fuel cap creation

fuel cap creation

the furthest thing on my mind

In August 2023,  my partner and I decided on a whim to purchase a narrow boat. It cost me my Classic Car  as a part exchange, and my Partner, Heather a dunk in the canal…

Our Purchase was subject to us hiring the said boat for a long weekend from Napton Narrow Boats. Heather had never been on a Narrow Boat before and was purchasing half of it with me. I drove my Classic Car up to Napton on one of the few days of great weather last year, where it was parked in the marina’s car park. We had a great time, so on arrival back from 42 locks in 4 days and a deliberate baptism of fire for Heather, we agreed to purchase the boat from Napton Hire Company. Meanwhile, however, Howard from Napton Narrow Boats had fallen in love with my cherished car, and asked if I would consider a part exchange… A few emails and days passed; I then had more space in the garage.

A couple of weeks later we picked up the boat to travel to our new moorings in Newbury. It took us 12 days, and once again we had a fantastic weather - an Indian Summer. We could not have planned it better. On Day 2 of the trip from Napton, Heather pushed us off from the towpath, decided to give an extra shove... and did a perfect impression of a gang plank… The result - at 08:15 of an October morning she fell flat into the Oxford Canal. When she came up with a mouthful of the canal’s finest, my immediate thought was she is safely stood up, unharmed physically, although mentally may take a while. But we are going to have to laugh at it... as being 'baptised' into Narrow Boating, or maybe the quickest ownership of a boat. Well, our friends expected it to happen. “Did you get it on video??” Sadly I did not … she has taken to boating like a duck to water. WhatsApp is fast ...

So now lets take our boat around the network and return home every 10 to 14 days to cut the grass, pick up post, etc. We are both semi-retired so can afford this luxury!

Pul Barnes Cap Lock

Gary - manufacturer

However, this would mean leaving the boat along an unsecured mooring for a few days at a time. As in most cases of purchasing a boat things needed to be added, repaired ready for the new season. Paint, heating, and fitting locks. Purchasing a fuel tank lock became difficult, it was just not going to happen. Many people had drilled into the top of the hull to fit a hasp (then risk water leaking into their fuel), or welded the hull. This was not my preferred method. After scouring forums and chit chat I found I was not alone.

So my idea...

Inspired by the KISS methodology (Keep It Simple Stupid) I thought simply place a ring under and held in place by the original Cap, Then Cap-it securely with a standard end cap. My neighbour Gary has access to most things metal and my thoughts were to use a piece of scrap off cut of tubing. Inside Diameter large enough to slot over the neck of the filler, secure a tab for a padlock. Source a cap from a piece of larger tubing with the Diameter to cover my existing cap. Weld another tag... bob’s your uncle - secure fuel cap!

The great thing about Gary is, that apart from being on the same page as me as to where the world is going wrong, and how to put the worlds to right (all over a beer), is that we both share a passion for perfection. It's so easy to cobble together some bits, but to engineer something to last and improve it, simply for the satisfaction of getting it right, is something else altogether.

The MK 1

With a Kellog’s Cornflakes box template, Gary cut enough for 4 ! I actually said I only want one and there was no rush, as we were not going out of our marina for a month or two. Gary’s reply was “There is: I am retiring at the end of the month!!" So time is paramount.

Soon the MK 1 was fitted. Just one week from idea to manufacture. It was perfect, and it looked brilliant. I then thought of a possible way of improvement for the cap so that it would take a determined thief twice as long to break in. You can't stop a determined thief, just make them take longer, so that hopefully they get caught, or at least move on). So in the process of designing a simpler way to build, Gary made it faster to assemble, and the more secure unit was created. We both thought maybe others may well be in the same boat (pun intended) so why not try to see if we could sell the Mk 2’s .. primarily to ‘p’ off the thieves.

I placed a simple listing on Narrow Boat Market Place, and 4 hrs later received so many questions, and thumbs up - and promptly sold out of the remaining units. Links were shared across Facebook with some great comments and encouragement from Gerry from CanalsOnline Magazine. It has been great!



We have refined the MK 2.2, registered our design and have gone to manufacture. I took some of the MK2.1’s along to a narrow boat festival to ask people if it would it be something they would consider purchasing in the future and any feed back was welcome good or bad.

Many people have a deck fitting … an adapter just needs to be tested out and available as an option, coming soon.

We have now manufactured the final product ready to sell, week 8 !! with some great features:

  • These units are high quality with a powder coated finish.
  • British Design and Manufacture.
  • No Drilling or Welding required.
  • Will fit if your cap has an air vent fitted. (2 options are available).
  • Costs Less than ½ a tank of replacement fuel should the worst happen.
  • Not only is it a deterrent it is a real heavy duty anti theft device.
  • The unit can be sold Naked in bare steel so if you would like to paint and colour match it to your boat, you also save £7.50.
  • Changing Boat? Take it with you!

Additional information you might not know

  • RCR’s Call-out Surcharge of £50.00 if you have no fuel, 2/3rds the cost of a cap.
  • Insurance Company advice is to consider a locking Fuel Cap not only to prevent the inconvenience of being stranded, but also against vandalism if some idiot decides to top up your tank with some liquid or solids, not compatible with a Diesel injector or filter…
  • Flushing a Fuel system, changing filters or removing tank debris is very expensive.
  • Prevention is always better than cure…

All good quality products come at a cost. Yes we could make it cheaper, but only if we wanted to see a Chinese or Indian manufacturer benefit. But we don’t. Our product is Made in Britain - to good “old” British Values and Engineering Standards. Nothing better!


fuel caplock

caplock logo

With "Caplock", Paul Barnes has come up with a highly polished product for boaters to secure their fuel. Made to British Standards, entirely manufactured in Britain, and at a price that will not break the bank.

07810 547754