FMS 1400MM P40B

[roofmann1@gmail.com]

Hi, watching Ryan's video of the maiden flight he said he moved the cg back to about 70mm.  Did he get the cg with the gear up or down?
Thanks

[WintrSol]

RE: FMS 1400MM P40B

Normally, one would set the CG in normal flight configuration, as the gear will tend to shift it forward, which is what you want for landing. Some models don't shift CG when the gear changes, but many will. Of course, if the gear somehow shifts it aft, then you want to set it gear down.

[ryramZ]

RE: FMS 1400MM P40B

Hi, watching Ryan's video of the maiden flight he said he moved the cg back to about 70mm.  Did he get the cg with the gear up or down?
Thanks

Hi,

Gear down and inverted.

Ryan 

[roofmann1@gmail.com]

RE: FMS 1400MM P40B

Thanks Ryan, I appreciate it. Now if you can just get FMS to make a 1400 mm P-39, that would be fantastic.

[Pheonix]

RE: FMS 1400MM P40B

Hi, watching Ryan's video of the maiden flight he said he moved the cg back to about 70mm.  Did he get the cg with the gear up or down?
Thanks

Hi,

Gear down and inverted.

Ryan 

Why gear down?  I understand the inverted part.

[ryramZ]

RE: FMS 1400MM P40B

Hey Pheonix
Gear down just because they already were. It's a matter of opinion for most. With twist and turn gear measuring cg with gear down will give you a more forward reading than with gear back. Pilots have to go with what works for them. I would have been even farther away from manual cg if I had gear back when measuring. Max chord or right behind the retract units is usually a good starting point for taildraggers regardless. I personally hate to add dead ballast to balance a plane. For maidens I prefer to be a little nose heavy rather than tail. I'm this case the callouts seemed way to far forward just looking at it so I went with instinct. Beautiful plane!

[roofmann1@gmail.com]

RE: FMS 1400MM P40B

Hey Pheonix
Gear down just because they already were. It's a matter of opinion for most. With twist and turn gear measuring cg with gear down will give you a more forward reading than with gear back. Pilots have to go with what works for them. I would have been even farther away from manual cg if I had gear back when measuring. Max chord or right behind the retract units is usually a good starting point for taildraggers regardless. I personally hate to add dead ballast to balance a plane. For maidens I prefer to be a little nose heavy rather than tail. I'm this case the callouts seemed way to far forward just looking at it so I went with instinct. Beautiful plane!

Hi Ryan, Have you tried balancing with the under belly tank in place, or is that so light and close to the cg that it shouldn't make a difference?

[Grossman56]

RE: FMS 1400MM P40B

I balanced mine with the tank on, but it's so light and so close (if not right on) the CG, I don't think it would have made a difference.  Its too bad that the tank isn't a snap on type, there's one screw that holds it on that threads through the top of the wing. 

Grossman56

[Konrad]

RE: FMS 1400MM P40B

I have to ask, do you guys threat (think) the CofG as a single point? Or put another way, that there is only one correct value for the CofG?

I set the CofG as stated in the manuals, unless I know there is a gross error, for the first flights. Then I move it around (usually aft) until the model flies the way I want, or as close to the way I want as possible. What the ruler says at that point is of no concern.

All the best,
Konrad

[Lon]

RE: FMS 1400MM P40B

I have to ask, do you guys threat (think) the CofG as a single point? Or put another way, that there is only one correct value for the CofG?

I set the CofG as stated in the manuals, unless I know there is a gross error, for the first flights. Then I move it around (usually aft) until the model flies the way I want, or as close to the way I want as possible. What the ruler says at that point is of no concern.

All the best,
Konrad

I'm the same as you Konrad. Go with the manual. Check it on my CG balancer. Fly, then move it around until the model flies the way I want.

[Konrad]

RE: FMS 1400MM P40B

I have to ask, do you guys threat (think) the CofG as a single point? Or put another way, that there is only one correct value for the CofG?

I set the CofG as stated in the manuals, unless I know there is a gross error, for the first flights. Then I move it around (usually aft) until the model flies the way I want, or as close to the way I want as possible. What the ruler says at that point is of no concern.

All the best,
Konrad

I'm the same as you Konrad. Go with the manual. Check it on my CG balancer. Fly, then move it around until the model flies the way I want.

CG Balancer? Other than lightening one's wallet what does a CG balancer accomplish that ones finger tips or the edge of a table doesn't?

I'm old school, I've been using my finger tips on my 13 inch peanuts all the way up to my 3.7 meter gliders.

All the best,
Konrad

[Lon]

RE: FMS 1400MM P40B

I have to ask, do you guys threat (think) the CofG as a single point? Or put another way, that there is only one correct value for the CofG?

I set the CofG as stated in the manuals, unless I know there is a gross error, for the first flights. Then I move it around (usually aft) until the model flies the way I want, or as close to the way I want as possible. What the ruler says at that point is of no concern.

All the best,
Konrad

I'm the same as you Konrad. Go with the manual. Check it on my CG balancer. Fly, then move it around until the model flies the way I want.

CG Balancer? Other than lightening one's wallet what does a CG balancer accomplish that ones finger tips or the edge of a table doesn't?

I'm old school, I've been using my finger tips on my 13 inch peanuts all the way up to my 3.7 meter gliders.

All the best,
Konrad

Well Konrad, I can tell time by the position of the sun....but i've broke down and lightened my wallet for a little more accuracy, by buying a watch.

[Konrad]

RE: FMS 1400MM P40B

How does it add accuracy? And if it actually adds accuracy, how does this added accuracy help with the long term set up of the model.

I think the area that the area of contact has to be kept broad otherwise the machine will dent (damage) the surface of the model. It is this broad contact area that will adversely effect the precision of the machine. Also how it is used such as with the weight of the model suspended underneath adds stability when we want a more unstable set up to narrow the dead zone response of the machine.

[Lon]

RE: FMS 1400MM P40B

How does it add accuracy? And if it actually adds accuracy, how does this added accuracy help with the long term set up of the model.  

I think the area that the area of contact  has to be kept broad otherwise the machine will dent (damage) the surface of the model. It is this broad contact area that will adversely effect the precision of the machine. Also how it is used such as with the weight of the model suspended underneath adds stability when we want a more unstable set up to narrow the dead zone response of the machine.

LOL..."How does it add accuracy?" When i look at the horizon and sun, well....the minute hand,  and second hand on the watch is much more accurate.

[WintrSol]

RE: FMS 1400MM P40B

How does it add accuracy? And if it actually adds accuracy, how does this added accuracy help with the long term set up of the model.  

I think the area that the area of contact  has to be kept broad otherwise the machine will dent (damage) the surface of the model. It is this broad contact area that will adversely effect the precision of the machine. Also how it is used such as with the weight of the model suspended underneath adds stability when we want a more unstable set up to narrow the dead zone response of the machine.

The CG machine I have uses pads that are about 2cm wide and padded with thin foam, so the risk of denting a model is lower than with finger tips, but the pad is mounted to a bearing, so the effective contact is very much smaller, giving a more accurate reading than within the area of you fingertips. I've used both methods on the same airframe, and the machine is repeatable, while fingertips vary by distance that keeps me from getting as far aft as the critical point for aerobatics.

[Konrad]

RE: FMS 1400MM P40B

Not a snide comment I really don't see any benefit to "CofG balance machines". They to my eye were/are a marketing gimmick. 

On the subject of time pieces I agree swiss time  has many benefits to staring at the sun.  Not the least improved vision! Today I like crystal oscillators or atomic clocks. But as to balance machines I see nothing that they add to the set up of the model. Particularly when in the end we move things around based of how the models flies not by some measurement off the leading edge.  

A bit about my style. I like to question assumption made.  Particularly assumptions I've made from time to time.  For example the "CofG balance machine". When they first came out I saw no benefit to them. In fact I saw them as being a pain to set up. And I thought (and still think) they give an impression that CofG needs to measure accurately on the bench.  For too many flier are not willing to experiment with the CofG placement because they think it is some magical value that must be accurately measure and adhered to per the manual. Nothing could be further from the truth.

So with the passage of time  I again ask why use a balance machine? What does it give one that the old finger tips don't? As I still have finger nails I can really get a knife edge reading and not have to worry about bearing drag effecting the sensitivity of my readings. 

Balance the model per the manual, flying test for proper responses, and adjust as these test indicate regardless of that the manual states. Good manuals with call out the CofG as the initial CofG for test flight. As they know the final location has as much to do with ones preference as it does with the aerodynamic layout of the ship.

All the best,
Konrad

[farmflyer]

RE: FMS 1400MM P40B

I'm going to have to agree with Konrad I set up close to the call out cog starting a little nose heavy. After most of my first couple of flights I've always had to adjust a little more to fit my preference for the given plane. On the cog machines I've tried a couple of them even made my own but have never found a great advantage over the old finger tips. On this issue I don't think there is an absolute right way to achieve cog because it comes down to personal preference to each pilot how the plane handles.

[WintrSol]

RE: FMS 1400MM P40B

Once you've found your 'best' CG for your preferences, a machine allows you to measure that spot so, if you have to replace the battery with one of a different mass, you can position it to achieve that 'best' spot before the first flight with that battery. I have more than four batteries I can fly in the same model, and, once I have my 'best' CG, all I need do is mark those of different size or shape (or both) so all I need do is put a battery in and fly - no guessing around, no 'it's close enough', then adjust. I can do the markings on my bench, and know it will be very close, without getting near the field.

[Konrad]

RE: FMS 1400MM P40B

OK, still don't see how it is more accurate than the finger tips. As vertical balance is also a concern of mine I still need to perform a few flight test to get the model trimmed out correctly with each size (weight and shape) battery I plan on using. It might help some of the arguments it someone can post a link to the machines they feel are of value along with the instruction on how to use the machine.

All the best,
Konrad

[ryramZ]

RE: FMS 1400MM P40B

OK, still don't see how it is more accurate than the finger tips. As vertical balance is also a concern of mine I still need to perform a few flight test to get the model trimmed out correctly with each  size (weight and shape) battery I plan on using. It might help some of the arguments it someone can post a link to the machines they feel are of value along with the instruction on how to use the machine.

All the best,
Konrad

Normally I won't call out cg unless the manual is way off which it is in this case. I use fingers. I think of cg like a range. If I maiden a plane that's off the charts like this one was I'm prepared before flight. For example this p40 with its aft of manual cg had me thinking I may need down trim if things get dicey after take off. This bird so happened to be perfect in my opinion.

You guys are going to love it!