Mark Gravatt
  • San Tan Valley, AZ
  • United States
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Mark Gravatt's Friends

  • Ian Robb
  • Jim Davis
  • Richard Wright
  • Jimmy Galvin
  • Chris M. Brammer, Jr.
  • Van Anthony
  • Larry Nelson
  • Pat Kelly
  • Clint L Gosch
  • David Griggs
  • Joe Spencer
  • Steve Freeman
  • Louis W. Ott
  • Rick Lindstrom
  • William Wynne

Mark Gravatt's Discussions

So, I am officially requesting to change my goal from 650 to 750.

Started this discussion. Last reply by Richard Wright Jan 16, 2020. 5 Replies

So here goes.With my move to Arizona 3 years ago, I started thinking about the CH650B that I had bought plans for, and contemplating what my new missions would look like.There are many back country…Continue

Conventional or Tricycle? Maybe both???

Started this discussion. Last reply by Tim Juhl Feb 27, 2015. 10 Replies

So I am plans building a CH650B and love the looks of the tail draggers that I have seen.  Andrew Elliot, I have a picture of yours over my desk as inspiration.  Yes, I like thousands of  others…Continue

Tags: conventional, zodiac, dragger, tri, Taildragger


Mark Gravatt's Page

Profile Information

Aircraft Model
CH 750 Cruzer
Project Status
Just started
Building From
Partial kit
Engine installed (or plan to install)
Building Experience
Have worked on airplanes before
Flying Experience
Private Pilot
Building and Flying Info / Your Profession / Other Background Info
PPSEL-1977/Aircraft Mechanic/Machinist/Precision Inspector/Mech Tech/Manufacturing Engineer/Procurement
Home Airport (ie. KMYJ)

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Comment Wall (6 comments)

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At 12:08am on September 25, 2021, Mark Jackson said…
Hi Mark
I have 650b and really would like to reduce the aileron pressures. I think the twin stick mod might be part of the problem and am concerned that the MGL autopilot that I have acquired will be overpowered by these forces. I did consider aileron servo tabs like they fit to the Glasair. Any thoughts?
At 9:55am on May 5, 2017, Jerry Latimer said…

Welcome aboard.  I'm based out of KCHD.  There are 3 601's based there.  I know 2 601 owners at FFZ and 1 650 owner at DVT.  Most are open to talking to new builders.

At 9:19am on August 13, 2014, Van Anthony said…
Hi Mark,
Your Aviation background is impressive. Wish you lived closer to GOO I could use your knowledge. My Warpdrive prop showed up Monday. Getting closer but still a long way off....
At 1:03pm on June 24, 2013, Louis W. Ott said…

Hi Mark,

Thanks for your comments. I'm pleased someone is getting some help from my builders log. I had to print it out for the DAR to review to get the airworthiness cert. He was quite impressed. Not having done this before I had no idea what was required.

I did make quite a few mods. Some I'd do over again and some probably not. The rudder mod is a keeper mostly because I like the way it looks. I'm thinking of making a whole new rudder with the shape of the modified one mostly because I'd save maybe a half pound of weight. That is pretty far down the list. I used two rows of upper wing skin reinforcing angles rather than the single row specified on the upgrade. I'd do that over again. I don't see any upper wing skin ripples or flexing in a tight turn or rough air like some others have reported. It feels very solid in the hard bumps. Almost Navion like. The CF turtle back makes sealing the rear of the canopy better and gives easier access to the rear baggage area. The 650 partly fixes that design flaw, but I don't appreciate all the extra plexiglass the 650 has back there so I might try a similar turtleback on that model too. Some changes I made after the builder log was finished is to add aileron spades at the outer ends of the ailerons. They partly act as aileron balances too so I don't need as much weight on the arms inside the wing. If I were to do it over again, I'd add the two aileron ribs as in the upgrade for the balance arm, but attach the external balance spades to the ribs. That's how I attached the spades. Pictures if you want them. The reason for the spades is to lighten the aileron control force which is normally very heavy as if the stick is stuck in a bucket of concrete. I added strips of 0.016" aluminum to the rear of the wing skin to cover the wide gap between the wing rear edge and the front of the aileron. This gives nicer aileron control response. It does not reduce drag as I can't see any speed increase. If I were to be building from scratch, I'd extend the lower wing skin on the rear edge about three inches to cover the aileron gap. I made a gap cover for the elevator too, but I don't see any improved elevator control and no speed improvement. I'll take those off. I did put on an anti-servo tab on the elevator that is on the opposite side as the trim tab. The anti-servo tab give a bit stiffer elevator control force to better balance with the ailerons. The elevator trim is inadequate to give enough nose up with full flaps extended. I'd increase the width of the elevator trim tab by 1.5 inches if I were doing it over. I am probably a bit too critical on the flying qualities since I just expect Navion characteristics and it is far from that. One other thing is that the (aileron) controls get quite sloppy just before it lands. I'll do some tuft tests to see where the air separation happens. I may need wing vortex generators and I'll try those to see if that helps. The Navion has a completely different airfoil section at the tip as at the root which keeps aileron control solid right into the stall. Maybe reflexing the ailerons up at the rear edge may work too but I usually don't like the flaps and aileron trailing edges to not line up. The left wing was heavy the same as many builders report. Some builders have fixed that by splitting the flap control tube and clamping in place with a little different flap angles when flaps are up. I didn't do that because I didn't know I'd have the left wing heavy when I was building. I put a "Gurney flap" at the outer end of the left wing on the lower side just in front of the aileron. The GF is 14" long and is a length of 3/4" angle. That fixes the left wing heavy situation and doesn't cost any speed.

I can't find anything that noticeably increases speed. The wheel pants maybe give 2 mph top speed. The wing root fairings is supposed to give some improvement, but I didn't fly it without the fairings so I cant comment. I have a 2

At 3:55pm on June 23, 2013, Louis W. Ott said…

Hi Mark,

I'm happy to have you as a Zenith "friend".


At 12:59pm on June 23, 2013, Andy Elliott said…

Let me know if/when you get into town.



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