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Engine basics => Engine set up tips => Topic started by: john ohnimus on February 10, 2016, 09:14:06 AM
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I recently acquired a .46VF and would like some info on setting this up for stunt. Any info would be helpful as to venturi size, fuel, starting pipe lengths etc..
Thanks in advance!!
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I recently acquired a .46VF and would like some info on setting this up for stunt. Any info would be helpful as to venturi size, fuel, starting pipe lengths etc..
Thanks in advance!!
275-290 venturie, 12x4.5 3 blade or 12.25 x4.25 2 blade, pipe length 18.5 inches center plug to first baffle, other setups are doable but these work very well, and has a nice wide range .
Randy
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Thanks Randy!!
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I recently acquired a .46VF and would like some info on setting this up for stunt. Any info would be helpful as to venturi size, fuel, starting pipe lengths etc..
Thanks in advance!!
Also refer to David's setup article from Stunt News.
Brett
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Hi Brett or Randy or others,
Do you know what year and issue David's set-up article was? Yesterday was my first day running the VF in the garage, all mounted and ready to go. I used a 5% Power master with extra castor to bring it up to 22%. Pipe length is about 18.5 inches, but I'll double check. Plug has an idle bar but can't recall the make of it. I had a little trouble going rich and lean.
Prop was an APC 12.25x3.75.
This is Jimby's old VF and I have a CF prop from him, but wanted a cheap alternative for the first few flights.
David
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I'm gonna talk to myself for a minute, but I'd still like to see where to find that 46vf set up article. But I discovered some bubbles where the head screws on to the motor. I tightened it down and what would you know, it holds a needle setting now. I may be ready to maiden this bird this week.
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I'm gonna talk to myself for a minute, but I'd still like to see where to find that 46vf set up article. But I discovered some bubbles where the head screws on to the motor. I tightened it down and what would you know, it holds a needle setting now. I may be ready to maiden this bird this week.
I will have to check tonight, I gave him some information and was the proofreader for that one, so I should be able to find it. I am sure David would be happy to tell you, but he might end up talking you in to helping him hang drywall in his garage.
Brett
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I'm gonna talk to myself for a minute, but I'd still like to see where to find that 46vf set up article. But I discovered some bubbles where the head screws on to the motor. I tightened it down and what would you know, it holds a needle setting now. I may be ready to maiden this bird this week.
If you need head shims for it I have them here, make sure the gasket is in good shape, You do not want to over tighten the head bolts
Regards
Randy
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I will have to check tonight, I gave him some information and was the proofreader for that one, so I should be able to find it. I am sure David would be happy to tell you, but he might end up talking you in to helping him hang drywall in his garage.
Brett
Do you know which month/year of Stunt News contains that 46VF setup article?
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OK, guys, I dug around for a while, and I cannot easily find which SN Issue that article appeared in. However, the last draft I have is from late 2009, so presumably, Nov/Dec 2009, or early in 2010. I also have the text, but I am not sure what if anything was changed for publication.
Brett
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........, so presumably, Nov/Dec 2009, or early in 2010........
Brett
Yes, the copy of SN where the article appears is called "Special Edition 2009", it is the same number on which "The Stiletto Chronicles Part III" appears (Part II is in Nov-Dec 2009)
So between Nov-Dec 2009 and Jan-Feb 2010.
Massimo
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Okay, I think something Brett said or wrote said pipe engines are supposed to minimize the speeding up and slowing down. I also saw a chart Randy made demonstrating changing the pipe length to help accomplish this. I plan on running a wet 2 cycle the whole time.
And thanks Massimo and Brett for the article reference. I'll be reading it today at lunch time.
David
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Here is a PDF the 2009 Stunt News article: Tuned Pipes for CL Aerobatics, by David Fitzgerald and Brett Buck.
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Well, I made what I could out of that article. I've had about 5 flights or so, frequently ending with the engine going lean from the header coming unscrewed. I suppose I need split washers to help hold it. Today however the engine held the same speed the entire flight, but that was, I believe...too lean. It just sounded a bit lean. Additionally, I was getting about 4.5 laps. So, my question is, am I too lean, (I was also much louder than usual), or do I need a flatter prop.
I used power master 10/22, APC 12.25/3.75, 65' lines. I heard you are supposed to control speed with prop pitch, but it still seemed a bit too lean. Any pointers. Oh, and weather permitting, Nov 21 I think should be tuned pipe day at Napa...weather permitting.
Thanks
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Well, I made what I could out of that article. I've had about 5 flights or so, frequently ending with the engine going lean from the header coming unscrewed. I suppose I need split washers to help hold it. Today however the engine held the same speed the entire flight, but that was, I believe...too lean. It just sounded a bit lean. Additionally, I was getting about 4.5 laps. So, my question is, am I too lean, (I was also much louder than usual), or do I need a flatter prop.
I used power master 10/22, APC 12.25/3.75, 65' lines. I heard you are supposed to control speed with prop pitch, but it still seemed a bit too lean. Any pointers. Oh, and weather permitting, Nov 21 I think should be tuned pipe day at Napa...weather permitting.
If it is both too fast, and too lean, the obvious solution is to richen it up. Unlike the 40VF, the 46VF was often run into a 4-stroke, and both the 40 and 46 have a *butter-smooth* break from 4 to 2.
Certainly use lockwashers, but as long as you use the sealant properly and have *perfectly flat* mating surfaces, you shouldn't have much problem with the header coming loose. The 40 and 46 have ZERO TOLERANCE for leaks at the header, if they leak, they tend to run with way too much boost and break (because the pipe is no longer constraining it) and also sometimes act like they are running on suction, speeding up/going leaner throughout the flight.
As always,
*face off both mating surfaces with 240 grit wet/dry sandpaper and oil, taped to a perfectly flat hard surface or lapping plate* Don't let it "rock" as you push it back and forth, you much have a perfectly flat surface on both sides from edge to edge
Clean both surfaces with lacquer thinner or acetone until it is perfectly, operating-room clean.
Clean the screws and clean the threaded holes to the extent possible, remove all oil it is possible to remove.
Apply silicone sealant in a thin film all over the mating surface of on the engine side (which is smaller than the header flange, no point on covering that), all around edge-to-edge. DO NOT USE A GASKET OF ANY TYPE. I use Permetex Ultra Copper car exhaust header sealant, but just about any silicone sealant will work.
Put the screws (with split or star lockwashers on them) through the holes, and allow just a touch of sealant to get in the screw threads.
Without allowing the flange and exhaust to touch, start both screws a few turns.
Push the two surfaces together then run the screws down tight. Torque them down until they are tight and read-to-go. Ignore any advice on the tube of sealant about just snugging them, waiting overnight, then hard-tightening them later to form a "cushion" of sealant. You don't want that, it might blow out, you want to squeeze it out as much as possible, leaving sealant only in the scratches made by the sandpaper.
We have *never* had a leak doing it this way, I have them that have been mated for 25 years with no leaks. I have also seen one or both screws back off, but the header stayed on just from the adhesive with no leaks. You *can* get it off later, but it's glued on pretty good.
And I cannot emphasize this enough, *do not, under any circumstances, use any gaskets (paper, aluminum, brass, anything)*. All that does is give something to blow out, and is definitely unnecessary to seal the joint.
Brett
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Thank you Brett, that is GOLD! I will set to work on that next chance I get.
Also, are you saying a bit of a 4-2 is okay on a 46vf? I thought I heard somewhere to just go straight 2 cycle, but perhaps I'm mixing up my LA 25 advice, which I finally bought for my black tiger, but that's a different story, and one that may be turning out with a happy ending once I replumb my tank again.
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Thank you Brett, that is GOLD! I will set to work on that next chance I get.
Also, are you saying a bit of a 4-2 is okay on a 46vf? I thought I heard somewhere to just go straight 2 cycle, but perhaps I'm mixing up my LA 25 advice, which I finally bought for my black tiger, but that's a different story, and one that may be turning out with a happy ending once I replumb my tank again.
I setup many o f these engines and most everyone ran a fast 4 stroke with beeps of 2 at the top, You can even run a typical 4/2 break with the 46 VF on pipes
Randy
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Certainly use lockwashers, but as long as you use the sealant properly and have *perfectly flat* mating surfaces, you shouldn't have much problem with the header coming loose. The 40 and 46 have ZERO TOLERANCE for leaks at the header, if they leak, they tend to run with way too much boost and break (because the pipe is no longer constraining it) and also sometimes act like they are running on suction, speeding up/going leaner throughout the flight.
As always,
*face off both mating surfaces with 240 grit wet/dry sandpaper and oil, taped to a perfectly flat hard surface or lapping plate* Don't let it "rock" as you push it back and forth, you much have a perfectly flat surface on both sides from edge to edge
Clean both surfaces with lacquer thinner or acetone until it is perfectly, operating-room clean.
Clean the screws and clean the threaded holes to the extent possible, remove all oil it is possible to remove.
Apply silicone sealant in a thin film all over the mating surface of on the engine side (which is smaller than the header flange, no point on covering that), all around edge-to-edge. DO NOT USE A GASKET OF ANY TYPE. I use Permetex Ultra Copper car exhaust header sealant, but just about any silicone sealant will work.
Put the screws (with split or star lockwashers on them) through the holes, and allow just a touch of sealant to get in the screw threads.
Without allowing the flange and exhaust to touch, start both screws a few turns.
Push the two surfaces together then run the screws down tight. Torque them down until they are tight and read-to-go. Ignore any advice on the tube of sealant about just snugging them, waiting overnight, then hard-tightening them later to form a "cushion" of sealant. You don't want that, it might blow out, you want to squeeze it out as much as possible, leaving sealant only in the scratches made by the sandpaper.
We have *never* had a leak doing it this way, I have them that have been mated for 25 years with no leaks. I have also seen one or both screws back off, but the header stayed on just from the adhesive with no leaks. You *can* get it off later, but it's glued on pretty good.
And I cannot emphasize this enough, *do not, under any circumstances, use any gaskets (paper, aluminum, brass, anything)*. All that does is give something to blow out, and is definitely unnecessary to seal the joint.
Brett
Hi Again,
So, I've done about five flights and everything was fine until yesterday. On my second flight the engine started going very lean again and sure enough, the header has come loose again. I'm not sure why, but I have two theories? I used soft aluminum screws to hold the header on. Perhaps a little too soft and didn't squeeze hard enough to stay locked in position? So, I'll go again with steel screws. Also, is there a super threadlock I could try on my screws. I just let a tiny bit of the copper silicone on the threads. It was the best so far, but six, actually, I think it was four flights until coming loose.
On a positive note, this is my Junar with oversized stab and I really am liking the way it flies.
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The aluminum screws are probably the problem in this case. They can expand with engine heat, especially right there at the exhaust. The silicone for loctite seemed to have worked for a while. Use steel bolts, as long as possible to grab as many threads as possible but with out bottoming out in the hole, and try the silicone for loctite again. If it comes loose again after several flights, look for the red permanent loctite and try that. If the word permanent bothers you, don't let it. You will be able to get it apart when necessary with some careful heating.
Good luck with it,
Dan McEntee
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I recently acquired a .46VF and would like some info on setting this up for stunt. Any info would be helpful as to venturi size, fuel, starting pipe lengths etc..
Thanks in advance!!
Assuming a ST spraybar assembly, *start* at .270 or .275, have a .265, .270, .275, and .280 available. Use 10% Powermaster RC sport fuel ("Air") or similar, NOT SIG. Depending on which pipe you are going to use, I would start at 17.5". Locals all used relatively small pipes like the Future Force, or the smaller Eather pipes. You do not need and probably do not want the giant "resonator" pipes with the large outlets.
Props are typically 11.25 -3.75 3-blade. It will turn *much* more prop than a 40VF but *don't do that*, you want to use the smallest prop that gives you acceptable vertical performance. It should be right around the break point in level flight, and it is OK to run in a 4-stroke in level flight - the break will be *extremely smooth* compared to 136 degree exhaust duration engines like the PA40/61.
Adjust the venturi to set the level flight setting at the desired speed, if it is having to run in a 2-stroke in level flight with a11.25-3.75 3-blade, then go up .005. Adjust the aggressiveness in the maneuvers with pipe length, too aggressive, pull out pipe, to flat, push in (unlikely...).
If it flames out late in the flight in inside corners, push the pipe in 1/4" until it stops, when it breaks in more, you can pull it back out.
We used Glo-Devil #300 plugs in the 40/40VF, but many others would likely be fine. DO NOT USE ROSSI PLUGS at any time.
Brett
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Hi Again,
So, I've done about five flights and everything was fine until yesterday. On my second flight the engine started going very lean again and sure enough, the header has come loose again. I'm not sure why, but I have two theories? I used soft aluminum screws to hold the header on. Perhaps a little too soft and didn't squeeze hard enough to stay locked in position? So, I'll go again with steel screws. Also, is there a super threadlock I could try on my screws. I just let a tiny bit of the copper silicone on the threads. It was the best so far, but six, actually, I think it was four flights until coming loose.
On a positive note, this is my Junar with oversized stab and I really am liking the way it flies.
Hi David
Never us e aluminum bolts to hold a header in an aluminum case, Where did you get 3.5 mm aluminum bolts from? Are you using the correct bolts for the 46VF, they are 3.5 mm x 12 to 13mm deep, using anything else will not work with the threads on th e case.
The 12.2 x 4.2 2 blade works perfectly fine on that engine, as so many people have used that in the past, it is a close to a bolt on and fly as you can get.
The small Aeropipe made for the VF 46 VF 40 is also perfect for that engine, and can be made in either a 9 or 10mm exhaust outlet, That is a standard pipe that has been used on 100s of VF engines, Do not believe anyone that tells you different
You can also use a 12 inch narrow 3 blade or a 3 blade standard width prop from 11.25 to 12 inch diameter that would just be a personal choice
Randy
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Hi David
Never us e aluminum bolts to hold a header in an aluminum case, Where did you get 3.5 mm aluminum bolts from? Are you using the correct bolts for the 46VF, they are 3.5 mm x 12 to 13mm deep, using anything else will not work with the threads on th e case.
The 12.2 x 4.2 2 blade works perfectly fine on that engine, as so many people have used that in the past, it is a close to a bolt on and fly as you can get.
The small Aeropipe made for the VF 46 VF 40 is also perfect for that engine, and can be made in either a 9 or 10mm exhaust outlet, That is a standard pipe that has been used on 100s of VF engines, Do not believe anyone that tells you different
You can also use a 12 inch narrow 3 blade or a 3 blade standard width prop from 11.25 to 12 inch diameter that would just be a personal choice
Randy
Hi Randy, this is an engine that belonged to Ed Southwick. Either he, or someone else modified the case (possibly out of necessity) and it takes 8/32 bolts. For the plane it was in (an impact) it worked for years and years, but when I got it I lost the bolts (like an idiot) and substituted the aluminum ones.
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Hi Randy, this is an engine that belonged to Ed Southwick. Either he, or someone else modified the case (possibly out of necessity) and it takes 8/32 bolts. For the plane it was in (an impact) it worked for years and years, but when I got it I lost the bolts (like an idiot) and substituted the aluminum ones.
Well David if the 8/32 threads are still good in the case, you can find steel bolts to use, I would do that, I think it maybe a problem with 8-32 heads clearing the header so watch for that very carefully, Use blue locktight AFTER you have cleaned everything
I use duct tape as a gasket, this is the very best thing you can use, and by duct tape, I mean the tape that A/C people use to seal the supply vents,it is a shiny metal looking tape with paper on one side, You peel the paper off, stick the header to the tape, cut out the screw and center holes, then you are ready to bolt it on.
The tape is very thin like aluminum foil so it will not crush and let the bolts get loose
Use the lock tight and tighten it all up, I never have things come loose using this technique
If it was Ed's It maybe one of the ones I did for him
Regards
Randy
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Hi everyone, good news is I got to go fly today. Good news, the header stayed attached, the engine ran even on the insides and outsides. But, it kind of chugged a bit, like it was too rich, but I'm not sure. It was more like someone was flipping a fuel switch very quickly at certain times in the flight. There was practically zero acceleration on the stunts, which was something new to me. So, it was about 52 degrees, 76% humidity. I think Brett or someone mentioned using 5% in the winter. I was still using my 10/22. I also made 4:20 or less with 5 oz of fuel. Maybe I'm still too rich, but I thought I'd ask about the nitro.
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David,
I don't use locktite on header bolts I do however use a split washer or a star washer if it all fits I prefer external star washers for a header also check the bolt tightness after the first flight then recheck every 3 or so flights for the next 15 or so flights then every once in a while.
Good luck , John L.
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David,
I don't use locktite on header bolts I do however use a split washer or a star washer if it all fits I prefer external star washers for a header also check the bolt tightness after the first flight then recheck every 3 or so flights for the next 15 or so flights then every once in a while.
Good luck , John L.
Thanks John, I do have locktite, but I'll need to get in a habit of rechecking them for a while. I also had quite a bit of oil exiting near the engine somewhere. I suppose I can find it by running the plane upside with the cowl off.
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Hi everyone, good news is I got to go fly today. Good news, the header stayed attached, the engine ran even on the insides and outsides. But, it kind of chugged a bit, like it was too rich, but I'm not sure. It was more like someone was flipping a fuel switch very quickly at certain times in the flight. There was practically zero acceleration on the stunts, which was something new to me. So, it was about 52 degrees, 76% humidity. I think Brett or someone mentioned using 5% in the winter. I was still using my 10/22. I also made 4:20 or less with 5 oz of fuel. Maybe I'm still too rich, but I thought I'd ask about the nitro.
If you have problems, recall that it is not intended to run rich, so increasing the RPM and reducing the pitch to match will generally make it run better. What prop at what pitch, and what was the ground RPM?
An alternative is to reduce the venturi, so you can run it leaner with the same prop. It's actually very critical, one time we were out with Scott Urabe and his 40VF. .270 venturi, and he had to launch rich enough that it would 4-stroke in level flight sometimes. .265 shifted it a bit leaner, and he picked up, and I do not exaggerate, 40-50 points in 3 flights.
If it is too "flat" in the maneuvers and everything else is OK, push the pipe in 1/4" and try again. But the effect of a proper piped engine run will feel like that if you are used to 4-2 break engines. First time I did it, I was almost afraid to do a wingover, because if had been an ST46 (like the previous week) it would have been far too slow to make it. Point the nose up, and it slowly grinds to the top of the circle, coming down, it was like someone was riding the brakes, absolutely amazing. Welcome to a new world.
Brett
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David, if you want to try the aluminum tape that Randy mentioned, just send me your address. I'll send you a chunk. Uline sells the good stuff for about $74 a roll. Like he said, it's for sealing, so it can be pricey. We use it to seal hydraulic ports that are too large for plugs.
https://www.uline.com/Product/Detail/S-10311/3M-Single-Coated-Tape/3M-425-Aluminum-Foil-Tape-2-x-60-yds?pricode=WB0161&gadtype=pla&id=S-10311&gclid=EAIaIQobChMI2ty2peLb7QIVnx-tBh2RQAAoEAQYBCABEgIRDfD_BwE&gclsrc=aw.ds
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David, if you want to try the aluminum tape that Randy mentioned, just send me your address. I'll send you a chunk. Uline sells the good stuff for about $74 a roll. Like he said, it's for sealing, so it can be pricey. We use it to seal hydraulic ports that are too large for plugs.
https://www.uline.com/Product/Detail/S-10311/3M-Single-Coated-Tape/3M-425-Aluminum-Foil-Tape-2-x-60-yds?pricode=WB0161&gadtype=pla&id=S-10311&gclid=EAIaIQobChMI2ty2peLb7QIVnx-tBh2RQAAoEAQYBCABEgIRDfD_BwE&gclsrc=aw.ds
Never use a gasket of any kind, use the Ultra Copper silicone sealant, properly applied it will last until you intentionally break it.
Brett
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I personally do not use a gasket. That applies to control line speed planes, all the way to rc helicopters.
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Never use a gasket of any kind, use the Ultra Copper silicone sealant, properly applied it will last until you intentionally break it.
Brett
Properly applied as I described the Tape will NEVER leak and will stay there until you remove it.
The reason people get into trouble using gaskets and the reason Brett thinks it is bad, is because they are thick and crush, then the bolts get loose from the crush, then after they crush, they leak, The THIN metal tape I use, and many many other hundreds of people use, at my suggestion, does NOT crush and , thus it does not promote leaking,
I have used this for 3 decades and have never had 1 problem, Many others have too.
So do not let anyone tell you this does not work great. It does, and in my opinion it worked BETTER than anything I have seen or heard about, Including any silicone or copper sealant
Randy
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IF the OP is thinking of using a prop other than CF, I've used the 11.5x4 and 12.25x3.75 APC. The prior was used stock or de-pitched. The the latter was completely re-carved and re-pitched, and worked a little better. It wasn't nearly as much work as you'd expect, but you have to SCRAPE the plastic and not really CARVE it. I made a template to fit the flat side of the blade, with a 1/4" dowel pin to locate on the hole. The TE was the other reference. The LE & tips are rough shaped on the belt sander, and then the scraping begins, followed by a bit of sanding. The prop actually looks pretty decent (scimitar) and works alright, but when we can fly on pavement, I'll use a 3 blade Brian Eather undercambered type, 11.5" dia., pitched up to about 4.5~4.75 in the last 1.5" or so. It runs smoother.
My .46VF is a Randy Aero AAC and uses Randy's pipe with a DuBro exhaust deflector on the outlet. Thunderbolt 4-cycle glowplug, venturi is about .272" or .275" from memory, with one of Randy's NV Assy.'s, 10% nitro, 18% oil with a couple ounces of Randy's Aero-1 added. Be sure to set the pipe length per Randy's pinned chart. Longer is ok, but avoid too short. D>K Steve
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The engine is running nice and smooth. No more problems with loose headers. I leaned it out a bit and went to 5%. Still using an APC 12.25x3.75 I think.
On 5 oz I'm running out of fuel at about 3 minutes each time. Laps are 5.25-5.4, which I don't mind too much. I think I'll measure the venturi as best as I can and consider going with a smaller venturi. I also have a CF 3 blade that was given to me with the engine. PRobably the same prop Ed Southwick used on the engine. I'm just not sure why I'm running dry so quickly. Also, plane doesn't turn inside and outside equally, which is a different thread, so don't worry about that one yet.
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Mine uses right around 5.5 > 6 oz of 10%, as I recall. If you're using a tin tank, I'd guess that there's a problem with the plumbing inside it. If you're using a clunk tank, I'd wonder if you store or transport the plane nose-down. That can cause the clunk to lodge in the front of the tank and doesn't work well. Remember that the more prop load, more oil, higher nitro, or heavier plane, the more fuel needed. y1 Steve
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The engine is running nice and smooth. No more problems with loose headers. I leaned it out a bit and went to 5%. Still using an APC 12.25x3.75 I think.
On 5 oz I'm running out of fuel at about 3 minutes each time. Laps are 5.25-5.4, which I don't mind too much. I think I'll measure the venturi as best as I can and consider going with a smaller venturi. I also have a CF 3 blade that was given to me with the engine. PRobably the same prop Ed Southwick used on the engine. I'm just not sure why I'm running dry so quickly. Also, plane doesn't turn inside and outside equally, which is a different thread, so don't worry about that one yet.
What venturi and spraybar are you using? I would have started with a .265 and a ST spraybar, but if you have a smaller OS spraybar that will be way too much.
Brett
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So, unfortunately I built it with a 5oz tin tank. The tank runs very dry each flight. Sorry to be old school here, but I still don't have an accurate micrometer or measuring tool. So, I'm using drill bits here. 17/64 fits, 9/32 doesn't. It has an ST spray bar. Perhaps the CF prop will help, but it needs a lot better fuel consumption. But, if 5 ounces is too small, then I already know what I need to do.
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So, unfortunately I built it with a 5oz tin tank. The tank runs very dry each flight. Sorry to be old school here, but I still don't have an accurate micrometer or measuring tool. So, I'm using drill bits here. 11/64 fits, 9/32 doesn't. It has an ST spray bar. Perhaps the CF prop will help, but it needs a lot better fuel consumption. But, if 5 ounces is too small, then I already know what I need to do.
Do you mean 17/64 fits and 9/32 doesn't? 9/32 is 18/64, so that's quite a jump.
Dunno what you mean by "runs very dry each flight" -- since that's kinda the point, I'm wondering how long your flights last?
As a last resort, if you doctor up your fuel with no more than 2oz of Coleman lantern fuel (AKA white gas) per gallon, you'll get about 10% more run time -- and slightly easier starting.
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Do you mean 17/64 fits and 9/32 doesn't? 9/32 is 18/64, so that's quite a jump.
Dunno what you mean by "runs very dry each flight" -- since that's kinda the point, I'm wondering how long your flights last?
Yes, thanks for the correction Tim. I fixed the post.
Steve mentioned problems with the tank. By running very dry, I'm just saying there is no problem with the tank...except possibly being too small.
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So, unfortunately I built it with a 5oz tin tank. The tank runs very dry each flight. Sorry to be old school here, but I still don't have an accurate micrometer or measuring tool. So, I'm using drill bits here. 11/64 fits, 9/32 doesn't. It has an ST spray bar. Perhaps the CF prop will help, but it needs a lot better fuel consumption. But, if 5 ounces is too small, then I already know what I need to do.
5 ounces is too small. 9/32 is .2812, which is bigger than I would start with, particularly with such a light prop. 11/64 is only .1718, so I presume that you mean 17/64, which is .2656. So, maybe .275, which is A LOT of power on a 46VF.
If it runs and performs OK otherwise, I would just stick enough fuel in to make it on 10%, and move on with life. But, I think you will want to at least look at getting a set. I got mine from Leonard Neumann, but I am sure Randy and Jim Lee have them or can make them.
My choices would be .260. .265. and .270, for a starter.
Brett
p.s. How is it running in level flight at normal speeds? I would expect it to be 4-stroking most/all of the time with that prop, OR, two-stroking but very "flat" in the maneuvers because the pipe is too long.
Don't do anything different until you can get complete flights in, but you can play off the pipe length against the venturi over small ranges to adjust how much boost/brake you get. You can set it up to 2-stroke with a .300 venturi if you run the pipe long enough, problem is that it will be dead as a doornail in the maneuvers. Pushing the pipe in would make it run richer at the same RPM, or, allow you to run a smaller venturi at the same mixture at the same RPM.
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Okay, thanks everyone. My next step is figure out how to get a bigger tank in there and order some smaller venturis.
Brett, I'm not sure I have the vocabulary for piped engines yet, running flat?
I did put it in a rich 2 cycle last time out. There wasn't a ton of authority, and seemed like almost zero surge in power. Although that was okay, it still pulled enough to do everything. But, I'll figure out the tank first. I have the pipe as long as I can get it, so hopefully I don't need to go longer. Glow plug to pipe end is about 20.25 (I think that's a tad too long.) Then I have an exhaust deflector, so 21.5.
I can't tell you what kind of pipe it is except it's CF. First one I've ever had, may or may not be the one that Ed used on the engine. My dad had about three and I just took whatever.
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Okay, thanks everyone. My next step is figure out how to get a bigger tank in there and order some smaller venturis.
Brett, I'm not sure I have the vocabulary for piped engines yet, running flat?
I did put it in a rich 2 cycle last time out. There wasn't a ton of authority, and seemed like almost zero surge in power. Although that was okay, it still pulled enough to do everything. But, I'll figure out the tank first. I have the pipe as long as I can get it, so hopefully I don't need to go longer. Glow plug to pipe end is about 20.25 (I think that's a tad too long.) Then I have an exhaust deflector, so 21.5.
I can't tell you what kind of pipe it is except it's CF. First one I've ever had, may or may not be the one that Ed used on the engine. My dad had about three and I just took whatever.
"Flat" means that is has very little boost or braking action in the maneuvers. If it is running that way with an oversize venturi, that strongly suggests that you have the pipe too long. It is regulating the RPM too well. A little longer, and you will go over the top, and you will hear it slow down in the maneuvers when it is supposed to speed up. It is very surprising to me that you can run it in a 2 stroke in level flight at a reasonable speed with that prop, that also suggests the pipe is too long.
Normally you measure the pipe length by sticking something into the front to measure where the first baffle is, that is, the one closest to the engine. That is just a reference mark, it means different things with different pipes. With a Randy pipe and an 46VF I would start at 17.5" to the first baffle and then adjust.
What I expect to happen with an oversize venturi is that it will be too rich in level flight and also vary too much during the maneuvers, when you have the pipe length otherwise right. Since it is 2-stroking in level flight and also too flat, apparently, it acts like the pipe is too long.
But, first things first, make a tank to get through the flight, then start messing around with adjustments. If you need to, make the tank thicker than 1" and just put the wedge, pickup and uniflow offset from the center so it lines up with the engine the same way
Brett
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So, for my last flight today I pulled out my Junar with the 46vf to see if the changes made a difference before tearing into the tank. Well, I put two ply silk over the venturi to simulate a smaller venturi. I also wondered what would happen if I turned my uniflow line around so it wasn't facing the wind. Brett, I got that idea from you when you mentioned making an air dam or something at Golden State. I still used the same APC. Oh, and I shortened the pipe, but only about 1/4 inch. Any further and I need to cut the header more. Well, it flew like magic. Okay, maybe not Harry Potter magic, more like Willow Offgood magic, but magic nonetheless. Those three little tweaks enabled me to get one lap past the clover before I went deadstick. Not only that, but I had more power than I've had before. Oh, and the tank holds more fuel if the plane is level while you fill it. I don't think I was getting the whole 5 oz into it previously. I'll be playing with it some more before I try swapping the tank (which will involve cutting out and relocating a bulkhead.
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So, for my last flight today I pulled out my Junar with the 46vf to see if the changes made a difference before tearing into the tank. Well, I put two ply silk over the venturi to simulate a smaller venturi. I also wondered what would happen if I turned my uniflow line around so it wasn't facing the wind. Brett, I got that idea from you when you mentioned making an air dam or something at Golden State. I still used the same APC. Oh, and I shortened the pipe, but only about 1/4 inch. Any further and I need to cut the header more. Well, it flew like magic. Okay, maybe not Harry Potter magic, more like Willow Offgood magic, but magic nonetheless. Those three little tweaks enabled me to get one lap past the clover before I went deadstick. Not only that, but I had more power than I've had before. Oh, and the tank holds more fuel if the plane is level while you fill it. I don't think I was getting the whole 5 oz into it previously. I'll be playing with it some more before I try swapping the tank (which will involve cutting out and relocating a bulkhead.
HI David
You have to know where you are at with your setup, The pipe length is measured from center of chamber in the engine, to the first reflective surface in the pipe, or a baffler, In my pipes, if you have a very old pipe, there should be a white or yellow marke near the back of the pipe, if it is one from the past 10 years the first baffle is located a the bump, near the middle part of the largest part of the pipe at the rear, If not Brett told you how to find it. Second set it at 17 3.4 inch with that 2 blade, and if you run a 3 blade it will set at 18 to 18.5 inches. Be very careful to NOT crush the front of the pipe, always keep the Zip Ties on the metal insert and never on the unsupported part of the pipe, it will crush and restrict the pipe. IF you have the system apart, Check to make sure the front of the pipe, is clear and no obstructions or it is not crushed down smaller
This time of year you should get plenty of power from 5% nitro. If you need extra run time, put 1 to no more than 2 ounces in a gallon of Acetone, or coleman fuel.
Let us know what is going on
Randy
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So, for my last flight today I pulled out my Junar with the 46vf to see if the changes made a difference before tearing into the tank. Well, I put two ply silk over the venturi to simulate a smaller venturi. I also wondered what would happen if I turned my uniflow line around so it wasn't facing the wind. Brett, I got that idea from you when you mentioned making an air dam or something at Golden State. I still used the same APC. Oh, and I shortened the pipe, but only about 1/4 inch. Any further and I need to cut the header more. Well, it flew like magic. Okay, maybe not Harry Potter magic, more like Willow Offgood magic, but magic nonetheless. Those three little tweaks enabled me to get one lap past the clover before I went deadstick. Not only that, but I had more power than I've had before. Oh, and the tank holds more fuel if the plane is level while you fill it. I don't think I was getting the whole 5 oz into it previously. I'll be playing with it some more before I try swapping the tank (which will involve cutting out and relocating a bulkhead.
Right - those are the sort of small changes you want to make, because if you make any bigger, you might jump over the proper settings. They are small, but unlike other systems that came before, they are reliable and repeatable.
Brett
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Okay, possibly my final update on this thread...(we'll see).
So, I only put in the 5 oz tank, so I was needing to replace it, but it was so close on run I decided to try the acetone in the fuel to see what happens. (Last week) So, I searched and searched and found out I was out of acetone. Then I went to the hardware store and bought some more. I got to the field and decided to try flying off of the old abandoned road next to the soccer field I often fly on. I searched for a crack big enough to pound in my stooge stake. Finally I found an area that was pretty bad off. Next I tried to open the acetone and it was way beyond child proof. Try as I may, I didn't have the tools to open that cap. So I decided to practice with the fuel "as is." I ran out my lines, the stooge, and then I discovered I didn't have my fuel syringe. So I flew the electric and came home. (sorry to waste your time with that one.)
(Today) I mixed up the acetone at about 100:1. First flight it seemed rather anemic, barely getting through the square 8s and the clover, however I made it three laps past the clover for the first time! Flight two: I leaned it out a bit more and it came on pretty good. Got the whole pattern in and I think 8 or 9 laps. So, no surgery to replace the tank at this time. Looks like 5 oz will do it. Oh, that includes me priming it from the syringe rather than from the tank.
With that said, thanks for all the tips, hopefully my next questions will not be related to the 46vf.