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

Custom patriot and webra 120

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Old 08-18-2003, 07:53 PM
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bpu699
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Default Custom patriot and webra 120

I just recieved this plane in a trade-

Scratch built patriot, fuse about 6 feet long, wing about 55 inches. The plane is immaculate, built better than I could ever hope. Weight about 12lbs with retracts.

Has a Webra 120 with stock mufller, which was new. Flew it on fai fuel, 14/10 prop. Spun 8800 rpm, and barely took off. It flies SLOW. I was expecting more from this combo. Midrange was horrible.

Swithced to 10% nitro, and now the motor ran beautifully. Plane is still slooow (?60-70mph). Changed props to 15/10, 16/8. Pulls about the same. Getting about 8500 rpm.

Is this all this motor puts out??? Does it need a lot of break in? (I have a gallon through it total at this point).

Honestly, the plane flies like a trainer, not a jet...

Any help appreciated.
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Old 08-18-2003, 08:33 PM
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Default BIG Patriot Go-Fast

I'm not sure there are any readily available engines to make a Patriot that size really fast. I am sure it won't be fast with a Webra 4 stroke. A YS DZ 140 on 30% or more nitro Might do it. Also a Rossi 90 RIRE with marine or DF port timing running on 25% or more is another possibility.

As a point of reference I'm planning a Jett 90 FIRE on my GP .46 size Patriot.
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Old 08-18-2003, 10:22 PM
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Default Custom patriot and webra 120

The webra 120 is a 2 stroke....
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Old 08-18-2003, 11:06 PM
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ChuckAuger
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Default Custom patriot and webra 120

You might try dropping down to a 13X10 or so, or 14X8...try to get a few more R's out of it. Sounds like it's running too much prop if it's just turning mid~hi 8's. A pipe would sure help, might not do much for the looks.


And please post some pics!!! I don't care if it's only doing 80, I'd still love to see it!!
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Old 08-19-2003, 11:43 AM
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Default Custom patriot and webra 120

A Two Stroke!!

Sorry about my lack of knowledge about Webra 120's. Unless there's some design limitation in the engine, You should be able to make it really scream and make monster power.

You need to double the RPM's 16K, To do this;
1) Raise the exh port to 160 degrees duration
2) Lap the top of the sleeve just enough to bring back to same compression ratio as before raising the exhaust.
3) Open up the carb throttle bore to .450" or replace with another carb with big throttle bore.
4) Clean up the flowpath and make sure the bearings are good and crank spins freely with prop nut tightened.
5) Setup with a full Nitro Pipe as a starting point use 17" from engine exh flange to end of converging cone.
6) Use 15or 20% Fuel and a 10.5X10 prop (cut down 11X10 APC)
If the 10.5X10 isn't enough thrust for takeoff then drop back to an 11X9.

I too would love to see some photos of the plane!
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Old 08-19-2003, 06:31 PM
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Default Custom patriot and webra 120

The webra 120 is a long stroke engine, it's meant for torque not RPM. 8800 is probably about all you'll get. You'll get a little more speed if you up the pitch of the prop, say a 13x13n or something, but you're not going to get mucy RPM out of it. I ran a webra 120 on a Pipe using 25% nitro on a 14x10 and got 9200. Not enough to warrant the extra weight of the pipe.

If it's only 12 pounds though, I'd take that boat anchor off the front (I never liked my webra 120 much) and put a JETT90FIRE on it. Or even put an OS91VRDF ducted fan engine with a prop on it, at least then you'll get some RPM's. 12 pounds isn't heavy for a jet, and with a propjet you'll have WAY better thrust than with a ducted fan.

Even try an APC 12x13n or something, or 12x12n (the n is for narrow blade) I think they even make a 10x12, but the thing is, this engine is not designed for high rpm, if you try to rev it to fast you'll just blow it up.
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Old 08-19-2003, 08:41 PM
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Default Custom patriot and webra 120

I've not been inside a Webra 120 but it sounds like it was designed to be as slow and weak as a 4 stroke 120.

With the mods I've suggested, It will definitely make power at 16K RPM however as Jeremy has suggested there may be design limitations that prevent this from happening. Such as:
1) Connecting rod too weak
2) Ring too heavy causing ring float
3) Insufficient transfer flow area in the crankcase
4) Too small a crankshaft ID for fuel/air charge at high RPM's

If none of the above are true; It could definitily be made to scream.
If any of the above are true then you need to look for another engine because no 2 stroke is going to give you the power to make that big Patriot fast below 14K RPM.
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Old 08-19-2003, 09:07 PM
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Default Custom patriot and webra 120

Thanks for the input guys. I'm not sureI want to invest in another motor, I'll probably fly it as is for awhile. When I get bored, I'll sell it. The webra actually runs very nicely, and will likely end up in another plane...
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Old 08-19-2003, 09:40 PM
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Default Custom patriot and webra 120

EW, how do you know so much about motor design & tuning? I've no clue as to whether what you've suggested makes sense, but would like to hear more! Will your formula work on smaller motors, like 46 - 50 size? I've got one that doesn't cut the mustard, and was thinking of replacing it, but if a little carving may turn it in to a beast, I'm game for trying!
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Old 08-19-2003, 10:19 PM
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Default Custom patriot and webra 120

It works even better on .40-.50 size engines... because they are less expensive when something goes wrong...

On smaller engines you could take the exhaust duration up to 165-167... this will make 'em rev up to 20000 rpm.

But remember this: sport engines have an exhaust timing of about 150... if you take 'em past 155-157 they will not run well without a pipe... an engine timed at 160 or more will be crap without a pipe...

You can also increase the intake timing of the crank. 5 or so should be enough to start with. You will notice that the engine will start to spit raw fuel out of the carb at part throttle after you have done this. That doesn't matter, as it is the full throttle breathing that counts.

Grind the scavenging ports in the sleeve so they point upwards about 30.
The exhaust port should be grinded so it points downwards.
This is also to maximise flow.

If the conrod is a rectangular piece of metal (they mostly are), grind away until you have a nice streamlined shape. Don't overdo this, because you can guess what will happen if you take too much meat off...
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Old 08-20-2003, 06:26 PM
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Default Patriot

Hey BP when you get ready to sell it let me know-the wife is
starting to ask me what I want for Christmas!

In the meantime you could sell the Webra (lots of people like them, myself included) and buy another engine. Any large Rossi,
K & B, OS or Jett ducted fan motor would spank the pants off the Webra
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Old 02-13-2004, 01:35 PM
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Default RE: Patriot

I can't believe no one has jumped on this subject in so long. I just wanted to add a couple things to this topic. The Webra 120 is not designed for small props and high RPM's. It is a high torque engine that spins big props with authority. Put a 16 or 17 inch prop on, to bring your engine alive. Don't use high nitro either. 0 to 5% is all that is needed. My friend used 10% until it seized. You should have seen the piston. Pre-ignition beat the crap out of it. Not a mark on the cylinder though. That is what you get from a true chrome cylinder.

If I recall correctly, the Webra 120 is considered the hottest 120 engine. It boasts unlimited vertical on a 14lb bird.
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Old 02-13-2004, 06:33 PM
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Default RE: Custom patriot and webra 120

I have an older Webra 120 about the best running engine I have had. With an APC 15x6 15% Power Master it turns 11,300 with a pitts style muffler same setup APC 16x6 turns 9600. I run it with the 15x6 on a H9 Ultra Lite Stick unlimited vertical from a 5 foot roll on take off. I have not tried a 14 prop but hope to soon.
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Old 02-14-2004, 11:18 AM
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Default RE: Custom patriot and webra 120

Webra also has the Racing 145 Aero X that should be an easy install
Or you might even think about a Moki 210-Not really made for high rpm's either, but has the power to swing lots of pitch.

BTW- Does this Patriot have nose weight? Seems like a 14 lb. plane wouldn't balance with a Webra 120-

WW[8D]
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Old 02-14-2004, 11:25 AM
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Default RE: Custom patriot and webra 120

Old thread...

I'd stick to the 120... prop it for about 11000 rpm, that's where it makes its power (about 3.2 hp if I remember correctly)... the 145X and the Moki are even lower revving engines, not really made for speed...
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Old 02-14-2004, 11:37 AM
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Default RE: Custom patriot and webra 120

You should sell it to Flyboy Dave! I sold him an engine that would be perfect for it! A Rossi 90 RIRE. At least twice the power of the Webra!
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Old 02-14-2004, 11:39 AM
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Default RE: Custom patriot and webra 120

You should sell it to ME! I'll find SOMEthing to make it move!!
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Old 02-14-2004, 12:01 PM
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Default RE: Custom patriot and webra 120

I flew the Webra 120 in a World Models Zero, I ened up sticking with a 13X13. It did about 120 mph
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Old 02-14-2004, 11:55 PM
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Default RE: Custom patriot and webra 120

From what I have experienced, if you need to spin a 14" prop fast, I would select a 90 size Rossi also. I don't think the 90 Rossi would do well with a 16 or 17 inch prop though, which is where the Webra 120 excels. If you look at many of the other threads on propping the Webra 120, I believe you will find this comment to be true. I am a firm believer in matching the prop to the engine.
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Old 02-15-2004, 11:37 AM
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Default RE: Custom patriot and webra 120

Since a standard size Patriot flys fastest on a 9 to 10" dia prop depending on engine. Why all this discussion about 16 to 18" Props
Even a 50% scaled up Patriot should should be fastest with 11 to 14" Props. If a Rossi 90 RIRE turning a 12X9 at 14400 won't make it fly fast and accelerate straight up; The model is way too heavy and draggy!
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Old 02-15-2004, 12:12 PM
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Default RE: Custom patriot and webra 120

Esten brings up a good point-If this large Patriot has been scaled up pretty close to the original lines, it should be fairly slippery...But if it's TWICE as heavy, it may be difficult to ever attain a decent speed

WW

Wing? What Wing?
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Old 02-16-2004, 09:32 AM
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Default RE: Custom patriot and webra 120

The only reason I bring up 16 and 17 inch props, is because I feel the Webra 120 is the wrong engine for this plane in the first place, based on props usually associated with this engine. If you want to spin 12 to 15 inch props, you probably need to be in the .61 to 1.08 range. The Webra 120 is a different animal. Since the plane apparently can't handle a larger diameter prop, it is likely overbuilt, which I think is what ewspears is saying. Without knowing more about the plane, I would guess this plane should have weighed in around 9-11 lbs, maybe less.
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Old 02-18-2004, 11:03 AM
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Default RE: Custom patriot and webra 120

Guys, I haven't flown this plane since I last posted. It likely will go up for sale soon (I bought a starfire ducted fan to replace it!). If anyone is inetersted, email me at bpu699@yahoo.com. I can get details such as weight and winspan, and so forth. The plane is immaculate, and is one of the best built planes I've ever seen...people just oooh and aaah at the field. I can sell with or without the motor (The plane was custom built around this motor). I'll try to get some pictures.

Shipping though, will be an issue. The wing is large, and one piece.
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Old 02-19-2004, 12:57 AM
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Default RE: Custom patriot and webra 120

When you do get some pictures, Post 'em right here on RCU so even those not planning on buying can still get a look at it if you would - Seriously, how often will anyone get to see something like this?

WW
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Old 02-19-2004, 12:45 PM
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Default RE: Custom patriot and webra 120

yeah, c'mon! Pics!!!!!!
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