200 ktas plus RV

[deene]

I built a fast RV8, IO390, James cowling, extended hub CS BA prop, rocket style turtle deck.

I could run at 200 ktas down low wide open. Posted 227 mph in a closed course SARL race.

As several postings pointed out, 200kts is VNE for a RV8...although I did enjoy 185+ cruise speeds, at 200 and above, you will be a test pilot.

[F1Boss]

Originally Posted by Toobuilder

Your requirements dictate a Rocket.

If you can get to 200KTAS, you will be high, and you still have to come down. This is where the 240KTAS Vne of the Rocket can help keep the parts attached.

Caveat: you cannot use the 200KTAS cruise power setting in descent, even with a Rocket.

The plastic candidates that fit into this performance requirement are numerous..but the mission profile will change dramatically: no sod field landings for one..

Carry on!
Mark

[vlittle]

Originally Posted by N395V

Cube Root of 30 is 3.10723250595 for a 3% increase.

The cube root of 1.3 is 1.091, i.e a 9.1% increase. It's easier to increase speed with an efficient prop, aerodynamic cleanup and lighter weight. I see about 211 KTAS at 8500' WOT in my HR-II but I usually cruise at 180 KTAS at 10 GPH Unless it's a long trip.

Question.... if you have to travel so fast to save a few minutes getting there, why are you spending thousands of hours building? Just sayin'.

[Mark Albery]

Originally Posted by N395V

Cube Root of 30 is 3.10723250595 for a 3% increase.

You need to take the cube root of the power factor 1.3 which is 1.091, so actually a 9% speed increase assuming drag coefficient is constant.

[FlyArmy]

Originally Posted by Adriaan Kleyn

I am new to RV's . I want ro buildt a aircraft that is can fly 200 kts plus, but it must be a RV. I am thinking of a RV8 with a IO 390. Is that realistic ? I understand that a RV8 with the bigger engine is nose heavy, is that a concern. I am not into aerobatics but want a fast aircraft for x country. My thinking for the RV8 is because I am 6ft5 and doesn't fit comfortably into the RV7 . I need some real life experience concerning this matter.

Lets say you have an RV8 that does 175-180ktas. On a 400nm trip, a 200ktas airplane would save you about 15-20 minutes. Half that for a 200nm trip. That's almost negligible. In the grand scheme of driving to the airport, preflighting, pushing it out, refueling if you need to, starting, taxiing, flying, landing, taxiing, parking, tying down, refueling, getting transpo to where you need to go, etc., 10-20 minutes of extra time in the air is almost nil, especially when the cost of getting over the 200ktas cruise mark is so high in the way of motors, mods, and lack of flying examples out there relative to stock RVs. If you can get your hands on a rocket and have the funds for it (and increased fuel and insurance), then that's your best bet. Otherwise a clean IO360/390 -8 is probably your best bet, taking a (IMO) negligible hit to enroute/climb times.

[jefferts]

You need to think about fuel too. My -8 has tip tanks (60 gal total), so it can do 1000nm legs with IFR reserves in a little less than 6 hrs. Your IO-390 will be a little faster but with no increase in fuel load over a stock (42gal) RV and I'm pretty sure I'll beat you home (if my bladder survives anyway!). The extra speed really helps on long legs, but you have to have the fuel capacity and then your -8 becomes a one place bird. I keep thinking that a Lancair 4P is what I really need, just gotta rob a bank. In the meantime, my -8 has been to both coasts and gets me where I need to go faster than the airlines within a 1000nm circle, albeit it is significantly less weather capable!

[RV7A Flyer]

Originally Posted by Mark Albery

You need to take the cube root of the power factor 1.3 which is 1.091, so actually a 9% speed increase assuming drag coefficient is constant.

Put simply in mathematical terms:

(Vnew/Vold) = (HPnew/HPold)^(1/3)

all other factors being unchanged (like Cd).

It takes a lot of additional power to get a little bit of additional speed.