RV-3 Baby Rocket

[Rdwrv4]

as far as weight goes it shouldn't be any heavier than one of the heavy weight 3's built in the past with an 0-360 and constant speed prop.

[David Paule]

With the RV-8 tail, it's more weight at both ends.

Dave

[KatieB]

I wonder about using larger longerons if you go with an -8 tail. The holes for the forward mount points for the HS have marginal edge distance with the stock 3/4" longerons. I added a mount bracket to the back of the forward HS spar because my existing holes were too close to the edges of the longerons. With the larger mass of the -8 tail, you'd have more stress on the longerons where the bolts pass through during engine start (tail shake!) and aerobatics. (Maybe you'd need larger bolts as well-- the -3 uses AN-3 bolts for this, does the -8 use AN-4?)

[F1Boss]

Too large. One just like it, but modeled for the -3 size, would be the right ticket (balanced control sfcs).

KatieB is right about the longerons too - go to 1x1". Bigger firewall weldments, etc. Heck - the firewall is gonna be bigger anyway. Easy choice there.

Be careful - John Harmon told me the -3 reverses elev control at about 5G..I cannot say if the HR1 does this or not.

Carry on!
Mark

[Rdwrv4]

Originally Posted by KatieB

I wonder about using larger longerons if you go with an -8 tail. The holes for the forward mount points for the HS have marginal edge distance with the stock 3/4" longerons. I added a mount bracket to the back of the forward HS spar because my existing holes were too close to the edges of the longerons. With the larger mass of the -8 tail, you'd have more stress on the longerons where the bolts pass through during engine start (tail shake!) and aerobatics. (Maybe you'd need larger bolts as well-- the -3 uses AN-3
bolts for this, does the -8 use AN-4?)

If I use the 8 tail I use the -8 bulkheads and deck at the end . Using -4 sized firewall weldments and 1 1/4 2024 angle already extruded to the more open angle. BTW I bought 1" angle 50 ft, it is too big to bend, trying to find 7/8 angle If not will use 3/4

[Doug]

Originally Posted by F1Boss

Be careful - John Harmon told me the -3 reverses elev control at about 5G..I cannot say if the HR1 does this or not.
Mark

Can you clarify what 'reverses elevator control' means.
Thanks,

[ChiefPilot]

Originally Posted by Doug

Can you clarify what 'reverses elevator control' means.
Thanks,

I suspect what was actually being described was a loss of positive pitch stability.

At higher angles of attack (required by the increased amount of lift required to maintain the increased load factor) the center of lift (CoL) moves towards the leading edge. When this happens, the CoL gets closer to the center of gravity and as a result lateral (pitch) stability decreases. As it approaches the point where neutral stability exists, the back pressure required for a given load factor is reduced and there will be no back pressure required to maintain the current load factor. At some point, you might find that you need forward stick pressure to prevent the load factor from increasing. This isn't really control reversal, it's really just negative stability.

ETA: I should add that I've never flown a -3 and the above is a theoretical description in answer to the question. I noticed during phase one on my -6A that stick forces got lighter as I approached 6G but never got the point of neutral, much less negative, lateral stability. Whether one encounters such or not will depend where the CG is located - if you start with something with a very aft CG, you're more likely to encounter it than you are with a forward CG. This is one of the reasons why a aft-limit balance point is specified along with the weight for aerobatic gross.

[Rdwrv4]

OK measuring and figuring , It is nice Harmon left his cowling narrow at the bottom. It looks like I can use RV-8 Firewall weldments with some modifications to the lower ones. I am trying to locate a Hartzell prop extension like the one used with the Sam James cowl. Also A 14 to 14.75 spinner , got a line on a super D 14.125" one it should be OK it is 3/8" smaller than the front of the cowl, not sure how noticeable that would be. Longerons ,I bought 1" angle but just looking at it you can tell it would be a b****h to bend, so I am going to cut it down to 3/4" except at the firewall end and leave that 1". my buddy swears his fine tooth carbide tipped table saw will do it perfectly. I really need a spinner and a spacer to get the firewall shape right. Also looks like an RV-8 fuselage end will work perfect and save a lot of time. FYI

[F1Boss]

Originally Posted by Doug

Can you clarify what 'reverses elevator control' means.
Thanks,

Control reversal means that the stick force used on a particular control surface reverses.

Ex: elev control should continue to be a 'pull' to increase positive G. Apparently, the -3 elev force switches from a pull to a push somewhere around 5G positive. I am also told that the trim direction on the F-102 reverses at some very high speed...no problem if the pilot knows this to be the case..

Clear as mud?

Carry on!
Mark

[F1Boss]

Get your hands on a red-tagged Hartzell M2 hub (you won't need an extension), and look for a spinner from a Commander 114 (or 112?). Vince at Flyboy Accys might have the spinner avail in composite soon - or maybe now?

Carry on!
Mark