Currently, members of the public are permitted to acquire, import, possess and use products containing Nitromethane if the concentration is thirty per cent w/w or lower. Anyone wishing to acquire, import, possess or use Nitromethane at concentrations higher than 30% (up to 100%) has to apply to the Home Office for a Poisons and Explosives Precursors License.

At the time of writing the Home Office are undertaking a consultation on amendments to the Poisons Act 1972. There are three proposals put forward:

Option 1 – Make no changes to the existing regulations

Option 2 – Strengthen and clarify measures within the current legislation, but not change the substances and concentrations that members of the public can acquire, import, possess and use provided they have a valid license. This would effectively enable members to continue using concentrations of up to 30% Nitromethane with no requirement for a license.

Option 3 – This would lower the threshold for the license requirement from 30% to 16% nitromethane.

Members of the public can respond to the consultation either online or by completing a downloaded form. More information can be found on the Gov.UK website

The Consultation closes at 11.45pm on the 10th March 2022. When we have any further information, we will keep you updated in future editions of Propwash and here on the website.

Everybody knows it’s there, but few, it seems, really know much about it. Although most seem to know- at least vaguely – that’s its primary purpose is to add power. At best, there is much misinformation regarding this somewhat exotic ingredient. Let’s see what we can do to clear some of it up.

What is model fuel made of? Why do I need such a special fuel? Can I use something cheaper?

Model fuel is a blend of methyl alcohol (methanol), Nitro-methane (Nitro), and oil. Methanol is the main ingredient and provides most of the power. Nitro is added to assist the idle and acceleration, as well as increase power. The oil that’s in the fuel is the source of lubricant for the engine.
Methanol is used for two main reasons:

• It can be ignited with a platinum-element glow plug.
• It releases more energy per pound of air than gasoline. It’s also very easy to obtain and is inexpensive.

Nitro-methane is used to enhance power output. It acts as an oxidizer as well as a “hot” fuel in its own right. It’s not used in large amounts in most model engines because it’s too powerful a fuel for the way model engines are made…it’s just too “hot”. It can also be explosive if it’s not handled correctly…ever see an AA-Fuel dragster or Funny Car explode?

Oil

Oil is used to lubricate all of the moving parts in the engine. Like all two-stroke engines, there’s no oil sump, so you can’t put oil into the engine and just add fuel. The oil is mixed into the fuel. Oil used in model fuels can be made from a single product, or a blend of products. The oil that used to be the most common was castor oil. This is a product refined from castor beans (like soybean oil comes from soybeans). It’s the same oil you’ll find in the drugstore, but it’s been processed to make it less gummy and with fewer solids than the medicinal type. Lubricating castor oil is not certified for human internal use, though, so it’s not a substitute for medicinal castor oil.

Castor oil has been replaced in most fuels by some kind of synthetic oil. The synthetic oils used in model fuels are basically synthetic versions of castor oil. The synthetic oils are used because they are: 1) less expensive than castor oil; 2) less gummy than castor oil; and 3) leave less mess on the model than castor oil. They are not “better” oils, but oils with different characteristics that are highly desirable. For “problem” engines, a fuel with some castor is highly desired, because it is actually a better lubricant at the operating temperatures a model engine can generate.

Blending

Nowadays, “Premium” fuels contain a blend of synthetic and castor oil, hoping to combine the best characteristics of each. “Sport” or “regular” fuels are usually 100% synthetic oil. Very few model fuels use 100% castor oil, but they are still available from some fuel manufacturers.
An “ideal” fuel blend for most model engines would be 20-22% oil, 10-15% Nitro, and the rest methanol. The various percentages of the ingredients are percentages of the volume of fully-mixed fuel. These numbers are controversial.
Some fuel manufacturers claim that their lubricant is so good that you need less of it, so they have lower oil content. Many advantages are claimed from this…some are even true. Lower oil will allow an engine to throttle up faster because there’s less oil to get in the way of the combustion process. There’s also less oil to give you a margin of error in case the engine gets a bit lean for some reason.
A lot of times, oil quantity is reduced so that the cost price of the fuel is lower, and the fuel manufacturer can increase profits by keeping the price at the same level as full-oil fuels. In fact, cost is the main reason most fuels are blended with about 18% oil. While it’s lower than the “ideal” fuel, it still has enough oil to give good protection.
Just about the only thing that can be added to a basic fuel are some ingredients that help the glow plug fire off the mixture inside the engine…these are called “ignitors”. Propylene oxide is an example of an ignitor that’s been added to fuel in the past. Some rust-inhibiting compounds can be added to help slow down rusting of the bearings and crankshaft, but their effect is limited because only a small amount can be added to the fuel before the fuel’s performance is affected.

Storage and fuel care

Yes, there are ways to care for fuel so that it will stay good while it’s being stored.
First off, it should not be stored in unsealed containers. This allows air to get into the fuel container. Moisture in the air will be drawn into the fuel because methanol has a very strong attraction for water. The two will mix easily and readily. Once model fuel becomes contaminated with water, the engine’s performance will suffer. It won’t idle, it will be hard to set the needle properly, it will tend to run hot…all in all, it will be a mess.
When somebody has running problems, one of the first things to recommend is to try running the engine with brand new, fresh fuel.

Nitromethane is just one of a family of chemicals called “nitroparaffins.” Others are nitroethane and nitropropane. Nitroethane can be used successfully in small quantities. (Top fuel drag racers, which generally run on straight nitromethane, sometimes add a little in hot, humid weather to prevent detonation). At one time, nitroethane was only about half as expensive as nitromethane, but its cost now is so nearly the same, using it to lower cost is hardly worth the trouble. Neither of the nitropropanes will work in model engine fuel. Incidentally, nitromethane is made of propane, in case you didn’t know (and I’ll bet you didn’t).

Powerrrr!

Yes, NITRO = POWER! But there are conditions and contingencies. First of all, it doesn’t add power because it’s such a “hot” chemical. Not at all. This may come as a surprise to most readers, but the methanol (methyl alcohol) in the fuel is by far the most flammable ingredient – nearly twice as flammable as nitromethane. As a matter of fact, if nitro were only 4 degrees less flammable, it wouldn’t even have to carry the red diamond “flammable” label! In actuality, nitromethane must be heated to 96 degrees F. before it will begin to emit enough vapours that they can be ignited by some sort of spark or flame!

So, how does it add power? We all know (I think) that although we think of the liquid part substance, we put in fuel tanks (in our automobiles or model airplanes) as the fuel, in truth, there is another “fuel,” without which the liquid part would be useless. Remember what it is? Right – just plain old air (in reality, the oxygen in the air). Every internal combustion engine mixes air and another fuel of some sort. In our case, a liquid – glow fuel. The purpose of the carburettor is to meter those two ingredients in just the right proportions, and every individual engine has a requirement for a specific proportion of liquid fuel and air. Try to push in too much liquid without enough air, and the engine won’t run at all. That’s the purpose of the turbocharger on full-size engines – to cram in a lot more air than a simple carburettor or fuel injection system can handle.

Now, suppose we were to find a way to run more liquid through our model engines without increasing the air supply? That would add power, wouldn’t it? Well, guess what – we can! An internal combustion engine can burn more than 2 ½ times as much nitromethane to a given volume of air than it can methanol. Voila! More Power! That’s how it works, and it isn’t all that complicated. Nor do we have to spend a lot of time thinking about it in the course of a normal day’s running. However, there are some factors we do need to consider. As a practical matter, virtually all our everyday running can be done on model fuel containing from 5% to 15% nitromethane. There’s probably no reason why 5% won’t work perfectly well. Need a little more power? Move up to 10% or 15%. In most of our sport engines today, that’s enough. Most of the popular engines on the market today are built to run on something very near that blend. Typically, European engines will successfully run on lower nitro blends, because they are built to do so. Why? In Europe, nitro is pretty expensive?

More than power

Nitro does more than just add power. It also helps achieve a lower, more reliable idle. One good rule of thumb for checking to see if a particular engine needs a higher nitro blend is to start the engine, let it warm up for a few seconds, set throttle to full idle and remove the glow driver. If it drops rpm, move up to a 5% higher nitro blend. If there is no discernible drop, you should be fine right where you are. One of the most popular misconceptions is that by adding substantial nitro, the user will immediately achieve a huge power jump. Just isn’t so. Most will be surprised to learn that in the 5% – 25% nitro range, you will probably only see an rpm increase of about 100 rpm static (sitting on the ground or on a test stand) for each 5% nitro increase. On the water, it will unload and achieve a greater increase, and it will probably idle better, too. If you have a model that’s doing well, but just isn’t quite “there” power wise, go up 5% in nitro. If that doesn’t do it, you need a bigger engine, not more nitro! Most of our popular sport engines in use today aren’t set up to run on much more than 15% or 20% nitro.

Increasing the nitro has the effect of increasing the compression ratio, and each specific engine has an optimum compression level. Exceed it and performance will probably suffer, not gain, and the engine will become much less “user friendly.” High performance racing engines, for example, are tuned entirely differently – compression ratio, intake and exhaust timing etc. – and are usually intended to run on much higher nitro blends. The first question that comes to mind, then, is, “Why aren’t all engines designed to run on no nitro, so we can all save a lot of money?” Ask any of the World-class competitors. Those engines are a difficult to tune and run, and are definitely not user-friendly! In fact, they are well beyond the skill levels of most average modellers.

There’s a price to everything. Another statement we read or hear frequently is that nitromethane is acidic and causes corrosion in engines. It isn’t acidic, and the manufacturers say it doesn’t happen – can’t happen. However, at least one noted engine expert and magazine writer insists that it does.

Costs

Why does nitro cost so much? While I have no clue as to the cost of manufacturing, other than it takes a multimillion-dollar investment in a large refinery to produce it, there is one pretty good reason: There is only one manufacturer of nitromethane in the Western Hemisphere. Figure it out for yourself. Also (and this will come as a big surprise), our hobby industry only consumes about 5% of all the nitromethane produced; and full-size car racing about another 5% or so. This means we have no “clout” whatever, and simply must pay the asking price. Where does the rest of it go? Industry, It’s used for a variety of things – a solvent for certain plastics, insecticides, explosives (yes, it was an ingredient in the Oklahoma City bombing) and I’m told it’s an ingredient in a well-known prescription ulcer medication (no wonder that stuff is so expensive!).

Boom!

Please note that while nitromethane is an ingredient in making some explosives, under normal use, it in itself, is not explosive. (Remember, the bomber used fertiliser, too). Hardly a month passes that someone doesn’t ask, “I hear more nitro will make my engine run cooler. Is that true?” Nope. The higher the nitro content, the higher the operating temperature. Fortunately, in most of our sport engines, the difference in operating temps between 5% and 10% is negligible, and there are lot of other factors (proper lubrication, etc.), that are much more important.

Finally…

Remember in the beginning of this, we said that nitro adds power because we can burn more of it than we can methanol, for a given volume of air? This also means that the higher the nitro content of the fuel, the less “mileage” (or running time) we will get. What’s the practical side of this? If you go to a higher nitro blend, be sure to open your needle valve a few clicks and reset before you run. Otherwise, you’ll be too lean, and could hurt your engine. Conversely, if you drop to a lower nitro blend, you’ll have wind it in a little.

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Let’s start with basics: Exhaust timing raises power band on a 2 stroke engine, but with too high timing comes a loss of torque. With modern boat set ups and remote adjustable pipe movers, you have the best of both worlds being able to adjust pipe length whilst in motion and under load.

Induction timing is another critical part of a 2 stroke engine for power gains. Closing the timing later and/or opening earlier can increase power, but this has to be balanced with transfer port time and exhaust. For example, too high exhaust or late closing induction can cause engine bogging and the higher the tuning the more temperamental an engine can become. But when you get it right you can get more torque and rpm and bhp.

Torque is key in model boats as it allows you to swing bigger or higher pitch props. With high nitro content fuel, you can gain a lot of torque and can raise other timings for improved performance.

Head squish is also a power gain area, but too high a squish will result in power loss, but the engine may rev higher. If the cylinder head volume is not correct, this will cause detonation, (Visible pitting on the head and piston) and too low squish will cause a loss of performance. A correct volume head with high nitro and correct engine timings will give you a powerful motor.

It’s all a balancing act to get the best boat performance – Pipe, fuel, gearing, props, engine mods.

Engine bogging can be seen quite often. Too high a timing of ports or the pipe being too short can cause this. Testing is the key to getting everything working together.

There are various engine tuning programs available for example Prestwich can supply one.

For tuning, typically you will need a Digital Vernier, Dremel with diamond burrs and polishing stones.

Thanks to Dave Pillman for this article. Related Article

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There’s no such restriction in model boat racing however, and the most successful racers will have tested extensively before the season starts, and do so continuously throughout the season. Importantly, this testing needs to be focused, evaluating one change at a time. We have seen racers run lap after lap of ‘testing’ with the only end result being more wear and tear on the boat and it’s components. We also see some racers making multiple alterations in one go and end up not being sure which change worked and which did not.

Weather and water conditions play a major part in boat performance. In the UK, pre-season tests are typically done in outside temperatures of 10deg C or even less. This has a major impact on engine performance, often resulting in less than optimal combustion temperature in high nitro content fuelled boats. Thus, successful testing is mostly comparative by nature rather than measured on say outright speed.

Endurance racing is all about lap time. The goal is to consistently produce low lap times. A boat that can corner quickly with little or no loading will generally beat the boat that has a couple of extra km/h down the straight but bogs in the corners. So you will typically start by trying to build a boat with low weight to achieve the highest power/weight ratio. You then perform comparative tests to determine the best gear ratio and propeller combination, together with fuel/air mixture, compression, tab settings and tuned pipe length.

The more sophisticated (And expensive) radio control equipment now offers real time telemetry including engine revs, temperature, battery level and speed via GPS. GPS speed readout is an invaluable tool for evaluating performance. There are limitations to GPS in that it is not always a true reflection of outright speed so it is best used for comparative testing at the same location. A key performance consideration when choosing a GPS telemetry system is the frequency of update as an endurance race is run on a relatively small (In GPS terms) course. Popular systems include Multiplex<, Futaba, FrSky and HiTec

Some of the main things that you might change in testing are:

• Gear Ratio – Endurance boats use reduction gearing to allow the engine to rev higher than the propeller. The purpose of this is to keep the engine in it’s peak power range providing the torque to turn larger propellers. Typically a 3.5cc boat gear ratio will be between 1.85:1 and 2.11:1. Testing with different gear ratios will determine the optimum balance of speed and corner pickup.
• Pipe Length – Most competitive racers these days will have a radio-controlled pipe length adjuster. This mechanism allows the racer to shorten the pipe length on the straights and lengthen it for cornering. There are many ways to operate the pipe adjustment – Some will do this with channel mixing, others manually via a transmitter control. Depending on the sophistication of the RC equipment, it is possible to setup the adjuster so it lengthens instantly and shortens slowly, potentially improving pickup. It is important to simultaneously richen the fuel/air mixture when shortening the pipe or the motor may run too lean resulting in blown glow plugs or engine damage. Tuned pipe theory from Prestwich models.
• Propeller Size – Propeller performance has improved dramatically since the arrival of accurate CNC machined props that require no balancing. The prop is the easiest thing to change on a boat. The goal is to find the propeller that provides the best speed without any loading or unwanted torque effects which may upset the handling of the boat. It is not always the case that largest is best, but rather the largest that is suitable for a particular gear ratio.
• Trim tabs – Most top racers will have at least one trim tab on their boat. On a 3.5cc boat this will be a torque tab to counteract torque effects of the propeller. Some 15cc boats will have 3 tabs left, right and centre and sometimes these are controlled by a gyro that automatically generates servo inputs based on the pitch and roll characteristics of the model as it travels along the lake. Generally you won’t see 3 tabs in a 3.5cc boat as the weight penalty would probably outweigh any benefit, but 2 is common, the centre tab being used to raise or lower the nose of the boat. During testing, you may adjust the mixing of the tab(s) with throttle or rudder.
• Nitro content – A higher nitromethane content in your fuel will give you more torque, but depending on ambient and water temperature, high nitro can result in less than optimal combustion temperature. There is also a cost and availability element to it. 25% is probably considered average with up to 40 or even 50% in the 3.5cc class at the extremes.
• Compression – The compression can be altered by adding or removing shims between the liner and head button. More compression is more power, but there will be a point where reliability is affected and breakages begin to occur.

So in conclusion, there are many parameters and components a racer can change on his boat and it is by methodical one step at a time testing that optimal performance will be achieved.

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Congratulations to all the Endurance qualifiers for the 2018 iMBRA World Championships:

Three team members had already claimed their place through great results at iMBRA Internationals during the season: Zack Humphries (3.5cc) with a fantastic double win in the European Championships in Hungary and the overall iMBRA Western League. Martin Fields (7.5cc) with great results including wins in Oudenaarde and the GB International qualifies through the iMBRA League, as does Ian Folkson (27cc) with a string of consistent podium finishes in Gonzaga, Oudenaarde and the GB International.

3.5cc – had the highest number of entrants and almost certainly the largest group of quality boats/drivers with the potential to qualify. GB Drivers Champion Mark Wraight set what proved to be an unbeatable score in the 1st round. Despite a mishap in round 1, Leon Morgan showed his big race experience by putting in a great 2nd round score, even making an unplanned fuel stop! Dave Marles drove a superb 2nd round to put all this seasons reliability issues behind him and help make up for missing iMBRA 2016. A few eyebrows were raised by the top class driving from Martin Hillstead to grab the other spot, leaving more than a few experienced international racers rueing what went wrong.

7.5cc – Dave Marles drove a perfect race with his best boat. Probably only Martin Fields can challenge Dave’s 7.5 when everything is working properly and many expected this was the class he was certain to qualify in. 2 out of 2 and Dave was on a roll. Geoff Parmenter continued his good form from the NDC races with a solid drive to qualify and make up for the disappointment in the 3.5. Experienced international racer Robert Daniel has had a lot of success with his 7.5 boat and he drove a measured race to ensure qualification. Julian Waumsley’s Pegasus was fast and reliable as usual giving Julian a fairly comfortable qualifying run. No real surprises in the 7.5cc class and many would have predicted these guys to make the team.

15cc – A walk in the park for Phill Fields. First in the water in both rounds and top scorer in both. 2 Perfect runs to complement his win at the GB International last month. That man Dave Marles makes it 3 out of 3 by reigning in the power when necessary and keeping out of trouble. Zack Humphries tiptoed his Boudicca through the race after a stop in round 1 to make sure of qualification. Zack can go a lot faster but he’s not 100% happy with the handling of his current boat and we expect we’ll see a new one for 2018. Sam Lincoln drove a faultless race to edge out Mikey Hillstead and maybe put a small smile on his dad’s face despite Mark not making it in 15cc this time.

27cc – No surprises here. James Taylor wins with a different boat in each round also setting the highest laps of the day. Mick Pain drove a steady race as usual to grab the second place. And would you believe it? It’s 4 out of 4 for Dave Marles who has qualified with every boat he entered! Dave was obviously as humble as ever taking the plaudits! Steve Baxter qualifies easily with his speed.