Thorp Air Command - T18.net

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

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

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

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.

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

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!

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

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
KEFD

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.

Interesting question.
My 2 cents worth:
As noted in publications and earlier posts, the air coming off the windscreen is very turbulent if there is no canopy there. I'll also note that a lot of guys put their air vent on the back of the canopy because there is a high pressure area there, and that same pressure tends to keep the canopy closed in flight. So lots of air curling around back there, but it smooths out aft of the canopy enough to give authority to the vertical fin and rudder.

So my thought, strictly as a mental exercise on how to make this workable:
- If you replaced the existing windscreen with a curved one that extended further forward toward the firewall (think like the front of a Zenith 601 type bubble canopy) to change how the air comes off the wind screen, so that the air flows more around the side instead of primarily over the top
- Even with that, you would probably want a dorsal fin (dorsal ridge) running forward to the back of the cockpit to add some stability

That might work, but IMHO the air would be beating you in the side or back of the head the whole time.

Bottom line, you might be able to make it work, but there are plenty of other airframes better suited to open cockpit flying.

Andrew

Actually, some did fly open cockpit with the original flat windshield and original high rear deck. Amazing what you can find online in the old EAA Sport Aviation Magazines. Nice cover in June 1965, open cockpit out front, shown below. March 1966 pgs 31-33 had a nice article on the original N12055, pic below, that Bob Kaergard built, open cockpit. N12055 has a very interesting history. It appears John Twigg has Bob Kaergard's second built T-18 N12055, closed cockpit. This brings me to Oshkosh 1966 which launched with "The 1966 Flight Rally". In the amateur-built catagory, Thorp T-18s got first and second places. That second place T-18 belonged to Bob Kaergard still flying open cockpit, pic below. Sadly, the first creation ended August 11, 1967 in a hangar fire.

Looks like Bob Kaergard flew over a year open cockpit with original high rear deck, including Oshkosh.

Included Bob's progression:
1) Bob Kaergard's T-18 flies Oct 10, 1965
2) Sport Aviation • 1966-Mar • Pg 31-33 Kaergard and His Komet By Dick Cavin
3) Sport Aviation • 1966-Oct • Pg 45-46 The 1966 AC Flight Rally (1-2 was Lee Hamlyn & Bob Kaergard, both T-18s) also Wood NL18 August 22, 1966 Lee won the AC Spark Plug Rally at the Fly-In. I am also happy that Bob Kaergard came in second.
4) Wood NL21 April 6, 1967 - As of Jan 15, 1967 Bob Kaergard cuts rear deck to add canopy, finds tail damage, had flown open cockpit till Nov 1966
5) Rockford '67, Bob Kaergard has canopy
6) Hangar fire destroys Bob Kaergard's T-18 Aug 11, 1967
7) Sport Aviation • 1967-Oct • Pg 42 In Memoriam (N12055 T-18 Hangar Fire) By Bob Kaergard

Oh Yeah, John Wallace flew with a bubble windshield closed cockpit, pic also below.

Shack

As you can see here…N137RT didn’t fly sans canopy very long. This is Rockford 1965, just months after it was on the cover of Sport Aviation without canopy.
And yes that’s me in front of the Thorp at 5 years old….

Terry, I wasn't aware your T-18 history went that far back. Reading your post in https://www.oldfartsfly.com/post/the-thorp-t-18-story , was informative. My Guardian Angel has saved me on occasion. Hopefully good T-18 times for everybody.

The cover picture showing Norm Ginn flying Ralph Thenhaus's T-18 N137RT, open cockpit at the time, doesn't look too bad. Norm doesn't look too uncomfortable, even though he wasn't wearing sunglasses. Maybe that rounded bubble windshield of John Wallace's T-18 would help with the airflow turbulence.





Of course, the article in "Sport Aviation • 1966-Oct • Pg 45-46 The 1966 AC Flight Rally" does have Bob Kaergard flying his T-18 open cockpit to a second-place finish at the EAA Fly-In Rockford 1966. In my brain, the EAA Fly-In will always be Oshkosh.







This also brings me back to the article "Sport Aviation • 1966-Mar • Pg 31-33 Kaergard and His Komet By Dick Cavin".







Here's a few copies and paste from the article:

"Bob's T-18, the fifth one to be airborne, is unique
in as much as it is built exactly to Thorp's original super-simple
airplane concept that he originally described in
the February '62 issue of SPORT AVIATION. Furthermore,
he has built it exactly to Thorp's drawings down
the line. EAAers are incurable experimenters and not
many can resist the urge to "customize" their projects,
so in all probability, Bob's T-18 will make its 1966 Rockford
debut as the one and only example of the "irreducible
minimum" T-18 that Thorp originally proposed. (The
first T-18 design proposal was a "plain Jane" airplane, with
an open cockpit, without the benefits of pressure cowling
or landing gear streamlining)."

"Performance-wise, Bob's ship is doing just about what
Thorp originally calculated. His airspeed indication is
almost worthless, since he doesn't have a static line in
it, but he has managed to get some accurate performance
numbers by flying formation with other airplanes that
have accurate airspeeds. His wide open speed so far is
155 mph. and he says this is just about the maximum that
he can take with the open cockpit. Seventy-five percent
power cruise comes out pretty close to the 144 mph. that
Thorp figured. An increment by increment clean-up
program will eventually provide some pretty good data
on how much increase can be expected from gear fairings,
canopy, etc. With the 125 hp. GPU that Bob uses
as a power plant it is expected that the top speed will
be about 175 mph."

Looks like Bob Kaergard's open cockpit original T-18 flew to specs.

Shack

Added Sources to my Sept 7, 2022 Post, no other changes.

Shack,

Thanks for posting these old articles and pictures of Bob Kaergard's first T-18. I thoroughly enjoyed reading them. I own Bob's SECOND T-18 and it has the same registration number, N12055. It's a beautiful plane and as far as I can tell, it is built exactly to John Thorp's plans as is described how he built his first plane in the article. Thanks for posting!

John

_________________
John Twigg N12055 SN.79 Pittsburgh, PA (KFWQ)