By the way I think those engine were my back ups. Many of them were (are) only bench run. Also many of my engines were back plate mounted. OK, not the CMB!
That Webra lived in a Hanno Supra Fly (Some 80's ARF) with an adjustable flat plate mount (kit stock).

Brian,
If you want to use a Jett muffler, the one that fits the Jett .50 will also fit the .HB .61 PDP. I lost my stock muffler in-flight and when searching for a replacement, I discovered the muffler off my Jett .50 fit perfectly. I did have to open the through holes in the case ever so slighly since the stock threads of the HB are 5-something and the Jett is tapped for 6-32.
I'm spinning a Vess 11-7 at 13,300 on 10% Wildcat with extra castor added. This equates to almost 1.8 HP on Pe Reivers HP calculator. That's about an 800 RPM boost over the stock muffler. I don't know how that compares to an OS .61 FX, but it's quite respectable.
I don't consider my HB .61 PDP to be any more "thursty" than any of my other engines. It really moves my Komet. Unlimited vertical and VERY fast straight and level flight.

Understandable questions considering my quarries.

I am 34 years old. I have been flying sice 1994. I have never been much of an engine guy. I have never had a lot of help in this area. I find most people claim to have this vast nowledge, but can never actually share it with me. Then, there are the people that can look at the thing without even firing it up and tell me to lean/richen it out, and they're right!

I have generally found 4 strokes easy to tune on my own, but I have fried a K&B .61 and a Magnum .46 two stroke. I even used the pinch test, heard a significant rpm increase (ON the K&B), and still fried the stupid thing. The magnum baffles me. It would lean out 1/2 way through each flight. I am told that the baffle in the muffler needed to be drilled out. I switched to the 4 stroke before I tried the fix. For some reason, I can get the 4 strokes to work.

My ST .51 and .90 fired up straight out of the box, and the adjustments I made there actually work. It leave a nice oil trail in the air that looks just like a little smoke.

I aquired my HB.61 PDP through a trade. Rather than try to break it in myself, I had a friend in Denver that was a wiz with engines I I gave it to to break it in for me. When getting it back to Minnesota, a slight adjustment was all that was needed on the high end, and WOW it ran well. But camparable to my Magnum .61 XL and my ST. 51, the economy is REALLY bad. Thus proving the addage- if you want power, you will pay for it.

My friend in Denver explained how the Perry Directional porting works. Even he was impressed with the power the HB PDP put out. Unfortunately, he passed away last month in an ultralight accident.

Until falling into classic pattern ships, I trained on a Telemaster (1994), a Tiger 60, flew a Goldberg Cub, 3 smith miniplanes (Yes, I enjoy building), a Hog Bipe, a GP Super Skybolt, a sportsman aviation corsair, my ever reliable GP stick, and built flown several other aircraft (which I can list if desired). I am bored with simply throwing an airplane around, but have found I am not impressed with the costs of modern pattern. I have, however, discovered I really like the older pattern designs and the way they fly- ON THE WING!

Hense, the venture into getting a handle on the two cycle engines. I have a few that that I can get running well, and run well at the moment. So I would like to get the proper setup on my UFO, Kaos, Miss Norway, and my J-Bipe. For me, except the J-bipe which will receive my .91 Magnum 4 stroke, "proper" means tuned pipe. The extra rpm and power are needed for the vertical and knife edge maneuvers anyhow.

I can fly them just fine. I am less confident on getting my 2 stroke set-ups right.

Too much information?

Brian

TMI, maybe but I'm also guilty of that!

I too flew a lot in the Denver area with the Jeffco Aeromodelers at Chatfield. I also flew a lot in Evergreen.

My 15 minutes of fame is that I built the engines that won the AMA FAI F3D pylon class way back in 89 I think. (No, I wasn't the pilot) So I'm a little arrogant in thinking I know a little about engines.

While I'm happy to help in any way possible. I will say that joining a club is the single greatest way to improve your skills. The second is to align yourself with the guys that seem to beat you in the competition arena. I strongly feel that competition improvers the breed!

A funny story about just looking at an engine and coming up with a diagnosis. A guy was having fits with an engine. I walked by and handed him one of my glow plugs. He said that wouldn't help much in that he had tried 3 new plugs. Well, the brand he was using had a bad production run and many would blow the ceramic insulator. I could see the small bubbles coming through when the engine came on pipe. Needless to say the engine ran great after the plug change out. I think this guy throw his glow plug wrench at me and said he was never going adjust an engine again and that it would be my job from now on!

I'd like to tell you the brand name of the glow plug but some would think I was bashing a brand.[:@] I still think this brand's glow plugs are a little weak for a tuned pipe. And for those reading this NO the brand is not OS!

All the best,

Konrad

P.S.
You need a good tach. I like analog tachs as you really just want to see the reversal point in the RPM reading. These are rather expensive. They are not in the $30 dollar range or the stuff one sees now. I think mine cost $200 20 years ago. A cheap digital tach is much better than your ear or no tach at all!

I am actually changing clubs next year. This has been an off year for me- not much flying. I have to say, the people that have an interrest close to mine in this area are no where near to me. It is amazing, every time I brought up the idea of any pattern or classic pattern contest or interrest, I got the 40 mile stare! It is really frustrating. Everyone was interrested in the aircraft, but they'd never try because no one wants to build or participate. Too much 3D, which is ok, I guess, but I think precision flying gets lost in translation sometimes.

There is a club north of me that engages pattern. These are the only guys giving me a chance to do the flying I enjoy. I simply haven't been able to hook up with any of them yet this year. They sound like a great group of flyers!

Maybe I can work with them to bring ballistic and classic pattern to the area. I'm hoping to get to the Chicago event next year. Rusty Dose has commented he thinks it will be put on next year as well.

I was a member in the M.A.S. club near DIA in Denver. There was talent there at the time as well.

I'll ge a new tach.

Thanks for all the help!

Brian

No, they do not. I'm certainly not expert on what they do and do not permit, but the customary tuned pipes that we are used to and flying with the retractable landing gear tucked up into their wheel wells are not permitted. I don't want to steal this thread talking about that stuff.

It's funny, but when trying to match the performance of an engine like the HB .61 PDP with a smaller/albeit higher horsepower smaller engine, it just never works out the way that some folks would like. The larger, older engine usually stomps the dickens out of the smaller engine with more horsepower. It's probably because the smaller engine has to turn a smaller prop faster in order to produce the lauted superior HP figure. This is something that I intend to experiment with in the coming months. I've flown an old original Kaos (60) size with smaller, but more powerful, engines and then compared the performance to the same model with K&B & HB .61 PDP engines. There is just something about the raw power of the larger displacement engines that the smaller, but more powerful engines, can't quite equal. I'm sure someone will have flown a sleeker old patternship with a smaller engine and liked it. But it just hasn't happened to me as yet.


Ed Cregger

At the SPA meets I have attended in the past, 90% of the engines were OS 91 Surpass variations.

But there were a few two strokes

Yep, the .91 four-strokes dominate SPA flying anyway, so worrying about a two-stroke engine is a moot point. I'd just like to be well enough to attend an SPA meet and fly now and then.

I have a Saito FA-91 and a Thunder Tiger .91 four-stroke that I would like to compare against the OS FS-91 Surpass Ixx engines running 30% nitro. I used to own the OS FS-91 Surpass II /pumped engines, but sold them off. They looked as though they were going to be too boring to be fun. You know OS four-strokes, they're very reliable (boring). I do have a Magnum clone of the OS FS-91 Surpass (II?), so there is a partial fall back position. Still, the lure of the old timey two-stroke engines is strong.

I still can't help but think that a really well set up OS .61 SF in a light model would have to equal the current stump pulling four-strokes.

Now you know why I never get anything done these days. I sit around in "analysis paralysis" most of the day.


Ed Cregger

Me too

There's all sorts of model stuff I could be doing out there but I'm here on RCU.

Do you have any pictures of the engine you built? I'd love to see it.

Good point. I too found this to be the case when I went to electric powered ships. The power curve (slope) is actually reversed relative to that of an IC engine. This means that the bigger the prop the more power an electric motor produces (well until the magic smoke comes out [:@] ) compound this with a deep gear box and an electric motor with 1/2 the power often can compete with an IC engine that is rated (measured) to be twice as strong. What I think this is getting at is that torque is the variable we need to look at. The larger, within some constraints like pitch speed, the prop disk the better the performance.

Now a counter argument is that, in my day we had to give the four cycle engine double the displacement to even hope to compete with the piped 10 cc pattern ship. And these four stroke pattern engine often needed super charging on top of that! So again follow the torque curve (ref. my earlier post). That and the simplicity and light weight made the pattern 10cc 2 cycle engine all but impossible to beat. Did a 20cc four cycle ever hold a FAI F3A title?

This is still on subject as we are talking pattern power plants?

All the best,

Konrad

Pics or it didn't happen, is that your point (logic)?

Like I said in another post (club Fox) I used the timed lap to measure my performance changes during my engine development. As it was pointed out, photo equipment often had too much variability to be of much use in the 28K to 30K operational range (26k RPM on the ground). I think I have some development junk in my junk drawers but these looks like most other trashed engine parts.

I hate to say it but, I wasn't clairvoyant when I sold the engine. I had no idea that the pilot was so good that he would drag my engines into a national title! Sorry no photos exist in my collection. The AMA magazine (NATS coverage for 89) did show part of one of my engines. If you find it please post it.

As I recall it would look like a thin walled Picco/OPS engine. (Lots of port bumps on the outside.) I modeled this after a long sprits (I think Jack)driven conversation with Henry Nelson at the 86 Rough River 1/4 midget races in Kentucky, that we were attending. OK, I just kept my mouth shut and listened to the words of the master. Something that could benefit all of us.

This is way off topic as the OP is interested in pattern engines!

Friends don't let friends fly nickel,

Konrad

Brian,
I see that you have been asking about fuel load. I have kind of danced around that issue. But If you look at that chart I posted (courtesy of downunder, thanks Brian) you will notice that the center graph is charting fuel consumption. So on pipe and at full power a 10cc pattern engine will draw 45cc to 50 cc per/min. for the 2 hp rating. So for a 10 minute flight you will need 16 fluid oz. But since you aren.t at full power all the time you can drop that down a lot 14 fluid oz. Now the HB really wouldn't be producing the power of a true pattern engine so you can drop that down again. So 12 oz to 14 OZ is a good number. I like the smaller tank as they result in less variability to the fuel head pressure. On the subject of tanks, take a very close look at the bladdered tanks (AKA. bubble less type). Again I like what Dubb Jett markets. Please be warned that 80% to 90% of engine troubles can be traced to the fuel, fuel tank and fuel lines! The other 20% to 10% can be traced to not following MY directions!

All the best,

Konrad

I don't mind the discussions and rabbit trails so long as the mods are okay with it. I posted these questions for the express purpose that everyone is posting here. I am greatful for all the insight I've been offered. I also enjoy the banter between those here that really understand what they are discussing. It is easy to see that becuase things are being explained in terms I can understand.

Actually, a few other questions I had have been addressed but I've been too embarrassed to ask. Now I am wrapping my head around those things as well.

Wow. I wonder if that is what I've been fighting.

Does a four stroke have more draw than a two stroke? This might explain why I've had better luck with them.

As per the per the SPA- again, trying to ask for help to bring that to this area is like asking for one's firstborn. I refer you to that 40 mile stare again... I like the piped 2 stroke on the front of a pattern ship. It just seems right to me.

Konrad-

With regard to the tank size, this is why I was really contemplating the pump. From my understanding, a 14 oz tank or larger could cause issues with the engine- leaning it out/fuel draw. The whole purpose of the pump is to counter this, am I correct? The fringe benefit to the pump is I can mount the tank further away from the firewall for more consistant flight in duration, which also frees up some room in the area for the front retract.

Going with a 14oz tank, would I be better off mounting a pump?

I realize you addressed this earlier, but it seems you have a better understanding of my goals now. So I hope you do not get frustrated with the reiteration of this question. If you think I would be fine without the pump, and a 14 oz tank, this is good too. I had a 12 oz tank mounted behind this engine with a stock set-up. The flight would consistantly last 10 minutes plus some change. I think I would like a little extra time for the UFO to get her on the deck again.

Brian

Brian,
Not an issue, I'm more than willing to beat you over the head with the same answer until you understand the answer or I understand the question!
This is apparently one of my flaws.

Sorry food calls I'll get back to this soon.

All the best,

Konrad

[sm=lol.gif]

Looking forward to it!

Brian

Brian,
I think you need to determine exactly what you want from this plane. Is it a weapon for carving patterns in the sky or a sport ship? I'm going to assume it is a dedicated pattern ship. (Now this attitude gets me in trouble, in that I tend to think there is no place for sport leisure in a competition applications. Go all the way or go home)

I would practice your flight routine (no sport flying), time it, land and measure the amount of fuel you used. Add 10% for safety. This is the minimum you need. It should be less than 12 oz.

Now the Pump was developed to allow one to gain a lot of power from the bigger choke area of a bigger carb. The larger the choke area the less power is lost to a restrictive carb. But and this is a big but, the fuel draw is drastically reduced. There is very little pressure drop at the spray bar as the velocity of the air is rather slow (The pressure differential between the engine and the tank vent is very low) and as a result there is little fuel flow. The pumps job is to offer more pressure to the carb so more fuel can flow into the engine. What I'm trying to show is that the pump does not add power but rather the power come from less atmospheric pressure being lost to the carb's venturi (choke). There is a very linear relationship to inlet pressure and power . This is why closing the throttle (choke) cuts down the power. Or conversely the more you open the choke area the more power (Duh). Now as far as the engine goes that's it

Now on the airplane as a system there are two issues here, fuel head pressure and balance trim. Staying with the feeding of the engine at various attitudes the ability of the fuel to flow to the carb and/or pump changes pointing the nose down and the fuel pours out the fuel line, Place the aircraft level and the flow slows until it stops level with the fuel discharge. Point the nose up and no fuel flows. This is called fuel head pressure. There is a lot if the fuel level is above the carb's discharge and little or even negative pressure if it is below. Add or subtract this pressure to the atmospheric pressure and it becomes clear why the engine needs so much mixture adjustments from a nose up verses a nose down. Now the smaller the carb's choke area the greater the atmospheric pressure differential (constant if the RPM stays the same). Therefore there is less total pressure (Tank vent to spray bar) change with the small choke verses the large choke as you point the nose up of down. Note this is the case with or without a pump again if looking from the tank's vent to the fuel discharge port (spray bar). Now the fuel pressure changes to the pump inlet as the tank is raised and lowered. So there needs to some kind of regulator in the circuit to compensate for this variability at the front of the pump so that the pressure is kept constant to the carb. Now if the fuel tank is kept close to the carb there is little stress placed on the regulator to keep the fuel pressure constant to the carb as there is less change in head pressure to the pump inlet. So far so good.

BUT BUT 14 fluid oz of fuel can account for a lot of mass change in the aircraft. Now put all that in the front of a 7 lb to 9 lb plane and you have a lot of trim changes you need to make from first take off to the last landing. Now place the tank on the CofG and re-trimming during flight is drastically reduced (there still needs to be some, as the angle of attack now has to be lowered as the total weight is about 12 oz less weight) sounds good. But the further the tank is away from the carb the more the regulator must work to maintain even flow. This is because the pump is adjusted for the worst condition (nose straight up) tank very low and far away from the carb. Now point the nose straight down and the regulator must deal with the extra flow from the added head pressure (gravity) and the over zealous pump!

So what to do? I'd like to see you keep the tank as close to the engine as possible (this is why most pattern ships actually have a rather short nose). And learn to use the CofG shift to your advantage. That is do the smooth axil rolls at the beginning of your routine and save the spins and post stall maneuvers for the end when the aft CoG will make these maneuvers easier. Now the problem with this is that you have to keep a little airspeed on landing. We kind of frown on a snap maneuver at the end of the runway as a closing salute!

Now I know this is just what you didn't want to hear the KISS principle! This is the best way to start pattern with a simple machine. Small carb, the smallest tank to fly the routine, a long pipe to keep the noise down and add rather constant muffler pressure to the tank. By the way this pressure tap should be at the high point of the pipe NOT in the header or manifold. This is a good place to find a good balance between peak pressure and constant pressure. Muffler pressure can be thought of as an atmospheric boost to aid fuel flow. It is a poor substitute foe a pump or proper tank and choke sizing.

Now if you want to flirt with that 20% to 10% I was mentioning earlier do think about placing the tank at the CofG and run as large a fuel line to the pump as possible. Use a regulated pump and a small choke carb. You should be able to find carb bodies that fit the carb boss of the engine case and have various choke areas (Interchangeable barrels) and have in flight mixture controls. There really should be no need to go with a choke that is bigger than 8.5 for your first pattern engine. That great CMB has an 7 mm choke IIRC.

All the best,

Konrad

Did you ever try a 65DF piston/liner in an OS 61VF?

Yes and no. I bought the .65DF piston/liner a short while ago, but I haven't installed it in the .61VF as yet.


Ed Cregger

Now again going a little off topic. If you guys are changing P&Ls have you looked at the P&Ls that were offered by Performance Specialties?
I'm showing the FSR on the left and the Hanno on the right please note the exhaust ports and materials.

Now why this is on topic is I want you to notice the shape of the port. The FSR is an arched port. It allows the exhaust port to open and closes slowly as the piston goes up and down. This makes for a milder but very good response to the pipe. The Hanno sleeve has what is known as a more muffin shape the port is very wide at the top this only narrows towards the bottom to make room for the transfer ports. Both sleeves are mild pipe timed. But the Hanno has more area and as a result will respond to a tuned pipe better.

Also Please note the "gold" color of those sleeves. This is something you don't see much anymore. These are from the golden era of the high performance 2 cycle engine! That shiny stuff on the sides of the ports is real chrome! No nickel here!!!

Friends don't let friends fly nickel,

Konrad

Konrad,

Thank you for the time you are taking to explain this so plainly so I can understand. If you will allow, I would like to try and see if I understand what you are saying.

It would be best, just to begin, to stay with the stock carb because:

1. Even though there is power loss due to a smaller venturi, the overall run will be more consistant because there will be less differential in atmospheric pressure. This will actually maintain a pressurized tank more efficiently and keep fuel pressure to the spray bar.
2. Because of the above, a pump will not be needed to compensate for the difference in atmospheric pressure at the different nose attitudes.
3. Due to the smaller venturi in the stock carb, a pump may not make a large change in power, but may actually complicate a well tuned engine.
4. A larger carb will give more power, but it takes a lot more to accomplish this job. Starting out, I will have more enjoyment with a stock set up by eliminating all this extra work. (I can always change my system in the future as I progress.)

It would be best, just to begin, to run a tuned pipe because:

1. Better fuel economy.
2. It will help move fuel past the baffle on my particular engine. This will keep fresh fuel over the cylinder and add power. (It will also harm fuel economy though-won’t it?)
3. It keeps with the overall reason for the purpose I am building the Model. I want to fly a classic Ballistic Patternship- the UFO.

It would be best, just to begin, to run a bubbles tank behind the firewall, not CofG because:

1. (regarding to tank location) A stock carb will not take a pump well. This ties my hands as far as tank location. However, the closer to the carb the tank sits, the less work load there is on the carb. This will keep a more consistant operation. Even creating more power in ratio to headaches.
2. The tank, pick-ups, and fuel delivery system to the carb are the probable cause of my headaches in the past. By installing equipment that will ensure good fuel delivery, I will have more success without the headaches of the past.

You are correct to determine my goal with my UFO is for creating a classic ballistic pattern flying airplane. I am tired of simply throwing the sticks every which way. If I have a reason and a goal to accomplish I keep my interest and actually learn something. I like the way you termed it: “a weapon for carving pattern out of the sky.�

In relation to the pump conversation, it seems as though a regulating pump is a better choice over the other pump.

Perry offers a regulating pump that maintains a constant .25 psi to the carb. Is this the choice to make regarding fuel pumps?
Brian

[link]http://www.perrypumps.com/prod02.htm[/link]

Konrad,

Have you ever considered offering online courses in operating 2 cycle engines?


Brian

I'll answer your points in post 44 when I get some time. But you got most of it right.

As far a classes I seem to get slapped for giving too much detail for the "average pilot". Too many folks think I'm been esoteric at best or arrogant at worse. I hope I give too much detail rather than not enough. You the (OP) are free to use what fits your needs. You will note that as time goes by some will try to say "but but he (you the OP) is sport flier and doesn't need all that detail". True most sport fliers don't need the detail I go into. But those that listen and use what I'm saying usually have that little edge that really improves ones outing at the field even as sport fliers. I'm just trying to help all that ask, get the most from our toy engines. And even some that are closed minded to the competition arena.

As long as you are asking smart (thinking) questions I't try my best to help. Also don't be afraid to ask for a drawing, if you think that will help. As you can see I can be rather verbose. This is odd as I can't spell english worth a damn.

All the best.

Konrad

My responses in blue ,I hope:

All the best
Konrad

WOW, Nobody picked up the baton while I was away. Come on guys our friend here deserves more than just my opinion.

I might be going off topic again. But as the OP thinks he might be having tank issues I'll risk the rathe of the moderators. Actually I'd like to thank then for their guidance through that VERY subjective "topic rule". (ref. Each forum has a different topic, so what is appropriate in one forum or thread may not be appropriate in another).
Here goes:


As I have stated earlier it is estimated that 80% of engine troubles can be traced to tank and fuel line issue. The fuel tank should be placed so that the tank center line is placed vertically within 5 mm of the spray bar when the aircraft is in its flight attitude. The fuel tank needs to be protected from vibration by loose fitting foam in the fuel tank compartment or use some form of bladder (bubbleless) tank.

Now what often trips up the sport pilot is the fuel line and its hardware. In the old days we tended to use brass or aluminum tubing to carry the fuel through the tank stopper or to splice the fuel tubing. These metal tubes often had a sharp burr that would cut very small pin holes into the silicon lines. Even if there was no burr the fact that the metal line ended with little or no radius would often result in cuts to the fuel lines. To solve these issues one should use polypropylene tubing for glow fueled set ups. Polypropylene can be flame polished to remove any burrs, it can also be formed ,by just keeping it in the heat a little longer, into a radiused retention barb. This keeps the fuel line on securely even with most pressured fuel systems, and eliminates the source of most cuts in the fuel lines. I hope the attached photos help make this clear.

Some have had issues with the term flame polishing. It is a term that has been used long before plastics came into the vernacular. It refers to any smoothing of a surface with heat. I think it was first used as it applied to glass work.

I get most of my thick walled Polypropylene tubing from left over Dubro Engine Control Cable P/N 165.

Please be sure the twist the tubing between ones fingers. (Note the use of an electric stove is actually preferred). The third picture has the retention barb outlined in yellow as a visual aid.

Friends don't let friends fly nickel,

Konrad