Worked great running down the small hill, feeling it lift up big time, until I put my sub-100 pound weight into the structure. I heard and felt a big snap, then took a little tumble down that hill....after falling about 10 feet!

My first aircraft design...

My first 0.1 ...

My first unofficial solo...

...ending up scraped up and a little bruised & bloody in a pile of broken PVC and bedsheets. Pride slightly bruised, but devoted more than ever to become an aeronautical engineer and test pilot.

@Allen , do not attempt to use PVC on anything structural. You can use a PVC structural foam in a composite sandwich application, but PVC is a no-go for structural!
 
Last edited:

Sockmonkey

Well-Known Member
Joined
Apr 24, 2014
Messages
2,070
Location
Flint, Mi, USA
At best a PVC pipe could be used as the internal form for a fiberglass structural tube. As in, wrap the pipe in fiberglass and then remove it.
 

Allen

Well-Known Member
Joined
Jun 3, 2010
Messages
51
Location
Key West
Thanks Victor, yours was the most informative reply I got. Not a high bar, though.
Your text sounded like you know how to stress test an airplane. I have seen 3X gross weight used for strength testing wings. Not 6X! It's not an acrobatic design.
Look at my photo at top of thread. It is a bi-plane with 1:1 ratio very low aspect sail wings. It is a cigar box frame made from 7 pvc 1 1/2" diameter spars that connect 4 styrofoam ribs.
These 7 spars will cost under $100 and weigh 35 total lbs. The 4 ribs cost about $300 and weigh 24 lbs. $400 is most of the 60-pound fuselage/wing cost. Cheap is right! Cheap is good. Otherwise poor people are never gonna fly.
The wing "box" is 15' square. How should I stress test it? How many sandbags, where, and how heavy? Where to put the supporting saw horses.?
What must be understood is that it does NOT have any skinny long cantileverd "wings" to bend and break. Look at the picture closely and understand it better before posting a reply. Keep this board informative and a supportive use of our time and resources.
It is a biplane with sails stretched across the top and bottom of a an external box frame. We're talkin ULTRa lite and ultra Affordable!!
The spars are 1 1/2" SDR-26 PVC pipe. <5 lbs apiece! 35 total lbs for spars. SDR-26 is thinner walled and about half the weight of schedule 40 pipe which is a thick-walled version for 330 psi pressure whereas SDR-26 pipe is only for 120 psi or pressureless drainage use . But it is just as stiff as thick-walled stuff. ;=] This SkyWing design yields a sixty pound bare airframe for four hundred dollars. It is modeled after a sled kite, simple and lite and flys Hi.





<<<<Multiply that 500 pound gross weight by 6, which will give you a conservative figure for flying through a strong and unexpected gust or turbulence.
Then decide if seven pieces of cheap plastic PVC will support 6 times 500 pounds, or 3,000 pounds (that's a small car) with your life at stake.>>>
 
Last edited:

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
14,613
Location
Port Townsend WA
The lift is mostly near the leading edge back to 25% chord. Place the sand bags on that first 25% chord. So use 2000 pounds (4X gross). Test to 6X if you want the usual 1.5 ultimate safety factor. (4x1.5= 6)
Aerobatic is 6G limit load and 9G ultimate. (6x1.5=9)
 
Last edited:
Top