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pwood66889
Well-Known Member
Welcome aboard, Allen.
And should your rather generously bladed prop ever point NW to 2J0, gimme a shout and I'll buy the coffee!
And should your rather generously bladed prop ever point NW to 2J0, gimme a shout and I'll buy the coffee!
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
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.
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.
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.
"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
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.
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.
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.
That's 75 pounds on each wire-braced spar. I'm searchin for total affordability. Maybe $6,000 with engine. Hirth F-33.
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.
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
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
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.
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.
cblink.007
Well-Known Member
Or any airplane for that matter!
- Joined
- Jun 28, 2020
- Messages
- 10
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.
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.
Aerowerx
Well-Known Member
And PVC will deform easily when under compression. Like in a bolted joint in shear.
pictsidhe
Well-Known Member
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
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!
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Sockmonkey
Well-Known Member
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.
WonderousMountain
Well-Known Member
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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)
Aerobatic is 6G limit load and 9G ultimate. (6x1.5=9)
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