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F-4 raider/Harmon Rocket Lite

Gt-401

Active Member
I don't post much here, but last month I managed to adopt Larry Vetterman's Harmon Rocket lite,(as he calls it) that was converted to an IO-360 instead of the popular 540. After searching, it looks as if there has been a fair amount of interest over the years, So I thought I would start a thread about flying, and modifing this rocket lite.

I plan on trying to wear it out this fall and winter, and I will be posting on its flying qualities and performance numbers, as well as try to answer questions that people might have about the combination.

Greg
 
Greg,

I know we've talked via email, but I look forward to hearing more flight reports!

Thanks,
 
Rocket 100 SARL Race

If things go right I am hoping to go to Texas and participate in the rocket 100 air race on nov 11. That way I can get some official performance numbers for all to see.

I'm also hoping to meet some fellow rocketeers and learn some about the big engine ships..
 
F4 Raider

I'm very interested in the F4 Raider. Before seeing the pictures from Oshkosh I didn't even know they existed. Seems like a perfect combination with the IO-360 up front. I don't have the room or budget for two planes so I have to decide if I want to give up my -4 to move forward. Having all that extra room would sure be nice though. I love the way the -4 handles but it is a rather snug fit, limited panel space and requires some attention to Wt & Bal when you have a back seater. I've gone as far as I go on a budget without putting in a full glass panel. Wish these were around when I got the -4. Hopefully Vince will go forward and eventually have a full kit.

Very tempting........
 
Weight and balance

Weight and balance has been a pleasant surprise. Empty weight on this plane is listed as 1091 lbs, which I understand is about the same as a heavy RV-4. I had a polished RV-4 before this, its builder was very weight conscious, to the extent that he didn't paint it, or install lights, with a Catto fixed pitch two blade prop, and it weighed 980 empty. The rocket was built light, but not to the same extreme.

With the rocket I get a gross weight increase to 1950 lbs. according to weight and balance calculations it is still aft cg sensitive, but in practice it is much less pitch sensitive than the -4. With 2up the rocket is comfortable in pitch and the trim is right in the middle if its travel where as the -4 was trimmed full forward in cruise and very pitch sensitive on landing, but that probably has more to do with the difference in props than the difference in airframes. the rocket has a BA
Hartzell.
https://imgur.com/gallery/2C5yp
 
results

~161kt to 178kt ground speed or so at 9GPH - close enough to call it 170kt TAS and about 155KIAS. Not too bad. Which model prop is on that ship now? I thought I heard Larry say he left the 540 prop on it...

Now we need average speeds from some of the 6cyl drivers...9GPH, and it looks like 3500MSL. What'll she do? No RPM mentioned, so just use some low-cruise MP and RPM.

Mine is an Evo, so that would not work as a point of reference. I do recall 7GPH/18"/1800 gives me an IAS of 140kt...OK in the summer when it's warm, but no can do in the winter: gets too cold.
 
More performance notes

I was at the hanger this afternoon and I grabbed my cruise notes, these are just hand written notes during cross country flights. The true airspeed are figured by the air data computer, but I have found it to be pretty accurate compared to the averaged speeds from the app.

Press alt. 11,500. Density alt. 13,360
GPH: 7.4
66% hp
MP 20.2. RPM. 2400
OAT. 42.2 f.
IAS: 150mph. TAS: 182 mph
This power setting was about 60 degrees lean of peak

Press alt 13,500. Density alt, 14,320
GPH: 7.4
64% power
MP: 18.6 RPM:2440
OAT:21 Deg F
IAS: 152mph TAS: 191 mph
This power setting was only about 20 deg lean of peak.

Press alt 9,500 Density alt, 10,900
GPH: 8
71% power
MP: 21.9 RPM:2370
OAT:45.1 Deg F
IAS: 163mph TAS: 194 mph
This power setting was only about 20 deg lean of peak.


I'm not sure why it is calculating percent power so hi, but since all fuel flows are lean of peak, there should be a simple calculation to figure HP, but I don't know the factor for a 9.5: 1 compression ratio.
 
~161kt to 178kt ground speed or so at 9GPH - close enough to call it 170kt TAS and about 155KIAS. Not too bad. Which model prop is on that ship now? I thought I heard Larry say he left the 540 prop on it...

This Rocket has a Hartzell blended airfoil prop. I'm pretty sure it was new when he changed the engine.
 
Rocket/raider

I have a very nice complete HR2 0tt airframe that would make a great f4 conversion. Complete wings, empennage, fuselage, tinted canopy,cowling,wheel pants, wing tips,fiberglass fairings, new style hr2 engine mount and gear, Dynon autopilot servos installed, I have some extra parts that will go with it. This bird could be in the air fast. If anyone is interested please email me @ [email protected]
 
....I'm not sure why it is calculating percent power so hi, but since all fuel flows are lean of peak, there should be a simple calculation to figure HP, but I don't know the factor for a 9.5: 1 compression ratio.

I use a very simple equation for any normally-aspirated engine:

% Power = (MP / 29.92) * (RPM / Max RPM).

It seems to get close enough, for me anyway, and is independent of compression ratio and leanness. This puts your final point at 64% power instead of the 71% power mentioned.

Dave
 
I use a very simple equation for any normally-aspirated engine:

% Power = (MP / 29.92) * (RPM / Max RPM).

It seems to get close enough, for me anyway, and is independent of compression ratio and leanness. This puts your final point at 64% power instead of the 71% power mentioned.

Dave

AFR, exhaust back pressure (related to altitude), ignition timing and IAT also affect hp to a significant degree.
 
AFR, exhaust back pressure (related to altitude), ignition timing and IAT also affect hp to a significant degree.

Wouldn't anything that affects horsepower also affect manifold pressure and rpm on a normally-aspirated engine? That suggests that the overall power will be affected, but not the percent power.

Example - leaning: as I lean the mixture, the power goes up, and then it drops. Fuel flow changes and so does airspeed. Since the engine can only make a certain amount of maximum horsepower, the percent power is changing along with the fuel consumption and airspeed.

Dave
 
Wouldn't anything that affects horsepower also affect manifold pressure and rpm on a normally-aspirated engine? That suggests that the overall power will be affected, but not the percent power.

Example - leaning: as I lean the mixture, the power goes up, and then it drops. Fuel flow changes and so does airspeed. Since the engine can only make a certain amount of maximum horsepower, the percent power is changing along with the fuel consumption and airspeed.

Dave

If we say X engine puts out 180hp at 29.92 inches and 15C IAT at SL, with all other significant factors (many more than MAP and RPM) taken into account, we may call that 100% power. Actual hp varies with these multiple parameters and can also be expressed as a percentage. Overall (actual) power and % of our nominal maximum are therefore really the same thing. 90hp and 50% power for example in this case.

On leaning, it depends where you start from- richer than about 12.5 AFR and yes, you'd will gain power as you approach 12.5 and then start losing power leaner than that.

With a C/S prop, rpm changes are masked since the governor tries to maintain the set rpm by changing blade pitch. AT WOT assuming minimal restriction across the throttle plate and throat, there would be little resultant change in MAP since MAP should be close to the same whether the engine is running or not.

MAP does not change significantly with IAT, nor exhaust back pressure either.

I agree, fuel flow, hp and TAS are affected by leaning.

There are so many factors that influence HP and therefore % of power, that's it's virtually impossible to calculate % of power at altitude accurately without significant testing of that particular engine in an altitude dyno cell. Some of the factors are quite interrelated, such as ignition timing and AFR.

I wouldn't attempt to split hairs by 1-2% based on a simple formula which doesn't account for all influences. Your formula would get you in the ballpark however.

I would do all flight testing at WOT to minimize pumping loss effects in the data. The same goes for rpm and AFR.

In the end, the aircraft does what it does for TAS vs. FF at a given altitude and power level. That's really what matters and really your "dyno".

I'm a big fan of the F-4 Raider concept BTW but you really need a turbo on there to get back the knots lost with 2 less cylinders. No reason why a good 360 turbo can't exceed atmo 540 numbers above 10,000 feet or a little lower running a bit of boost. The price delta is significant these days and the lighter weight is also a big plus to get back some of the climb performance. If you're going to have a Rocket of sorts, make it one in performance too which is the main reason people want Rockets rather than RV8s IMO.
 
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The performance of a 540 Rocket has significant appeal no doubt, but the ergonomics of the Rocket are also compelling when compared to the RV-8. I'd bet this fact alone will drag some potential RV-8 people over to the dark side.
 
Rocket

Hey guys can someone tell me if I can list a rocket airframe in the main classified page? I don?t want to upset anyone but didn?t know who to ask.
I?m currently flying a 200hp fast back rv8 that is a blast to fly. I had a hr2 290hp before the 8 and put close to 500hrs on it. I was figuring out my fuel exspenses for 2016 a few months back and they are very close within 2%. The insurance was 600.00 more on the rocket for the year. I think the F4 will be a very popular option and will have many advantages over the rv8.
 
Turbo rocket!

"I'm a big fan of the F-4 Raider concept BTW but you really need a turbo on there to get back the knots lost with 2 less cylinders. No reason why a good 360 turbo can't exceed atmo 540 numbers above 10,000 feet or a little lower running a bit of boost. The price delta is significant these days and the lighter weight is also a big plus to get back some of the climb performance. If you're going to have a Rocket of sorts, make it one in performance too which is the main reason people want Rockets rather than RV8s IMO."


That sounds very interesting, but I'm afraid I know just enough about turbo installations to know that I don't know nearly enough to do it right. It sounds like maybe you, RV6ejguy, have done a couple, and might know what it would take to do it right, how would you setup A turbo 360 in a rocket? Would you use twin turbos? Would you use intercoolers? Automatic wastegates? Or would the simple approach be the right one, one turbo, no waste gate, no intercooler. :confused::confused:
 
"I'm a big fan of the F-4 Raider concept BTW but you really need a turbo on there to get back the knots lost with 2 less cylinders. No reason why a good 360 turbo can't exceed atmo 540 numbers above 10,000 feet or a little lower running a bit of boost. The price delta is significant these days and the lighter weight is also a big plus to get back some of the climb performance. If you're going to have a Rocket of sorts, make it one in performance too which is the main reason people want Rockets rather than RV8s IMO."


That sounds very interesting, but I'm afraid I know just enough about turbo installations to know that I don't know nearly enough to do it right. It sounds like maybe you, RV6ejguy, have done a couple, and might know what it would take to do it right, how would you setup A turbo 360 in a rocket? Would you use twin turbos? Would you use intercoolers? Automatic wastegates? Or would the simple approach be the right one, one turbo, no waste gate, no intercooler. :confused::confused:

You have lots of space behind the engine so I'd be tempted to use one turbo mounted up high to avoid an oil scavenge pump. Would certainly use an intercooler and automatic wastegate- all automotive type stuff, not archaic, clunky aviation hardware.

You could do a nice installation with all that cowling space. :)
 
Wouldn't anything that affects horsepower also affect manifold pressure and rpm on a normally-aspirated engine? That suggests that the overall power will be affected, but not the percent power.

Example - leaning: as I lean the mixture, the power goes up, and then it drops. Fuel flow changes and so does airspeed. Since the engine can only make a certain amount of maximum horsepower, the percent power is changing along with the fuel consumption and airspeed.

Dave


Consider the real world example of ignition influence I found when testing CPI - I get to my cruise altitude, power (WOT) and RPM setting. I'll go LOP and the airspeed sags (as expected). This would normally be your "calculated" % power setting (MP, RPM, FF) on the EFIS. However, when I flip the LOP switch for another few degrees of advance, the TAS creeps back up a few knots, yet there is no change in any of the aforementioned parameters.

Eking out a few more knots after you hit the drag wall is a noteworthy change in power - yet it wont show up in a EFIS algorithm. As Ross indicates, the best dyno is the one you fly.
 
turbo/super charger

I do like the idea. I have also kicked around the idea of a small supercharger that would only boost a little, say 75% power up to 15,000. This airplane is not well suited for high altitude cruising, short wings, non-insulated cockpit, no O2. I have heard that there is a fairly steep fuel penalty for turning a supercharger, but i am wondering if it could be minimized by turning down the boost that it produces. Seems like it could possibly be simpler and lighter?

In the end I think the simple normally aspirated io-360 is the best choice for this air frame, the way I intend to fly it. Last week i attended a formation flying clinic. I loved it and intend to do a lot more of that kind of flying, I would hate to use a turbo in that environment. With all the big power adjustments that have to be made I would worry about over boosting the motor. The same applies to aerobatics I think?
 
I do like the idea. I have also kicked around the idea of a small supercharger that would only boost a little, say 75% power up to 15,000. This airplane is not well suited for high altitude cruising, short wings, non-insulated cockpit, no O2. I have heard that there is a fairly steep fuel penalty for turning a supercharger, but i am wondering if it could be minimized by turning down the boost that it produces. Seems like it could possibly be simpler and lighter?

In the end I think the simple normally aspirated io-360 is the best choice for this air frame, the way I intend to fly it. Last week i attended a formation flying clinic. I loved it and intend to do a lot more of that kind of flying, I would hate to use a turbo in that environment. With all the big power adjustments that have to be made I would worry about over boosting the motor. The same applies to aerobatics I think?

No worries of overboosting with a wastegate and formation work is fine too with a turbo. Outside of the exhaust system and mount to support the turbo, IMO it's far simpler, more flexible and more efficient than a supercharger with all the issues of pulleys, belts, tensioners etc.
 
HR2 project

Thanks For the info Mike. I?m going to get my rocket/f4 project listed for sale soon. Somebody will get a real nice ride!!! I hate to see it go.
 
The perfect turbo rocket project

It looks like robertcropdust has the perfect candidate for a turbo 360 installation... :)
 
Wow, I get busy for a few days, sorting out the new Mk3 tail kits, and all sorts of cool stuff pops up!!

There are some great ideas being kicked around here. I can't wait to see some in the air.

Someone asked early in the thread about QB kits. Any hired gun shop can take our stuff and do that for you. There are QBs underway as I type.

We're working on it, but we still lack some easily made, or easily purchased, parts, but we keep adding more and more to the parts we have. Anyone who has built an RV or Rocket before has all the skills to build one of the new F1s or F4s.
 
A few more numbers

I went flying yesterday before changing the oil, and i took the opportunity to get a few more numbers.

I timed a full power climb from brake release @ 3,660ft to level 15,000, and it took 12:36 min. for about a 900 f/pm average. The plane weighed 1600 lbs at takeoff, me and full tanks.

On the way back down I stopped at odd alts to get a speed check. I kept the mixture at about 100 deg rich of peak, so fuel burns may seem a little high to most. RPM was set at 2450 and wide open throttle. Temp was close to standard, i only figured density alt at 15000, and it came out to 15,550.

15000 tas=183mph fuel burn 6.3gph
13000 tas=195mph 7.4
11000 195mph 8.5
9,000 202mph 9.2
7,000 206mph 10.4
5,000 208mph 11.3
 
Rocket Aerobatics

Since I missed my chance to go go to Petit Jean this weekend, fog and low ceilings, I took the opportunity to get better acquainted with the new rocket lite. I took about two hrs this weekend to start exploring its aerobatic envelope. I?m no Rob Holland and I barely know enough to get through the basic maneuvers safely, but here are my impressions and questions.

Rolls. Holy Cow does this thing roll fast. I almost banged my head on the canopy when I threw the stick over. Add in a decent amount of rudder pressure and the roll rate increases even more. I did notice some aileron buffet at full deflection, and the nose drops a fair amount unless I push the nose up a little half way through the roll.

A straight aileron roll is so quick it is over almost as soon as it begins, but a proper barrel roll is just a slow gentle thing of beauty. It is the funnest maneuver I?ve tried so far. The slower the better!

I?m still trying to do a good loop in te Rocket. Playing around with entry speeds, and how much to pull in the first half, and how much to let up over the top. I could use some advice there. I wish I had a G-meter. I haven?t tried any spins or snaps yet. I don?t think my prop is rated for those kind of maneuvers .
 
Based on your questions I highly recommend that you get some professional help before proceeding further. Rockets are slippery and if you happen to fall out of a manoever they will rapidly exceed redline speeds. This can cause an over speed of the prop with damage to the prop and engine. Training with someone who is knowledgeable about rockets and aerobatics will greatly add to your safe enjoyment of the aircraft.
Give serious consideration to the fact that you are flying a rare aircraft. You could possibly be the first person to be doing a particular manoever in the four cylinder version of the rocket. The six cylinder rockets have the advantage (and curse) of the extra nose weight if something goes wrong.
 
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Tom Martin question ?

Tom,
You comment that a Rocket could get you in Vne trouble quickly. How is that different than -4 ? The shorter wing ?
 
Larry
Even the RV4 is dramatically different then the "normal" aerobatic aircraft, citabria, Pitts, etc. It is very easy to exceed Vne in a RV4 if one was to enter a split S too fast, as an example. I have not flown a F4 and I expect it would be more similar to a RV then a six cylinder rocket but as you mentioned, there is that shorter wing. I like the idea of the F4, there is definitely a market niche for this aircraft as the lines are so beautiful and the 4 cylinder will lower the price point. Before the RV 10 came along you could purchase a good used 540 for less then a 360.
I was just pointing out the hazards of self taught aerobatics in a not only new to owner aircraft but a new model as well.
 
Rocket aerobatics

Rockets are a blast for basic acro. I would stay away from snap rolls. I?ve been advised by a few very exspericed Rv builder/pilots no snaps.
 
F4 vs RV-4 acro

I did all of the previously mentioned maneuvers also in my RV-4 with a fixed pitch Catto prop, and I found the F4 slower on the down lines, because of the constant speed prop I think. As far as the cg goes for acro, I think it is very close to what it was with the 540, because the prop flange is in the same place , and the battery was moved from the tail, to the firewall. The cg for this flight was at 90.7. How does that compare to a normal rocket with a single pilot and full fuel?
 
I went back to my 2003 F1 rocket. It had an empty weight of 1196 lbs. The engine was a stock I0540 C4B5, Battery in the aft baggage compartment.
With a 175 pound pilot and full fuel, 52 gallons, the C of G worked out to 88.2" with no passenger or baggage.
This was the standard F1 wing, which would be very similar to the short HR2 wing in weight.
 
Thanks for the info Tom, that is exactly what I was looking for. I redid my W&B with a 175 lb pilot, and my cg moved to 90 in. I am a little surprised that I am as far forward as that compared to the big motors, but I bet moving the battery accounts for most of the change.

Greg
 
Some CG notes

Max fwd CG is 87.7; max aft CG is 97.4". The pilot is at sta. 104.5, so the pilot shifts the CG aft, as does everything but the fuel (almost).

Looks like the CG on the example in the spreadsheet has it's EW CG at sta. 86.6/1177lbs.

PAX is at sta. 131.5; fuel; is at sta. 89.25; fwd baggage is at sta. 157. I doubt you have a aft compartment - if you do, don't put you bowling ball back there.

If you want a Sport wing CG XL spreadsheet, send me your email address and I'll send it along.
 
Well, sort of...

Rockets are a blast for basic acro. I would stay away from snap rolls. I’ve been advised by a few very experienced Rv builder/pilots no snaps.

Snaps are approved - but the entry speed is very low - 80KT. Spin entry is around 60KT...if you can get it to spin.

Tail slides are prohibited.

My testing showed the ship reluctant to spinning - the -4 fin/rudder are a bit small for the fwd CG range, so it tends to fly out of the 'spin' after 1.5 turns or so. The -8 emp allows for full spins to develop.

That is the reason for the larger F1 empennage.
 
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Snaps are approved - but the entry speed is very low - 80KT. Spin entry is around 60KT...if you can get it to spin.

Tail slides are prohibited.

My testing showed the ship reluctant to spinning - the -4 fin/rudder are a bit small for the fwd CG range, so it tends to fly out of the 'spin' after 1.5 turns or so.

That is the reason for the larger F1 empennage.

FWIW, my 540 Rocket (RV-8 tail) spins just fine.
 
Sport air racing league

I ran my rocket lite in the Rocket 100 Air race this weekend. The course was 150 mile closed course with 5 turns and a flying start and finish. The rocket lite turned in a time good for a 213 mph average speed. Not too bad for my first try.
https://imgur.com/gallery/v1FB4
v1FB4
 
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Vince,

Just curious if the F1/F4 use the HRII/RV-4 style flap system, or did you go to the RV-8 style? I was looking to rebuild parts of my system (the idler link), and ultimately decided it would be nearly the same work to fabricate the RV-8 style mechanism. I did, and not only is it far less friction, better kinematics, and stronger, but I saved over 1 pound!

If you have not explored this, I'd encourage you to take a look.
 
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