Clever solutions for mounting hardware onto an inaccessible space?

[Franziska]

Hi,

I'm looking for a clever low-cost solution for mounting something onto an inaccessible void.
I do not want to use installation hatches for it.
A hardware solution would be easiest, alternatively I describe three possible fiberglass solutions below.

The usual dowels one would use in a house will not work, as they are not watertight, might rust or are not string enough.

Two examples for such a problem:
1)
Mounting lifting padeyes into the corners of a rigid inflatables double floor.
At the bow I can install through the keel, no problem, but in the stern that's not possible.
There is an 80mm void between floor and keel.
So I need a way to mount there. I do not trust the glued on fittings on the tube.

2)
Mounting spinnaker bow fittings.
I can not access the area right behind the stem as it very narrow and a collision bulkhead is located 1500mm aft.

I am aware of two solutions but like to hear if someone else has another clever idea.

The three possible solutions I know of are:
1)
In the case of the bow fittings, glue the bolts in with epoxy using oversized blind holes.
Problem is that this only works if the material is thick enough, which is the case at the stem, but not at the adjacent deck.
The bow fitting is angled over the bow with mounting holes on stem and deck.
The deck is only 12mm thick and underneath is a void.

2)
Dyneema loop glued into a fiberglass plate.
Slit the deck corners, slide the glass plate in sideways and glass over the slit just leaving the Dyneema loop exposed to the outside.
Anyone DIY'd this successfully before?
I feel it should work, but Dyneema is slippery stuff...

3)
Dyneema rope unraveled at both ends, pushed through a hole in a round fiberglass plate and glassed in on the underside of the plate than bond the resulting flat composite padeye to the floor.

Looking forward to hear how others tackle this.
Thanks for commenting.

[mvweebles]

Three ideas come to mind. Cannot speak to strength.

Well nuts
https://www.mcmaster.com/products/well-nuts

Rivet Nuts
https://www.mcmaster.com/products/nu...ant-rivet-nuts

Pop rivets

[Franziska]

Originally Posted by mvweebles

Three ideas come to mind. Cannot speak to strength.

Well nuts
https://www.mcmaster.com/products/well-nuts

Rivet Nuts
https://www.mcmaster.com/products/nu...ant-rivet-nuts

Pop rivets

That an interesting solution. Should work for not too loaded hardware.

[boatman61]

What prevents you from fitting 2 eye bolts on the inside of your transom to use as lifting points..

[mvweebles]

Finally found Jack Nuts in stainless. These would be the strongest of my suggestions.

https://www.amazon.com/pcs-Stainless.../dp/B07VC5TYBP

Good luck.

[SailingHarmonie]

Properly installed rivnuts are really strong, and can take very high loads, especially in shear but...

One of the issues with mounting to any thin(ish) panel, especially of fiberglass, is for a high load you NEED to have a backing plate or other way of spreading the load. The strongest hardware is no help if the panel itself rips.

Sorry, not a solution, but just something to keep in mind as you evaluate things

[Pete7]

Originally Posted by boatman61

What prevents you from fitting 2 eye bolts on the inside of your transom to use as lifting points..

Hmm, my thoughts too, particularly as the transom takes the weight of any outboard fitted as well.

Franziska, you have a bow (well actually 2 on the cat) with a bulkead 1.5mm back but no way of accessing this space. How would you know if it was full of water? How about a waterproof Whale TCL4 clear hatch? this would give you access to fit a re-enforced backing pad.

Pete

[Franziska]

Originally Posted by boatman61

What prevents you from fitting 2 eye bolts on the inside of your transom to use as lifting points..

Touché, I got that idea today as well.
Didn't see the forest due to all the trees being in the way. Lol.
Thanks.

Still, for future situations, how could it be done if that would not be possible?

[Franziska]

Originally Posted by Pete7

Hmm, my thoughts too, particularly as the transom takes the weight of any outboard fitted as well.



Franziska, you have a bow (well actually 2 on the cat) with a bulkead 1.5mm back but no way of accessing this space. How would you know if it was full of water? How about a waterproof Whale TCL4 clear hatch? this would give you access to fit a re-enforced backing pad.



Pete

I have a round inspection hatch in there but it's 1.5 meter from the spot where the fitting will be mounted.
Indeed I use that to for any water in this space.

My arms are not long enough to reach from this hatch to the fitting and I do not want to add a hatch in the deck...

I tend now to do add Dyneema composite padeyes to the stem for the kite.

[boatman61]

Originally Posted by Franziska

Touché, I got that idea today as well.
Didn't see the forest due to all the trees being in the way. Lol.
Thanks.

Still, for future situations, how could it be done if that would not be possible?

Its also a good security feature for your engine and fuel.. run SS chain through the ob handle, tank and an eye bolt and secure with SS lock.

[leecea]

https://thmarinesupplies.com/product...gle-anchor-kit

There are a variety of toggle anchors that might work - the ones above are an example.

[Franziska]

Originally Posted by leecea

https://thmarinesupplies.com/product...gle-anchor-kit



There are a variety of toggle anchors that might work - the ones above are an example.

That looks great! Nice find. Thank you.
But, I just noted it's not metric, which is an issue over here in Europe...

[deblen]

Variety of blind nuts-but the deck must be strong enough.
https://www.mcmaster.com/blind-nuts/


If you require real strength,the best solution may be to holesaw a hole thru deck,install 2 parallel flat bars of G10 that are thick enough & epoxied to underside of deck. These 2 bars will have SS bolts inserted up thru them,the holesaw cookie,& the new hardware.
Epoxy repair the holesaw seam.


You could hide this holesaw cut by putting a suitable wood,metal or plastic trim piece between deck & hardware.



Cheers/Len

[JPA Cate]

The suggested method for using the dyneema seems to me that it would be difficult to replace it. After about 4 yrs. in the sun, it gets a little fuzzy, and it has to have degraded considerably. Spinnakers generate a lot of force. We need to find a better way, or make it easier to replace prophylactically. Tricky.

Sorry to not be much help.

Ann

[Franziska]

Originally Posted by JPA Cate

The suggested method for using the dyneema seems to me that it would be difficult to replace it. After about 4 yrs. in the sun, it gets a little fuzzy, and it has to have degraded considerably. Spinnakers generate a lot of force. We need to find a better way, or make it easier to replace prophylactically. Tricky.

Sorry to not be much help.

Ann

Agree sun could be an issue.
I could perhaps put a protective sleeve around the exposed part of the loop.