Slow Goodyear Racing - How to get into it!

Slow Goodyear Racing - How to get into it!

Postby ash » Tue Mar 12, 2013 11:19 am

Do you have a need for speed, but not too much?

Slow Goodyear is the easiest class of racing to get into, easiest to survive, easiest to beat the experts and is now by far the most popular in NZ and NSW. This thread is the repository for any information we can collectively collect, to help new people get involved and existing people improve their race craft.

The rules can be found here, starting on Page 15: http://www.modelflyingnz.org/Docs/Gerenal/S03-CL.pdf

The NZ records are here: http://www.modelflyingnz.org/nzrecords.htm

So, for the uninitiated, What Is Slow Goodyear?

It's a simple form of Control Line team racing, the team being made up of a pilot and pit-crew. In practice, people who own a model usually enter as an individual and recruit a pilot or pit man on the day. Best results generally come from teams where both halves of the team know each others' talents and the quirks of the equipment. Three teams race simultaneously in the same circle, for 80 laps in a heat or 160 laps in a final. Fuel tank capacity is not limited, but you are required to stop and refuel twice in a heat, five times in a final. First to complete the required laps is the winner. The top three heat times on the day qualify for the final. Here's a video of the recent Waikato Champs final for illustrative purposes:



You'll notice that the above race was flown over a proper tarmac circle, which is nice, but not available in many places. One of the great merits of Slow Goodyear is that it can easily be raced over a reasonably smooth grass surface. Cricket and soccer fields are good. All it takes is a bigger wheel mounted slightly further forward than the plans usually show.
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Re: Slow Goodyear Racing - How to get into it!

Postby ash » Tue Mar 12, 2013 11:46 am

The Models

Here are some pictures of Slow Goodyear models racing in NZ. The class is based on the UK's Class II or British Goodyear class. A simplified version of the original Goodyear racing class that makes the models easier and cheaper to build and maintain, slower flying and lighter. The models are 1/8 scale profile models of the full size Goodyear and Continental Cup pylon racers of the USA in the '50s and '60s. Profile construction and external workings keeps everything simple. Take a look at the rules linked in the previous post for more details and the pictures below.

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Rather than the array of technical restrictions employed in the UK, our class condensed all that into one rule - a speed limit of 26 seconds per ten laps - 138km/hr. The contest director will generally time the fastest model in a race and warn anyone found exceeding the speed limit. Three warnings means disqualification. The upshot of the speed limit is that you can use whatever 2.5cc engine you like, whatever fuel you like, whatever tank system, shutoff and plastic propeller you like. No need to go crazy on rare or expensive gear. My engine is a $70 ASP15 running on 10% nitro fuel. Others are using ex-F2C Nelson diesels. Some are using Chinese Oliver Tigre clones. All are capable of winning as long as the human elements do their jobs properly. And that is exactly the point of Slow Goodyear.

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Models are generally of light balsa covered in 1-1.5oz fibreglass cloth and epoxy. Wing and tailplane edges are lined with spruce to prevent too much damage in handling and pitting. Strength in the nose region is of critical importance, so there are hardwood engine bearers buried in the fuselage, to which are screwed/glued steel or high grade aluminium engine mounting plates. These are there to provide a hard and tough surface for the engine to bolt to and to spread the loads and vibration out over a wide area. The inboard side opposite the engine is reinforced with a balsa cheek cowl which is covered with several layers of glass cloth. This structure is intended to stiffen the nose against impact or vibration, and to improve the joint between the fuselage and wing.

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Things to come:

Race procedure
Pitting skills
Engine, tank and shutoff installation
Suggested engine list and requirements
Control system details
Fuel bottle and filler valves
Model construction, plans and materials
Regular race meetings, dates and venues
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Re: Slow Goodyear Racing - How to get into it!

Postby ash » Tue Mar 12, 2013 12:11 pm

My slow GY set-up:

~ Clarkson Mr D (Aeromodeller) as per plan, but with external controls/leadouts and a smaller, non-recessed tank.
~ Tank is front feed, suction with a self-sealing filler valve. Overflow splits to vent tube up by the venturi and the exhaust prime.
~ ASP15 (blue head), head clearance lowered to 10 thou, exhaust prime fitted, Brodak 25 NVA, venturi area equal to about a 5mm diameter hole.
~ JXF or APC 7x4 prop
~ Fuel = 10% nitro, 20% Cool Power Pink oil
~ Preferably a Taylor Comp glow plug, but they're out of production now, so I'm looking for something else.
~ Bellcrank is an aluminium Fox 2" one with a steel bush and 1mm wire leadout clips. Leadout guide is made of fibreglass PCB. Lines are 12 thou solid steel or 15 thou stranded stainless.
~ Undercarriage for tarmac is a 1" wheel on a 1/8" wire leg located about 1" forward of the CG. The Grass wheel is a bit under 2" and about 2" forward of the CG.

Image

Of vital importance:
~ Fuel tank is SECURELY mounted via 1mm steel tabs to hard wood + metal threaded insert mounting points epoxied into the fuselage. Vibration, bumps and refuelling action knocks WILL break it loose otherwise.
~ 12 thou stranded stainless lines are NOT strong enough for long life. It works for a while, but after a bit of wear will break at the leadout guide or connections, either during a pull test, shut-off or racing incident.
~ Undercarriage mounts need to be VERY sturdy. Attach with high tensile cap screws, through metal threaded inserts into hard wood mounting points or the engine bearers. If it can rip out, it will.
~ Cheek cowls are there to stiffen the engine mounting and bind the wing to the fuselage. Don't skimp on the fibreglass.

Image
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Re: Slow Goodyear Racing - How to get into it!

Postby ash » Thu Mar 14, 2013 9:59 am

Because I have engines on the brain today, I'm going to start the list of suitable 2.5cc engines for Slow Goodyear.

The only rules regarding the engine are that they must be under 2.5cc. The speed limit rule is a little harder to translate, but suffice to say, there are engines that struggle to go fast enough to threaten the limit and some that want to go a lot faster. Diesel and glow are both acceptable, only your personal preference and maybe the local availability of fuel should affect that choice.

Prerequisites in order of importance:

~ 2.5cc capacity (or less... 2.2cc RC car engines are also perfectly suitable once converted).
~ Runs well, and preferably capable of at least 15k rpm on a 7x5 or 18k rpm on a 7x4 (on the ground).
~ Hot re-starts! This means a good piston/cylinder fit and knowing what it likes. More later.
~ Not too heavy - Anything between 130g and 190g is ok.
~ Not too fragile - hard to gauge, but an engine prone to crankshaft failure or wearing out quickly might not be much fun.

Engines currently in use:
ASP15 (blue head) Glow x 3
Nelson 15 Diesel x 2
Nelson 15 Glow
MVVS 2.5 DFS/R Diesel x 2
K&B 15 RI/SE Glow
Parra 2.5 Diesel
Fora Jr Diesel
Super Tigre X15 Gow
PAW 15 G Diesel
PAW 15 GTS Diesel
CS Tiger Diesel x 2

Out of that lot, the pick of the bunch is probably the Nelson 15 in either Diesel or Glow format. Hard to find and expensive, but they are proper racing engines. At the other end of the scale, the ASP 15 is cheap and easy to get, but they do very well. Probably the easiest way into Slow GY. The PAW Diesels have a great track record in the UK, but not so flash here. The fancy Goodyear tuned ones are very expensive and the ordinary ones are too slow. If I was to make a new Slow GY model, I would seriously consider fitting either a Parra or Fora Jr (the Schnuerle ported one) in standard diesel form (they come with a glow head also). They are light, fast, start well, beautifully made and readily available.

Fora Jr source: http://technohobby.com.ua/online-shop/e ... new-diesel
Parra source: http://www.clubtamaran.com/parramotorING.htm
ASP 15 source: http://www.himodel.com/engines/ASP_S15A ... rsion.html

Other good options
AP15
Cox Conquest 15 Glow
CS 15 Glow (Rossi clone, normal timed liner)
ЦСТКАМ or CSTKAM 2.5 (Rossi speed clones, F2D combat practice engines and possibly others)
MVVS GFS/R
MVVS D7 or TRS Diesel
MVVS DF or DR, GF or GR (front or rear induction, diesel or glow)
Magnum 15S, SC15 (same as the blue head ASP)
Moki C-1 or O-1
OS Max 15 CV-A
OPS 15 (most of the non-pipe-timed ones)
Rossi 15 Mk1, Mk2, Mk3 (Normale timing)
Super Tigre 15 (most of them, although probably best saved for Classic A TR)
Star 2.5 Diesel
Taipan 2.5 Gold-head Glow
Taipan 2.5 Diesel (ballraced ones in good running condition)
Typhoon 2.5k F2D practice engine
Post 1990 Fora, Profi, Cyclon, Stels, Zorro et al F2D engines (will need to be slowed down!)
Pre 1990 F2D engines like Nelson, USE, etc (might be a little easier to tame)
Old F2C engines should work as well as the Nelsons do
Old F1C engines (no geared drives!)
2.2-2.5cc RC car engines (normal prop driver types, of course. Side exhaust preferred)
And many other to be added as they are suggested...

Basically any 2.5cc, Schnuerle ported ABC or AAC engine stands a pretty good chance as long as they conform to the prerequisites above.

Notes on the above:
Some of those will be perfect in stock form, but some will need tweaking. Those with built-in spinners like the various Rossi clones will need the spinner removed and replaced with a conventional prop driver. Other than avoiding the pointy, bulky, weighty spinner, it's a pain in the butt to change a prop in a hurry when it's hidden behind one!

Needle valves and venturis may also need to be looked at for size and practicality. Diesels will probably want to be in the 3.5-4.0mm range. Glows in the 4.0-5.5mm range. This of course depends on how powerful the engine is to start with. Ex-F2D engines with a stock 4.0mm venturi will be way too fast and might not run properly on suction as their venturi is designed for bladder pressure. They also have low-profile needle valves that can be tricky to adjust in a hurry. Replacement with a Super Tigre style needle valve assembly is recommended for all that don't already have one. More details on that another time. If you don't have the skills or equipment to perform such mods, just ask here or on CLNZ. There are lots of capable volunteers around.

Glow engine heads can often be improved in various ways. Getting the head clearance down to around 10-12 thou is good for power and re-starts. The actual figure depends on the head volume an other factors, of course, so experimentation may be required. In an ideal world, a head suitable for Nelson glow plugs would also be recommended. They are much tougher than normal glowplugs and can deliver more power. That's strictly optional, though. Not many people have bothered outside of the regular Nelson users. More info on engine mods will come at a later time.

Fora Jr - Excellent option:
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Cox Conquest - would need the spinner and F1C brake removed:
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Stels 15S F2D engine - would need a new small diameter venturi for suction and ST NVA. Already has a Nelson Glowplug head:
Image

ASP 15 - Cheap and quite capable of winning. Has a home made venturi and Brodak 25 NVA:
Image
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Re: Slow Goodyear Racing - How to get into it!

Postby FerARG » Sun May 14, 2017 11:30 am

Hi, mi name is Fernando Magnetti; I`m from Argentina, we are currently flying control line goodyear with diesel engines, but find ether its getting very hard, so I want to try a glow engine, Some fellow have tried with some succes with as old OS15FP.
I have see your posts about the ASP s15a so I have get one from aliexpress, I first want to say thanks to Ash that give us a lot of precise information, but I want to ask for explanations about the head clearence, what do you mean with "head clearance lowered to 10 thou"?. You increase the compresion by lowering the head 10 thou, or lowering the head "to" 10 thou from the piston o cylinder?
My english is not precisely "native" as you can see, So I`m very gratefull from now for your time and patience
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Re: Slow Goodyear Racing - How to get into it!

Postby ash » Wed Aug 23, 2017 7:55 pm

Hi Fernando,

Head clearance is the distance between the piston face at top-dead-centre (TDC) and the squish band of the head.

Image

On a standard ASP15 it might measure as much as 25 thou (0.635mm), which is not close enough for racing. I increased compression by lowering the head until it was 10-12 thou (0.25-0.30mm) away from the piston at TDC. You can do it by removing the head gasket or using a thinner one, or by using a lathe to cut away the head deck where the gasket seals against the head.

Here's a simple way to measure head clearance. Be careful not to damage the engine when squashing the solder. Use very soft solder.
http://www.ausrc.com/forum/showthread.p ... -Clearance
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