Avon sr4 transom/deck questions.

[Barrel Rider]

Hello,
I picked up an Avon sr4, my first ever boat, as a winter project, with an aim to using it as a dive rib next summer. It is quite old (1977 I think if I'm reading the serial number correctly) and I will have to replace the transom and the deck but the tubes and hull are in surprisingly good condition. I replaced a few of the patches on the tubes which were failing and it now holds air indefinitely, and apart from some dings in the hull it is also sound.

When I removed the capping on the transom I can see the ply is wet so it's probably rotten I will replace that, I expected doing this considering its age. About 600mm of the deck at the stern also feels soft so I would like to remove that and replace as much as is neccessary.

I'm wondering, am I better to replace the transom right down to hull level? At the moment it only goes down to around deck level.
And is there anything I need to bear in mind when removing and replacing deck, I can see through the hole in the hull that there are buoyancy chambers below the deck?
I am going to fit a four stroke around 95-98kg so would like to get everything sound and solid so wondering if I should glass knees also from transom to hull?
Thanks for any advice.
Apologies if this has all been covered before, I did use the search bar first! If there is a good thread on it please send me the link.

[Tim M]

Hello and welcome. A great project you have there! Many many threads on Searider rebuilds on here if you search - probably one of the most written about models of RIB. A true classic! I did the same once - it was some years ago and I can't remember if full thickness of the transom should go all the way to the hull. Logic would suggest if you're going to all the trouble of taking the deck off you may as well beef up the transom and go all the way to the bottom of the hull regardless.

As for what's under the deck - very little apart from a buoyancy tank near the back. You'll need to put that back in so the boat sits at the right height (and water doesn't come over the transom) when the hull floods. That said when I did the deck on one I blocked up the hull at the same time do didn't bother with the tank.

As well as loads of info on here, there's a very active Searider group on Facebook - search for "Avon Searider Owners"

Good luck!

[Livid]

I'm getting the whole deck and transom done on mine, if you're going for a heavier engine then definitely strengthen the knees, also if you're doing more then 40hp its a good idea

[IainK]

Hi "BR", One wee point I should make is that if you are using this as a dive RIB then having the Wet Hull in-tack will be an asset in the sea otherwise it will be a little bumpy when anchored. As the guys advise raising the transom up a little in the mid-section with added 4-stroke engine weight would be good. There are others here with more Searider knowledge than me on this aspect though. Also when upgrading the transom, consider recovery from the sea for the divers perhaps? Rope ladder fixings?? best wishes Iain

[Barrel Rider]

Thanks
Yes I'd like to retain the flooding hull so will put the buoyancy tanks back in. I'm not sure if I'll have room to glass in two knees going down to the inside of the hull though. I think the original ply in the transom is 18mm, I plan on redoing it with 24mm of ply.

[Livid]

My uncle did glass knees on his only to the floor

[GuyC]

Originally Posted by Barrel Rider

Thanks
Yes I'd like to retain the flooding hull so will put the buoyancy tanks back in. I'm not sure if I'll have room to glass in two knees going down to the inside of the hull though. I think the original ply in the transom is 18mm, I plan on redoing it with 24mm of ply.

In addition to the thickness, the quality of ply will make a difference. I'm not sure whether a 1/4 sheet of marine ply would be sufficient but people like Robbins sell 1/4 sheets of marine ply in 18mm - 25mm.