Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

My new speed plane...advise needed

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Old 01-19-2008, 02:50 PM
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Zman39
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Default My new speed plane...advise needed

Hey all,

Here is my new speed plane. Scratch built fully foam sheeted laminar wing airfoil. Thickness of wing maxes out at 1". the wingspan is 42" and all up weight with a Sport Jett .50 is 2.9 pounds. I did some testing today using a GPS in straight and level flight. My speed was 154mph using a 8x9 prop. This prop gave a ground rpm of 18600. I desperately need about another 16 mph (or more) for it to fulfill my goal when I put it together. I tried several different props (pylon, sport, NN) but 154 was my best run. Anyone have any other prop ideas or whatever that may help me gain some straight level speed? here is a pic :
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Old 01-19-2008, 03:07 PM
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SpeedBoy
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Default RE: My new speed plane...advise needed

Maybe I'll try an 9x9 or one 9x10 cut off to 8x10

But we are going to see that the experts say
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Old 01-19-2008, 03:21 PM
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Zman39
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Default RE: My new speed plane...advise needed

Didn't try a 9x9 but did try a 8x10 sport, lost about about 5mph . I am all ears. This Jett has the regular red muffler on it, wonder if there is a differnt muffler that will give it an extra boost?
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Old 01-19-2008, 03:22 PM
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Default RE: My new speed plane...advise needed

Get a Super Sport, or maybe even a Quickie muffler to get the rpm up... then use a slightly cut down pylon (Q500) prop.
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Old 01-19-2008, 03:29 PM
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Mike Connor
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Default RE: My new speed plane...advise needed

Considering the weight and wingspan I would think you could get away with a 8" prop if it is clean enough. You don't have wire gear of fat wheels under there, do you? The prop hasn't been cut down from something larger? My calculations show 165+ mph is possible but only if the airframe drag would allow the optimal 10% prop slippage. Do you have any #'s using a sport 9x8 prop? With the light load of that prop I would be using the SS or black Q-500 muffler as Rudeboy suggested.
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Old 01-19-2008, 03:53 PM
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Default RE: My new speed plane...advise needed

How about a few more pictures?
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Old 01-19-2008, 04:29 PM
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Mike Connor
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Default RE: My new speed plane...advise needed


ORIGINAL: SpeedBoy

Maybe I'll try an 9x9 or one 9x10 cut off to 8x10

But we are going to see that the experts say
Speedboy, It is Saturday and good weather. You are supposed to be flying that Patriot, not wasting time on these forums.
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Old 01-19-2008, 04:34 PM
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cncswiss1
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Default RE: My new speed plane...advise needed

a spinner and a cowl perhaps.. I'd suggest a quick and dirty cowl using glass cloth and CA like CP does.
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Old 01-19-2008, 05:26 PM
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Default RE: My new speed plane...advise needed

ORIGINAL: Mike Connor

Speedboy, It is Saturday and good weather. You are supposed to be flying that Patriot, not wasting time on these forums.
Sorry Mike , today it is impossible to be able to fly for me , because other personal obligations do not allow it and believe me nobody laments it than I []

I hate need to hope for the next weekend [:@] the new number will be pending but...... is a fact that will be

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Old 01-19-2008, 05:33 PM
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Default RE: My new speed plane...advise needed

Im not very good with props....these guys will lead you right....but I do see a few areas where you can reduce drag. Dont know what gear or the underside looks like, but the underside needs to be slick moreso than the top in general. streamline everything you can.

You might be able to radius the verticle stab a bit more, and lower the height. Mike?

You can round the tips on the horizontal stab or taper them. sharpen all leading edges. and cowl / spinner as said before.

my 2c.
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Old 01-19-2008, 05:51 PM
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Mike Connor
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Default RE: My new speed plane...advise needed

ORIGINAL: gooseF22

You might be able to radius the verticle stab a bit more, and lower the height. Mike?

You can round the tips on the horizontal stab or taper them. sharpen all leading edges. and cowl / spinner as said before.
A typical Q-500 will have a fairly low fin volume coefficient running an area about 5% of the wing area. Sharp edges on tail surfaces but it seems that deltas get away with a sharp wing leading edge better then conventional aircraft.
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Old 01-19-2008, 06:15 PM
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Default RE: My new speed plane...advise needed

Zman, super looking plane! I have never tried this, but I've heard that it is possible to heat shrink soda bottles over wood molds to make cowls. Otherwise, unless you want to go through the entire process of making your own custom fiberglass cowl, you might find an ARF cowl that is close enough of a fit with your planes' fuselage.
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Old 01-19-2008, 07:17 PM
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Default RE: My new speed plane...advise needed

Thanks all for the help. I will look into a cowl. I did have a little brainstorm..............maybe. I have one of Performance specialties Ultra thrust racing version muffler that I can make bolt up. Anyone have any idea whether this will give motor more of a boost than the stock red tuned muffler that comes with SJ50?

To answer a few of other questions: I am using "racing wheels" and the gear is just stock aluminum gear. Maybe I should sharpen the leading edges on it? I think the real question is as far as I know, there isnt a kit or arf built Quickie type plane out there using a laminar airfoil. In the design stage, my thoughts were that this would actually help top speed but maybe something else is happening. This plane turns well but doesnt have the airfoil to turn "hard" like a quickie but my intentions were for a straight line speed plane not pylon.

Z
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Old 01-19-2008, 07:59 PM
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Default RE: My new speed plane...advise needed


ORIGINAL: Zman39

Maybe I should sharpen the leading edges on it?
Z
Round the leading edge of the gear, leave the back square for Camm effect. You don't want knifes flying at 170mph.[X(]

I think a cowl would get you there, you're up to a speed where drag reduction is far far more important than any Hp gain you might be able to get. Maybe a little tear drop flaring behind the engine cylinder.

I wouldn't sharpen the leading edge of the wing either, that will only give you a pitch sensitive plane. Sharp fronts don't help until about .85 Mach. Sharp trailing edges of the wings will help though.
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Old 01-19-2008, 09:24 PM
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Default RE: My new speed plane...advise needed

i dont realy know if it will work but you can try and use a 3 blade prop with slightley less pitch and try a cowl and spinner
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Old 01-19-2008, 09:43 PM
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Default RE: My new speed plane...advise needed

You cant' build a laminar flow wing by hand... You just can't achieve the accuracy that is needed, unless perhaps you spend 2 years shaping it to perfection with laser cut gauges.
Forget laminar flow.

If you are looking for straight line speed, start by making your wing only half as thick. 1" is way too fat.
Build a decent fuse, instead of a square box.
Use a rear exhaust racing engine, and cowl everything. If you insist on side exhaust, at least cowl the engine as good as you can.
Airfoil your tail.
All internal linkages.
Loose the landing gear.

If you use a Q500 muffler, you must prop the engine to run at Q500 rpm: at least 19000 rich on the ground, preferably a bit more and unloading in the air. I don't know if the SJ50 will support that though...
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Old 01-19-2008, 11:03 PM
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Default RE: My new speed plane...advise needed

from looking at he firewall some creative carving and triangle stock should reduce the bug ole blunt corners.
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Old 01-20-2008, 12:58 AM
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Default RE: My new speed plane...advise needed


ORIGINAL: cncswiss1

from looking at he firewall some creative carving and triangle stock should reduce the bug ole blunt corners.



I was thinking the same thing...some soft Balsa, a bit of carving/sanding and a spinner would clean up the nose quite a bit.
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Old 01-20-2008, 04:10 AM
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Zman39
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Default RE: My new speed plane...advise needed

You know rudeboy..........ah nevermind.

Anyway, my goal was to never set a world record speed, just a bit more then what I have achieved so far.. I had a Jett laying around and slapped together a fuse much like quickie planes and then had my "laminar" wing cut from a foam cutter. I then sheeted it, etc etc. So far the guys here have had some good ideas. If I dont get there, so be it, it is still a fun plane to fly around with and I had fun with the project.

Z
ORIGINAL: Rudeboy

You cant' build a laminar flow wing by hand... You just can't achieve the accuracy that is needed, unless perhaps you spend 2 years shaping it to perfection with laser cut gauges.
Forget laminar flow.

If you are looking for straight line speed, start by making your wing only half as thick. 1" is way too fat.
Build a decent fuse, instead of a square box.
Use a rear exhaust racing engine, and cowl everything. If you insist on side exhaust, at least cowl the engine as good as you can.
Airfoil your tail.
All internal linkages.
Loose the landing gear.

If you use a Q500 muffler, you must prop the engine to run at Q500 rpm: at least 19000 rich on the ground, preferably a bit more and unloading in the air. I don't know if the SJ50 will support that though...
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Old 01-20-2008, 04:27 AM
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Default RE: My new speed plane...advise needed

Rudeboy, don't tell people the truth, tell them what they want to hear.
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Old 01-20-2008, 06:26 AM
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Default RE: My new speed plane...advise needed

Combatpig,

I can take truth anytime, no problem here. But a total change of plane and design wasnt what this thread was about. This thread is about is what I slapped together and would like to gain just a little more and if anyone had any ideas. Rudeboy idea of starting all over because what I got is crap wasnt very helpful. I can go on internet right now and buy an arf and everything I need to reach blistering speeds but that wasnt my intentions. My intention was take some scrap wood, an engine that wasnt being used and see if I can get in the 170mph range. It has been fun and rewarding trying.

Btw: Thanks for the compliment on the pic, like I said, it is a fun plane no matter what happens.


Z
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Old 01-20-2008, 08:15 AM
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Default RE: My new speed plane...advise needed

i totaly agree with you zman39 good luck getting to 170 mph

ps i think you did a bloody good job of the plane...
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Old 01-20-2008, 10:44 AM
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Default RE: My new speed plane...advise needed


ORIGINAL: Zman39

I have one of Performance specialties Ultra thrust racing version muffler that I can make bolt up. Anyone have any idea whether this will give motor more of a boost than the stock red tuned muffler that comes with SJ50?
The short UT racing muffler would probably work better then the long stock Jett muffler when you use the 8 x 9 prop. It just doesn't seem right putting a UT muffler on a Jett though but if you have one...

I really think the APC 9x8 sport prop would shed some light on what prop would work best for you.
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Old 01-20-2008, 10:56 AM
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Default RE: My new speed plane...advise needed

Zman, after re-reading your first post, you don't sound so DESPERATE for advice anymore?
A guy sitting at his computer in Belgium is good enough to take the time and share some speed knowledge. Then the recipient of the knowledge takes it as some kind of an insult. I'm not just talking about what happened here, this same scenario has played out many times in the past on other threads. Some American will ask for speed avice, a European will chime in with the blunt truth, then the American ends the exchange by saying, "Well, I'm not trying to set any speed records, just have fun". When Der STEUERMANN used to post his knowledge here, this same scene played out over and over until he got tired of wasting his time and moved on.
What you're DESPERATELY looking for is a 10% increase in speed with the same engine on a plane that is already fast. I don't call slapping together another fuselage to reach your goal "starting all over", just a small bump in the road to "getting there".
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Old 01-20-2008, 11:47 AM
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Default RE: My new speed plane...advise needed

let me get the quick calc right, with the power going up with the cube of the speed, does he really need 1000% mo powa?!!

or is it 30% more power or 30% less drag or some combination of the two?

is this in the spirit of the $100.00 speed airframe idea? if so you are darn close!

if it were me, and keeping wth the keeping it simple idea, I'd get the black jett quickie muffler, glue some big tri stock to the firewall and sand accordingly, and a big ole 2"-3" spinner to match your balsa cowl. and airfoil the gear as the guys suggested.

another idea if you do want a more rounded fuse as CP suggested, but in the Q&D fashion, make another box style fuse but use gigantic tri stock in the corners, put a large blind nut in the firewall in the center of the round whape you want, chuck it on the ole cordless drill, use your finger for a center on the other end, spin it and apply it to a bench grinder with a wire wheel on it, it'll be round in seconds, then some quick finish sanding (best with a helper to hold emery paper like one holds a towell to dry one's nether regions after a shower).... may not set any best finish awards, but it's quick, cheap, and easy.
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