Epoxy with Fiberglass cloth for reinforcement for Foam flotation

Blue Robotics Products Buoyancy and Ballast
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I have been thinking about Epoxying my Flotation on My ROV. i have seen several topics on Epoxying the Flotation on the ROV, but have not seen where anybody is using any sort of reinforcement with the epoxy such as Fiberglass cloth or Matting with the epoxy. Seems like it would help with strength and abrasion.

Thanks
Jim

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Hi Jim,

I haven’t had reason to try epoxying buoyancy foam before, but I’d imagine many people that have done so didn’t require the extra strength and abrasion resistance of including a fibreglass or other mesh, particularly given

  1. the extra work and cost required
  2. the additional weight on something which is supposed to be a source of buoyancy, and
  3. the extra volume, which makes it harder to fit a pre-cut piece of foam in a fixed size location.

Note also Rusty’s response here, which suggests that coating the foam is more for stopping water ingress at depth than protecting it from impacts or abrasion. I’d imagine the intent is for a protective cover like our BlueROV2 fairing to still be used, in which case the coating shouldn’t really ever be at risk of getting hit or rubbed against something rough.

Perhaps some others in the community have some additional insight :slight_smile:

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Thanks Eliot

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Hi Jim and Eliot:

Here at Mission Robotics we’ve switched to epoxy-coated floats on all of our BlueROVs. The original intent was to allow deeper diving, as the Last-a-Foam 3318 is only rated to 250m in its uncoated form. We do a lot of testing in Lake Tahoe, which is 500m deep, and wanted to be able to routinely operate in any portion of the lake.

After we started playing with epoxy-coated foam, a number of other advantages became apparent. First, by skipping the plastic fairing and attaching the floats directly to the structure of the vehicle, we could make bigger floats and obtain greater flotation, even more so than the machined foam that Blue Robotics currently sells. This is important when operating in fresh water, which has less buoyancy than salt water. Second, as there is no fairing, there is no air gap between the foam and the fairing, which needs to be “burped” upon diving, and drained upon surfacing. Third, we could shape the forward flotation blocks to mount the upper lights inside the side plates of the ROV, eliminating a “tether trap” that exists when operating a 6-thruster BlueROV2 with 4 forward lights.

The downside, as your post suggested, is that the epoxy coating is not very strong, and hitting anything with a float while exploring will cause cracks in the epoxy, which needs to be repaired. We made a fiberglass-covered (vacuum bagged) set of floats for a BlueROV2 heavy, and although the results were good, it’s not clear that the result was worth the effort involved. This fall we’re going to be experimenting with syntactic foam floats for doing deep diving with ROVs derived from the BlueROV2. You can get syntactic foam in the range of 22-24 lbs/ft3 (compared to the Last-a-Foam 3318 18 lbs/ft3) that is good to at least 1000m. If the foam gets dented it won’t cause structural issues with the remainder of the block, so our current plan is to paint it as opposed to glassing it. Syntactic foam is about 2-3 times the cost of Last-a-Foam, but should require less labor to make completed floats.

If you’d like to see what our epoxied floats look like, you can get a good view of them in this YouTube video where we dove to the bottom of Lake Tahoe (500m):

There’s no particular rocket science involved in the floats, I think we used Total Boat marine epoxy, and we staked stainless-steel threaded inserts into the bottom of the floats.

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Greeting Walt, do you use the total boat epoxy paint (bilge paint) or the 2 part kits to cover the foam? Thanks!

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Hi @FairweatherIT

It’s the 2-part epoxy. I just looked in the storage locker, the stuff we used was Total Boat High Performance 2:1 Epoxy. I suspect other marine epoxies would work as well, this just happened to be what we used.

-W

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Thanks Walt! We have some West Systems 2 part marine epoxy that we used to glass some USV hulls. I’ll have my epoxy guy try some out on some buoyancy foam we have in the shop.

Cheers,
Ian

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Hi Walt
The epoxy you have should work fine as long as it is not to old, a lot of epoxies have a expiration date on them,I have not epoxied my flotation in the ROV yet,I have been laid up since last winter but am getting better and will hopefully get back to working on the ROV, I use a lot of epoxy on my fiberglass boat, and i always use a two part epoxy, The 2 part has always worked best for me in the past

Good Luck.

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Hi Walt,

how thick is this coating on the foam?

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Hi @nihat.keyikci

It’s not much, whatever the thickness of 3 coats of epoxy is. Perhaps 1 mm?

-W

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