Rocket vs 8 Vs Super 8

mkjprice · #1 07-27-2011, 10:40 AM

I am still a newbie here, and I have pretty much decided on building an 8/8A. I was just watching on youtube some videos about a Super 8 and a Harmon Rocket. I realize the climb rate, and the speed is faster, but it also has higher empty weight and increased fuel burn.

Now for the sticky question. Is it worth it to build a Rocket/Super 8 over a standard 8? I know a lot of this comes down to what your mission specifics are, but is the increased weight, horsepower, climb performance, and fuel burn worth the extra expense or would it be better to put a higher performance 360/390 in an 8.

I don't want to see a whole lot of arguing, but I would love to hear what different opinions are out there. I also realize that it will likely be next week before I get a lot of responses since many on the board are in Osh this week.

Wish I was there too!

Thanks in advance.

xavierm · #2 07-27-2011, 11:16 AM

Great information can be found here:

http://www.mstewart.net/super8/

Kahuna · #3 07-27-2011, 11:59 AM

Quote:

Originally Posted by mkjprice

Now for the sticky question. Is it worth it to build a Rocket/Super 8 over a standard 8? I know a lot of this comes down to what your mission specifics are, but is the increased weight, horsepower, climb performance, and fuel burn worth the extra expense or would it be better to put a higher performance 360/390 in an 8.
Thanks in advance.

Your question is not answerable. "Worth" is in the eye of the beholder. You can get 100 people to say no, and a hundred to say yes. It means nothing. Bout all you can do is look at the performance, cost, and other factors that are readily available and decide for your self. Id suggest a facts based approach. We have no way here to put any weight on the factors for you. You have to weigh them yourself.

If you have some fact based questions that dont seem to be answered in other places, bring them on and we will try and sort out the fact from fiction.
Happy to help.

tjo · #4 07-27-2011, 12:21 PM

May I suggest that you:
1) Make a list of the reasons/features why you are choosing an 8/8a
2) Put the list in prioritized order
3) Take a shot at evaluating which of these a Rocket 8 would enhance over a standard 8.
4) Ask the same questions here of the experts to get their input as to whether it ould work out as you expect, or there are tradeoffs that you are not seeing.

Tim

pierre smith · #5 07-27-2011, 01:10 PM

Mike, is it not true that you can cruise alongside an IO-360 equipped -8 and flow the same fuel, throttled back to his speed?

Thanks,

mkjprice · #6 07-27-2011, 01:18 PM

I didn't mean to start and argument - My question roots about what is the best performance bang for the buck? I saw Kahuna's video on youtube and that is what got me thinking about it. He had a 6 now has a super 8, and that is what got me thinking.

From what I can figure it is about 20K more to build a super 8 vs a standard 8. I agree, more power is always better (especially when field elevation is around 5000'), but at what cost.

Also from what I can gather, there are still airframe limitations that limit the use of the full power capabilities of the larger engine. Does Vne change in a super 8. In the Evo Rocket it seems to.

Again by no means did I want to start an argument, and in no way do I want to say one is better than the other, I was simply trying to start a discussion of the pros and cons from different perspectives between the different aircraft.

mkjprice · #7 07-27-2011, 01:30 PM

Quote:

Originally Posted by xavierm

Great information can be found here:

http://www.mstewart.net/super8/

Good reading - Thanks

Kahuna · #8 07-27-2011, 01:32 PM

Quote:

Originally Posted by mkjprice

I was simply trying to start a discussion of the pros and cons from different perspectives between the different aircraft.

Suggest you search, advanced search, title only, super 8.
All perspectives have been covered in lots of threads over the years.

RV8R999 · #9 07-27-2011, 01:33 PM

Great welcoming environment here huh?

Welcome to VAF... beware the opinion based questions - you'll get more than you want every time.

Install a 600Hp gas turbine and call it a Super-Duper-8 then put a wood prop on the front and see what you get

Whatever YOU build and fly will be what YOU think is best anyway!

Once you wade through the chaff, VAF is an invaluable resource.

Good Luck!

Kahuna · #10 07-27-2011, 01:52 PM

Quote:

Originally Posted by pierre smith

Mike, is it not true that you can cruise alongside an IO-360 equipped -8 and flow the same fuel, throttled back to his speed?

Thanks,

No.
The primary factor is compression.
A higher compression engine than mine will generally do better.
All other things being equal, of course they never are, and the only difference being 4 or 6 cylinders, I will typically do better for reasons of reduced efficiency of air flow through the engine at high MP settings. Restated. At a given airspeed, my MP is much lower. The 4 cyclinder higher. Higher MP settings result in more turbulent air flow through the engine and therefore slightly less efficient. At least that is how it has been explained to me.
What we see from lots of field testing across a lot of cross country flying with a spread over many different RV's, is that the higher compression engines do better, the same compression does slightly worse. The difference is so slight its really not worth mentioning. +-.5gallon over a 35 gallon flight.