F1 Empty W&B Numbers

[Ironflight]

I weighed the airplane yesterday with it ready for flight except empty of fuel and with 10 quarts of oil (more than I want to fly with to prevent dumping it out the breather, bit recommended for W&B). Thought I’d share since I had ben wondering what other guys have. It woudl be interesting to compare to Harmon numbers, but I’m mostly interested in what F1 folks have.

Mine has an empty weight of 1245 (lb.) with an empty CG of 88.445 (in.). Scales were tested accurate to a pound using heavy weights and against each other.

Anyone else want to share?

 

[GyroF-16]

My F-1 is 1271 lb empty, with an empty CG of 85.63.
MT prop, Mk 1 tail. EarthX EXT900 battery in cargo area (traditional location).
With a pilot in the front seat and full fuel, it’s at 88.25.

I’ve been flying with ballast in the cargo area to move the CG a bit further aft.

 

[Full Throttle]

What's the CG window. Three inches difference seems like a lot.

 

[Ironflight]

CG range is just about 10 inches : 87.7 to 97.4

There is quite a bit of variation wit the type based on prop weight and which tail it has. Even though the F1 is a well-defined design, there have ben three tails (each a bit stronger and certainly heavier) and the tail is obviously at the back end of the airframe so small weight differences are significant. Similarly, a metal Hartzell versus a composite prop hanging on the nose can significantly drag the empty CG forward.

I did some sample loadings, and it is pretty hard to get mine out of the CG envelope and remain under the 2,000 lb Max Gross.

 

[theduff]

I weighed the airplane yesterday with it ready for flight except empty of fuel and with 10 quarts of oil (more than I want to fly with to prevent dumping it out the breather, bit recommended for W&B). Thought I’d share since I had ben wondering what other guys have. It woudl be interesting to compare to Harmon numbers, but I’m mostly interested in what F1 folks have.

Mine has an empty weight of 1245 (lb.) with an empty CG of 88.445 (in.). Scales were tested accurate to a pound using heavy weights and against each other.

Anyone else want to share?

I'm assuming this is unpainted ?

 

[Ironflight]

I'm assuming this is unpainted ?

Nope - this is painted.

The Reveal - F1 Almost Ready for Flight!

For those interested - yet another John Stahr paint job was rolled out this morning for the neighbor’s to see! While the F1 is still technically a “project” - Airworthiness Inspection is scheduled for next Friday - there is pretty much nothing more to do except go over critical things one or two...

vansairforce.net

 

[Little Al]

My F1 empty with oil is 1226lbs can't remember the cg range I'll look when I get to the hanger. I Remember it's impossible to load and exceed the foward limit. Mk3 tail, 1" longerons, Whirlwind 330 prop. EarthX battery up front in the RV4 location. Got 2lbs off with lots of titanium in the tail wheel area.

 

[F1 Rocket]

N14ZM is 1279lbs at an empty CG of 87.4”.
Whirlwind 330
MK3 tail
EarthX 1200 in the stock location behind the rear seat.

 

[PaulRomano]

I weighed the airplane yesterday with it ready for flight except empty of fuel and with 10 quarts of oil (more than I want to fly with to prevent dumping it out the breather, bit recommended for W&B). Thought I’d share since I had ben wondering what other guys have. It woudl be interesting to compare to Harmon numbers, but I’m mostly interested in what F1 folks have.

Mine has an empty weight of 1245 (lb.) with an empty CG of 88.445 (in.). Scales were tested accurate to a pound using heavy weights and against each other.

Anyone else want to share?

My F1 came in at 1277lbs, 88.2, empty. I still have 2 Odyssey batteries (2 separate busses) at station 170. That should change later this
year when I move to 2 EarthX batteries to replace the 680s. That should shave 20lbs.

The early F1s flew with either the RV-4 or the -7/-8 empennage because Mark and the Czech team didn't have the F1 empennage ready. I believe
there were only about 25 Mk I empennages sold. They were quickly superceded by the MK II, which I am currently flying. The difference in weight between an RV-4 empennage and the MK III is significant--about 17 lbs if I remember correctly. Vince and I went over this a number of years ago, he should have the correct numbers.

Great paint, BTW! If you and Little Al can make it to OSH this year, Vince will have a star studded display -- sorta like when Bob Baker and Daryl Hudec were there.

 

[RWoodard]

I guess mine wins the chubby girl contest… but she shore is purdy!

My HR2 is 1303# at 85.29”

It has a 3 blade MT prop and an EarthX battery in the baggage compartment.

I am at 87.79” with me and 30 minutes of fuel onboard. The limit is 87”. I prefer to have my CG a little more aft, so for solo flight I carry 60# of lead shot in the baggage compartment. The good news is that it’s pretty much impossible to load it aft of the allowable 97.4” CG point.

 

[Ironflight]

My F1 came in at 1277lbs, 88.2, empty. I still have 2 Odyssey batteries (2 separate busses) at station 170. That should change later this
year when I move to 2 EarthX batteries to replace the 680s. That should shave 20lbs.

The early F1s flew with either the RV-4 or the -7/-8 empennage because Mark and the Czech team didn't have the F1 empennage ready. I believe
there were only about 25 Mk I empennages sold. They were quickly superceded by the MK II, which I am currently flying. The difference in weight between an RV-4 empennage and the MK III is significant--about 17 lbs if I remember correctly. Vince and I went over this a number of years ago, he should have the correct numbers.

Great paint, BTW! If you and Little Al can make it to OSH this year, Vince will have a star studded display -- sorta like when Bob Baker and Daryl Hudec were there.

Interesting history on the tail Paul - thanks for that! My kit (serial # 29) had the Mark I tail components, but Vicne and Mark only sent me the skins when I took delivery - then Vince made me the Mark III skeletons and shipped those before I built. Mark’ quote was “we don;t want Paul’s tail to fall off….”

I have sen various variations of the RV-4 tail installed on Harmons, almost all of them beefed up to some extent. One I saw has the “original” RV-4 horizontal stab, and it looks extremely under-designed for the task. I mentioned it to Van a while back and he cringed - he upgraded the tail of the RV-4 to a more robust design in an abundance of caution once he had engineered the tail for the -6 (I think that’;s what he said). Those reinforcements are now included on all the short-winged RV’s. Frankly, seeing an original RV-4 on a Rocketized airplane is pretty scary.

BTW - I have two Earth 900 batteries and a WW-330 prop, so that lightens my ship quite a bit over standard.

 

[Little Al]

I guess mine wins the chubby girl contest… but she shore is purdy!

My HR2 is 1303# at 85.29”

It has a 3 blade MT prop and an EarthX battery in the baggage compartment.

I am at 87.79” with me and 30 minutes of fuel onboard. The limit is 87”. I prefer to have my CG a little more aft, so for solo flight I carry 60# of lead shot in the baggage compartment. The good news is that it’s pretty much impossible to load it aft of the allowable 97.4” CG point.

I hate to knock you off your chubby girl contest podium but we currently have that one in the trailer headed for home. F1 Evo with a Continental 550 and a metal Hartzel prop weighted in at 1474lbs. No wonder she has been sitting in the hanger and nobody wanted to play with her. We will be putting her on the treadmill to see if we can't get her to shed a few lbs

 

[Freemasm]

You guys started it and sorry for the drift.

Anyone know for certain why John Harmon strongly preferred the 4 emp to any others, specifically against the 8?

The quote I remember when calling before starting this mess.

“Purchase the RV4 empennage. The 8 will work if you have to. Nothing else.”

 

[PaulRomano]

You guys started it and sorry for the drift.

Anyone know for certain why John Harmon strongly preferred the 4 emp to any others, specifically against the 8?

The quote I remember when calling before starting this mess.

“Purchase the RV4 empennage. The 8 will work if you have to. Nothing else.”

Yeah, and this one is apt to drift far and wide.

I haven't heard this statement from John, but my guess is that it is the lightest of all the empennages I listed above and also
dimensionally has the least amount of area, so may give a few more knots at speed (pure hand waving here). It will have less control authority on landing because of the smaller elevator/rudder. And a F1 with an IO540/IO550 with a Sport Wing comes down very quickly in an engine out, so some consideration needs to be given to landing speeds and how much kinetic energy needs to be dissipated. And that means control authority at low speed is important.

There really are a lot of issues here, and a number of tradeoffs. The Mk I, II (Evo), and III F1 tails all have the same amount of area, but structurally are different. The horizontal stab area is about 20% greater than an -8. They all use a NACA 0009 symmetric airfoil. And a simple hand calculation will show that at Vne, if the elevator is deflected about 7 degrees, the Mk series of tails will generate roughly 800-900 lbs on the semispan. The -8 will be about 20% less. Please note that if the elevator is abruptly deflected this number is higher.

Vince has a Mk I stabilizer hanging on his wall that failed at about 900lbs on the semispan.

 

[vfrazier]

You guys started it and sorry for the drift.

Anyone know for certain why John Harmon strongly preferred the 4 emp to any others, specifically against the 8?

The quote I remember when calling before starting this mess.

“Purchase the RV4 empennage. The 8 will work if you have to. Nothing else.”

The HR2 debuted around 1991 and the RV-8 around 1995. John didn't have a lot of other choices way back when.

The RV-8 elevators, if I recall correctly, have less elevator chord than the RV-4 elevators do. I recall some early Rocket owners with RV-8 tails say that the elevator authority was marginal for the landing flare.

FWIW, that would make them land similarly to the Stinson 108s, IMHO. I recall that the Stinsons had problems flaring well unless you kept the speed up.

 

[ronrapp]

I used to fly a 108 and never noticed any issues in the flare. This was a model which had been converted to the metal skinned wings, so maybe that has something to do with it. It was definitely what the F1 guys apparently refer to as a "chubby girl"...

--Ron

 

[F1 Rocket]

N14ZM had an RV8 tail set until the current MK3 set was installed. Overall, I preferred the lighter stick forces but it was hard to 3 point when flown solo with full fuel.

 

[Toobuilder]

HRII with RV-8 tail. Dual lead acid batteries, dual Generators, EFI, metal Hartzel 2 blade…. 1251 @ 86.65