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Cox Reed Valve FAQ

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Old 04-21-2006, 07:53 AM
  #51  
jetpack
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Default RE: Cox Reed Valve FAQ

This might be off topic a bit, but the topic came up and thought I would shoot in a quick question.

The reedies and the TD both share the same type of knurled steel insert for the needle, and I have a few needle valve bodies from the TD I would like to send out and have re-anodized with some other parts to brighten up my collection.

Has anyone tried to remove these and re-insert them, and if so what method do you have, or whats the drawbacks.
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Old 05-06-2006, 06:35 AM
  #52  
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Default RE: Cox Reed Valve FAQ

hi everybody
i have a question about the possibility of using an AC adaptor for cox glow plug and how many volts and ampers should be.
Thanks .
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Old 05-06-2006, 11:35 AM
  #53  
Remby
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Default RE: Cox Reed Valve FAQ

gocartdude,

A interesting project. The output to the plug must be D.C., and 1.5 volt. Also, I would think the setup would require up to three amps, so your idea is workable, but finding the combo of outputs may be a pain.

Perhaps using a selectable DC power supply could get the job done, provided good insulation protection for the user (you). The use of A.C. and fuel must be kept well apart for safety, but is not imposable.

I would first try a rechargeable battery setup first to see if that gets the job done for you.
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Old 05-06-2006, 03:50 PM
  #54  
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Default RE: Cox Reed Valve FAQ

thanks,
In fact this is what I will do ,im gonna charge a 1.5v battery with i think, a 3v charger ,i wish the glow element will not turn into a barbecue ,LOL.
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Old 06-08-2006, 09:00 PM
  #55  
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Default RE: Cox Reed Valve FAQ

I tried to update post #2 but there was no edit button. The link has changed so here is the new link http://www.freewebs.com/doughtyhobbies/049tips.htm

Enjoy

______________________

New link copied to Post #2 to avoid confusion- BMatthews Oct 15 '07
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Old 06-08-2006, 11:00 PM
  #56  
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Default RE: Cox Reed Valve FAQ

gocartdude:

I think the concept is doable but you didn't supply enough specifics to chrunch any numbers for you. I doubt that glow plugs care (like light bulbs or other heating coils whether they get AC or DC voltage as long as the power is right). One wonders since when is AC more convenient than a DC battery. Still if you insist who am I to question. Maybe you have a long cord. Here goes...

The issue is Power or Wattage. (Volts) X (Amps) = Power (Watts). I use a power panel to light up my glow plugs and heads and it uses 12 volts, not 1 ½ volts The current is varied to create more or less Watts. This is what causes the element in the plug to glow.

Using hypothetical numbers, if a glow head uses 1 1/2 volts and 3 amps to glow that’s 4.5 Watts. (1 ½ X 3 = 4.5) If you wanted to use 110 volts to get 4.5 Watts you would need to supply 0.040 amps. (4.5/110 = 0.40) How you’re going to do that is up to you. Good luck.

HTH - Steve B.
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Old 06-13-2006, 09:52 AM
  #57  
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Default RE: Cox Reed Valve FAQ

thanks burtcs
As u said it will be hard to find the right voltage and amperage so , i will take a 12 v power panel, and in this case it must supply 0.375A to produce the 4.5Watt .
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Old 08-22-2006, 09:19 AM
  #58  
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Default RE: Cox Reed Valve FAQ

SPI and Cylinder bypass. If SPI was a good thing why would you NOT put it on a cylinder? Same for the bypasses...it seems there should be an optimum number. After reading about the myriads of Cox cylinder variations I don't understand why they haven't settled on one or two that seem to work best.
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Old 08-26-2006, 06:58 AM
  #59  
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Default RE: Cox Reed Valve FAQ

Non SPI cylinders (for me anyway) seem to have better "fuel draw", slightly better fuel "mileage" and the needle is less sensitive. SPI helps to produce more top end rpm at the expense of some tractability, IMO.

Exhaust throttle sleeves function much better on non SPI cylinders as well.
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Old 11-08-2006, 06:40 AM
  #60  
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Default RE: Cox Reed Valve FAQ

ORIGINAL: burtcs



The cylinder had TWO intake ports like the Black Window - no SIP as near as I can tell. It was not a single port design like the Baby Bee. It used a rectangular type Mylar reed valve with the plastic gasket/retainer, this works well. The Tank was off the wall. It has a very small passage from the needle valve to the reed valve. This was smaller than the 5.1cc Baby Bee tank. This was where Cox did their throttling. I wouldn't worry about it, the Baby Bee tank with mylar reed valve works fine.

Cox used a five fin glow head on this engine, it looked cool but the three fin sport heads (the ones we're taking off of the Sure Starts) work just fine - save them. Why they put a five fin glow head on this engine I don't have a clue, somebody must have thought the engines would overheat. They don't. The real problem these engines have is they run cold and die. Retarding the ignition with head gaskets keeps them from overheating - so, you have to warm them back up. To do this I elected to go with the Cox muffler. This allows the engine to stay warm and it also throttles it down a bit. The really cool thing about the muffler is the engine purrs like a kitten. It turns the engine into a flying cartoon - excellent.

Since S.A.M. rules specify Cox reed valve engine, that's what we gotta use. The rules do not say whether it has to be new or worn out. I wear the piston and cylinder out with lapping compound - 800 mesh or finer. I want the piston to protrude from the cylinder about 1/16" with no noticeable drag. The downside is this lets the engine rev up, the upside is that when you lower the RPM with head gaskets you've recovered the lost fuel for the run. Every time the piston goes up and down you've just used up .049 chi of fuel mix, you might not have needed to do this if the model will fly with less RPM. The engine need not prop over in a snappy fashion; I'm using a starter spring to do that.

Reed valve needle valves are a traditional pain in the neck. They are too loose in the threaded needle valve seat and the springs don't hold them in place. At one time the firm (now gone) Kustom Kraftmanship offered a Texaco backplate with a needle valve extension. It also happened to have a collet-locking nut on it and fine threads. I got three Texaco units and one Black Widow backplate. These needles no longer turn in or out from engine vibration. It is unlikely that you can find one of these available now; you'll have to devise your own way of doing this. Silicon tubing and a washer is the first place I'd start. The fine thread is no big deal. Mine tank backs aren't for sale.

The fuel line Cox uses in the tanks is also an issue. It works ok for the first year, then you had to replace it. When they're new they work fine. After about a year they get stiff and they begin to straighten out drawing fuel from the center of the tank - not good. With the current price of rebuild kits, this gets expensive (did I mention I'm also a cheapskate). Use a piece of K&S aluminum tubing to make a new permanately curved fuel line that picks it's fuel from the back of the tank. KK used to sell these, toughen up and make your own. Your engine will now suck down all the fuel in the tank.

Thanks for all the good information. For Texaco, I settled on a 315 sq. inch wing, and a standard Baby Bee. It has single fuel bypass, and non split exhaust, ie, has sub piston induction. I don't understand why the official Texaco engine has twin fuel porting, and split exhaust porting, if fuel economy is the aim. My combination works a charm with a 7x4 master narrow for the heavy event (postal international), and a 7x5 narrow for our rules. Weights 17 3/4 vs 11 1/2 oz.
My engine run times range from 2:30 to 3:30, depending on me and the weather, and 10% nitro is used. 20% Synthetic oil to keep things clean.
I use fuel tubing to seal the needle valve. The thin O ring on the tank centre post must be good, or air will be sucked in as the fuel level drops to it.
For the fuel pick up tube, I may try retract pneumatic tubing as a replacement when needed.
Finally, someone explained to me the secret of starting these little fellows, and he is correct in what he says. The biggest problem is that we can't "choke" to get the fuel up. The reed valve has to pump it up. This is achieved by two or three priming firings. Make sure that you open the needle valve one turn richer before prime starting, so the fuel gets up easier. Once it is running, the correct needle valve setting is exactly one turn in.
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Old 01-29-2007, 07:34 PM
  #61  
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Default RE: Cox Reed Valve FAQ

All,

I just received 5 sure starts from Cox. Last night I was changing out some parts from the sure start to my black widows. I ended up with an extra back widow cylinder, so I changed one of the sure start cylinders (4 thin slots) to a black widow cyliner (2 wide slots). Should I expect the engine performance to change much. It is really cold out right now, so I can not test the difference.

any thoughts?

chad
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Old 02-17-2007, 05:20 PM
  #62  
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Default RE: Cox Reed Valve FAQ

I have acouple of Sure starts and want to ask.
Are the glow plugs replacable?
What glow plugs are recommended?
How do I set up a tank with air vent when the sure start has no muffler with a back preassure nipple?
What is the ideal tank position in relation to the fuel inlet on the back plate?
How does one firewall/radial mount the sure start with its snorkel in the way?
Can a tank be fitted to a sure start ?
Are they still available?
Do they run inverted or side mounted?
How many turns from fully closed should the needle be for first starting?
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Old 02-18-2007, 03:05 PM
  #63  
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Default RE: Cox Reed Valve FAQ

ORIGINAL: universe.avenger

I have acouple of Sure starts and want to ask.
Are the glow plugs replacable?
What glow plugs are recommended?
How do I set up a tank with air vent when the sure start has no muffler with a back preassure nipple?
What is the ideal tank position in relation to the fuel inlet on the back plate?
How does one firewall/radial mount the sure start with its snorkel in the way?
Can a tank be fitted to a sure start ?
Are they still available?
Do they run inverted or side mounted?
How many turns from fully closed should the needle be for first starting?
1. Glow plugs can be replaced.

2. The least expensive approach is to buy another SS -- think of it as an inexpensive plug with a free engine attached. You can get the #325 standard glowhead from [link=http://www.selecthobbies.com/]Select Hobbies[/link]. A second combination which has proven to perform as well or better than the COX glowhead is the Galbreath head/NELSON plug combo available thru Larry Driskill at [link=https://ssl10.mysecureserver.com/kittingittogethercom/index_store.html]Kitting It Together[/link]. Another new arrival is the Turbohead conversion that uses the turboplug from [link=http://www.hypercolor.biz/Accessories.html]HyperColor Anodizing[/link] -- I have not seen any performance figures for the TurboHead.

3. The vent is ambient air -- some folks will have the vent pointing forward for a ram-air effect. Don't have it at 90 degrees to the airstream since it can act like a siphon and suck fuel out. Keep the fuel line as short as possible and use small diameter tubing.

4. Center of the tank with the needle seat -- where the choke tube turns into the backplate.

5. Use a couple of plywood spacers to provide clearance or you can remove the choke tube.

6. The SS crankcase will fit any of the existing integral tanks for the COX .049

7. They were last week -- they are out of stock this week -- keep an eye on the COX Models site. There will probably be another batch show up in the near future.

8. They will run both ways -- if inverted, starting is usually easier if you flip the plane over and it reduces the chance of hydraulic lock. I normally run upright or side mounted.

9. I start at 3 1/2 and lean out. 2 1/2 to 3 1/2 will usually get you in the ballpark.
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Old 05-08-2007, 07:24 PM
  #64  
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Default RE: Cox Reed Valve FAQ

any one have a source for a back plate and tank/w.screws etc. got a little control line plane kit I used to fly when I was a kid, off ebay and it came with a engine when I opened the box(it looked as if it had been run over by a truck) the BP and tank assy. was just a mess, bent and broken.
I have been searching for replacement parts to no avail any tips?
the plane was OK thankfully.
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Old 05-08-2007, 11:06 PM
  #65  
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Default RE: Cox Reed Valve FAQ

Virginia Hobbysport still has some Cox parts in stock. You might try them:

http://www.virginiahobbysport.com/index.htm
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Old 05-08-2007, 11:58 PM
  #66  
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Default RE: Cox Reed Valve FAQ

thanks I will call then tomorrow looks like they might have what I need
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Old 05-12-2007, 05:29 PM
  #67  
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Default RE: Cox Reed Valve FAQ

I'm fairly new to R/C in general, and have only been flying electric for about 6 months. There's just something missing, and that's the noise of an engine! I've always liked Cox engines and I plan on converting an electric ARF to a Cox driven one. I really don't care if it's .010, .020, .049, etc., I just want it to be 1/2a .051 and under. Are there any general guidelines as to what weight aircraft each engine can handle?

Thanks,
Cal


Answer from BMatthews-
There's a fairly wide range of model sizes and weights that you can fly with a Reedie .049. The popular DNU Ugly Stik variaiton that is popular here is a real hotrod with a reedie at 32 inch span and around 14 to 16 oz. More common are the 36 inch span models with around 250 sq inches of wing area and weighing from 14 to 24 oz. The lighter options being higher performance and the heavier ones flying faster, climbing slower and landing faster. At the other end are the "powered gliders". The SAM old timer Texaco 1/2A event models are full sized or scaled down copies of the old prewar free flight models and run up from 260 to 300 sq inches, are required to weigh a minimum of 8oz/sq ft of wing area and typically come in around 16 to 20 oz. Finally there's real gliders from 60 ot 78 inch span that use an 049 to climb at best and "glide uphill" at worst. These powered gliders can range from 24 to 36'ish oz and still get up high enough to catch thermals.
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Old 05-12-2007, 09:44 PM
  #68  
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Default RE: Cox Reed Valve FAQ


ORIGINAL: liquidice

I'm fairly new to R/C in general, and have only been flying electric for about 6 months. There's just something missing, and that's the noise of an engine! I've always liked Cox engines and I plan on converting an electric ARF to a Cox driven one. I really don't care if it's .010, .020, .049, etc., I just want it to be 1/2a .051 and under. Are there any general guidelines as to what weight aircraft each engine can handle?

Thanks,
Cal
As an example, 1/2 A Texaco requires models to have 8oz per sq. ft wing loading. My Playboy has a 50 inch span, and ends up weighing 17 1/2 oz.

Under light lift conditions, I have managed 15 minute flights off engine runs of around 2:50 (We must use the small 5cc tank that comes with the engine. For some reason, the Cox Texaco engine comes with the larger 8cc tank, which we may not use). The secret is to have the wing do the work, rather than depend on engine power to make them fly.
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Old 05-13-2007, 12:18 AM
  #69  
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Default RE: Cox Reed Valve FAQ

aeomaster32:

If I may ask, whose Playboy are you using? I use the Reynolds Playboy which also wieghs 17 1/2 oz. I fly it at 5-5100 RPM.
In the old days with the 8cc tank I used to get 7 1/2 - 7 3/4 minute engine runs. I used to spin it down to lower altitude twice before the final climb. Good stuff...

regards - Steve B.
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Old 05-13-2007, 09:39 AM
  #70  
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Default RE: Cox Reed Valve FAQ


ORIGINAL: burtcs

aeomaster32:

If I may ask, whose Playboy are you using? I use the Reynolds Playboy which also wieghs 17 1/2 oz. I fly it at 5-5100 RPM.
In the old days with the 8cc tank I used to get 7 1/2 - 7 3/4 minute engine runs. I used to spin it down to lower altitude twice before the final climb. Good stuff...

regards - Steve B.
I use a Cleveland Playboy Snr. from a "Classic Models" plan. I use a Master narrow 7x4 prop which gives around 8000 rpm. Here, in Australia, I only use the heavy wing loading for the International Frank Ealing contest (USA rules).

Australian SAM rules allow you to build as light as you dare, and the same model comes out at 11 1/2 oz. I use a 7x5 prop with the lighter model, as it climbs with lower rpm (needs less power). I don't know how you got that heavy model to climb at 5000 rpm, but the way I do it, the engine quits at my eyesight limit anyway. I have found that too slow a climb can finish you if there is sink around, or your engine is struggling. I just don't think another 30 seconds of engine run makes up for the draw backs.

I never knew they ever used the 8cc tank, but considering the USA weight loading and 15 minute maxes required, I can see why they did. We have a 6 minute max, but unless you have everything right, it is not assured. Most engine runs are 2 1/2 minutes, although I did manage up to a minute more occasionally.
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Old 05-14-2007, 04:23 PM
  #71  
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Default RE: Cox Reed Valve FAQ

I just came across two new cox cylinders/pistons/crankcases to use as spares with my current engines. I noticed the fuel ports are similar to the picture of the venom cylinder at: http://www.mh-aerotools.de/airfoils/cox_venom.htm

I've placed a picture of my cylinder below(hopefully, this is my first time uploading pics). Is this a high performance cylinder?

Also, I've had a hard time finding 1/2a fuel locally so I have been using O'Donnell 30% nitro RTR. They say it has a high percentage of synthetic and castor, but won't tell me the ratios or total percentage. My question is whether this fuel will destroy my engine or is it ok to use?
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Old 05-14-2007, 07:26 PM
  #72  
aeomaster32
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Default RE: Cox Reed Valve FAQ

First, about the fuel. I have run on as little as 5% Nitro, but settle in 10% for Texaco competitions. (Higher nitro increases fuel consumption.) As for oil, I use 20% Synthetic, but make no claims, other than to say it has worked for me so far. Unlike caster oil, you are less likely to end up with gummed up reed valves and pipes.

From your picture, I can only see one inlet port; some later engines, and hotter versions have two ports. Once again, for my purposes, one port is likely more fuel efficient than the more powerful two porter.
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Old 05-24-2007, 01:35 PM
  #73  
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Default RE: Cox Reed Valve FAQ

If the cylinder has the large opening for the exhaust take the slotted end of the wrench and after turning the prop so the piston is out of the way insert the wrench in the port and turn the cylinder off. Let me guess the cylinder is the one with the twin narrow slits. take you exacto knife and with the handle on the #11 blade insert it in the slit like you would the wrench and turn it off. You might break a blade but out of the thousand or so I have built rebuilt I never have. Course I try to make sure that I get the blade all the way from one side of the cylinder to the other. I also try to make sure that I hold far enough down the crankcase not to cut my hand off either. Do this gently as if it is cross threaded it is taking some of the aluminum from the crankcase with it already. take care dray GOSH did I say thousand motors? it may have been more than that. I quick count says I have over two hundred on my work bench right now. Hmmmmmmm
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Old 05-24-2007, 02:01 PM
  #74  
Tim Wiltse-RCU
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Default RE: Cox Reed Valve FAQ

liquidice,

What you have is a common Cox Sure Start engine cylinder. I can see the twin exhaust slits in it's sides. Now it's a little hard to tell from the angle in the picture but if the bottom slit on each side of the cylinder is bigger than the top slit then you would have a Killer Bee cylinder. As for the bypass porting(ports inside the cylinder) the Sure Start shares the same bypass porting with the Venom, Killer Bee and late model TeeDee .049/.051's. The difference the Sure Start has is the exhaust porting lacks sub piston induction that the others have resulting in a slower running engine. I hope this helps.

LAter,
Tim
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Old 05-24-2007, 02:39 PM
  #75  
MJD
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Default RE: Cox Reed Valve FAQ

ORIGINAL: liquidice

I just came across two new cox cylinders/pistons/crankcases to use as spares with my current engines. I noticed the fuel ports are similar to the picture of the venom cylinder at: http://www.mh-aerotools.de/airfoils/cox_venom.htm

I've placed a picture of my cylinder below(hopefully, this is my first time uploading pics). Is this a high performance cylinder?

Also, I've had a hard time finding 1/2a fuel locally so I have been using O'Donnell 30% nitro RTR. They say it has a high percentage of synthetic and castor, but won't tell me the ratios or total percentage. My question is whether this fuel will destroy my engine or is it ok to use?
Any company that won't tell you the total oil content and basic makeup (i.e. 35/65 castor/synthetic for example) is a loser IMHO. "High" oil content in car fuel terminology is not necessarily the same as our definition of the term. In which case the oil might be low for 1/2a use. If so, the engine might forgive you for a while but it is intuitive to say that the wear rate would be higher than normal. The ball and socket joint will likely suffer the most but overall the engine will be wishing it had more and will repay that thirst with shorter service life. How much shorter, 10, 20, 50%? No idea, never tried to wreck one myself (well, not intentionally).

For sport 1/2A se 15% nitromethane minimum, 20-30% better. 10% makes for finicky running in most cases. They burn so little why be chintzy on nitro content? 1/2A's drink nitromethane like milk. Sig Champion fuel with 20% oil is a good alternative if you can find that. Cox 1/2A fuels are 22% oil or so IIRC. In any case, 18% oil is sort of okay and many people use it as I have when faced with no other choice, 20% is more better and personally I would generally be content with it, 22%-ish recommended by Cox and others and I agree.

There's gotta be a hobby shop somewhere around you that carries decent fuel for 1/2A's. Or.. by any chance does this same hobby shop have a bottle if SIG castor oil? If so get some. I don't know what oil percentage this fuel you have is, but if it is 16% like some car fuels I've seen, adding 4-5% castor by volume will bump you up to 20-21%. If you find out what the oil content is by some miracle, add enough to bring it up to 21-22%.

.049/.051 sport models will fly at weights up to the low 20's in ounces - of course this depends on the design. Ther are many classic 1/2A sport models whose typical ready to fly weight was 20-22 ounces. But I cringe at those weights. For good performance you want to hit 16oz or less IMHO, and frankly with the plethora of small reliable radio gear we have off the shelf these days there is little ecuse not to hit that mark. A lot of folks here pride themselves (or at least taunt the others about it) at building sport 1/2A models at 12 ounces and less.

MJD
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