- Thread starter
- #41
Changing it to 24-25 and 26-27 seconds sustained turn using 1.1-1.15 CL, respectively at SL and 1000m
Last edited:
J7W1 Shinden & Engine Performance - Grok Edition
- Thread starter Laurelix
- Start date
Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
Changing it to 24-25 and 26-27 seconds sustained turn using 1.1-1.15 CL, respectively at SL and 1000m
Holtzauge
Senior Airman
Sounds like a step in the right direction. It's interesting to see how Grok responds a bit like a human being when contradicted: It tells you not to "swallow his post whole" and then tries to shore up its position. 
But on a more serious note: The problem with AI's as I see it, is that they are very syncopathic, and try to reply perceiving what answer one would like to have, so it's difficult to get a straight answer out of them for complex questions IMO.
But returning to the subject of the Shinden's turn performance, below is an excerpt from a paper I was working on earlier, but have but away for now, so remains unpublished. And while the Clmax on profile level and in theory certainly can be substantially higher, it seems to be difficult to get the trimmed Clmax on aircraft level on a canard to high values once you start taking stall characteristics and stability aspects (deep stall avoidance) into consideration. And yes, the Shinden's canard has both slats and flaps, but then the main wing itself is symmetrical and thus not very good for high Cl's, while the wing profiles on the VariEze are more efficient.
"The maximum trimmable Clmax for the Shinden was probably in the order of 1.05 to 1.15 at best but in order to be generous, the Clmax for the J7W1 has in the turn simulations in this paper been assumed to correspond to this upper value. And this Clmax figure of 1.15, is therefore most likely leaning more towards the optimistic, given that the VariEze Clmax ranges from 0.97 to 1.17 and that the Clmax for the XP-55 is around 1.08. Another argument suggesting this to be a generous assessment is the fact that Burt Rutan's VariEze seems to have a trimmed Clmax of in between 1.09 and 1.17[1] depending on the center of gravity position. Note that this value includes the "up" force contribution of the canard, and given that the VariEze has a comparatively larger canard surface in comparison to its main wing than on the Shinden, this should endow it with much more control authority than the Shinden, yet again suggesting that a trimmed Clmax figure of 1.15 for the Shinden (accounting for both the canard's and main wing's lift) is in fact optimistic.
[1] In NASA's technical paper 2382, Wind-Tunnel Investigation of a Full-Scale Canard-Configured General Aviation Airplane, by Long P. Yin, gives trimmed Clmax 1.4 to 1.5 (page 51 ), but that this is based on a reference wing area of only 53.6 ft² which is the exposed wing area, and using the total wing area 68.9 ft² (as per convention), the Clamx is reduced to 53.6/68.9*1.4= 1.09, and 53.6/68.9*1.5= 1.17."
But on a more serious note: The problem with AI's as I see it, is that they are very syncopathic, and try to reply perceiving what answer one would like to have, so it's difficult to get a straight answer out of them for complex questions IMO.
But returning to the subject of the Shinden's turn performance, below is an excerpt from a paper I was working on earlier, but have but away for now, so remains unpublished. And while the Clmax on profile level and in theory certainly can be substantially higher, it seems to be difficult to get the trimmed Clmax on aircraft level on a canard to high values once you start taking stall characteristics and stability aspects (deep stall avoidance) into consideration. And yes, the Shinden's canard has both slats and flaps, but then the main wing itself is symmetrical and thus not very good for high Cl's, while the wing profiles on the VariEze are more efficient.
"The maximum trimmable Clmax for the Shinden was probably in the order of 1.05 to 1.15 at best but in order to be generous, the Clmax for the J7W1 has in the turn simulations in this paper been assumed to correspond to this upper value. And this Clmax figure of 1.15, is therefore most likely leaning more towards the optimistic, given that the VariEze Clmax ranges from 0.97 to 1.17 and that the Clmax for the XP-55 is around 1.08. Another argument suggesting this to be a generous assessment is the fact that Burt Rutan's VariEze seems to have a trimmed Clmax of in between 1.09 and 1.17[1] depending on the center of gravity position. Note that this value includes the "up" force contribution of the canard, and given that the VariEze has a comparatively larger canard surface in comparison to its main wing than on the Shinden, this should endow it with much more control authority than the Shinden, yet again suggesting that a trimmed Clmax figure of 1.15 for the Shinden (accounting for both the canard's and main wing's lift) is in fact optimistic.
[1] In NASA's technical paper 2382, Wind-Tunnel Investigation of a Full-Scale Canard-Configured General Aviation Airplane, by Long P. Yin, gives trimmed Clmax 1.4 to 1.5 (page 51 ), but that this is based on a reference wing area of only 53.6 ft² which is the exposed wing area, and using the total wing area 68.9 ft² (as per convention), the Clamx is reduced to 53.6/68.9*1.4= 1.09, and 53.6/68.9*1.5= 1.17."
- Thread starter
- #43
Did you however take into account thatSounds like a step in the right direction. It's interesting to see how Grok responds a bit like a human being when contradicted: It tells you not to "swallow his post whole" and then tries to shore up its position.
But on a more serious note: The problem with AI's as I see it, is that they are very syncopathic, and try to reply perceiving what answer one would like to have, so it's difficult to get a straight answer out of them for complex questions IMO.
But returning to the subject of the Shinden's turn performance, below is an excerpt from a paper I was working on earlier, but have but away for now, so remains unpublished. And while the Clmax on profile level and in theory certainly can be substantially higher, it seems to be difficult to get the trimmed Clmax on aircraft level on a canard to high values once you start taking stall characteristics and stability aspects (deep stall avoidance) into consideration. And yes, the Shinden's canard has both slats and flaps, but then the main wing itself is symmetrical and thus not very good for high Cl's, while the wing profiles on the VariEze are more efficient.
"The maximum trimmable Clmax for the Shinden was probably in the order of 1.05 to 1.15 at best but in order to be generous, the Clmax for the J7W1 has in the turn simulations in this paper been assumed to correspond to this upper value. And this Clmax figure of 1.15, is therefore most likely leaning more towards the optimistic, given that the VariEze Clmax ranges from 0.97 to 1.17 and that the Clmax for the XP-55 is around 1.08. Another argument suggesting this to be a generous assessment is the fact that Burt Rutan's VariEze seems to have a trimmed Clmax of in between 1.09 and 1.17[1] depending on the center of gravity position. Note that this value includes the "up" force contribution of the canard, and given that the VariEze has a comparatively larger canard surface in comparison to its main wing than on the Shinden, this should endow it with much more control authority than the Shinden, yet again suggesting that a trimmed Clmax figure of 1.15 for the Shinden (accounting for both the canard's and main wing's lift) is in fact optimistic.
[1] In NASA's technical paper 2382, Wind-Tunnel Investigation of a Full-Scale Canard-Configured General Aviation Airplane, by Long P. Yin, gives trimmed Clmax 1.4 to 1.5 (page 51 ), but that this is based on a reference wing area of only 53.6 ft² which is the exposed wing area, and using the total wing area 68.9 ft² (as per convention), the Clamx is reduced to 53.6/68.9*1.4= 1.09, and 53.6/68.9*1.5= 1.17."
XP-55 has no wing slats and J7W1 does?
The reason I didn't give single direct number but 26-27 at 100% and 24-25 with WEP is it's both values, 1.10 and 1.15 CL
Holtzauge
Senior Airman
Yes, slats and flaps are part of the estimate. But the problem as I see it for canards and flying wings with a forward control surface, like the XP-55, is the control authority: Sure, you can trim out a higher Clmax by having a more rearward CG or by making the canard larger or giving it a wing profile with a higher stall angle. And this will allow you to get to a bit higher Clmax on aircraft level. However, that will also allow you to place a higher load on the main wing, and once you start to get flow separation on the main wing, then you lose lift behind the neutral point (NP) and you risk a violent pitch-up, and a deep stall that you can't get out of if you are unlucky. And this is why stable canards without FBW have such low trimmed Clmax: To get anywhere near decent control characteristics, you have to load the canard heavily, and/or make sure it stalls well before the main wing.
- Thread starter
- #46
yeah i have it as 26-27 at military power in the OP nowLaurelix :In Grok's reply to you above, Grog brought up the issue of the Oswald factor. Now since the Shinden has a very unconventional twist scheme on its wings, I decided to ask for a clarification:
View attachment 894155
Holtzauge
Senior Airman
OK, sounds good. Just wanted to give you the new info about the wing twist.
Very unconventional design choice really. I never heard of anything like it on any other aircraft so it would be interesting if someone has any more info on this.
I see that
Shinpachi has posted a lot of interesting information of Japanese aircraft before, so maybe he knows something about this?
