Category Archives: Hovercraft

A weekend’s racing – Hackett’s lake

Last weekend, 25-27th May, saw Spindizzy out and about with the HCGB National championships. We were racing at a big lake in Nottingham known as Hackett’s lake.

The weather was sunny and quite still for Saturday. It became very windy by Monday afternoon.

Spindizzy had a few technical problems. Lumpy starting, pull-start ropes snapping. It’s been treated to new plugs, caps and leads. With the help of Kevin Foster the ignition timing was set up properly and it was starting fine after that. Unitl… Monday morning when it died on the water and I’ve not been able to start it since. Hmmm…

 

Steering

In June 2012 I took Spindizzy as a work in progress to a race meeting in Nottingham and it’s at events like this when you find out who your friends are.

The Sweetman clans saw how I was getting on and descended “en masse” to help out. They helped me fit a pair of rudders, pinched from RO3, some bike handlebars , routed the cable and generally moved the project on a great deal.

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Β 

This next photo shows the morse cable going inside the hull at the front to reappear at the back. Any guesses as to where the silver metal piece came from?

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Engine and Fan frame

0822c6ba7a7c14b34cd9f429b5060a2bRO3 was going to be a bit gnarly but for Spindizzy I didn’t want anything too fierce. In addition I also wanted an engine that would be easy to start and relatively trouble free. Nothing too close to the edge.

For those reasons I chose a Rotax 447 microlight engine. These engines have been around since God was a boy and are well used and understood. They are no longer in production but there are plenty about. the also have the advantage the because of a quirk in the UK racing regs they can be used in F3,my old stomping ground, F2, because they are between 250 and 500cc two stroke, F50 because they are weedy enough and FJ for the same reason.

It’s a twin cylinder two stroke making about 40BHP so it’s not going to set the world on fire but it’s good enough.

I had the engine frame made by Ken Rigley of K&M products near Newark. Ken has been doing Rotax frame for a long time and he just needed the diameter of the duct at the point furthest forward and the height of duct. He didn’t ask me what colour and I didn;t think there would be a choice. I was a bit surprised when it turned out red but as I was building a red craft anyway it didn’t seem to matter.

Hull, duct and planing surface

So, for this build I was going to need a hull and planing surface as before.

When I originally bought the moulds for the Outlaw I got a plug from which I pulled a mould. I still had this plug.

It is basically a top deck, a little heavier than I would like but perfectly servicable and good to go. It needed a lick of paint but that could wait.

85ffe21bfadbd70eecb52846a680a80aNext, a planing surface. As you know by now I have a mould and so I pulled a planing surface from that. The construction was just the same as Randomorbit 3’s planing surface.

So now we’re up and running.

I asked Les Bran of Bran Fibre to make me an 800mm duct and he duly obliged. I made a GRP box to fix it to the hull but didn’t take any photos of the process. Oh well.

Random Orbit 4 – Spindizzy

716aa4a3c46345cd7fbf08f91640a668Progress was slow on Random Orbit 3. This was a big build and was taking too long.

I decided a change was going to have to be made. My Son was fast approaching eleven and here in the UK junior racing starts at eleven.

I though RO3 was going to be a bit too powerful and gnarly for Jack and so I decided to shelve this build and start another, simpler, craft that we could both race.

Now, I am not one to waste a good name and so this one is Spindizzy.

As I now had the moulds and because I really liked the design, it made sense to go with another Outlaw.

A temporary halt

Things have been going very slowly on this build as you can tell.

The plan was to build a gnarly F3 shaft drive and see what I could do in that. However, it has taken too long to get this far and my Son is now 11 and old enough to race. The problem is that I don’t want to put him in a big heavy F3 that he will struggle to control.

So, I’ve decided to put this build on hold a make something he and I can both drive.

Here’s to Spin Dizzy.

Flow straighteners

After fitting the duct to the hull it is time to fit some flow straightener vanes. There are some basic rules here.

  • You need a different number of flow straightener to the number of blades you have. This avoids a nasty beat frequency as all of the blades pass in front of all of the straighters at the same time.
  • They need to have some shape to guide the air from its swirling path off the blade to a flow parallel to the sides of the duct.

I borrowed some moulds to make a set and all was going well unitl I tried filling them with foam for strength and the deformed beyonr recognition πŸ™ My old freind Dan came to the rescue wth various vanes he had lurking in his collection. Not only that but he came rounod to help me fit then and also had a pair of rudders. Top man.

The duct

VLUU L200  / Samsung L200The duct is 1M in diameter, quite large for an F3 but I figured it would be about right for this craft. The duct was made by my old friend DanΒ  who was doing it as a plug for a duct he was building and it was no longer required.

I collected it on a filthy night, strapped to the roof of the car as you can see. You can make out the Kevlar containment area that should hold everything together if a blade lets go and tries to leave through the side.

There is also a flat “plate” running all round the duct. This is to help to keep it circular, particularly where the blades run. It’s quite hard to stop a duct from flexing and as long as the part with the blades in stays circular, the rest can move around a little.

The planing surface

074456a094d63b73f15a88acce6a5b13The Outlaw mould was made ready to take part

Next the various layers of Chopped Strand Matting (CSM), Diolen and Kevlar are cut/torn and laid out on a ground sheet until needed.

36f33050fbe0ffb8392f327294b95707The finished part was popped out of the mould after a few days…

But took an amount of mould with it.

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