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Knots 2 U
Posted: Mon Dec 21, 2020 11:42 pm
by thejetjerk
Hi 170 Folks,
I have read everything on the site I can find regarding 170B performance mods. Knots 2U sells a flap gap seal kit for $600 and claims it take about 7 hours to install. They also claim 100-150 FPM rate of climb increase. If this is true it seem like a lot of bang for the buck. Does anyone have any experience with this company or this mod? Do you believe this claim of 100'-150' ? I have seen some opinions here that it may negatively affect flap design, any thoughts on this opinion?
https://www.knots2u.net/cessna-flap-gap ... dels-cfgs/
Re: Knots 2 U
Posted: Tue Dec 22, 2020 1:13 am
by Vertical
They are fantastic. I think it’s more like 250fpm and another 20knots cruise. I have a used set with all the paperwork and plans that I’ll sell you for $200!
Re: Knots 2 U
Posted: Tue Dec 22, 2020 10:55 am
by Bruce Fenstermacher
They are so fantastic you see them on every bush plane. And Cessna added this mod later. Oh you don't see it on bush planes and Cessna never added it? Wonder why? I'm seriously just thinking. And I'm thinking the answer is right there.
I don't have any personal experience with them but do understand the aerodynamics of the original design of the flap. I don't believe the mod would do anything for flap performance. I do believe the seal will increase cruise somewhat from decreased drag. How much I don't know but if it was 20 knots cruise, every Cessna would have them. Maybe that was a typo and was suppose to be 2 knots which I'd believe.
Re: Knots 2 U
Posted: Tue Dec 22, 2020 4:08 pm
by GAHorn
Bruce Fenstermacher wrote:They are so fantastic you see them on every bush plane. And Cessna added this mod later. Oh you don't see it on bush planes and Cessna never added it? Wonder why? I'm seriously just thinking. And I'm thinking the answer is right there.
I don't have any personal experience with them but do understand the aerodynamics of the original design of the flap. I don't believe the mod would do anything for flap performance. I do believe the seal will increase cruise somewhat from decreased drag. How much I don't know but if it was 20 knots cruise, every Cessna would have them. Maybe that was a typo and was suppose to be 2 knots which I'd believe.
Re: Knots 2 U
Posted: Tue Dec 22, 2020 4:48 pm
by rnealon1
The Knots 2 U listing advertises 3-4 mph cruise speed increase.
Our plane has the B & M seal kit, not sure how it compares. I can't make any direct comparison as it was installed 41 years before our purchase, but I cannot observe any large variations from "book" performance.
I do notice that actual stall speed is way below book, even accounting for lower weight. Like maintaining sustained level flight at 35 mph IAS with full flaps. My technical feeling is that if anything the flap seals would have a negative impact on stall speed, but I am not an aeronautical engineer. In the words of Charlie Ryan, she "just won't stall".
Bob
Re: Knots 2 U
Posted: Tue Dec 22, 2020 9:43 pm
by thejetjerk
Thanks for the responses, I guess that Vertical is joking. I am more interested in better climb performance. Other than a pilot diet I think that for $600 that might be the cheapest mod out there, if it really does give another 100 -150 FPM climb.
Re: Knots 2 U
Posted: Wed Dec 23, 2020 3:53 am
by Vertical
How about $100?
In all seriousness, I might be removing my B&M kit (I think that's the manufacturer). Any member here is welcome to it if you pay for shipping + 1 six pack. I have good paperwork, install instructions drawings etc. It has a 2017 professional white paint job.
I would be interested in any recommendations on how to fill the many empty rivet holes it will leave behind. I don't think there is enough access to buck soft rivets. So maybe pop rivets are the only option?
As to what its benefits may or may not be, I would agree with others that it likely inhibits the flap function, and possibly adds a meager cruise increase. I can't speak to whether or not it would add climb performance. I'm usually trying to go slower, not faster.
If you want to climb faster (in order of expense), go on a diet, carry less fuel, gut the interior to save weight (headliner, PAX seat, back seat, side panels, hat shelf etc), swap for lightweight starter and alternator, buy an 80/40 prop, add a Sportsmans. Or something like that anyways.
Re: Knots 2 U
Posted: Wed Dec 23, 2020 5:22 am
by cfzxo
If you want to remove your flap gap seals, the easiest way is to score the seal along the wing skin and leave the rivets in place . I would think that something sharp like and old arborite knife would possibly work. This is not my idea ,but was told to me by the late Dick Lemmon.
Re: Knots 2 U
Posted: Wed Dec 23, 2020 11:21 am
by GAHorn
Vertical wrote:
I would be interested in any recommendations on how to fill the many empty rivet holes it will leave behind. I don't think there is enough access to buck soft rivets. So maybe pop rivets are the only option?.
https://www.aircraftspruce.com/catalog/ ... -00981.php
Re: Knots 2 U
Posted: Wed Dec 23, 2020 11:53 am
by ghostflyer
It’s my belief that you can’t get something for nothing so putting “aerodynamic aids “ on flaps you will loose something some where . The following is directed at 170A owners only. But due to the flap design where the flap hingers on the lower surface of the wing there is a gap between flap and skin of the lower wing. I tape up this gap spa wise with T-REX tape .[supplied by aero Home Depot.] I can’t really measure the extra performance but have noticed it has affected my cruise speed [positively] when the throttle is opened up. Now looking for pixie dust also.
Re: Knots 2 U
Posted: Wed Dec 23, 2020 4:29 pm
by cessna170bdriver
ghostflyer wrote:It’s my belief that you can’t get something for nothing so putting “aerodynamic aids “ on flaps you will loose something some where . The following is directed at 170A owners only. But due to the flap design where the flap hingers on the lower surface of the wing there is a gap between flap and skin of the lower wing. I tape up this gap spa wise with T-REX tape .[supplied by aero Home Depot.] I can’t really measure the extra performance but have noticed it has affected my cruise speed [positively] when the throttles are opened up. Now looking for pixie dust also.
Since you used “throttles” in the plural, I’m guessing the extra performance is coming from the additional engine(s) you have installed.
Re: Knots 2 U
Posted: Thu Dec 24, 2020 3:03 am
by ghostflyer
Nah, it was typo or could be the pixie dust .