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Old 13 June 2003, 05:18   #1
Country: UK - England
Town: plymouth
Make: avon searider 13ft
Length: 13ft
Engine: johnson 55 1979
Join Date: Jun 2003
Posts: 1
Stop Flooding Hull Flooding Advise Please?

I have a avon searider 13 ft with johnson 55hp 1979.

I use the boat in the harbour at low speed in very calm conditions mainly.

I am considering sealing of the flooding Hull to see if the boat handles better at low speed(full of air not water). It seems to be pushing a Ton of water infront of it all the time, even at a couple of knots!

Can I do this?

If I can , has anyone any advise about doing it.

What is the design reasons for the flooding hull?

many thanks


David Hills is offline   Reply With Quote
Old 13 June 2003, 05:47   #2
Country: UK - England
Make: Ribcraft 6.5
Length: 6m +
Engine: Suzuki DF175TG
Join Date: Apr 2002
Posts: 929
Hi Dave,

Welcome to the forums..

Have a look at the thread below, some info on the sealing of a Avon 5.4 Searider.

DJL is offline   Reply With Quote
Old 13 June 2003, 06:20   #3
Country: UK - England
Town: Whitstable
Boat name: Tango
Make: Avon and Narwhal2.4m
Length: 4m +
Engine: 60HP Yamaha
Join Date: Oct 2002
Posts: 966
Blanking plug

Hi David

I've also got a 4.7 metre searider and the flooding hull is blanked off, i've been told the flooding hull allows the hull and tubes to sit lower when the boats at rest, this is needed as Avons have a steep v shaped hull that sits and rides high, this gives it that increadable sea keeping ability which even the smaller boats have in larger seas. Mines blocked at the transom with a small plastic screw in bung and the two holes on the bow are filled with big screws which i assume are sealed in in some way, this was done by the previous owner and i've not experimented with taking the bung and screws out yet and probably wont, as the boat runs great with it blanked and sits ok at rest, i have however checked and the hull is air sealed as when the screw bung comes out there is a rush of air, maybe when looking at boats this would be a good indication if the hulls air tight or not, mine in this case seems to be.
I can get my boat to plane at very low speeds even with my small 50 on the back she runs extremely well reaching speeds of 30 knots on a flat sea and corners like its on rails and even in very tight turns at full speed i seem to have very little problem with cavitation.

Bilge Rat is offline   Reply With Quote
Old 13 June 2003, 17:25   #4
Country: Ireland
Town: Ireland
Boat name: Ally Cat
Make: Several
Length: 6m +
Engine: Several
Join Date: Oct 2000
Posts: 333
Hi David,

The Searider range are essentially a military craft designed for boarding and dive support operations.

The mother of the range was (is) the SR 5.4 metre boat generally fitted with twin 40s or a single 90. There are now a wide range of seariders from 4 to 7 metres.

They have several unique design features. The flooding hull with a large 4-5" hole in the transom below the floor to let in and vent water and a 1" hole on either side of the bow below the floor to allow air in to allow the water at the stern to vent out is common to all.

The benefits are that the boat sits on the tubes at rest and displacement mode making it easier for divers to board a lower craft. Also you have the inertia of 1/4 tonne of water in the hull which makes for a much more stable platform while at rest in heavy seas. The downside is that she takes a few second longer to get on the plane while a 1/4 tonne of water is dumped out the stern. If you hammer on the power from rest you just get lots of cavitation / ventilation.

Another feature is that the consoles are usually set off to starboard allowing more room on the port side to move from fore to aft. This is vital on a military craft for boarding ops.

They are a boat I have a soft spot for . The boats we used for the original Shannon Sprint record in 1992 were bog standard Naval Service Seariders with twin 40s. I still have a 1980 5.4 in active service here with the Army Boat Squad as an old retainer alongside her sexier Lencraft Lynx and Halmatic / RTK stablemates. She now is slightly over engined ( for Combat Dive support ops) with a 115 Yam but she still has the original hull, transom and tubes !

If you want to block off the holes I would strongly reccomend building in a good quality bung at the lowest point of the stern plug. Water (mainly rainwater) will still enter the hull through the floor and will gradually build up . This will of course slow the boat and affect its stability. Use a good quality Stainless steel bung ( euro 15 - £stg10 each) - much better than the cheap little white plastic numbers!

Best wishes,

Stuart McNamara
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