How to make fibre glass tube

There's a fair amount of surface area to dissipate the heat so it shouldn't become excessive. The wax sold for arthritis sufferers to use in hot wax baths stays solid at hot-to-the-touch temperatures; not sure what it is - probably paraffin wax.

 

A mass of epoxy can easily catch a mixing cup on fire, so how good is that wax really?

 

I cant imagine ever wasting that much epoxy. Im pretty good at judging the right amount.

 

The slit may not need any filler at all. With 1" thin wall PVC an initial spiral wind of fiber would close the gap with the slit edges butted together. After cure, start on one end and pry one side of the slit in toward the middle to offset the edges. Apply torsional force and pulling force on this and the whole thing may pop loose inward. If needed a tool could be made that you would pull through on the inside to get one edge of the slit offset to the inside along the full length.

With the slit, thin wall PVC would be pretty floppy. For any significant length, a cradle would probably be required to keep it straight.

 

The slit shouldn't make the pipe too floppy provided the side os the slit cannot slide in opposite directions; this occurs when the pipe is torqued but it doesn't need a lot of "stick" to prevent it happening.

 

MIght want to paint a light color. In the sun dark could be 150 F which probably would not seperate the composite from the pvc but who knows.

I still like the plastic wrap on the mandrel, it worked for me, and if I was making 4 meter long shafts vaseline and double wrap sounds better.

My thoughts are similar to Terry's method. Slit a tube with the correct table saw blade, I would prefer aluminum tubing because of the superior size range (diameter) available. Wax may work but my thought was to maintain the slit width (blade kerf) with internal support. Wax or tape will bridge the gap. I think a square tube would be clever because the corners could be rounded to match the mandrel inside diameter or increased in size by application of narrow poly tape down the length of the four corners (one or multiple layers x four corners) for a tight fit. An option in the US would be using telescopic aluminum tubing (.058" wall thickness). There is clearance for an application of poly (3M) packaging tape (.5"width) applied the length of the mandrel support tube in maybe 4 or 5 lengths distributed around the tube. I may be wrong but I believe the removal of the mandrel support could be easier without full mandrel /mandrel support contact and certainly without direct aluminum/aluminum contact. As long as there is a cradle to support the tube during the cure the mandrel support could be two piece and pulled from opposite ends with less effort. I would still wax the mandrel and wrap with poly sheet/film.

Frosty, I like your solution for a single project that does not need ultralight weight. An abrasive on the PVC before the epoxy/glass application and I doubt the materials will ever seperate know matter what the temperature.

 

The PVC tube I propose to use is very thin white. It is so thin you can squeeze it together with your fingers to the shape of an egg. I feel that a couple of layers will make it very rigid as they will only be 44 inches long. I do not intend to remove the mandrel but leave it inside.

The rigid awning will look similar to a coffee table hopefully not identical,-- so 44 inches of glassed legs I feel will be strong enough for squalls and 24 knots effecting to the side of it. I will align slightly down at the front to as not to cause lift.

Awning being prepaired today but very hot here and I am working in the sun in the marina dock side,--not easy.

 

Having made several 'glass tubes for various things over the years, the biggest issue I've found is, no matter what you use, some level of adhesion will take place. You have to break this adhesion or removing the mandrel is imposable. A split mandrel works, but you have to be able to grab the mandrel half and physically move it (typically twisting) to break the adhesion, before removal. Other then maintaining shape issues associated with this technique, I've found you have difficulty doing this on all but short tubes.

This is one reason I use compressed air and sacrificial layers of plastic sheeting or tape. The air will, usually quite violently, shake the laminate right off the mandrel, making withdrawing it, often with the sheeting or tape still partly attached as it comes out (attesting to the adhesion issue) quick and easy.

Another technique I've seen that works on solid or stiff mandrels, is a multiple tape system. Layers of plastic packaging tape or sheeting are applied, the last being applied upside down (if tape) and plastic sheeting or more tape applied over it. This makes a removable layer that you can grab with a vise grip and yank out, breaking the adhesion bond and providing a little space to slide the tube off.

 

Regardless of the fact that I am not removing the mandrel I have decided to use a 4 inch pipe to hold up a relative awning for no other reason than looks or fashion. I hate the ubiquitous stainless swivel fold down with blue Sunbrella, is there a boat in the world doers not have that.

I think 4 inch will give the awning a modern look like that made by Africat and many others. The look of strength and I have confidence that a 4 inch PVC thin wall will become extremely stiff at 44inch length to take the squalls and the 24 knts the boat will give it.
The awnings that I had made 80 inch by 60 inch was just 2 layers and yes very floppy but now with a star like web it is way strong. This may seem obvious to you guys that glass but I am amazed and enjoying every minute of it and t to be honest im very pleased with my neat laminating.

I have used 1 inch square hard black foam similar to flip flop shoe material rounded at the top and flared fillet at the bottom, super glued in place and glassed over.

ITS EASY.

 

G'day hey. 4" will look a tad over-large - try 3" - looks fab. Also maybe U want to think about glassing some ridges(stringers) neatly on the outside top of the bimini. Placed in the right (what the hell's that) position they can be several things all at once. - Look good - very stiff for weight - great to mount items on top of - supa for catching rain-water to top up water-tanks. - semi hidden piping can run down the inside of the 3" support struts. All easy to do - out of sight - outside of damage - keeps cool - less algi & 'kiss' to do. ciao, james - - - - - save a few 'sundowners' please.

 

Quickest way to make a small fortune boat building? Start with a big fortune!

 

G'day 'Perthy' bloke. Ha ha ha etc etc.

Thanks for that - - I'll 2nd that by 100's.

That'll keep me going for at least the whole day.

Did the 'fibreglass yacht building etc' thing for over 30 years - full time - had fun - didn't get to sail as much as I wanted - to broke & to busy fixing everyone else's yachts.
Started building 'fibreglass electrical' parts & things - mabe much more money - could afford to go sailing - had the time to do just that.

Now semi-retired & selling the 15 acre rural property & going back sailing ASAP or sooner. Ciao, from the other coast. james in Cairns.

 

Ive made the pipe!!

I used a brush to lay on the resin then roll on one full length with overlap if 1/4 inch. Ist layer is a doddle, second layer tends to get air. I found that dabbing the brush stretched the matt and made it bubble , best to just paint it on. This also makes an attractive wave pattern on the matt strands.

The thin wall 3 inch pipe is now approx 3 -1/4 . I shall give it a good grind down with a 16 grit on the grinder. Stiffness is excellent and im sure will do the job.

The pipe mandrel was severly sanded and is not being removed as the weight is insignificant.

 

I have seen CF tube in 2m lengths on very slightly tapered mandrels done with autoclaved prepreg, but I was going to suggest a polystyrene foam sacrificial core that could be dissolved out with acetone after cure of an epoxy laminate. I would hang foam rods from the shop roof trusses so there is no gravity to cause a bend. Guaranteed core removal!

 

I dont see the absolute necessity to remove the mandrel. In my case the extra material is strengthening and as mentioned the weight is miniscule.

The cost of a liter of thinners and the mess is pointless.