Bow bench supports

[blackrose]

I'm into the rivnut idea. I guess stainless rivnuts is the way to go. I've seen them on eBay but it doesn't seem to state what wall thickness of substrate that they're going into they're suitable for.

 

Edit: Just seen the price of rivnut tools. Scrap that idea, I'll stick with nuts and washers!

8 minutes ago, Tigerr said:

That's sort fo my point -the entire construction might be best done as a freestanding, but closely fitted, item in suitable weatherproof material. Standing on whatever is the available lowest base. No hull/tanks screwing. 

Not looking for a fight and quite possibly I have missed the point of the Op's challenge. I am sure others will know better, so happy to back out. 

Thanks, no problem. All ideas are welcome but freestanding will tend to tip when someone stands on the edge. I used to have a big aluminum care which was filled with various lumps of hardwood and other stuff. It was really heavy but it could still tip of you stood on the edge.

Edited December 31, 2020 by blackrose

[GUMPY]

Get a welder in to build lockers around the bow, then have either hexboard or steel lids. Lots of extra storage and no bolts, win win

 

[David Mack]

58 minutes ago, blackrose said:

 

Edit: Just seen the price of rivnut tools. Scrap that idea, I'll stick with nuts and washers!

 

You don't need a rivnut tool if you're only setting a few.

 

58 minutes ago, blackrose said:

I'm into the rivnut idea. I guess stainless rivnuts is the way to go. I've seen them on eBay but it doesn't seem to state what wall thickness of substrate that they're going into they're suitable for

 

From a quick google this would seem to meet your needs.

https://www.rivetwise.co.uk/productrange/nutdetails.asp?item=m10fro_l_t_flat_head_serrated_open_end_rivet_nuts_stainless_steel_716_1008

 

(Other suppliers are available.)

 

Edited to add:

If you are setting rivnuts by hand you would be better with aluminium rather than stainless. Cheaper too.

Edited December 31, 2020 by David Mack

[BEngo]

Rivnuts are great, till they spin.  Then they are a bloody nightmare.  You can't get the bolt out, cos the rivnut spins, you cannot drill them out bolt and all  because the whole lot spins. 

N

[David Mack]

7 minutes ago, BEngo said:

Rivnuts are great, till they spin.  Then they are a bloody nightmare.  You can't get the bolt out, cos the rivnut spins, you cannot drill them out bolt and all  because the whole lot spins. 

N

Indeed, but you aren't much better off with an ordinary nut and bolt if the nut is inaccessible behind the bulkhead, and just rotates with the bolt.

[LadyG]

1 hour ago, Tigerr said:

I accept I mat have misunderstood the detail of the challenge. But as I understand it a very solid construction could be made with hex board, jigsawed to fit and once screwed into place it would certainly support both step and seating.  I repeat I  may have missed a key point. I lined my well with hex board to enable exactly that sort of construction, in order to avoid potentially corroding hull drilling. Still looks new 10 years on. 

 

I had my well deck seating pretty much over engineered, with brackets welded and angle iron to form a frame, which supports the hex board which is sealed with epoxy, I just sling my coal bags on to it, no worries about any oversize crew breaking it either. I painted the angle iron and welds before they had a chance to rust.

Looks very smart, its a sort of brown criss cross finish on the ply. I'm considering having the rear doors made of the same material, no maintenance.

[blackrose]

1 hour ago, Loddon said:

Get a welder in to build lockers around the bow, then have either hexboard or steel lids. Lots of extra storage and no bolts, win win

 

Yes I could do that but it's a lot more expense plus t they'd need scuppers from the deck so I'm sure in the end they'd just be permanently damp and full of leaves and spiders. Plus all that welding would lift my epoxy paint off the inside of the water tank. I'd rather just have the benches/steps.

56 minutes ago, David Mack said:

 

You don't need a rivnut tool if you're only setting a few.

 

 

From a quick google this would seem to meet your needs.

https://www.rivetwise.co.uk/productrange/nutdetails.asp?item=m10fro_l_t_flat_head_serrated_open_end_rivet_nuts_stainless_steel_716_1008

 

(Other suppliers are available.)

 

Edited to add:

If you are setting rivnuts by hand you would be better with aluminium rather than stainless. Cheaper too.

Thanks, but wouldn't aluminum rivnuts be susceptible to cracking or loosening after a while?

[blackrose]

37 minutes ago, David Mack said:

Indeed, but you aren't much better off with an ordinary nut and bolt if the nut is inaccessible behind the bulkhead, and just rotates with the bolt.

If I use nuts they'll still be accessible and they aren't that much of a hassle to fit. 

[AndrewIC]

3 hours ago, blackrose said:

I'll drill though the cabin bulkhead and attach the brackets with bolts as I don't want to weld and burn off the sprayfoam inside.

If you are going to have to remove whatever cabin lining is in place, cut out the sprayfoam, then make good the foam from a can, and then put the lining back again ... why not get the brackets welded? No holes to let the water in, no need to be able to remove the lining again if they work loose?

[Opener]

I never considered a fixed solution so arguements/advantages were never considered. A man who knows what he is doing - an ex furniture shop prop. made a couple of free standing boxes. Very simple foredeck, single skin all around but with a full cratch so weather not a major issue.

Boxes maybe 1metre long by half metre cross section. Sit on low ball feet to keep them clear of the deck and very stable. Solid wood with varnish finish. Long piano hinge on one long edge and down the centre of the lid. Lid folds on itself then folds under gunwhaleto get into box.  Edge of lid finished in non skid tape - never had a problem with stability - step on foredeck lip then box lid then deck. Boxes house infinite amount of painting bits or solid fuel.  Paint box can actually migrate into cabin over Winter. Can move under lip or out onto foredeck to provide seating.

[Jen-in-Wellies]

3 hours ago, Loddon said:

M10 is too large a thread pitch to tap into 5mm steel its 1.5mm so thats only 3 threads in the bulkhead, M8 would give you 4 threads which is just about ok.

So if you want to use M10 it has to be nut and washer.

This ^^^^. I've trusted my life to M8 bolts when caving and they are more than adequate. Having enough threads in to the steel of the bulkhead is more important than diameter. Use proper high tensile bolts, 8.8 standard, or better, not some monkey metal ones from B&Q.

 

Jen

Edited December 31, 2020 by Jen-in-Wellies

[GUMPY]

1 minute ago, Jen-in-Wellies said:

This ^^^^. I've trusted my life to M8 bolts when caving and they are more than adequate. Having enough threads in to the steel of the bulkhead is more important than diameter. Use proper high tensile bolts, 8.8 standard, or better, not some monkey metal ones from B&Q.

 

Jen

That is the reason I used M6 stainless for my fairleads rather than M8 which they should have, M6 gives 4 threads in the steel M8 gives 3 hence better holding with M6, 

[blackrose]

1 hour ago, AndrewIC said:

If you are going to have to remove whatever cabin lining is in place, cut out the sprayfoam, then make good the foam from a can, and then put the lining back again ... why not get the brackets welded? No holes to let the water in, no need to be able to remove the lining again if they work loose?

It's fairly simple really. I will just use a hole cutter on a drill using the same hole that came through from the outside to cut out a small piece of the lining and sprayfoam. Then put the bolt through from the outside, put the nut and washer on, tighten it up using a socket and put a blob of sprayfoam on top. There's no need to replace the lining as it's inside a cupboard as I said.

 

As I also said, if I got the bracket welded on it would burn off the sprayfoam on the other side anyway. 

33 minutes ago, Opener said:

I never considered a fixed solution so arguements/advantages were never considered. A man who knows what he is doing - an ex furniture shop prop. made a couple of free standing boxes. Very simple foredeck, single skin all around but with a full cratch so weather not a major issue.

Boxes maybe 1metre long by half metre cross section. Sit on low ball feet to keep them clear of the deck and very stable. Solid wood with varnish finish. Long piano hinge on one long edge and down the centre of the lid. Lid folds on itself then folds under gunwhaleto get into box.  Edge of lid finished in non skid tape - never had a problem with stability - step on foredeck lip then box lid then deck. Boxes house infinite amount of painting bits or solid fuel.  Paint box can actually migrate into cabin over Winter. Can move under lip or out onto foredeck to provide seating.

 

Thanks, and I'm sure it works for you on your boat, but that's not what I want.

[blackrose]

20 minutes ago, Jen-in-Wellies said:

This ^^^^. I've trusted my life to M8 bolts when caving and they are more than adequate. Having enough threads in to the steel of the bulkhead is more important than diameter. Use proper high tensile bolts, 8.8 standard, or better, not some monkey metal ones from B&Q.

 

Jen

 

I think high tensile is a bit over the top. I'll be using stainless bolts - I've learned though bitter experience not to use anything that corrodes.

17 minutes ago, Loddon said:

That is the reason I used M6 stainless for my fairleads rather than M8 which they should have, M6 gives 4 threads in the steel M8 gives 3 hence better holding with M6, 

Yes that point was taken and it's a good point, but it's academic since I'm using nuts on the inside.

[Jen-in-Wellies]

1 minute ago, blackrose said:

 

I think high tensile is a bit over the top. I'll be using stainless bolts - I've learned though bitter experience not to use anything that corrodes.

Stainless would be fine for this.

[blackrose]

6 minutes ago, Jen-in-Wellies said:

Stainless would be fine for this.

Thanks everyone. I'll get to remember to post a picture when it's finally done. Might be a while...

[Sea Dog]

Hmm, interesting how the idea of M10 bolts seem to be so popular: I wonder what the sheer strength is of a 10mm bolt is? 

 

My well deck bench brackets in angle aluminium are held by M5 stainless screws tapped into the steelwork, 3 in the longer fwd brackets and 2 each in the pair of shorter brackets aft. Experience suggests this is beefy enough.

[Alan de Enfield]

5 minutes ago, Sea Dog said:

I wonder what the sheer strength is of a 10mm bolt is? 

If it is any help 10mm galvanised anchor chain has a 'Minimum Breaking Load' of 5,000 kgs

 

 

[Sea Dog]

11 minutes ago, Alan de Enfield said:

If it is any help 10mm galvanised anchor chain has a 'Minimum Breaking Load' of 5,000 kgs

Well, it might not be the same as the sheer strength of a threaded bolt, but its a good starter if nothing else!  It does rather support my thought that M10 is huge overkill.

 

Thanks Alan - I shall continue to sit or stand on my benches with confidence!

 

Edited January 1, 2021 by Sea Dog
missing words

[blackrose]

13 minutes ago, Sea Dog said:

Well, it might not be the same as the sheer strength of a threaded bolt, but its a good starter if nothing else!  It does rather support my thought that M10 is huge overkill.

 

 

 

Yes that's correct, I think the rule of thumb is that the sheer strength of a bolt is about 60% of its tensile strength - and a bolt isn't an anchor chain.

 

But I agree M10 is overkill - I did say I was a fan of over-engineering ?

 

I ordered some M8 stainless nuts & bolts earlier today, which is probably still huge overkill, but the difference in cost between M6 and M8 is pennies and bigger fasteners are easier to work with and can be undone more easily if required, without burring or damaging them.

Edited January 1, 2021 by blackrose

[Sea Dog]

9 minutes ago, blackrose said:

 

Yes that's correct, I think the rule of thumb is that the sheer strength of a bolt is about 60% of its tensile strength - and a bolt isn't an anchor chain.

 

But I agree M10 is overkill - I did say I was a fan of over-engineering ?

 

I ordered some M8 stainless nuts & bolts earlier today, which is probably still huge overkill, but the difference in cost between M6 and M8 is pennies and bigger fasteners are easier to work with and can be undone more easily if required, without burring or damaging them.

No worries BR - I was just trying to make the point that you needn't fret too much about the bolt size and thus increase your options and potentially to include tapped holes if desired.  

[blackrose]

7 minutes ago, Sea Dog said:

No worries BR - I was just trying to make the point that you needn't fret too much about the bolt size and thus increase your options and potentially to include tapped holes if desired.  

Oh I see. Yes, I'm sure tapped holes would have been fine too, but I'd rather have the sheer forces on a bolt with a nut and a washer behind it if people are going to stand on it.

[system 4-50]

I'd go for freestanding plus glue.  

[blackrose]

8 minutes ago, system 4-50 said:

I'd go for freestanding plus glue.  

 

Let us know how it goes.