What glues bottles?

Footy Class General Discussion (Footy)
1

Gentlemen,

I have shrink-moulded a footy using lemonade bottles, but the length of available bottles meant that I have to make the hull in two sections.

So I am joining the sections together with a 1/2 inch (12mm ) overlap joint and am looking for the ideal joining material or method.

The material is PET, and I am informed that there are no solvents for this plastic (please tell me if there is).
So I will rely on adhesive joining
I have tried PU adhesive (Gorilla Grip) - it does not adhere well (I had slovent cleaned and abraded the surfaces with wet-and dry paper

My current thought is hot-melt adhesive - so I will need to apply a very thin layer to one surface, assemble the two bits on the former, and gently iron the two parts together without shrinking them more.

Has anyone got any better ideas for adhesive joining that makes a strong and flexible joint?
andrew

2

I have built 2 bottle boats, but have had little success with glue. My first boat was much like yours, with 2 Pepsi bottles. There was about an inch of overlap, and I used 60-minute epoxy. It was OK in an initial bathtub test, but began to separate a few days later as the hull flexed. I covered the joint with electrical tape, and it is still watertight a year later.

The joint between the bottle and the deck was another problem. Mailing tape worked very nicely, except that it wrinkles at compound curves, and leaks at the wrinkles. So that was just used at the straight sections. Silicone bathtub caulk was used at the curved sections, and was covered with a new “flexible” tape from 3M. It still wrinkled, but the tape gave strength and the caulk stayed water tight. It has also lasted a year.

I tried 2-sided sail tape to attach a false prow, but it requires a lot of pressure, and eventually leaked, so I just taped it in place and allowed it to leak, but filled it with foam

I have also made some tests on small strips with other candidates:

CA glue looked good initially, but did not seem to cure properly, and eventually was easily broken.

3M 5200 Marine Caulking seemed to work, but the bond was no stronger than the bathtub caulk.

Conclusion: I am still looking for a good solution, and making do with tape. IMPORTANT: tape needs a very smooth surface to adhere well, so if you are using it at a joint with wood, the wood needs to be sanded very smooth and painted or lacquered and sanded smooth again.

Good luck with your endeavor, and please let us know if you find a better glue.

3

PET is one of the most stable polymer. It is used to store chemical products except acid as they destruct is chain.

If you have some acids at home try them but please do that outside as fume might be harmful, sligly brush some acids on the edge of each bottle.

Have you think about brazing ? This method is widely used to make big thanks in polymer for the chemical industry, but your biggest problem is going to melt and not burn the plastic. That is part of your idea with the iron except that I used a piece of PET to join both part of the hull. I even think that technically is not brasing but welding…

I hope that’s help good luck for the test.

4

Some more information and ideas

Epoxy appears to work OK in places where the plastic can’t flex. For instance, I have epoxied a ping-pong ball into the neck of the bottle at the prow, and this works very well, because the compound curve of the bottle gives it more stiffness in that area. This was tested by dropping the bottle on its nose, with no adverse effects.

With regard to welding PET, it is the same stuff as Dacron sail material. If you have one of those thermal sail cutting tools that look like a soldering iron, they have their temperature regulated at a point which will melt but not burn the plastic. A conventional soldering iron is set at a higher temperature, and will start to burn the plastic.

If you try to weld, you will need to practice your technique first. Welding melts the material, and as soon as it melts, it will want to run. Welding thin material is very tricky. You may need some kind of mold to hold it in place, so you don’t just make a bunch of holes in the material. Perhaps a “welding rod” will help; this would be a strip of additional plastic material to be fed into the joint while welding.

I have briefly tried welding a pointed prow, but the plastic does not conduct heat very well, so the iron only melted the small area that it was touching. A joint was obtained, but it was quite weak. A welding rod would probably have helped, but I got lazy and just taped it together.

5

Thanks very much for the help, Walt and Le petit Normand

Your experiences, Walt, are pretty much what I expected. I know that PET will need a very flexible bond to last, and I have thought of double-sided tape - perhaps reinforced with PVC tape on the inside.

For attachment of the deck edge I was again thinking of hot-melt glue to attach, say, 1/8 sq balsa then glue a ply deck to that.

I will research and try acids to get a sorta solvent weld. At least with a teenager in the house I have plenty of material to experiment with.

I discussed the problem of not being able to find a bottle which is long enough to shrink-mould a complete hull in one piece with my “material advisor”. He immediately suggested pulling a heated bottle until it is long enough! Good direct thinking that man!

We also wondered if the top was sealed and the bottle heated carefully if the very heavy base and top neck could be persuaded to soften and extend under the internal air pressure?

If I get a moment I will give that a try - then there is not even a deck edge to attach. Getting the balsa plug out MIGHT be a challenge tho!

Thanks for your contributions
andrew

6

How about using silicone adhesive used to repair fish tanks? Flexible and waterproof
Bob

7

Some interesting facts that have come from this discussion:

Le Petit Normand has mentioned that the PET is sensitive to acids

I have successfully used silicon bathtub caulk, but not relied on it for strength

It was also suggested by Bob

But silicone bathtub caulk releases acetic acid when curing (it is on the warning label). Perhaps this helps it bond to the PET, and maybe it is much better than expected.

It probably cures at the edges exposed to air, and the cure slowly works its way inwards, so you probably want a very small bead of adhesive, and a relatively thick edge exposed. This will cause an undesirable discontinuity in the streamlined hull, but it might be acceptable. But a very thin layer might never cure.

But more importantly, I am overwhelmed with curiosity about how you formed the hull. Did you use a heat gun? Whenever I have tried something like this, the pre-stressed portions of the neck have shriveled and crumpled.

And a safety warning - Be careful how you heat a closed bottle. It might explode and cover you with molten plastic.

8

Actually, Walt, I was not refering to bathtub caulk. It is not waterfroof, only water repellant. There are special silicone adhesives to repair underwater leaks in fish tanks. Not sure, but I think Goop makes one. Also bathtub silicone is not an adhesive and I would not trust it.
Bob

9

Just for grins, I tried the 3M 200MP single-sided pressure-setting tape on a Perrier bottle. Sticks like crazy.

http://www.tapecase.com/c.108.1.1/200mp-high-performance.aspx

Cheers,

Earl

10

Andrew - You might try googling “geodesic aerolight”, it is a boat building method pioneered by Pratt Monforth. It is basically skin-on-frame construction with diagonal reinforcements of Kevlar roving, all covered with dacron cloth that is heat shrunk taught. He uses a double sided tape which is heat activated to attach both the roving and the dacron skin to various parts of the wooden framework. It is waterproof and I imagine it has some degree of flexibility to it because skin-on-frame boats have some give inherent in them. The tape is applied to the surface and adhered with the heat from an ordinary iron.

I haven’t looked into this method in a while, but if I recall corectly, the supplies are available from Stimson Marine up in Maine, here in the US. I have no idea about its availability in the UK. Good luck with your search.

11

I don’t think that the small quantities of Acetic acids can do anything for us in this case, you can clearly smell it when you use bathtube caulk but it is in small quantities. If you want to see if something happend betwen the PET bottles and the acetic acid, just brush some vinegar on the bottles and check it out.

But if you want to try acids, I’ll go for Sulfuric acid or chloridric acid but with a lot of precaution, hand gloves, safety glasses and OUTSIDE to avoid the fume as much as you can.

I don’t think the bottle is gonna exploded, these bottle can handle a lot of presure and they will probably just melt somewhere because of iregular heating, if I have to heat the bottle, I’ll use the oven at a low temperature. Sorry I don’t have access anymore to a handbook to get the right temperature to use but it is probably under 200 °C there is some test to do …

12

Interestinger and more interesting.

Part of my background is in elastomers and polymers (thats rubbers and plastics) and several points have been raised in general and in particular:

Silicone rubbers that come in only one part are generally known as bathtub caulk or sealant. There are at least three types of cure, and the cheapest and most common is the acid type which as you say produces acetic acid as it cures
(Good wheeze - if you need foam silicone rubber mix this type with sodium bicarbonate (baking soda). Mix well and the acid produced causes the soda to produce co2 and form bubbles. Viola! Foam silicone)

The fishtank type are neutral cure, and designed to not kill fish, and there are other types including a low modulus type which is used with polycarbonate roofing (it doesn’t attack PC)

2-part silicones I use to cast lead bulbs for footys - its getting near the top of thier temperature range, but the mode of failure is to gradually go less “rubbery”

Sorry, I’m pontificating.

Back at the plot:
I will try welding - I have a temperature controlled iron, and could perhaps fit it with a wheel to maks a sealed seam.
Any adhesive would have to adhere well, and be flexible - that’s a tall order as we have found - probably hot-melt adhesive is the closest here.
Tapes - single and double-sided stick very well to clean PET so that suggests that the neoprene glues (Evostick family in the UK) Do you have smelly contact glues in the US (still)?
I have joined by hull halves with double sided tape, after making a test piece which convinced me completely. I stuck the inner half (stern) over the plug applied tape, peeled off the backing and then carefully aligned the bow part, then stuck it down VERY firmly with a rounded burnisher.

Difficult to photograph, but pics attached

I have taken pictures of my trials with shrinking PEt (pop) bottles onto the footy former - are these or a description of the technique of any interest to anyone?

Thanks LePN for your thoughts and safety concerns - I will try some acids (with care) and see if any of them weld/dissolve/affect the plastic.

regards
andrew

Pics attached of the hull at dawn today

13

A couple of further hot-melt thoughts - which I will try tonight.

“Hemming tape” is a felt of hot-melt glue - very thin and designed to be activated by a hot Iron - worth a try. I think it may in fact be a pva glue (for what its worth ALL PVA/ carpentery/white glues are to some extent hot-melt - try it)

I have edging strip from a joinery shop - real wood about 1mm thick with a good layer of hot melt glue applied to Iron on to the edges of things. I aim to use this in a 1/4 wide strip to iron an inwale into the PET hull. Then I can stick a deck support easily to it!

All the manufacturers of iron-on aircraft (airplane) covering make a heat-activated adhesive for overlapping film covering or applying film which has no adhesive built-in. This might work.

THOUGHT - the same manufacturers also knoe about all the plastics (PET is a polyester, and they make polyester cloth coverings). Solarfilm, for example make Prymol to etch and bond to polyester and other plastics.

I’ve rambled again - but may be onto something - must have a word with Derek!
andrew

14

I do have a master in Material and polymers but then I decide to switch to metallurgy and lost all my knowledge (well it was not so extensive.)

The more I think about it the more I feel that tape will probably be the answer even though it is not the best one.

The real problem is that you are working with a very thin material and the limit between heating it and other heating it is very closed but gees it is worth to give it a shot

Good luck for your tests

15

I haven’t tested it but i think Goop is the answer. It has stuck anything I have tried it on and is flexible and very strong. Apparently it won’t stick to silicon.
Don

16

Don,

Thanks for that - seems quite likely. It is not readily available this side of the pond, but I used to have some, and may still.

It’s what I would describe as a rubbery, solvent adhesive, and as you say is very sticky.

That remidns me that there are glues made for the repair of trainers, and these are of the same generic type - they might be successful, too.

Very little sticks to silicone, except silicone, its all to do with surface energy. We used to plasma-treat silicone (and PTFE) so that they could be stuck and printed on.

andrew

17

Andrew
Trainers are sneakers, right? If so that sounds like the stuff. Goop makes “Shoe Goo” and “Marine Goop”.
http://www.amazinggoop.com/amazinggoop/index.html
If you can’ find a comparable product PM me your address and I’ll mail you a tube. I’ll go out to the shop and test it on a Coke bottle and let you know tomorrow if it works
Don

18

Having followed the thoughts of others on the merits of lemonade bottles as a construction material, but I must admit that I prefer to think of them as something to retain liquid rather than to keep it out. Nevertheless the posts on this link have made me think as to how two such bottles could be welded together and thereby saved from the incinerator if not the bottom of a pond.
My brief experiments followed the following path:
Fig 1. Ensure the the mould(s) have square ends in order to produce a flange on the resultant shrunk product
Fig 2. Match up two such sections and weld them with a hot iron on the inside.
Fig 3. The result is a rigid watertight frame within the product which can also serve as a mounting point for those servos, batteries etc. but as you will see there does remain the task of filling the join on the outside to a smooth finish.

19

AndrewH,

Roger Stollery uses a Corrugated Polypropylene called Correx for his Bug 3.

He seems to put PVC insulating tape around the outside of the panel joints, but on the insides he uses Evo-Stik Sticks Like Sh*t.

How Polypropylene relates to PETs, Polyesters, Elasomers and Polymers I really don’t know - but at least it is waterproof and available in the U.K.

Cheers,

firstfooty

20

Andrew
I cut a 340ml bottle in half and glued it together with “Marine Goop”. I overlaped the joint about 3/8" and put a 1/16" bead on the joint. Clamped it and left for 20 hours. I can pull it apart if I clamp one end in the vice and pull. It was still a little tacky so maybe a longer curing period would help. It might also never cure. I think it would work though. You can contact them through their website, they might have suggestions. I found them very helpful.
Don