Anchoring to Wooden Floor

jimbojambo · 25 August 2010, 13:09

Hi,

Does anyone have a good way to anchor fuel tanks, etc, to a plywood floor? I don't want to put anything right through the wooden floor, in case it damages the material behind, so have been looking at things like pronged tee nuts - but I cannot find stainless ones for love nor money. I did get some BZP ones, but am trying to stick to A2 grade for all fixings (my OCD is getting the better of me

). But if anyone has used BZP and it's not rusted then I'll certainly consider it.

Any other ideas for fixings? I'd probably like to put a few anchor points in various places, as I imagine they would be useful for a variety of things (including keeping things secure when towing).

Any suggestions/pictures will be much appreciated!

Thanks

Downhilldai · 25 August 2010, 13:20

What about using a countersunk machine screw from the underside of the deck to fix the tank straps with washers and domed nuts on top?

Northern Tim · 25 August 2010, 13:48

How about simply drilling/cutting a small hole in the floor, through which you could pass a rope or webbing straps to tie the tank down? That way, the only thing under the floor would be soft and wouldn't damage your inflatable.

kelson · 25 August 2010, 14:36

I have installed stainless steel footmans loops on my wooden forward floor sections. I used a spade bit on the bottom to accomodate the bolt head and a washer and then filled with epoxy resin and fiberglass strands. Sand flush and you won't ever have wear issues under the floor. The ss footmans straps are very strong. They stick up a bit on the floor, but I haven't stubbed a toe on them... yet. The counter sunk bolt head method sounds good, but I tie down some heavy loads and I didn't want the bolt pulling through the flooring. Just one more option to consider. I looked at d ring mounting plates that could be screwed to the deck, but I knew they would rattle about when not in use.

jimbojambo · 25 August 2010, 15:25

Thanks to you all who've replied.

I also want to get something non-moving and non-rattling, so will try the countersunk machine screws and dome-nuts combo, with these on the upper side:
http://www.screwfix.com/search.do;js...h_search=22320

I might err of the side of over countersinking the hole, and I like the idea of using epoxy resin to bring flush with the wood to save wear and tear on the material.

I will hopefully do this in the coming days and will post pictures if I remember!

Thanks again

Downhilldai · 25 August 2010, 15:42

An M8 csk bolt, penny washer and eyenut would be easier.

Like this:

http://www.force4.co.uk/3593/Force-4...-Nut---M8.html

jimbojambo · 25 August 2010, 17:05

Good suggestion Downhilldai, I've just bought some off of fleabay for £1.20 each. Will get machine screws from screwfix and job's a good'un!

Downhilldai · 25 August 2010, 17:11

Quote:

Originally Posted by jimbojambo

I've just bought some off of fleabay for £1.20 each.

Good price - got a link?

jimbojambo · 25 August 2010, 17:47

Here you go:

http://cgi.ebay.co.uk/M6-6mm-1-4-Mar...Accessories_SM

M6, rather than M8 - but for what I'm using it should be more than enough.

Downhilldai · 25 August 2010, 18:52

Quote:

Originally Posted by jimbojambo

M6, rather than M8

Thanks, that explains the good price. Still decent value for M6 though.

Bear in mind the head of the screw will be smaller and have less purchase on the underside of the floorboard. If you're just holding down lightweight stuff, M6 should be ok.

kelson · 25 August 2010, 19:42

For lightweight stuff the counter sunk head on the bottom of the floor board will be fine, but if you intend to blast about I highly recommend using a pan head bolt with a washer. If you are going to fill the depression anyways why not make it as strong as possible? I pull my auxiliary ten gallon gas tank off my floor regularly. The footmans loop is low profile and fits my web straps perfectly without posing a hazard.

Add a ss teflon insert locking nut on top and you are good to go. I would hate to kick a large ring or an eye nut. I can step on my footmans loop without grief (I ground the bolt flush to the top of the self locking nut).

It's all good, no matter how you go. Much better to tie everything down than try to retrieve it from the sea!

jimbojambo · 25 August 2010, 20:59

I would go for as much strength as possible, but I think the wood is only 12mm thick, so using a spade bit to recess enough for a nut and a washer on the underside wouldn't leave much wood left to provide support. I'm concerned it might break out under strain.

What thickness is yours, Kelson?

kelson · 26 August 2010, 15:12

My Futura has two forward wood floorboards that are 1/2 " (12mm) thick. The recess I cut with the spade bit is just deep enough to allow me to cover a thin panhead bolt and washer with the resin and fiberglass strand mix. Technically it is a panhead slotted machine screw. There is plenty of plywood left. The machine screw and washer are much less likely to pull through, even with the wood removed, than a small flat head machine screw in a counter sunk hole. You have to use a pretty small bolt or screw to go through the footmans loop openings. The self locking nut goes on top not on the bottom in the floor. I ground down the excess machine screw length so it isn't protruding. The footmans loops and nuts are fairly low profile, you can step on them and it's isn't a big deal. I use four footmans loops with two straps to hold down a ten gallon gas tank on my bow. I have had to throttle hard to get up and over a head high almost breaking wave. My console base cracked, but the tank stayed put.

jyasaki · 26 August 2010, 16:09

How about using a SS carraige bolt from the bilge upwards? Nice smooth round head shouldn't cause any wear problems.

jky

C-NUMB · 29 August 2010, 08:23

How about increasing the thickness of the floor partially by epoxy gluing piece's of plywood on top of the floor? That way you will have more material to work with, even possibility to use screws only. Need proper preparation to be strong though.

jimbojambo · 29 August 2010, 15:29

Hello all,

All done now - I ended up buying a pair of these: http://www.screwfix.com/prods/36070/...-8mm-Pack-of-2

I took the advice, and decided 1 M6 countersunk machine screw going into an eyenut was going to be a bit of a concern, so using the eye plates (each with 4 holes) - I could use the same technique but have 4 times the strength.

I used my calipers to measure the floor - and it's actually only 10mm (9mm ply + fibreglass [?] coating. Recessing into this without building up the floor was going to be a bit close.

All good now - went for a trip out today and they're spot on (and very useful!!)

Thanks for all the help
James

9D280 · 31 August 2010, 14:13

I was about to suggest a couple of lengths of yacht "block carriage" track - use multiple smaller thru' bolts to haold it don, the carriages (no block version) can be moved to suit whatever you are or aren;t wanting to hold down, , and the load is shared by numerous bolts rather than just one or two.

I suspect the price may be the down side!