Rubber Seal

General Composites Discussions Composites Talk
#1

After weeks of Internet grazing I’m having a very hard time getting any solid answers.

What I’m making is essentially a trunk. --A case. Luggage. I depend on the structural integrity of the composites for the safety of it’s contents from physical forces, but for moisture I do not as of yet have the perfect solution. This appears to be a much guarded secret in the trunk/luggage industry. :wink: (Who would know!)

Unfortunately, much debate has unfolded on this topic here internally. I get that it must be aesthetically acceptable, as it’s a very visible sort of product. Most people I’ve seen use a U or H shaped rubber seal. I’ve tried a sample of U shaped TrimLok, but it’s not very discreet looking.

So, these are my concerns:

  1. In a general sense, how must I seal the composites I cut, (i.e. the flanges), so that the elements, (immersion), will not affect it’s integrity? (I guess that’s a basic boat question.) I use Epoxy resin BTW. My assumption is that I’ll epoxy the trim on, and that will probably just do it? On a boat that’s sealed in the gunwale, right?

  2. What do others do to seal mating members of composites from being lightly immersed, (i.e. floating) in water. What about being under 10’ of water? In many ways it’s like a hatch, but the surfaces mate exactly.

I need to get straight in my mind exactly what is needed, and find a source for getting some without an up front $15k engineering fee. :wink: There must be something off the shelf that will work.

Any advice or direction is welcome! :smiley:

#2

Can you show a picture (total and close-up for the edges). This way we can see what is possible and what is not.

#3

All I have is an extremely poor, hand layup, vacuum bagged, prototype. Which essentially was a way to prove: “That shape is acceptable.” I’m embarrassed to say, the workmanship is very misguided. I guess it goes to show you what happens when you trust bad council. :frowning: (A FG supplier.)

The exhibits do not accurately depict the recent results I’ve been testing with, over the last month, (those all still have flanges on them), but what I show will give you an idea of what the edge will be similar to. Albeit the same basic plug, the mold and methods have all changed!

The pictures show three layers of 19.8ozy CF with an off-center 1/8" core of end-grain balsa. :nuts: (The current design is 4 layers of CF with Soric SF3 core at the center!) I intend to machine the flanges off them flat similar to the first exhibit. The second exhibit is an example of a corner. The third is an example of the corner with a small sample of TrimLok around it.

#4

Based on your basic image what i would recommend (no expertise what so ever) is that you do a tongue and groove design. So basically on the bottom peice there is an indentation that is carved out and then a rubber insert is in the groove (can use solid rubber roll). Then on the top would be the positive image aka the tongue. So when closed with glasps or whatever to keep pressure it will seal it off. So that when closed it looks like your first picture but is sealed completely. I dont know if i explained that clearly but that is what i would try to see if it is sufficient.

GL with your project

#5

A nice option would be a tongue and groove in aluminium, with embedded silicone seal. I know these profiles exist.

This will at least give you 1 barrier, if you like to upgrade things, think about adding a second water barrier.

I guess it goes to show you what happens when you trust bad council. (A FG supplier.)

Not all of them are bad, trust me.

#6

I would second herman’s option you should be able to find an alloy extrusion that would fit on the inside edge of the case this would leave a top bottom join lines clean as shown in your first picture.

Instead of an O ring google image “quad ring seal” it will give you a better seal at a lower pressure.

As for sealing the composite edges I might think about incorporating a solid plastic/darvic ring section within the laminate. Which would be cut into when machine trimed. This could be polished and would leave a solid surface so no core was visable and be black or a contrasting colour such as red and be made a feature of.

What about taking a look at some gun cases for ideas?

#7

Your suggestion crimsonmt is fairly congruent with my initial thoughts. In my original drawings I have complementary OG sort of cuts into the composite, but the original design was thicker walled. I prefer a “no seam” look. That view is not shared however, and I don’t know if I’ve got enough “meat” to machine things with any integrity.

Herman, your suggestions always seem to come from the best of motives. :slight_smile: It’s unfortunate, my original vendor had become technologically stagnant and only provided answers which included their line of, (old school), products. :frowning: I still buy some things from them, but not like before.

Fat aluminum, “valance” is out. Silicone… Hmmm… Maybe some sort of discreet silicone “gaskets”??

You’re getting a glimpse of what a bear this topic is. :confused:

#8

Glue it closed. It won’t leak then. :smiley:

#9

From a different angle.

What about a waterproof zip the type they use on dry suits for diving/watersports etc which are glued on and very strong? If the zipper was black it may be aesthetically acceptable and blend in with the carbon with only the black zip teeth showing on the join when fastened. It might also be possible to use the zip backing material as a hinge giving a totaly waterproof seal if the zipper part only went round three sides of the case one face might be used as a stiff fabric type hinge. Have a clasp lock which covers the zipper when done up to keep all secure.

#10

OK, so it should be the smallest of seams then. I have no idea of the number of cases you would be making, but making a custom extrusion in aluminium, which can be buried in the seam, could be an option. Or press moulding the desired profile in carbon and epoxy.

Or ask your supplier, he might have a solution in alternating woven roving and mat… :slight_smile:

#11

If water tight is the goal…have you selected your external latches yet >?

It will require multiple points for clamping to balance the pressure all around the seal’s perimeter.

#12

The problem lies in the butted seam. But. (no pun intenteded) I think a simple inside mold line L flange with a viton rubber seal would be perfect. This might complicate your hinges but at the same time you could easily engineer a hinge that would be suitable for a hidden design. Or a clean designer off the shelf hinge. There are many viton rubber fabricators in the USA. You could do a solid compressed o ring.

#13

So you’re thinking something like this??

#14

A quote from the Carbon forum on linkedin:

We are doing carbon fiber laptop and iPad cases. All padded and lined with a special water resistant zipper. We make them right here in the USA. Ultra high end with Alcantara interior and embroidered logo.

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