Narrowboat Horizontal Sringers

[Lee Crook]

Hi All,

 

What dimension/thickness of angle iron is generally used for the horizontal stringers used to to strengthen narrowboat shells? Also, there seems to be a few different configurations...

 

1. Two full length stringers on each hull side.

2. One stringer around half way up the hull.

3. One stringers just before the fold to the gunwales with vertical angle iron lengths running down to each floor bearer.

 

Which of these would be the best/strongest option?

 

Thanks in advance.

[Tracy D'arth]

4 minutes ago, Lee Crook said:

Hi All,

 

What dimension/thickness of angle iron is generally used for the horizontal stringers used to to strengthen narrowboat shells? Also, there seems to be a few different configurations...

 

1. Two full length stringers on each hull side.

2. One stringer around half way up the hull.

3. One stringers just before the fold to the gunwales with vertical angle iron lengths running down to each floor bearer.

 

Which of these would be the best/strongest option?

 

Thanks in advance.

I would prefer option 3, its the classic way.  Takes more steel and more labour than 1 and 2.  

[Lee Crook]

2 minutes ago, Tracy D'arth said:

I would prefer option 3, its the classic way.  Takes more steel and more labour than 1 and 2.  

Thanks Tracy.

 

What spec of angle would you go for? I was thinking 40x40x6mm.

[David Mack]

I don't think there's a standard way. Working boats didn't have any longitudinal stringers, and some builders of leisure narrowboats have followed the same practice.

[BEngo]

22 minutes ago, Lee Crook said:

 

What spec of angle would you go for? I was thinking 40x40x6mm.

The strength is in the shape, so there will not be much gained from thicker metal provided the toe of the angle is continuously welded to the side plate.  On that basis 40x40x 6 mm is more than adequate. 40x40x 4 mm would be sufficient,  is adequate to fasten battens to  and is about half the price to boot. 

 

 N

 

[Lee Crook]

1 minute ago, BEngo said:

The strength is in the shape, so there will not be much gained from thicker metal provided the toe of the angle is continuously welded to the side plate.  On that basis 40x40x 6 mm is more than adequate. 40x40x 4 mm would be sufficient,  is adequate to fasten battens to  and is about half the price to boot. 

 

 N

 

Thanks 👍

[Lee Crook]

Hi All,

 

Thanks for your advice.

 

Here are some picks of the progress. I had some 60x60mm angle which I ripped down to 60x40mm and this was used on the top with 40x40mm angle on the lower horizontal.

 

Also moved the window openings and installed a 40x40mm angle framework having removed the previous angle from the cabin side as the new windows will be clip in.

 

 

 

 

[jonathanA]

thanks Lee - really interesting to see - wish I could weld as neatly as that 🙂

 

am I seeing things or are there lots of nice round holes in your base plate ?

[Jen-in-Wellies]

13 minutes ago, jonathanA said:

thanks Lee - really interesting to see - wish I could weld as neatly as that 🙂

 

am I seeing things or are there lots of nice round holes in your base plate ?

They are to let the water out. Cheaper than a bilge pump. You don't see any water in the photos, which proves they work.

[Lee Crook]

14 minutes ago, Jen-in-Wellies said:

They are to let the water out. Cheaper than a bilge pump. You don't see any water in the photos, which proves they work.

 

Hi Jonathan

 

Thanks for your comments.

 

The holes are to secure a new baseplate to the existing. The original plate was 6mm but had some deep pits in areas. I've managed to get a single sheet of 7mm steel as the boat is only 32ft long.

 

I also fitted new bearers/subframe to support the new baseplate.

 

 

20 minutes ago, Jen-in-Wellies said:

They are to let the water out. Cheaper than a bilge pump. You don't see any water in the photos, which proves they work.

 

They help to reduce condensation, too. That and the lack of windows 🤣🤣

[Alan de Enfield]

17 minutes ago, Lee Crook said:

The holes are to secure a new baseplate to the existing. The original plate was 6mm but had some deep pits in areas. I've managed to get a single sheet of 7mm steel as the boat is only 32ft long.

 

Just be very careful about the effect on draft, stability and buoyancy that the additional weight will have. Ensure that you have suffficint height for any hull fittings (drains etc).

[Lee Crook]

1 minute ago, Alan de Enfield said:

 

Just be very careful about the effect on draft, stability and buoyancy that the additional weight will have. Ensure that you have suffficint height for any hull fittings (drains etc).

 

Hi Alan,

 

I've removed over 330 engineering bricks (3.4kg each) plus the replacement engine/gearbox is around 200kg lighter i.e. Lister TS2/PRM vs ST2/LH150.

 

The original water tank was integral and probably held around 600 litres. The replacement tank holds 380 litres.

 

 

Additionally, I have raised the gas locker floor (in the bow) by 5" along with the welldeck floor and drains.

 

All other skin fittings (close to the original waterline) will be welded up and an assessment will be made once we test float.

 

Hopefully, all things considered and the weight saved vs extra weight from overplating I don't think there will be much difference but I'll report back after the test float. The plan is to leave it with the crane slings around the boat for 24hrs to ensure we have no leaks. 🤞

[BEngo]

With the new floor supports fitted there seem to be a number of closed boxes with no drain (limber) holes to let any water that gets below the floor run to the stern.  IF this is the case it would be worth making some limber holes now.  Easier than finding you need to when the floor is down☹

 

N

[Lee Crook]

24 minutes ago, BEngo said:

With the new floor supports fitted there seem to be a number of closed boxes with no drain (limber) holes to let any water that gets below the floor run to the stern.  IF this is the case it would be worth making some limber holes now.  Easier than finding you need to when the floor is down☹

 

N

 

Hi BEngo and thanks for your comments.

 

I had considered the points in the comments but that raises more questions than answers 😀

 

I have left gaps and cut the bearers back at an angle along the sides of the hull to allow for water (hopefully just condensation) to move aftwards but this just end up pooling at the engine bay bulkhead which has always been fully welded so would need a bilge pump under the floor to clear.

 

The main questions I have now are...

 

1. I'm planning to heavily insulate the boat with using a combination of pir boards fixed with spray contact adhesive and seal any gaps with closed cell spray foam. 65mm insulation under gunwales, 50mm cabin sides, 40mm roof and a minimum of 30mm under the floor. Windows are brand new Caldwells double glazed/ thermal break. Realistically, how much condensation such i expect?

 

2. I've seen lots of other boats with a complete subframe but no limber holes and do they encounter problems?

 

 

3. If water (condensation) does fun down hull sides and gets to the more central compartments, then surely it can get out, too via the same route?

 

4. Many boat have poured concrete ballast up to the top of the bearers. How do they combat this issue?

 

I know, another can of worms well and truly opened but we're here to share and learn so I welcome any and all advice/comments.

 

Thanks in advance.

Edited December 8, 2023 by Lee Crook

[Tony Brooks]

12 minutes ago, Lee Crook said:

I have left gaps and cut the bearers back at an angle along the sides of the hull to allow for water (hopefully just condensation) to move aftwards but this just end up pooling at the engine bay bulkhead which has always been fully welded so would need a bilge pump under the floor to clear.

 

I would suggest that the majority of modern leisure boats are like that. The build up does not seem to be that fast, so a trap in the floor at the back to allow you to pump & sponge the water out is perfectly adequate. In any case, for much of the time the water down there would not be deep enough for a bilge pump to remove much if any at all. You will also find that bilge pumps always leave some water behind.

 

[BEngo]

Limber holes are filed under "Never say Never".

 

Windows may leak,  sometimes lockside  piddlers squirt through windows of vents, a rude lock gate may dump some water in through the doors etc.. You want to be able to get that out.

 In my case it was the water pipe deciding that if no longer liked the water pump, after 25 years or so, dumping a tank full of fresh into the bilge.

 

We do have poured concrete ballast. It has wooden floor bearers onaàa top. The floor bearers have  limber spaces at their ends, so the water tank contents  eventually drained themself to the back of the cabin where it was wet vacced, and sponge mopped out.  A bit of judicious 'leaning' helped with getting the last bits to the back.

 

In your case, if eater can get to the centre from the sides then it can indeed go back the same way.  The side holes will get it to the back.  A bit of a list ( though not a to-do list) will help if needed.

 

N

[MtB]

I've seen a few shower trays with leaky wastes that can't be seen due to the location of the waste on a shower. These are the source of the water in many a wet bilge that is supposed to be dry, I reckon. 

 

[Lee Crook]

5 minutes ago, MtB said:

I've seen a few shower trays with leaky wastes that can't be seen due to the location of the waste on a shower. These are the source of the water in many a wet bilge that is supposed to be dry, I reckon. 

 

 

Hi MtB and thanks for your comments.

 

Luckily, being a small boat (32ft) the wetroom is going to be on the port side and start at the engine bay bulkhead. The shower trap should only be around 6" from the bulkhead and I'm hoping to be to access this via an access panel under the steps.

 

 

I think I'll drill a series of holes with the mag drill between all the sections. Like a girder that's has holes to reduce weight without compromising on strength.

 

It will also reduce the extra weight of the overplating. 🤣

[MtB]

You do seem to be thinking things through very well! 

 

 

[Lee Crook]

10 minutes ago, MtB said:

You do seem to be thinking things through very well! 

 

 

Thank you 😊

[magnetman]

A full length 7mm plate is interesting. Where did you get it ? 

[system 4-50]

3 hours ago, Lee Crook said:

 

❤️❤️

[Lee Crook]

8 minutes ago, magnetman said:

A full length 7mm plate is interesting. Where did you get it ? 

 

Hi,

 

I bought from P & D Northern in Oldham.

 

https://pdnorthern.com/

 

Dealt with Warren who was very helpful!

 

 

[MtB]

15 minutes ago, magnetman said:

A full length 7mm plate is interesting. Where did you get it ? 

 

Fell off the back of a lorry?!

 

😅

[Lee Crook]

1 minute ago, MtB said:

 

Fell off the back of a lorry?!

 

😅

Yes, just need a big trailer! 🤣

 

Am part way through building a SUPER STRENGTH pallet. Will have the pallet lifted onto stands and then the boat on skids on the pallet/steel. Will then lift the bow and counter, accordingly to remove the skids. Will then use sleepers to jack up the plate, starting in the centre and working outwards.

 

Half a day should do it! 🤣