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OS30 FS fuel...


Jonathan M
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I have an OS30 four-stroke, bought new a few years ago, which I'm about to run in (and for which I'm about to build a suitable airframe).

 

I very happily use Model Technics Bekra 10 (18% mixture of EDL and Klotz oils) in my Irvine 53 - I particularly like the fact that the residue it leaves on the airframe is relatively un-sticky, etc.

 

Am I correct in assuming the wee modern four-stroke will run perfectly well on this, from run-in onwards?

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I'm sure it'll be alright.

 

I run my Japanese and Chinese four-strokes on Southern Modelcraft Synthetic Based fuel which contains 10% nitro and 17% oil made up of 15% synthetic, ML 70 oil, and 2% castor oil. I plan to go fully synthetic once current stocks are exhausted.

 

Incidentally, a few weeks ago I accidentally forgot to pack my four-stroke fuel and arrived at the flying field with fuel containing the same oil content but only 5% nitro. The Japanese four-strokes ran quite happily on this fuel without much needle twiddling.

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Oh dear. . . A thread which asks for advice on fuel is guaranteed to get locked fairly quickly. 

 

There is a certain fuel which is quite probably the best fuel in the world but if anyone dares to recommend it, it will result in shouty posts from someone who will pour scorn on the stuff and will tell you it's rubbish. 

 

It's a shame really. 

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32 minutes ago, Brian Cooper said:

Oh dear. . . A thread which asks for advice on fuel is guaranteed to get locked fairly quickly. 

 

There is a certain fuel which is quite probably the best fuel in the world but if anyone dares to recommend it, it will result in shouty posts from someone who will pour scorn on the stuff and will tell you it's rubbish. 

 

It's a shame really. 

You must be talking about 30% Nitro and 20% castor oil😀, for added protection you can always add a bit more oil.

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3 hours ago, Jonathan M said:

I have an OS30 four-stroke, bought new a few years ago, which I'm about to run in (and for which I'm about to build a suitable airframe).

 

 

I run 3 of this size Jonathan, in a Seagull Decathlon 40" ? span, A Seagull Jumper, and a homebuilt airframe,  all around 3lb AUW and importantly found that the prop was more affective than fuel, as the same motor in 3 similar airframe would not fly on the same prop?

To comfortably fly 3lb Decathlon 9 x 5, Home built 3lb 30" 1 0 x 6, and the Jumper 9 x 6.

So as always considering fuel, try a few props too.

 

Found a picture. The little electric Decathlon with modified engine bulkhead

IMG_20231028_083836.jpg

Edited by Denis Watkins
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The bekra wont hurt it but it will be a bit messy and thirstier than it needs to be. I think the bekra klotz contains castor too but need to double check as i think opti might have changed the recipe. 

 

Ideally i would recommend the fuel i always do being 5 nitro and 15 synth oil. I use this in all of my OS's and while i dont have a 30 any more i do have a 26 and a pair of 40's so have it surrounded. 

 

The TLDR is the brekra will be fine for it but may not be optimal. It will however be better than other options that are likely to be promoted. 

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2 hours ago, Brian Cooper said:

Oh dear. . . A thread which asks for advice on fuel is guaranteed to get locked fairly quickly. 

 

There is a certain fuel which is quite probably the best fuel in the world but if anyone dares to recommend it, it will result in shouty posts from someone who will pour scorn on the stuff and will tell you it's rubbish. 

 

It's a shame really. 

When did Carlsberg start making model fuel? 

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35 minutes ago, Learner said:

Impossible on here Jonathan

 

You'll get yes, no, maybe, maybe not, a few links to you tube and google and 50 pages later you'll just have to try it and see😉

...and thank the Universe that is the case. It would be a very tedious forum with just Yes or No answers, or worse still those queries which request an answer by email or PM  or close the thread if the questioner considers that their question has been answered.

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3 hours ago, leccyflyer said:

...and thank the Universe that is the case. It would be a very tedious forum with just Yes or No answers, or worse still those queries which request an answer by email or PM  or close the thread if the questioner considers that their question has been 

Maybe but the op asked for a yes or no answer. I stated he wouldnt get one and you proved the point!

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Jonathan: I have an OS 20FS, and I ran it for years on Bekra 16% without issue. Its currently in storage awaiting a suitable model's turn on the building board, but I had a look at it recently, and its still in excellent condition. Bekra 10% should be absolutely fine. Heli fuels are generally intended to run in hot environments, such as found in helicopters - and 4-strokes!

 

Jon (Laser) & MikeT: Bekra doesn't have any castor at all. It is pure synthetic, mostly Klotz Techniplate with a trace of EDL IIRC. It is "Super-Techniplate" that has castor. I have no idea what Optifuel are doing with it, but the original formulation definitely had no castor at all. If it had, I wouldn't be using it!

 

Ben Godfrey (original owner of Bekra) who formulated it had a lot of experience with racing two-strokes, as he was heavily involved in the Yamaha motor-bike racing team many years back. Sadly, he's no longer with us to consult, but my son and I were involved in the testing of Bekra fuels during their development. The only change made to it from the original formulation was increasing the oil content from 15% to 18% because of OS's warranty conditions. All that did was make more mess........! And Ben HATED castor oil! 😉

 

--

Pete

 

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2 hours ago, Jonathan M said:

Thanks to everyone who's contributed.

 

The next step (and ultimately more important I'm sure than the choice of fuel) will be to ensure that I run the engine in as carefully and fully as possible.

 

If the engine is new and unrun i recommend removing the rocker cover and cam cover to allow plenty of 2 stroke oil to be tipped into the engine. Turn it all around, then stand it up in such a way that most of it will drain out of the crankcase breather over night. OS do pack their engines well, but its been many years since that engine was discontinued so i would be tempted to throw some more oil at it. 

 

After that fire it up or something small ish from the range of props. run it rich at half throttle for a minute or two to warm up, full power, tune for about 90% of peak and throttle back. Get the slow run setting half decent (remember the carb is air bleed and the screw works in the opposite way to a twin needle). Run it in this state of tune up and down the throttle range with a few full throttle blasts about 5 seconds long. Once you have about 10 minutes on the clock pinch the fuel off to stop it, let it cool, restart, tune for peak power and then go flying. 

 

The OS instructions are more conservative than the above to help defend against those who's throttle only has two positions. If you can fly a normal flight with full use of the throttle up and down there is no need to mess about. 

 

Oh, and make sure the tank is in the right place. Top of the tank, centre of the carb. Small engines are less tolerant of this sort of thing and the image below is lifted directly from the OS30 manual. I know they show the top of the tank above the carb, but the fuel level is clearly indicated and as most of us never have an air gap at the top of the tank its easier to just line up the top of the tank with the carb. 

 

877852314_feultank.jpg.061e67e19c2263e7e1889111d10112df.jpg

 

 

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I can confirm Jon's assertion about the fuel tank position! I mounted my 20FS inverted in an Attilla, and had no end of issues with it until I cut a new hole in the bulkhead and lowered the tank to the floor! Even a Perry oscillating pump wouldn't fix it with the tank in the model's designed position!

 

And yes! It was a pain cutting a new hole in the bulkhead of a completed model! But it completely cured the problem!

 

--

Pete

 

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Pete - good to hear your experience and the extra detail on Bektra, thx.

 

Jon - thanks for the advice on running it in, and the pre-oil too.  I'd read the instructions through a couple of times, your method effectively does the same thing in less time.

 

BTW I needed to move home a year ago and, with a ton of stuff to lose from the old gaff plus thinking I was going to wind up in an urban flat, I needed to be radical and took the decision to sell my IC models, and gave away associated kit and sundry accessories to a club-mate.  I did however keep my modest collection of mostly NIB engines (this OS 30FS, a 35AX, a SC32, the ASP 70FS from my old Acrowot, and a Laser 80).  I'm now actually renting somewhere with a garage and small garden, so I have recently bought back the Irvine 53-equipped Gangster 63 Lite I built a couple of years' ago and my flight-box etc.  The local club is very close by and fine with IC (although everyone else flies electric) but the Gangster really needs a bigger patch, and I'd prefer to keep the noise levels down for the broader (future) benefit of the club, hence the decision to to get the quieter 30FS up and running and build a suitable model for it... what that model might be will be the subject of a separate thread!

 

PS - how come I can't buy any 1/8" fuel tubing anywhere?!

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1 hour ago, Peter Christy said:

Jon (Laser) & MikeT: Bekra doesn't have any castor at all. It is pure synthetic, mostly Klotz Techniplate with a trace of EDL IIRC. It is "Super-Techniplate" that has castor.

Thanks for clarifying/correcting, Pete.  Just shows what a minefield this topic can be.

For instance:  you have to wonder why Klotz chose to use the prefix "Super" on the version of Techniplate that does contain castor!

Like many, I'm sticking to SM, where a little castor helps the rest of the oil slip through...😀

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I just had an afternoon flying my Baron with its OS 30fs, I had changed my fuel from a greasy oily castor mix to one so called std 4 stroke mix, I flew my Saito100 with it all of this week ( 2 litres of fuel ) with just a tweak of the main needle, but the OS 30Fs it didn't like it one bit !,

it even needed the main needle opening 1/2 a turn as I could hear it starting to sieze up, so I will be adding some of my favorite sticky oily stuff to it.

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1 hour ago, Jonathan M said:

PS - how come I can't buy any 1/8" fuel tubing anywhere?!

 

3/32 i/d is standard tubing and more than man enough for the job. I use 3/32 on every glow engine i own and there are no fuel flow problems even up to 50+cc engines. 

 

40 minutes ago, Paul De Tourtoulon said:

so called std 4 stroke mix

 

'4 stroke' fuel is a marketing thing. All fuel is the same with methanol, nitro and oil in it. I do not know why the 4 stroke fuel thing started. It was probably to try and flog people two gallons of fuel and not just one. 

 

40 minutes ago, Paul De Tourtoulon said:

I could hear it starting to sieze up

 

No you couldnt. Running fine to total seizure takes fractions of a second and it will all be over before you know its even happened. I have seized a few (or more) engines testing things at work and there is no way you can hear it and take any action to prevent it happening. The best i have managed is to detect it and throttle back preventing the rod snapping and minimising my cleanup work. It might not be locked solid, but the rod bush will have seized and the rod will need replacing. There is no way you can hear it, do something, land, throw bean juice in your fuel, and then go again with no damage. If it had seized it would be dead in an instant. 

 

Its more likely the engine got hot or was mistuned and this was the labouring/loss of power you heard. 

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10 hours ago, David Davis said:

I'm sure it'll be alrig

 

I run my Japanese and Chinese four-strokes on Southern Modelcraft Synthetic Based fuel which contains 10% nitro and 17% oil made up of 15% synthetic, ML 70 oil, and 2% castor oil. I plan to go fully synthetic once current stocks are exhausted.

 

Incidentally, a few weeks ago I accidentally forgot to pack my four-stroke fuel and arrived at the flying field with fuel containing the same oil content but only 5% nitro. The Japanese four-strokes ran quite happily on this fuel without much needle twiddling.

Hi Dave a wise move going over to fully synthetic .The fuel you describe i think is SMC Double lube Hi . Thier synthetic fuel is just that and doesnt contain any castor. I have used this for years now and have mine mixed with lower oil content at 17% and recently moved to their Laser mix that contains 15% synthetic oil and whatever % nitro I want/ need and found it to be very good. I have heard through the grapevine that SMC will be taken over at the end of the year and the new owner intends to start mail order.

Four stroke fuel from years gone by had a couple %  extra oil in it and made propper mess. But back then engine production techniques werent as sophisticated they are mow so may be those old engines needed extra oil to run in . Like cars back on the 1960's you could buy a special "Running in " oil. Remember that all oils have improved a great deal over the years and As Jon says it was probably continued as a a marketing ploy just to sell more fuel.

 

I have heard through the grapevine that SMC will be taken over at the end of the year and the new owner intends to start mail order.

A big thanks to Dave Watts and his wife for their fuel and friendly chat at the shows over the years. They will be missed.

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14 minutes ago, Engine Doctor said:

Hi Dave a wise move going over to fully synthetic .The fuel you describe i think is SMC Double lube Hi . Thier synthetic fuel is just that and doesnt contain any castor. I have used this for years now and have mine mixed with lower oil content at 17% and recently moved to their Laser mix that contains 15% synthetic oil and whatever % nitro I want/ need and found it to be very good. I have heard through the grapevine that SMC will be taken over at the end of the year and the new owner intends to start mail order.

Four stroke fuel from years gone by had a couple %  extra oil in it and made propper mess. But back then engine production techniques werent as sophisticated they are mow so may be those old engines needed extra oil to run in . Like cars back on the 1960's you could buy a special "Running in " oil. Remember that all oils have improved a great deal over the years and As Jon says it was probably continued as a a marketing ploy just to sell more fuel.

 

I have heard through the grapevine that SMC will be taken over at the end of the year and the new owner intends to start mail order.

A big thanks to Dave Watts and his wife for their fuel and friendly chat at the shows over the years. They will be missed.

 

 

I don't think so ED. The fuel I bought from Southern Modelcraft contains 15% sysnthetic and 2% castor as stated above. See 10% Nitro Synthetic Based in the attached list. The Double Hi Lube contains 9% synthetic and 9% castor as this June 2023 listing confirms. https://www.southernmodelcraft.co.uk/model-fuels.php

 

I did buy a gallon of Double Hi Lube from Dave on my way to Dover several years ago. This was intended for my HP VT engines but I sold one and gave another away. I still have a 49 and a 25 which I ought to sell really as I have no plans for them.

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Hearing it siezing up, is when you are flying flat out for a few seconds, even though you have peaked it out on the ground and for good measure opened it up at least a 1/4 of a turn before take off, is when you can hear the rpm dropping off  shutting down for a few seconds to cool it down then flat out again and the rpm drops off again, thats what i call an engine siezing up, to hot as not enough lubrification.

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