Black Ditch

One week and counting

With one week to go before Black Ditch everything was looking OK - not great but OK. I would drive down on the Friday towing the craft, ready for the Saturday morning. What could possibly go wrong?

Well, the wife decided to crash the Discovery. Especially in the headlight area - the sort of damage that the police really notice when you're driving down the motorway, pulling a weird load...

I no longer had a towing vehicle that could make the trip, but I wasn't going to be put off that easily. I phoned around the local hire companies for a car with a tow ball. Nobody had one. What about putting the craft in the back of a van and sleeping in it when I got there? I'd need.a Luton van for the extra width (for the hovercraft not me). Eventually I found a company that had one that was just big enough inside to take a 1.9 metre wide hovercraft, but not with the tail lift mechanism on the back! The hovercraft was 8cm (3 inches) too wide!

Things were getting tricky...

Ready to go
Then suddenly I had an offer from a hovercraft club member (who I had never met) who was going to Black Ditch, didn't have a hovercraft, and was happy to tow mine all the way there and back.

What could I say?

YEEEEEEEEEES PLEASE !

<----- You might recognise these lovely people.


We arrived mid afternoon in time to help with picking up the grass from the course mowing operation. As evening came, more and more people arrived, and someone started putting up their tent next to mine in the beam of their car headlights. It turned out to be Henry Evans (a familiar name from the bulletin board but no relation). Henry introduced me to the others and we went off to the cider tent for the evening, to try a pint or two of Cheddar Valley...


A neat solution! A neat solution!
An interesting solution to hovercraft transport and on-site accomodation all in one!

It reminded me of something from Thunderbirds but this is Team Spectrum.


My main goal for the weekend was to get the craft scrutineered. No one with any hovercraft knowledge had ever seen my craft, and although I had followed the club's Construction Regulations to the letter there was always a chance that I had misinterpreted something. Failing scuitineering wouldn’t be the end of the world though, as I was happy to correct any mechanical faults over the Winter and get it retested at the first race meeting in the Spring of next year. What I was really worried about was the floatation test. That’s where they send you out into the middle of the lake and you switch off your engine and sit there for 5 minutes to see if it can float like a boat. My worry was that the hovercraft might simply be too heavy, and water would then come in through the air feed holes in the underside of the hull. If that happened then it would be fundementally too heavy (and it would sink). Therefore, it could never pass scrutineering and the whole hovercraft project would have been a disaster.

So when I woke up on Saturday morning I wasn't very confident because today was:


Judgement Day


I warmed up the engine and gave the throttle a blip - the short grass was very different to the cow field I had practised on and I got lift at low rpm - things were looking good. I had a very technical discussion about my engine overheating problem with real Engineer-types Paul FitzPatrick and Tony Broad. This resulted in me getting to the bottom of the problem and borrowing Tony's radiator cap during the weekend, which completely solved the boiling problem. Thanks guys!

Scrutineering

I was just attaching my race number (N143, which Pam in work had made for me) when Jon Spedding the scrutineer came over to do the mechanical inspection. He is the club’s chief technical guru. He looked it over thoroughly and asked for a little extra guarding around the prop shaft (not an immediate problem), but apart from that he seemed very happy with it.

Sink or swim

Then there was the dreaded floatation test. With the compulsory life jacket on I approached the lake and stopped above the entry ramp . At the bottom of the 10 metre long ramp the bank seemed to meet the water at a sharp angle – the sort of angle that might make the bow dip under the water. I sat there for a while, waiting while they cleared a pair of swans off the lake, then suddenly spotted a 6mm hole in the floor panel – the hole that I had used as a centre point when cutting out the curved front of the floor panel, and hadn’t got round to plugging. I got out, explained the problem, then legged it back to the pits to get a nut and bolt to fill the hole.

Having plugged the hole it was time to hit the inevitable water. I edged forwards and the craft slid down the ramp and onto the water. There was no splash, no jolt, just a smooth transition onto the surface of the water, and off I went towards the middle of the lake. I may as well have been driving on ice. The craft wasn’t floating – it was planing over the surface, and because it wasn’t displacing any water there was negligible wake – a weird feeling indeed. I got into the test area, and switched off the engine, allowing the craft to drop into the water and hopefully float. Everything looked OK and I started counting. I had 300 seconds to wait. I kept looking around for signs of leakage, and to check to see whether I was floating level. The inner cockpit area was dry, but was there any water seeping invisibly into the air chambers inside the hull? I couldn’t tell but I seemed to be floating sufficiently high that at least the 70mm air feed holes to the skirt (all 57 of them!) would be above the water line. I moved around a bit and wound the rope around the starter cup ready to go again ASAP.

The seconds ticked past very slowly and I eventually, on my count of 320, Jon waved me back in. What a relief. I pulled the rope, the engine fired immediately and I turned to face forward, but as I turned, my knee pulled the lanyard safety line and the engine cut out again! I rewound the starter rope and tried again. This time the rope slipped and it didn’t start! I told myself not to panic and tried again. It started fine and I revved the engine to generate lift, and edged forward. I was now still creating a hole in the water, but there was a 6” air gap beneath the craft and I had to get over the hump of water in front of me. This is a well known problem in hovercrafting and there is no guarantee that a new craft will have the power to weight ratio to achieve it.


Floatation test


I increased the power and I could see that I was slowly catching up with the ripples that were trying to move away from me. I leaned forward to transfer my weight to the front and suddenly I was back in planing mode, accelerating over the water. I headed for the exit point and went up the ramp as smoothly as I had come down, no bump, no contact with the ground, just a wallowy ride up to ground level.


 
Success
I drove carefully back to the pits with a huge smile on my face. The hovercraft worked, it really worked!


Safety

Following the floatation test I had a safety talk (from Dave Polfrey) about warning flags, stopping distances, collision avoidance etc. Dave's talk taught me a lot  and really made me think. Then we did a driving test which was more about attitude than aptitude, (which was just as well since at that time my total hovercraft driving experience amounted to around 1 mile).  The stopping distance experiment showed that even at a slow speed it took me about 7 metres to stop in a straight line, so sometimes it might be better to go round a stationary craft rather than try and stop before you get to it.


Timing

Timing tag
I was given a timing tag to fit to the top of the duct.

Keith Oakley has developed a computerised timing system for hovercraft racing. This transponder is triggered when it passes through an infra-red beam at the start-finish line. It then transmits its id by radio to a receiver which logs its time. Very clever indeed.



Racing

Then I was ready for my first race. As a novice you need to complete 15 races before you are allowed into proper Formula 3 races. Entering a race doesn’t count as completing a race, so if you break down, crash, sink, or get thrown out too early the race won’t count towards your total.


Ready...


Picture from Paulz Video at http://www.hovercraftvideo.co.uk
Used with kind permission
If you want a DVD of the highlights of the year's
hovercraft raceing check out his website


I approached the starting grid, expecting to be put at the back, but for some reason the starting marshal called me to a space on the front row. I stopped my engine and waited for the 2-minute board. Then one of the marshals pointed out that one of my race numbers was missing! I got out, ran back to the pits and grabbed a roll of gaffer tape and my other race number and legged it back to the grid with Tony Broad. We stuck the race number to the side of the duct just in time.

The red lights came on. All four of us revved our engines to get cushion pressure and the lights changed to green! We were off – well they were off. I had no intention of racing into the first corner. I was just concerned about getting around the course as many times as possible.


The first corner was a sweeping 180 degrees which took a bit of getting used to, especially as another craft suddenly appeared from behind me – maybe they had started from the pit lane. Then there was a 200 metre straight (easy bit) before a bit of a dog leg on the approach to the lake. The entry into the lake was exciting to say the least. I had tried it during my floatation test, but this was now at a much faster speed. Again the craft slid down the bank and I out across the lake towards the first water corner. I turned to the right, but the craft carried on, sideways now, and I could feel myself sliding quickly towards the bank. I turned further, so I was then travelling backwards and revved the engine hard. The extra thrust slowed me down, but then I was back in displacement mode, crawling along. I gave it more power and moved my weight forward and within a few seconds I was going again. I headed across the lake towards the exit ramp, which now looked like a wall of mud in font of me. Again the craft had no trouble getting over it and once again I was back on dry land heading for the starting line which meant that I had completed a lap.

Expert

   This is how it's supposed to be done - Conrad Beale in his Pintail


As I got used to driving, things got a little easier. I managed to get round the water corner without stopping or hitting the bank, and started to plan the corners a bit better. At one point I was lapped by a faster driver / better craft and the sides of our craft met. But as we were both going in the same direction this was not a problem. The real problem was when I got overtaken and the thrust air from the back of their craft caused me some difficult handling problems.

After a couple of laps I noticed that the steering had started to get a bit loose. I could turn, but there was a lot of play in the system which meant precise steering was impossible. This even made maintaining a straight course difficult, and as I approached the water entry ramp I got it completely wrong and ended up on the bank to the right of the ramp facing backwards. The marshals started waving their flags and I thought my race was over, and that they would try and pull me back onto firm ground away from the racing line. I hadn’t really had enough of a race at that point and I was rather disappointed. Some helpers came over and I realised that I had the option of being pushed into the lake to carry on, so I motioned to them to give me a push, and I was quickly back on the water and back in the race.

In the lead ?

Although it looks like I'm in the lead, here, the truth is that everybody else is coming up to lap me!




Two laps later I was rounding the land corner and the combination of sloppy steering and lack of experience meant that I spun out into a shallow ditch in the infield where the grass was uncut (it’s difficult to get lift in very long grass). I was unsure of what I should do. Was I allowed to leave the engine running, get out and pull the craft back onto the course, or was I supposed to wait it out? After the safety briefing earlier that morning, and the dodgy steering, I decided I would wait it out, and as I had been lapped (maybe more than once) it didn’t take long for the race leader to go passed the chequered flag. The recovery car soon turned up with the trailer, and so with me sitting in the craft we were towed back to the pits. OK so I didn’t complete the race but I had gained a lot of experience, and I didn't come last!

As it turned out I was allowed to get out and pull the craft back onto the racing line – as long as it was safe, but with the steering problems I probably did the right thing in sitting it out. Someone told me that it’s only after you have been towed back can you call yourself a proper racer.



fool!


Sunday’s race was similar to Saturday’s. It was a case of gaining experience, rather than trying to win.


Vrooooom


At one point I realised that I had lost most of my lift and on turning round I saw that all six corner skirt segments were flapping loose. In addition, the steering was getting worse (again) so after 3 laps I ditched the hovercraft in a safe spot off the circuit and waited for the race to finish. I still didn't come last though!
back to teh pits
This time when the recovery car came round I decided that I would try and get back to the pits on my own, and I managed to limp home back to my parking area under my own power, which was satisfying.



Smile


<-----   It's hard to look miserable when you're so happy!


What a great weekend. A well organised event, very friendly people, success with the scrutineering, a little success with the racing (I didn't crash), and to top it all some wicked cider drinking.

Saturday was the culimination of 1000 hours of work over nearly 2 years and was probably the most exciting thing I’ve ever done. So thanks to everyone who worked on the event to make it so successful.

 
 

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