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Adding weight to the flywheel to improve aft CG limit on an -8

jarheadatunm

jarheadatunm

Member
Searched all the "flywheel" threads and couldn't find anything about adding weight to the flywheel. Obviously, most folks want to get a lighter one, but in my case, my 8 is very light with a Catto prop. Of course, putting on a CS prop would be ideal but it's not in the cards. I can only find one guy who sells any "solution", in the form of a 5.6lb ring of stainless steel that bolts on.

I created a station at 16" in my Foreflight W/B to add 6lbs (accounting for hardware), and this definitely moves the CG to inside the envelope when wanting to fly with a buddy in the back. Not sure if this is perfectly the same as adding the weight and reweighing the airplane given that this is a specific weight at a specific station, not just the weight blended into the weight registered on the wheels scales. Also not sure if adding that weight the flywheel will adversely affect performance of the engine to negate this idea. The airplane also has the EarthX battery in the tail, so moving that forward to the firewall, would further improve things.
For reference:
Weight and Balance:
Right wheel: 480lb, 68.75
Left wheel: 490lb, 68.75
Tailwheel: 60lb, 251.06
Total: 1030Lbs
CG: 79.37

Photos are the load with and without the 16" station.

Any thoughtIMG_2032.pngs on this idea?IMG_2031.pngIMG_2030.png
 
In my 9A I had the same issue with my catto prop. I ended having a heavier crush plate machined by Saber Manufacturing (I got my prop extension from them) I think it may be a common thing because he knew exactly what I wanted when I asked about more weight in the front.

Aitor
 
Moving the battery to the front will save weight due to the elimination of the long, fat cable(s). As @Mikeyb said, 1030 lbs seems very low. What engine do you have? Did you weigh with the aircraft in level flying position? Is this a new to you aircraft?
 
If you can find a Landoll Harmonic Balancer, bolts right to the flywheel adds considerable weight as well balancing. Had one on my 0-360 RV6 with a Prince P-Tip prop. Additionally it increased static rpm by 40.
 
Is your tail heavy by flying observation or only number crunching?

I agree you have a very light plane. Here are my numbers (IO-360M1B, Hartzell BA two blade aluminum prop, Grove main gear, full paint, one PC-625 mounted in the forward baggage well, one PC-625 mounted in the normal aft location):
Left main: 524
Right main: 535
Tail wheel: 59#
Empty CG: 78.18”

I get close to the aft CG limit with low fuel (5 gallons), 75# aft baggage, and a 135# passenger. This drives my conservative W&B operational boundary to be no more than 180# passenger plus baggage.

If you don’t bite the bullet and mount a CS prop (my preference) or add nose weight, you might need to establish your own W&B comfort rule for aft passenger and aft baggage limit.

Carl
 
Get more engine and a C/S prop.

Kidding, but I did just go about trying to solve the opposite problem of a nose heavy 8A with tail ballast. My aluminum Hartzell is like 65# or so and that adds a lot. I really like my angle valve 360 and sometimes wish it was a 390.

But your plane is amazingly light. I bet it's incredible solo.
 
The lightweight tail wheel I bought weighs one pound less than the stock one. On a -8 that will move the CG forward a whopping 0.06”
 
Is anyone reverse engineering the Landoll Balancer and making them? Seems to be a massive want for one but they are hens teeth.
 
jarheadatunm said:
Searched all the "flywheel" threads and couldn't find anything about adding weight to the flywheel. Obviously, most folks want to get a lighter one, but in my case, my 8 is very light with a Catto prop. Of course, putting on a CS prop would be ideal but it's not in the cards. I can only find one guy who sells any "solution", in the form of a 5.6lb ring of stainless steel that bolts on.

I created a station at 16" in my Foreflight W/B to add 6lbs (accounting for hardware), and this definitely moves the CG to inside the envelope when wanting to fly with a buddy in the back. Not sure if this is perfectly the same as adding the weight and reweighing the airplane given that this is a specific weight at a specific station, not just the weight blended into the weight registered on the wheels scales. Also not sure if adding that weight the flywheel will adversely affect performance of the engine to negate this idea. The airplane also has the EarthX battery in the tail, so moving that forward to the firewall, would further improve things.
For reference:
Weight and Balance:
Right wheel: 480lb, 68.75
Left wheel: 490lb, 68.75
Tailwheel: 60lb, 251.06
Total: 1030Lbs
CG: 79.37

Photos are the load with and without the 16" station.

Any thoughtView attachment 122466s on this idea?View attachment 122467View attachment 122465
Click to expand...

I put your numbers in a spreadsheet. You are well within the CG envelope with a 225# pilot and 200# passenger. IMG_0747.png
 
Saber is your best contact for prop extension or maybe a Crush Plate. I adjusted the CG on my RV9 with a weighted crush plate on a FP prop. Yes, the CS prop would be a better choice but the crush plate still keeps it simple and corrects for a light weight composite prop where maybe a Metal prop could have been a better choice. Confirm you numbers on your initial CG weigh in and be sure the fuselage is LEVEL. As others seem to think the original weights may be a bit light for an 8 .
 
Mikeyb said:
It’s unusual to find a -8 with a too far aft empty CG. How confident are you in your W&B estimate? 1030# is near record lows.
Click to expand...
Plane is new to me and I'm basing this off the original builders, and current, W&B. Glad I asked this group, because I didn't suspect an issue with the weight, but apparently it is. Going to weigh it and get a new W&B. Thanks!
 
rv8ch said:
Moving the battery to the front will save weight due to the elimination of the long, fat cable(s). As @Mikeyb said, 1030 lbs seems very low. What engine do you have? Did you weigh with the aircraft in level flying position? Is this a new to you aircraft?
Click to expand...
Original W&B and new to me, so going to weigh it and get a fresh W&B. Thanks for the advice!
 
Carl Froehlich said:
Is your tail heavy by flying observation or only number crunching?

I agree you have a very light plane. Here are my numbers (IO-360M1B, Hartzell BA two blade aluminum prop, Grove main gear, full paint, one PC-625 mounted in the forward baggage well, one PC-625 mounted in the normal aft location):
Left main: 524
Right main: 535
Tail wheel: 59#
Empty CG: 78.18”

I get close to the aft CG limit with low fuel (5 gallons), 75# aft baggage, and a 135# passenger. This drives my conservative W&B operational boundary to be no more than 180# passenger plus baggage.

If you don’t bite the bullet and mount a CS prop (my preference) or add nose weight, you might need to establish your own W&B comfort rule for aft passenger and aft baggage limit.

Carl
Click to expand...
Based entirely off the current, and only, W&B. I don't have a reference to compare to, but it does seem pitch sensitive, but nothing out of "ordinary". If that makes sense.
Clearly I need to do a new W&B so I know what I'm definitely working with. Thanks!
 
Just for information and comparison I originally had the sensenich metal FP prop on my -7 and with the hub it weighed 44 lbs, the replacement Catto 3 blade weighed 14 lbs, a big difference hence the need for weight up front. Even with the added weight the performance was way better.
 
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