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shackwd
PostPosted: Sun Jan 23, 2022 5:31 pm 
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Couldn't resist, I have two Stupid Dumb Questions on a Bubble Windshield.

Boy, do I have a can of worms for everybody. Just something I've been mulling over for years. Not sure if most Thorp people would think it's sacrilege, stupid, or dumb.

The two Stupid Dumb Questions:

1) Is it possible to fly a Thorp with a bubble windshield with a deck that's not cut down?

2) What are your thoughts on the flight characteristics?

I've been emailing with Steve Hawley in SC. It's my home state. I asked him his thoughts on it. I'm hoping his huge wealth of knowledge and his love of open cockpit airplanes, he grew up with them, will help. Not sure what his reply will be this time, he did work with John Thorp. We both flew a Thorp without a canopy on a cut down deck, had the same experience of maybe not surviving, I thought about kissing the ground afterwards.

Don't know about modifying what I have, but maybe building or buying a new fuselage. Maybe having two Thorps. The following quote is from the EAA Feb 1965 Sport Aviation Magazine - Building the T-18 (PART 13) By John W. Thorp.

"Bill Warwick's T-18 did fly its first 50 hrs. without a canopy. A vicious burble off the sharp upper edge of the windshield caused the aft fuselage to vibrate and rumble. The combined effect of wind blowing down your neck and the fuselage rumble was very uncomfortable. Furthermore, the drag of the discontinuous flow at the windshield's edge materially affected the climb and speed.

It is possible that a bubble-type windshield could be used by those desiring to retain the T-18 as an open cockpit airplane without paying the performance and comfort penalties."

I do love open cockpit airplanes. Maybe I was a dog in a past life, I ride motorcycles and drive convertibles. Was just thinking the Thorp open cockpit, dirtied up with no wheel pants and exposed cylinders to slow it down, with a simple panel, might be fun, maybe some aerobatics. Thorp's original picture in the EAA Feb 1962 Sport Aviation Magazine inspired me, pic below. Just maybe someone knows if the conversation ever came up with John Thorp?

I know most people want speed, maybe keeping it clean is also a possibility. Thorp did say "without paying the performance and comfort penalties."

Just wandering if it's possible, considering the Macchi M.C.72 open cockpit 1934 world speed record still stands as the world's fastest propeller-driven seaplane (440.682 mph, 382.942 kn).

Thanks for the help,
Shack
N921JK T-18C


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shackwd
PostPosted: Sun Jan 23, 2022 6:33 pm 
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Maybe I should have Titled it, "A Bubble Windshield and a Dream". Of course, it could get to cold up there, and I say the hell with it. I was even considering putting the Ercoupe Bubble windshield with the sliding side windows it has, but I figured it would make more sense to stick to what Thorp designed.

Shack
N921JK T-18C


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Hagle347
PostPosted: Sun Jan 23, 2022 6:37 pm 
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I'm a firm believer in that the only 'stupid' question is the one not asked. You pose an interesting question. My first inclination on seeing your reasoning is still - Why would somebody want to do that to a Thorp? You are one up on me - I didn't get to fly one without a canopy, but I did read the reports and that's good enough for me. It seems most here are of the opinion that the airplane is just fine the way that John Thorp designed. Once modifications outside the plans are made, at some point it ceases to be a Thorp. There are renditions out there with Thorp fuselages and some type of straight no dihedral wing. Not a Thorp.
I remember being told that many things are possible - sometimes one must ask WHY and whether that airplane already exists.

Blue Skies,
T


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shackwd
PostPosted: Sat Feb 05, 2022 6:51 pm 
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Terry, you're right about asking questions. I believe the same thing. Sometimes making light of the situation brings that point across. I do appreciate your response, it appears to confirm my thinking that most Thorp people would say to leave the T-18 as is. It's hard not to agree, the canopy that was offered as an option gave her that P-51/Corsair look. She looks fast just sitting there. However, John Thorp first designed the T-18 as an open cockpit, with his quote from above saying "It is possible that a bubble-type windshield could be used by those desiring to retain the T-18 as an open cockpit airplane without paying the performance and comfort penalties."

It's now been about two weeks since I first posted at the top. I've lost count of my editing. My whys at the top are good reasons, but I'm still figuring out the total "Why?" I do believe the open cockpit with a bubble-type windshield would give me more ways to enjoy the Thorp safely. Perhaps, as John Thorp originally intended.

Thanks,
Shack
N921JK T-18C Orig Airfoil - John Kenton built, son Jack owned 26 years, I own/fly now.
N711RF T-18 - Roy Funk built, I flew about 200 hrs - Sold

Deleted in order to edit, I also deleted my extra redundant bubble windshield posts.


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James Grahn
PostPosted: Sat Feb 05, 2022 10:27 pm 
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The Sky Scooter was a high back airplane. I have one here in Vegas that I may some day put back in the air. But a Thorp with a cut down fuselage (ie a “normal Thorp” with a turtle deck) is a very poor substitute. I’ve spoken with many who have tried to fly it with the canopy off. Everyone said it was damn near uncontrollable.
I don’t see losing the lines or speed of our current design.
Cubes


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stevehawley
PostPosted: Sun Feb 06, 2022 1:20 pm 
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Many years ago, I think back in the early 80s, Dick Cavin dropped by my house in Skiatook, OK for a visit. His brother, don’t remember his name, lived north of me up in Kansas. One thing led to another and we decided to fly up there in my T-18 and visit him. His brother had an early built T-18 with the original high deck. It is and was the only one I have ever seen. The airplane was very rough and in my view kind of ugly compared to the cut down deck of later design. I can see why the first T-18 was safe to fly without the canopy. I made a very foolish decision to fly my plane without the canopy one time and can state without reservation that the plane is just barely controllable. Flying with your head out in the wind is great but I do not believe the T-18 is the best choice for the experience. I learned to fly in a Waco UPF-7, built and flew an open cockpit Stits Playboy back in the 60s, and still fly a Bucker Jungmann. Yes, I love getting my nose sunburned. Flew my T-18 a couple of days ago, it was around 55 degrees and I was very comfortable. The Bucker will sit in the hanger until the temperature is above 65!


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shackwd
PostPosted: Tue Feb 08, 2022 4:20 pm 
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Cubes and Steve, as always, I do appreciate your help and insight. You're both right about the cut-down deck. In the late-80s, I was able to complete one traffic pattern in the T-18 at Corona, with the flat windshield and no canopy, with the cut-down deck. The wind felt like it was occasionally making contact with the tail. I made very gradual shallow turns to complete that one pattern and land. Felt lucky to get back on the ground safely. Afterwords, giving Thanks to my Guardian Angel. Except for that one time, I've flown the Thorp like every other Thorp person, with the optional canopy that has now become standard as the only T-18.

You're both also right about the lines and speed. As mentioned above, the T-18 has the P-51/Corsair look. I agree, I think the Thorp is the best as she is.

My question. What if the bubble windshield that John Thorp said was possible, not the standard flat windshield, could be used with a good-looking, bolt-on aerodynamic fiberglass piece, on the cut-down deck, in place of the canopy?

I did find both of your replies in "Canopy jettisonable?" interesting. viewtopic.php?f=6&t=7648 Steve your comment " I doubt very much if a pilot could ever get out of a T-18 with a parachute on in uncontrolled flight." might be taken care of if there wasn't a canopy. Yeah, it's risk management.
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How can I make the bubble windshield work in the T-18 with a cut-down deck?:

I came up with questions. Would it make that much difference to replace the flat windshield with a bubble windshield? Keeping the bubble windshield basically the same size, using the same roll bar, maybe allowing the canopy to work with it. Building a bolt-on aerodynamic fiberglass piece on the cut-down deck in place of the canopy. As a preliminary study, maybe using the CFD program in SOLIDWORKS Flow Simulation to determine surface air adhesion. I'm not sure what flow analysis Thorp used in determining how the bubble windshield would work. Sounds like experience combined with pencil, paper, and a slide rule. My understanding is that he had over 30 years of experience as an aeronautical design engineer before he even started work on the T-18.

As you know, others might not, John Thorp was brilliant and prolific. Wikipedia shows the T-1 thru the T-28, I'm sure they left out a lot of history on him. Thorp did the preliminary design on the Cherokee, having worked with Fred Weick and Karl Bergey, putting him in league with the best. These aeronautical engineers were three of the keenest aeronautical minds in GA at the time. It's one of the reasons I respect the work Thorp put into designing the T-18.
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This time two quotes from the EAA Feb 1965 Sport Aviation Magazine - Building the T-18 (PART 13) By John W. Thorp:

"Because of the emphasis on cleanliness, canopy and cowling become very important and, along with flaps for reduced landing speeds (and Canadians), I am now committed to furnish drawings for these optional features."

"Bill Warwick's T-18 did fly its first 50 hrs. without a canopy. A vicious burble off the sharp upper edge of the windshield caused the aft fuselage to vibrate and rumble. The combined effect of wind blowing down your neck and the fuselage rumble was very uncomfortable. Furthermore, the drag of the discontinuous flow at the windshield's edge materially affected the climb and speed. It is possible that a bubble-type windshield could be used by those desiring to retain the T-18 as an open cockpit airplane without paying the performance and comfort penalties."
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"Why?" All the reasons I want a T-18 with an open cockpit bubble windshield:

Well, it's a difficult choice. I'm still deciding if I can actually do it. Why mess with perfection. Some T-18s are that good. N921JK T-18C could be cleaned up and use some paint, but she's still beautiful as she is. I was thinking of just doing the bolt-on fiberglass piece first. Maybe make different shapes and then test flying. Either way, it sounds like she would need new W&B, flight testing, and new aircraft operating limitations. As far as safety, Bill Warwick's T-18 with the original high deck was flown the first 50 hours without the canopy.

After I bought N921JK T-18C, I got to thinking. In the 90s, besides money, the other big reason I stopped flying N711RF T-18 was safety. I flew her over some pretty desolate areas, with no place to land. Looked like no survival if the engine stopped or I had a control failure. I figured I couldn't open the canopy anyway. Didn't know about carrying a punch, not even sure if somebody in a T-18 has used one. Back then, I did know about the ballistic parachute. I figured it cost too much, weighed too much, and was too complicated, really didn't want a rocket near my head.

So now, I'm thinking a T-18 that has an open cockpit bubble windshield with the bolt-on fiberglass piece might be safer while flying regular or aerobatic. It might help to have the option of jumping out wearing a parachute during an emergency egress since you don't have to open the canopy. A parachute would fit a whole lot easier with no roof. Yeah, if there is a place to land, I will stay with her to the end, and if need be I will not take her anywhere that might endanger people on the ground. What about after an emergency landing? I could find myself and the Thorp upside down on the ground, maybe a fire starting, the time difference could be life or death. I know as in all flying conditions, it's good old risk management again.

For landing, drag could help. Just wonder how much less the landing roll would be in an open cockpit bubble windshield T-18. The best I've done from the numbers in a canopy Thorp is 1500 feet. I'm sure others have done better.

For aerobatics, another reason for drag. I think a slower open cockpit bubble windshield T-18 with some drag would be safer. I remember a CFI in the mid-80s trying to show me a barrel roll in N711RF T-18. We ended up in a Split-S hitting 200 mph plus. My head was pinned to the canopy, no safety harness back then. I'm lucky he didn't pull the wings off. Yeah, I know about a Pitts, in the late-80s, Michael Church showed me a Lomcovák near the Queen Mary in a Pitts S2B. Since I can only afford one aircraft, I'd rather stay with the Thorp and go some places. The Thorp T-18 is still the best aircraft for the dollar. Again, I'm biased, I think she's the best period.

I was imagining that twinkle in John Thorp's eyes wearing a helmet and goggles, using modern technology and his brilliant mind to make a 1930s open cockpit aircraft more usable in the form of the T-18. I want what John Thorp originally wanted. Use and feel the wind to be part of the aircraft. To me, She's not just transportation.

For IFR, I rather keep her light, not install an autopilot. I know they're essential in hard IFR, but to me, IFR is a means to get thru a cloud layer. Per PilotWorkshops, once I get my IFR rating, I'll use flight simulation to stay proficient in IFR. Do have 20 hrs in a Link GAT-1, but that was way back.
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Thanks,
Shack
N921JK T-18C Orig Airfoil - John Kenton built, son Jack owned 26 years, I own/fly now.
N711RF T-18 - Roy Funk built, I flew about 200 hrs - Sold


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leewwalton
PostPosted: Tue Feb 08, 2022 4:44 pm 
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To be clear ... the windshield design has not changed since day one John Thorps original vision for an open cockpit aircraft used the same windshield we all use today. It turned out that John Thorp simply underestimated the airflow disturbance coming off the windshield. If you want an open cockpit aircraft there are options. That being said the T-18 should not be considered as one of them. I don't know about the rest of you but I can feel very much feel 'part of the aircraft' with a canopy over my head.

_________________
Lee Walton
Houston, TX
N51863,N118LW
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shackwd
PostPosted: Sun Feb 20, 2022 4:50 am 
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Lee, Thanks for the response. I highly respect your opinion. You grew up breathing T-18. I imagine you could put one together in your sleep.

To all, I should have worded the original title and content of this post differently and asked a more simple straightforward question. I did try to delete all my posts on the bubble-windshield and start over. I determined the only post I couldn't delete was this one since Terry had already responded to it, so I decided to stay with this post.

The T-18 didn't have the normal prototype development. It's my understanding Bill Warwick was building his T-18 as Thorp was drawing the plans. I know the drawings had the original flat-windshield, which had turbulence. Considering the speeds the T-18 was developing, the logical answer to the turbulence was a canopy. Of course, everybody went with it. Looks like most pilots and spouses didn't want an open cockpit anyway. Thorp understood this emphasis on cleanliness. An enclosed cockpit is considered by most to be more comfortable and practical for travel. For me, weather permitting, I feel more comfortable in an open cockpit, especially with the option of going faster than most any other two-seat open cockpit, which I do believe the T-18 could provide.

Terry asked why. Depending on who you ask, and who they're talking to, a why answer can range from a basic reply to a very in-depth one. My tendency is to give a fairly complete answer, including some emotion if needed. I understand we each have our own reasons why we do stuff. I was trying to go back in time to figure out what I wanted and what other people were thinking, including John Thorp. Perhaps be safer and learn something myself.

The most direct answer to why is simply to say John Thorp offered the bubble-windshield as a possibility for those who wanted an open cockpit, which is referenced in my posts above. That should be the only reason needed. Cash is the only thing holding me back, I will take it step by step. I was hoping for some aeronautical engineers or anybody who spoke with Thorp about the bubble-windshield, to offer their opinion. I will perhaps be the only person to take John Thorp up on his offer.

For the money, I can't find another two-seat aircraft that even comes close to the T-18 in overall handling and speed. Depending on the weather and a parachute, I do believe the T-18 would also be safer in flying regular or aerobatic, handling, and in an emergency, if there wasn't a canopy in the way.

Just one person's thoughts.

Thanks,
Shack
N921JK T-18C Orig Airfoil - John Kenton built, son Jack owned 26 years, I own/fly now.
N711RF T-18 - Roy Funk built, mid 80s to early 90s I flew about 200 hrs - Sold

Deleted my Feb 09 & 17 Post: Edited to clarify and not repeat myself too much.


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