View Full Version : Bristol Channel Cruise May 2010

Ross Floyd
15-Sep-09, 11:51 AM
22nd May 2010 Weston/Clevedon/Portishead area Cruise

Just a heads up for those with craft that are suitable for operation in the somewhat treacherous conditions of the Bristol Channel.

I am trying to arrange a cruise which will be a first for hovercraft and likely to get quite a lot of media attention. All entrants will need to collect about 100 in sponsorship as a minimum as it will be in aid of one of the local rescue services.

You will need fuel for about 4 hours ( including safety ) and suitable emergency gear for tidal conditions. Your craft must be reliable - rescue in our area is good, but recovery of the craft can be a nightmare.

Also - and this is important - craft will have to operate for a long time at 10 kts efficiently and without dropping below hump speed.

I have approval in principle for this trip, although there are many pitfalls - however if you want to do something that will be fun and as far as I know a first, then keep the date clear.

I'll post more information when we have it but at this point it is just a heads up for anyone interested.

Sorry to be vague - those who know the area will probably guess where we hope to go, but as ever, it is sensitive to make public until everything is in place.

If anyone is interested can they PM me please.


15-Sep-09, 03:53 PM
Also - and this is important - craft will have to operate for a long time at 10 kts efficiently and without dropping below hump speed.

Just before I sold my craft which was capable of very slow speed cruising, I tested it's ability to achieve a speed of 8 knots which is the speed limit on the Medway. The measured hump speed was 12 knots with a realistic slow cruising speed of 15 knots.
I doubt that any craft could achieve an over hump speed of 10 knots. If someone's got one that can, I'd like to see it.

You may have to re-evaluate this rule.


Ross Floyd
15-Sep-09, 04:23 PM
My BBV3 will Gavin - a bit on the edge but she will hold that speed without continuous power changes.

Its a worst case issue and I hope we will be given some leeway - but if not then it could become important.

John Robertson
15-Sep-09, 04:42 PM
I puttered into a harbour with a 3knot speed limit a couple of times this weekend. I was probably doing 6mph rather than 3 knots (I haven't got a replacement GPS yet :o) but the craft was still out of the water apart from the extreme back end. Technically it wasn't over hump (about 12mph or so) but the hump wave was under the back end meaning it was in low spray mode and wasn't dragging the skirt or needing large amounts of power to move.

15-Sep-09, 05:59 PM
i got five months to finish building me craft :)

are you going to try to fly into the dock?

Ian Brooks
15-Sep-09, 08:36 PM
Last year a bunch of craft, led by a Griffon 2000, did a circuit of Portsmouth harbour at 10 knots. We were under strict instructions not to pass the Griffon which kept the 10 knots - and no-one did. It's do-able.

Technically, the hump speed depends on the craft length - it appears at a Froude number of 0.57, and works out at 6 knts for a 10 foot craft, or 8 knts for a 18ft craft. Having said that, this is theory and not many hovercraft have read the books!

The key to it is being lightly loaded - with a low cushion pressure the hump wave is less steep and spray is less.


Ross Floyd
16-Sep-09, 07:43 AM
Last time we were out I was trying to see how slow we could go before falling off hump and my GPS made it about 6 kts before she sat down in the dip. I doubt speed will be a major issue but we can NOT go blasting along regardless - and nothing is finalised at this stage....


16-Sep-09, 08:20 PM
I was one of those men at Portsmouth and 10 knots can be done. Ross this is great stuff and look forward to more details. But for now sign me up i will worry about fuel when more details are revealed.