STEWART RAE (Aka ‘SCOOP’) with some useful thoughts about painting and construction techniques
I was hoping to report on the second of the Willen Winter Series (Alf Price Trophy) of races from Milton Keynes, but if you cast your mind back a few months you will remember that a lot of snow fell upon us with freezing temperatures for several weeks around Xmas. Now iced up lakes and model powerboats (well almost any model boat in fact) do not mix very well so the race scheduled for January was cancelled with just a few days to go as we were hoping for a quick thaw, but it never arrived! Willen MPBC were hoping to reschedule the meeting for a later date during February, assuming the weather does not intervene again.
I have received a note from Mike ‘Digger’ Barnes (who was the lucky recipient of the OMRA AA Class boat build in the August 2009 issue of Model Boats) regarding the painting of his boat. Mike has never spray painted a boat before and advice was sought from fellow OMRA members Mark Wild and Stewart Rae.
The advice given, was make it look good but don’t spend ages on it, the reason being that when you are racing it’s going to get scratched, bumped or worse still wrecked in the inevitable collisions which happen occasionally (tongue in cheek)!
We understood Mike’s desire to do a proper job for the paint work so the necessary advice was given and here’s how he set about it. I must say at this point that the photos really do not do the quality of finish Mike has achieved justice. The boat arrived at Mike’s via Santa in the usual white gel coat so this had to be prepared in order for the paint to properly adhere to it.
First, the hull and deck were sanded down using a fine wet and dry sandpaper to ‘roughen’ up the glossy gel coat surface to allow the primer/sealer to bond to the hull. The grab handles, aerial, propshaft, rudder and internals of the hull were then masked off using low tack masking tape and paper. Normally hulls are painted before any hardware is bolted on to them, but in this case it would have meant stripping everything off the hull, Mike therefore chose the masking route.
The hull was then suspended from the garage roof at a height to allow access to all areas and the hull and decking were washed down to remove any dust or sanding debris and then left to dry.
Once thoroughly dry, the hull and deck were sprayed using a clear sealer/primer to ensure good adhesion for the following coats of primer and finish. After a few hours of drying time three coats of grey primer, with a good half hour between coats, were applied and this time it was left for three days for the paint to harden. He then sanded down the hull and deck to remove any imperfections before applying another two coats of primer, whence the boat was then left for one week for the paint to harden before it was given a very light sanding with fine wet and dry sandpaper ready for the top coat.
Mike had chosen a bright red top coat but with a white lower section. Normally hulls below the waterline are left in the gel coat finish but he wanted to use this hull (as it was his first experience in paint spraying) to see how good a finish he could obtain using two different colours, if only for his own satisfaction.
The first three coats of red paint were applied leaving thirty minutes drying time between coats and then left to harden for three days before another very, very, light wet and dry sanding to remove a few bits of dust that had settled in the paint. Then another three top coats were applied and the whole thing was left to harden for a week.
The hull was then masked along the chine line ready to apply the white topcoat to the bottom of the hull and these were applied in exactly the same manner as the red paint. The hull was then left to harden for a week before four coats of clear lacquer were applied which gave the whole boat a deep shine. (The quality of finish was that good you could use it as a mirror for shaving - Scoop)
Whilst all this was going on, Mike had prepared the driver figures for painting as it is an OMRA rule that any model with an open cockpit requires at least one ‘head and shoulder’ driver to be fitted. Both driver and navigator figures were mounted on a piece of timber to allow easy access to all surfaces for painting using Humbrol enamels. The time taken together with a steady hand was well spent. There are a few parts left to be refitted such as the exhaust, figures and cooling water outlets (one for the engine and one for the exhaust) before applying the transfers and then finally get off to the lake for testing. So this is how Mike Barnes described the task to OMRA News in January this year.
Mike has achieved an excellent finish on his boat and should be proud of it. This was an exercise which not only tested his new found skills but also his patience as on its third race outing another boat was seen to scramble over the top of it, decapitating both driver and navigator figures and also putting deep gouges in the lovely paint work!
Ah, well! At the other end of the spectrum I (Scoop) use a can of primer, a quick wet and dry sand (the hull not me), a few top coats using Halfords spray car paint, then ‘T’ cut and polish off any overspray and off I go to the lake. Not the best paint job in the world close-up, but it looks okay on the water and it doesn’t matter if it gets a few knocks and scratches on the way, that’s racing for you! Mike took the sensible route into offshore racing by running one of the smaller less powerful boats for a year so he could learn the trade at a reasonable pace, but he is now building a D Class petrol boat ready for the 2010 season which just happens to lead me into the next article.
What do you actually need to build a petrol D Class boat?
First of all when building any model boat you need to be aware of the Health and Safety implications. Glue’s, resins, paints etc. are toxic, so use in a well ventilated area. Dusts generated by sanding, filing and cutting are also a health risk so use a good dust mask over your nose and mouth. Goggles or some form of eye protection are a must as well (you only get one pair of eyes in this life so look after them!).
Some of the chemicals used can also cause skin problems so a pair of protective vinyl gloves is a good idea (my wife often ‘loses’ her marigolds!) and as you will also be using power tools plus very sharp cutting instruments and abrasives, always comply with the manufacturer’s instructions when using these chemicals and tools. Take care and think ‘safety first’, because if you think what you are doing could be a bit on the dangerous side, then it probably is!
I have listed here the basics for a D Class powerboat build, and this is roughly the same for any powerboat project apart from using different engines and fuels, but I don’t want to give too much away as Mark Wild will be writing an in depth step by step guide to building a petrol powerboat in a future issue(s) of MB
Requirements for building a D Class racing boat
A hull, typically 58 inch long and around 14inches in beam.
Petrol engine, usually 26cc in stock or tuned form.
Tuned pipe, made from aluminium, steel or stainless steel.
Fuel tank, stock or custom built, and typically1.5 litres capacity.
Radio box, again a stock item, or it can be custom made, but needs to be waterproof.
Propshaft, coupling, stuffing tube and propeller.
Rudder, trim tabs and turn fins.
Radio gear, 27/40MHz or 2.4GHz.
Floatation foam or airbag in the model.
Fuel and water tubing.
Various glues, resins, paints, cleaning solvents, fibreglass matting and tape.
Petrol, two stroke oil, greases.
Power tools and associated equipment, files, knives, sanding papers and masking tape.
T Cut and polishes.
P.P.E. (Personal Protective Equipment)
These are made from glass fibre and resin, carbon fibre/epoxy or a mixture of both, There are many hulls available such as Pacer, Phantom145, Magnum, Stealth and Apache.
26cc petrol engines come either in stock or tuned form; typically Zenoah, Sikk, RCMK or the new British designed and built Shy-Tot 26cc tuned motor from Arrow Racing Products.
There are many available from various sources, you get what you pay for.
These are made from petrol resistant plastics, aluminium or steel as stock items or can be custom built. 1.5 litres in size is normally good for a half hour run using a tuned motor.
These can be made from almost anything. Stock items are usually plastic and have a rubber sealing ring fitted in the lid. Do not use Vaseline as an aid to the seal as it is a petroleum by-product and will react with the rubber sealing ring, I use a silicone based grease on my radio boxes.
Propshafts, stuffing tubes, stingers and propellers
Flexishafts or solid shafts are made from steel or stainless steel and usually inserted in a Teflon coated bush. The stuffing tubes (propshaft outer tube) are made from either brass or stainless steel. Stingers support the propshaft and a few different makes are now coming to the market, normally made from aluminium and containing the bushes to support the propshaft. Propellers come in various sizes and are usually made from aluminium, copper/beryllium or stainless steel. Please note that when balancing and sharpening a propeller the dusts generated are highly toxic.
Rudders, trim tabs and turn fins
Rudders are normally made from good quality aluminium; turn fins come in either aluminium or stainless steel; trim tabs are normally stainless steel.
This is available from all model shops. For surface use in the UK you may only use 27 or 40MHz or 2.4GHz equipment. The quality varies and you get what you pay for. Two channel r/c is the minimum you need with one channel for the throttle and one for steering. Always purchase a quarter scale servo for steering as the standard servos are not powerful enough for our boats. Recently I have received a few comments regarding temporary loss of control when using 2.4GHz sets, which appear to have been affected by the Bluetooth technology in some mobile phones. However, these 2.4GHz sets are becoming more common, mainly because of their not requiring any frequency xtals.
If your boat flips over and there’s no buoyancy in it, then it’s more than likely going to sink. Do not use the white polystyrene that comes in packaging, I know it floats but it is also readily dissolved by petrol causing a gooey and highly inflammable mass. You will need to set aside approximately 20% of the internal volume of the hull for floatation. I use the swimming tubes (the ones that look like huge candy bars) available from most good sports shops. They are easily cut to shape and can be bonded in with a bit of silicone sealant.
Fuel and water tubing
Always use ‘Tygon’ tubing for petrol as this fuel will affect silicone tubing and you will end up with a white gooey residue in your fuel filter or worse still the carb. Silicone tubing is fine for the water cooling of your motor/exhaust.
Glues, resins and paints etc.
There is a vast choice on the market, so ask a fellow powerboat builder what he uses is your best bet for a sensible answer, but typically superglue, Araldite, polyester/epoxy fibreglass resins, David’s Isopon P38/P40, Halfords car spray paints, HyCote and Humbrol enamels to name but a few.
Petrol and two stroke oil
I run a tuned motor which requires super unleaded petrol with a 16:1 oil mix. Stock motors use either a 20:1 or 25:1 fuel/oil mix.
Fire extinguisher and PPE
Need I say more, the stuff you will be using is either toxic in its raw state and or inflammable so remember ‘Safety First’ and always work in a well ventilated place and wear your personal protective equipment.
Before spending your cash on any old boat you see on eBay etc., why not pay a visit to one of our race venues and see what is really required to build a petrol boat. Ask any OMRA member for advice, which no doubt will be eagerly given. We don’t bite and we might even save you a bob or two.
Hopefully next month I will be reporting on Round Two of the Willen Winter Series, weather permitting of course.
If you would like further information regarding OMRA please visit our website: www.omra-uk.org where you will find links to suppliers plus a plethora of information. Prestwich Models website: www.prestwich.ndirect.co.uk or Ian’s Boats website: www.iansboats.co.uk are both sources of materials and equipment, but do ensure you make it clear that your requirements are for offshore racing rather than multi-racing as there can be differences. Alternatively, please give the OMRA PRO (Stewart Rae) a call on tel: 07711 594063.