Zenith CH-701 thread

[Marty_d]

Yes, it's all good information.

 

My problem with it is that I'm not a qualified engineer or aircraft designer, so I'm stuck with, for better or worse, following the plans. VG's may be brilliant and people have done a lot of testing with them - but I've also talked to a builder in Launceston who bought a crashed 701, and he said the reason it crashed was that the pilot took off the slats and replaced them with VG's then tried to fly it the same way he had before.

 

The beanie mod is good, I've seen that done before. But again - the original flat roof design is to allow prop wash onto the tail. Are there situations where the beanie mod could blanket the tail? Spin recovery perhaps? I don't know so I'm not prepared to "fix" the design in order to stop buffeting. The 701 tail is relatively short (small area as it's all flying) so perhaps aircraft like the Savannah that have the "beanie" over the cockpit have taller tails.

 

Same with the HS - there must be good reasons why Chris Heintz designed something that looks like a thick inverted airfoil rather than symmetrical. I don't have enough knowledge to change it.

 

I agree that sleeving the round tube struts with an airfoil/teardrop profile is good in any case. Later models come standard with faired struts. Even with that though I'll be talking to Zenith to find out if there's an "approved" or best practice way to sleeve them (I don't particularly want to use heavier extruded ones if there's a good way to fair my existing chrome moly ones.)

 

The only other thing I changed was the elevator design, to incorporate the trim tab in the trailing edge rather than a flat plate hinged behind it. This follows the design of the 750 elevator in any case and I looked at a LOT of photos of 750 elevator construction before I copied it.

 

 

[eightyknots]

Yes, it's all good information.My problem with it is that I'm not a qualified engineer or aircraft designer, so I'm stuck with, for better or worse, following the plans. VG's may be brilliant and people have done a lot of testing with them - but I've also talked to a builder in Launceston who bought a crashed 701, and he said the reason it crashed was that the pilot took off the slats and replaced them with VG's then tried to fly it the same way he had before.

 

The beanie mod is good, I've seen that done before. But again - the original flat roof design is to allow prop wash onto the tail. Are there situations where the beanie mod could blanket the tail? Spin recovery perhaps? I don't know so I'm not prepared to "fix" the design in order to stop buffeting. The 701 tail is relatively short (small area as it's all flying) so perhaps aircraft like the Savannah that have the "beanie" over the cockpit have taller tails.

 

Same with the HS - there must be good reasons why Chris Heintz designed something that looks like a thick inverted airfoil rather than symmetrical. I don't have enough knowledge to change it.

 

I agree that sleeving the round tube struts with an airfoil/teardrop profile is good in any case. Later models come standard with faired struts. Even with that though I'll be talking to Zenith to find out if there's an "approved" or best practice way to sleeve them (I don't particularly want to use heavier extruded ones if there's a good way to fair my existing chrome moly ones.)

 

The only other thing I changed was the elevator design, to incorporate the trim tab in the trailing edge rather than a flat plate hinged behind it. This follows the design of the 750 elevator in any case and I looked at a LOT of photos of 750 elevator construction before I copied it.

I had communication with Chris Heintz about removing the slats of a CH-701 about seven years ago (before I found out the Savannah existed). I cannot find the emails but the upshot was that he was not against removing the slats and replacing them with the VGs per se, but recommended to keep the slats all the same.

 

 

[Marty_d]

It's interesting that the 750 Cruzer has a small "beanie" (still lower than the top of the airfoil) - and symmetrical HS, but they've gone to a regular fin/rudder setup which looks a lot taller than the 701.

 

Interesting that Chris wasn't opposed to the replacement with VG's. If I were doing it I'd want to use a wing that was designed for it - like the Savannah VG wing - pretty sure it wouldn't be as blunt in the LE as the 701. So in reality, if I wanted a 701 with VG's and beanie mod and symmetrical HS etc... I'd buy a Savannah. Or build a Cruzer, which wouldn't have the STOL performance but looks like a good general purpose high-wing.

 

 

[mcrowley]

What is the width of the firewall of the CH701? Thanks!

 

 

[Phillip King]

Hi mcrowley.

 

715mm.

 

Cheers Phil

 

 

[rick morawski]

730mm on my plans

[Phillip King]

Hi Rick

 

What Page number is that on your plans ? Went through my two sets of plans old and new cant find that page.Measured my fire wall again with glasses on this time and got 720mm.

 

cheers Phil

 

 

[rick morawski]

Page 7-F-1 dated sept 2003

 

 

[Marty_d]

Page 7-F-1 dated sept 2003

730mm on mine too - plans dated April 2006

 

 

[derekliston]

Finally have my aeroplane back together. Took a bit longer than expected, life gets in the way. SAAA inspector turning up on Sunday so after that should be good to go. Engine prop strike inspected and returned to nil hours by Jabiru, new Jabiru composite prop so as long as I don't make the same mistake again, all should be sweet!

 

 

[derekliston]

Does anyone on the CH701 thread have any idea where I can obtain a pilot's operating handbook, preferably for a Jabiru 2200 engine version?

 

 

[jetboy]

the best flight manual I have seen is CZAW Zenair CH701 STOL edition 4- th CZ - March 2002

 

there is a similar one Zenair CH701 SP 4th edition CZ- January 2003 but this is full of errors

 

they were adapted from the Zenith manual which has never been updated.

 

 

[Kyle Communications]

Are you back on the horse yet Derek?

 

 

[rick morawski]

Does anyone on the CH701 thread have any idea where I can obtain a pilot's operating handbook, preferably for a Jabiru 2200 engine version?

I have a copy of the CZAW CH701 POH, 4th edition, January 2003, but for Rotax 912, any good?

You would need a PDF editing program to modify it.

 

 

[derekliston]

I have a copy of the CZAW CH701 POH, 4th edition, January 2003, but for Rotax 912, any good?You would need a PDF editing program to modify it.

I actually googled it and found one for a Jab engine version which I saved and modified. Speeds were in mph instead of knots, capacities in gallons not litres etc. Thanks to all for their suggestions.

 

 

[derekliston]

Are you back on the horse yet Derek?

All good to go. Should be this week sometime I hope. Had to do 100hrly/annual today, ridiculous when it only has about 15 hrs but there you go! Hopefully get Bob Molony to do some circuits with me until I am confident I wont repeat my mistake!

 

 

[Marty_d]

I had communication with Chris Heintz about removing the slats of a CH-701 about seven years ago (before I found out the Savannah existed). I cannot find the emails but the upshot was that he was not against removing the slats and replacing them with the VGs per se, but recommended to keep the slats all the same.

I just found this article by Chris Heintz online. Interesting conclusions, wonder if JG has any data on landing/takeoff distances.

 

Vortex Generators (VG) and Leading Edge Slats

 

 

[jetboy]

The best handling notes I've seen - although dated - here

 

CH701 STOL

 

 

[eightyknots]

The best handling notes I've seen - although dated - here

 

CH701 STOL

 

Classic quote from that site, not particularly a handling issue:

 

"Glove boxes are more important than silly dials!", insisted my wife.

 

 

 

 

 

[derekliston]

Any CH701 drivers please tell me what tyre pressures they are using please?

 

 

[jetboy]

30 psi and top them up every other year

 

this is for the big Matco wheels originally came without tubes but now 2 of them have tubes inside - the tyre has "tube type" printed on it

 

 

[derekliston]

30 psi and top them up every other yearthis is for the big Matco wheels originally came without tubes but now 2 of them have tubes inside - the tyre has "tube type" printed on it

Thanks for that.

 

 

[skyfox1]

Hi Derek what did your 701 empty weight end up being .

 

cheers Geoff.

 

 

[derekliston]

Came in at 276.3kg Arm 363mm Moment 10030. will be a kilo heavier on the nose now with the composite prop instead of the wooden one.

 

 

[skyfox1]

Mine is 263kgs at the moment trying to do the CofG so l can put the battery in the right place ,l have 72 inch two blade IVO prop with inflight adjustable pitch .