yard-dart

My Feedback: (35)

I've been trying to do my homework on which engine to buy for a Diamond Dust. A buddy of mine has one with a Jett FIRE .50 on the nose. Good performer GPS'd at 172 MPH. Before launch, we tached it right at 17.8K. We're assuming it's unloading somewhere around another grand in the air. Anyway, with all of this being said, I want something faster. I've been looking at the Rossi .45 (5 port). The site is claiming the performance specs are 27K RPM @ 2.4 HP. Does anyone here own this particular engine, and if so, are these numbers legit? I know that the Rossi weighs more that the Jett, but the Rossi website doesn't give very much info as in engine weight, prop range, etc.... I'm needing feedback on this engine if anyone has any. Thanks.

wjvail

My Feedback: (3)

A Jett .50 FIRE is at least 99% of anything you will find in a ".45" class engine and probably 150% of all but an extreme few. I own a Rossi .53 5 port and to be sure it is a very strong motor but I don't think you will see a clear performance improvement over a Jett .50.... Especially on a Diamond Dust. Again, the Rossi may be +/- a few % of a Jett but not clearly stronger. The 2.4 HP @ 27K may be realistic but 27K on a Diamond Dust is not. In order to obtain 27K you would need to run a prop that would not work on a DD.

Going fast is hard. I can't tell you the number of times I've radar-ed someones hot rod and told them it does 135 mph. In order to beat your friends 172 mph I would target turning 10" of pitch at around 19,000 rpm. You also could shoot for 8" of pitch at around 24,000. If you'd like to use the ".40 standard" 10x6, you could target around 32,000. To use Rossi's 27K you would need somewhere around 6.5" of pitch. I'm only guessing but for a Rossi to to get close to this you would find yourself somewhere around a 6x6.5 and 27K and that will not make a DD go. These numbers will get you to around 180. Also, these numbers make quite a few assumptions but are a good starting point.

If you want to go faster than your friend, you need a different plane.

You could have asked your question here:
http://www.rcuniverse.com/forum/m_86...tm.htm#8670550

Bill

Mike Connor

My Feedback: (5)

It will be easier to get more speed by cleaning up the airframe rather then adding more power.

yard-dart

My Feedback: (35)

How would you suggest cleaning up the airframe?

wjvail

My Feedback: (3)

If going fast is your only goal, you will eventually decide you need a tail, a MUCH large aspect ratio, and a straight wing (i.e. un-swept)

Bill

Mike Connor

My Feedback: (5)

Here is a good example of a clean airframe and you can get speed from a delta. It was built from a kit I sold (Screamin Demon). This plane has now been clocked at speeds at the 200 mph mark and has a nelson Q40 engine in it. You need to cowl engine and no exposed fuel tank or radio gear.

I think the plane shown may be for sale RTF but it isn't cheap.

wjvail

My Feedback: (3)

Is that a Perry carb on a Nelson Q40?

lfinney

My Feedback: (44)

its a large bore perry carb.......

MJD

My Feedback: (1)

That's sold, as in you don't no more?

MJD

Mike Connor

My Feedback: (5)

Yes, like lfinney said. And I don't disagree with you on what airframes are fast. However, I noticed a few deltas showed up at the German speed cup last year.

Mike Connor

My Feedback: (5)

Not sure what you mean. The owner contacted me a couple of weeks ago and said he would consider selling it RTF or ARF at the right price. Have not heard from him since.

MJD

My Feedback: (1)

Maybe I am mixed up, but wasn't it you that was doing those kits? That's what I was getting at, and wondering if so, if you still do. I thought it was your design.

I-Love-Jets

Well,

the truth is that deltas will never be competitive in R/C speed flight when it comes to F3S competition.

What you mean apparently is the Me 163 type of flying wing design being quite different from a delta layout!









Compared to deltas these German flying wings feature a very different wing aspect ratio that enables turns without losing much top speed. Right now these flying wings are almost as fast as a conventional type of speed plane design because of their special S-type wing airfoils and their aerodynamically highly efficient spindle-shaped fuselage.

With a fully enclosed high performance 10 cc nitro engine/pipe (modified OPS 60 VAE for instance) such a flying wing can probably smash the 250 mph “barrier� in future. Last year several times about 380 kph were reached – averaged in both directions over the 200 m speed trap distance (however non-FAI legally because of too large engine capacity).

More info you will find if doing a RCU-forum search here using the term “Messerschmitt�. You will also find pics of a supplier of very fast Me-163s that can be even powered with 15 cc ducted fan engines. [sm=devious.gif]

In the past I have posted several videos here that show some speed training flights of these fast Messerschmitt style flying wings...

http://www.rcgroups.com/forums/showthread.php?t=984610

Mike Connor

My Feedback: (5)

In post #6 I said "It was built from a kit I sold (Screamin Demon)." Yes I did design and sell the kit. I am on break right now. It is just a hobby.

Mike Connor

My Feedback: (5)

Some type of flying wing may end up being the best of both worlds. It seems I do remember seeing a picture of a true speed delta at the German speed cup. It may not have been competitive or even there to be competitive. I will look for the picture when I get some time.

MJD

My Feedback: (1)

Could have simply been a kit you bought and then sold you see.. so wasn't sure.

Think you'll do more after a suitable break? Have a buddy mumbling about a delta kit.

MJD

Mike Connor

My Feedback: (5)

I see where you are coming from now. The whole thing was my project.

I made so much money selling the kits I bought a retirement home in Switzerland and don't need to work anymore. [X(]
Or maybe I finally broke even and got tired of all the work. Yea, that was it. Not sure if I will ever come off break. Right now the economy is bad and Diamond Dust is back in production so is it worth it? I offered the whole business to a few people for almost nothing so maybe not.

wjvail

My Feedback: (3)

http://www.rc-network.de/forum/attac...6&d=1222551454
http://www.rc-network.de/forum/showthread.php?t=118568

No doubt these deltas are fast! And their size and shape make them look even faster.

For the purposes of the original poster a delta is a great choice; however, since his friend is apparently already over 170 with a "40 class" engine, going faster is going to get hard.

Yard-dart... not to ruffle you feathers, but you are asking engine and airframe questions that suggest that you might have taken on a pretty big project. Are you sure the time is right?

Bill

Mike Connor

My Feedback: (5)

Some time ago in one of the German speed cup threads, there was a fully cowled (blue I think) composite looking delta in the seat of someones car. It seem like I Love Jets, or one of the German guys, made a few comments about it. Maybe two seasons back. No time to look for it now.

MJD

My Feedback: (1)

http://www.rcuniverse.com/forum/m_53...Cdelta/tm.htm#

Mike Connor

My Feedback: (5)

Bingo!