How to make fibre glass tube

[Frosty]

I was thinking just roll some wetted fibre glass matting around a PVC pipe and leave the PVC pipe in rather than cut it out and re join the pipe!! or should I cut it out.

How would 'you' make some pipe approx 2/3 inches dia.

[Olav]

Frosty,

I made some carbon tubes for the hiking wings of my International Moth.

They are of larger diameter than your 2/3" (44 mm and 29 mm, both with 2 mm wall thickness), but I think the same principles could be used in your application also.

Mandrels were PVC pipes from the local DIY store (40 mm drain pipes (http://us.123rf.com/400wm/400/400/naumoid/naumoid1012/naumoid101200052/8466187-grey-pvc-sewer-pipes-background.jpg) and 25 mm electrical conduits (http://i01.i.aliimg.com/photo/v0/243618797/PVC_electrical_conduit_electrical_PVC_conduit_PVC.jpg)). It's important to apply mould release wax thoroughly.

Layup was carbon unis in axial direction plus some fibres in +/-45° to prevent the whole thing from splitting under bending load and a final layer of 80 g/m² glass cloth to finish the tube later (something to sand into). I used to wet out the fibres on a workbench, lay the mandrel on top and reel it in to keep the fibres straight. Everything was compressed and consolidated with a really tight wrap of peel ply that also squeezed out excess resin.

Demoulding was easy: Since the mandrel was longer than the carbon tube, one could grab it at the carbon part and slam it down (axially) on the ground (concrete floor) to release the tube from the mandrel. As the PVC tubes are rather flexible the carbon tubes went off quite easily (compared to metal mandrels) but they may be too soft if your glass tubes have to be really straight. In that case you might be able to find some metal tubes or rods that fit inside the PVC tube to stiffen it while the resin cures.

Another technique I used successfully is to reel the mandrel with a layer of paper, wrap parcel tape (the brown stuff) around and apply release wax. By doing so you get a sleeve that doesn't stick to the mandrel at all and that can be pulled off with no effort. Thanks to the parcel tape and the wax you can then remove the paper sleeve from the finished carbon or glass tube (use a stick to peel it off everywhere).

[Tim B]

There are some websites that talk about doing something similar for model aircraft, but add the idea of vacuum bagging to really consolidate the structure.

I have had success using non-stick oven paper for polyester and epoxy layup. It comes off very easily as long as you don't have any wrinkles. Unfortunately you don't get the best finish ever; but hey, inside the tube...

The other question is do the glass/carbon tubes available from the 'net meet your requirements? there are a few suppliers around.

Tim B.

[Frosty]

Thanks very much guys I think the bit about putting some paper between the mould and the fibre woulf be a good diea , my mind is already racing with ideas of allumium foil.

Im goin to look today for some very thin wall PVC water pipe.

I assume furniture wax applied copiously would suffice,--its going to have to. Ive used furniture wax before but did not polish it ,I left it quite thick on the surface.

[PAR]

Wrap your mandrel with two separate layers of clear plastic sheeting. The 'glassed tube can be easy slid off, as the one layer of plastic sheeting scoots past the other, which will be very lightly stuck to the 'glass work. It may resist at first, which you should be accustomed to with trying to find a date, but a blast of air from an air chuck, between the two exposed layers at one end of the mandrel will usually free it up.

[Frosty]

Seems easy enough then, I mean making the pipe not getting a date.

What if I wanted to make a rounded mould as I would with say a 3 inch plastic flexible pipe held in shape and glassed.

I guess I would need to split that and cut it out,---yes?

What about a PVC pipe split in half and the 2 halfs glassed inside the 2 halfs then joined and clamped. The thickness of the cut on the PVC pipe would be similar to the ammount of glass in the join????

[groper]

what about infusing the layup, has anyone done this?

What im thinking is to wrap the layup dry around the PVCtube/mandrel held neatly in place with spray tack glue followed by the peel ply and use a resin transfer media over the top and seal the bag to the exposed ends of the PVC tube - not bag the whole thing so the tube itself isnt under vacuum and wont draw resin in the void. The resin feeder lines might be rings around the tube at 500-700mm intervals and infuse it from one end to the other.

I dont like the idea of trying to wrap wet glass around a tube - would be a messy affair and probably end up with lumps and balls of fibre everywhere... Infusing it would be neat, clean, and provide a high quality laminate with probably alot less work than trying to lay it up wet - and minimal fairing afterwards...

leaving the tube in or removing it - i dont see a problem with either - depends on how weight sensitive the part needs to be...

Id be inclined to use around 2/3-3/4 of the layup as uni directional and 1/3-1/4 double bias...

[tunnels]

Biggest problem with making tube is getting off the mandral or mould it can be anything steel pipe plastic pipe steel shaft what ever depends on the dia you are wanting !, Petroleum jelly and a wrap or mylar ! Coat the mould with a nice coat of petrolium jelly and then a wrap of mylar and the jelly holds the mylar in place and allows it to slide off gently and the mylar will leave a beautiful smooth shiney surface inside
First layer use tissue glass, then csm 450 and then your woven any width and more csm then more woven and if the tube is able to turn slowly then you wrap the glass tight the resin bleeds all the way through and can finish off with peel ply . and no steel rolling is required
You can make nice looking tube using glass braid in the form of a sock any size any length in Glass , carbon , kevlar .

The pipe will slide off the mandral with a little effort but do it at a early stage not days later or the resin will have shrunk and tightened up !!,a rope glassed to one end on the glass pipe and a rope on the other end of the mandral and use any method avalible to pull the two apart , a car on one end and a fence post or something solid and gently drive away . We used a crane in the factory and a chain dyna bolted to the floor , made 6 metre lengths one after the other all day long from 50mm dia to exhaust pipe 6inchs dia vinylester resin gel time 25 minutes cure 3 hours and off . Made any thickness for any situatuation !!
:D

[PAR]

A tube can be made without having to split the mandrel or the tube in the process. Also wrapping 'glass around a mandrel is easy and not lumpy, unless you're fairly messy about your work habits. Bagging can improve the resin/'glass ratio, personally, I think infusion would be a waste of setup time and materials for such a small task, unless setup previously to infuse.

Simply put, the double plastic wrap trick works well for the spar tubes I've made. You can usually pull one layer of the plastic wrap out, between the mandrel and laminate, particularly if you've slit into a few inch wide strips. I've found the air chuck thing to be just the thing, it pops the light bond and even can scoot the tube off to a small degree.

[Herman]

I am still not getting it about the date, about getting stuck, and blowing to release things. You mean I need to blow my date, instead of vice-versa? :confused: :)

Anyhow, I also saw someone winding fish wire tightly around a mandrel, then applying thinned down plasticine over it, to get a good releasing mandrel. Lot of work, though, and a bit masochistic. I think the double-plastic one is most easy.

Another customer of mine makes masts by making a very thin glass laminate over a suitable mandrel, cutting it open, removing it, then beafing it up with more laminate.

[jim lee]

Another customer of mine makes masts by making a very thin glass laminate over a suitable mandrel, cutting it open, removing it, then beafing it up with more laminate.

I was thinking about trying that! Actually, two half molds. Wasn't thinking very hard about it, but its good to see the process works and I wan't crazy to consider it.

-jim lee

[P Flados]

I have thought on this subject more than once. My plan was:

Start with thin wall PVC.

Do a spiral wrap of plastic sheeting strips with 50% lap to ensure release.

Build a cradle to set the whole thing in and keep is straight (two 2x4s screwed together to for a L section)

Cap one end of the pipe and insert an expansion plug with pressure tap in the other. Pressurize the PVC to 125# air pressure to expand it slightly.

Apply glass/carbon/epoxy to suit

Wrap exterior in a spiral wrap with plastic sheeting. If it is thicker than normal this can be applied with sufficient tension to compress the glass/carbon/epoxy quite a bit.

Place the assembly in the cradle to keep is straight while setting up.

Depressurizing the mandrel should make pulling it out a sure thing.

[Frosty]

As I posted before I think If I do this I would do the thick wall pipe cut down its length and fibre glass the insides and slop it together with a couple of G cramps or wrap with tape with edges dripping out the sides.

This would with no doubt come apart and the process could be repeated very quickly.

No fairing required or very little once the sharp edges ground off. Taking into consideration fairing and labour, sand paper etc this method works in my head best.

[magnus]

I have used a mandrel with the double poly wrap with good results on very short pulls (1.125" mandrel in a split oar blade mold, a 6" pull). I would like to do long pulls (6' or more with a 1.125" or 1.5" mandrel). My project would also be fairly light (thin walled) so I am not sure the crane pull is an option and still have a tube in one piece. Paul MacReady used thinwall composite tubes in his Gossamer Condor (human powereded flight Kremer prize winner). They were willing to use a sacrificial mandrel of thin walled aluminum tubing in very long lengths, wrapped and cured with a very thin composite then soaked in a trough of acid to dissolve the aluminum. Clever solution for a tough problem with a lot of money and prestige on the line, but not the solution for most of us.

My first thought here is that temperature and coefficients of thermal expansion, CTE, could be an ally here. A plastic mandrel (PVC, polyethelene, etc.) still double wrapped in poly but cured with the composite sleeve at elevated temperature (limited of course by the plastic chosen) could after cure and return to ambient temperature or below give up the part more easily. I am thinking, of course a low shrink epoxy, and carbon or Kevlar sleave. One would have to support the part/mandrel in a horizontal oven with perhaps a well supported angle of steel or aluminum opening up "V".

This is an older thread, but any thoughts or experience with this would be of interest so please comment.

[Herman]

These are several options. If you want to do the heat trick, but want to keep things straight, choose aluminium. You can double-wrap it, release coat it with a high-slip release (semi perm, for instance Zyvax, one of their high slip versions) or apply self adhesive teflon film to the tube.
Then laminate your pipe, and install a heat gun which blows through the pipe, or toss the thing in an oven. You need 80C or more to have this work really well.

Another option for long, thin things is to wrap a tube with fish wire (laboursome, but doable). Then smear thinned plasticine all over it, to smooth it off. Laminate your pipe, then pull the mandrell out, which should be relatively easy. Then pull the fish wire out, and clean up.

[Frosty]

An idea came to me this afternoon as a woman threw away the inside card board roll of a some cling film. It was about 6 feet by 3 inches tube .. Others were talking of sacraficial mandrels and it occured to me that this cardboard could be soaked in water and then blasted out with a pressure wash.

[Jimbo1490]

As long as the tube is straight or only slightly curved, heat shrink tubing can be used for compression of the layup. Heat shrinkable plastic is also available as a continuous strip which can be spiral wrapped around the layup, including any curve, then shrunk to provide compression. I know with certainty that this technique works because at least 2 different commercial manufacturers are using this exact technique to make composite tubes.

Jimbo

[PAR]

Frosty, the main problem with a laminate wrapped mandrel, is the laminate sticks. Even if the mandrel is wrapped with a release agent or plastic, etc., it still sticks, maybe not so well, but well enough over a huge amount of surface area, that just over coming a 1 pound shear strength attachment is equal to imposable.

The solution is a mandrel wrapped with a multiple layered release system (as I mentioned previously). One layer can stick to the laminate all it wants, as the cured tube is removed, sliding over the inner most layer, which typically is also stuck to the mandrel. If you want to get really clever, you can make a set of release sleeve sections, much like what I've described and pull them out of the tube as you wrestle the tube off the mandrel.

What air does, if forced in with a chuck, is drive the release film (plastic sheeting) up and off the mandrel and down and off the laminate. This creates a cushion of air for the tube to slide on as you're pulling it off.

Lastly I've used heat shrink tubing and wrapping in layups. It works and makes for a clean, smooth surface when done as well. If spiral wrapped, you'll have some spiral seams, but these are easy to knock off.

[sabahcat]

How I have done many times is to:
Coat mould/tube in release agent (I use wax followed by PVA)
Once dry, wrap one layer of glass (440 to 800db) around mould
Once green, slice down length of tube with sharp utility knife and break/release slightly
THEN, continue with remainder of glassing.

Roger Simpson, an Australian Multihull designer, suggested for rudder tubes, doing multiple coats of epoxy thickened with graphite powder first, then 1 layer of glass.
When green, follow steps above, end result is a rudder tube with graphite bearing.

[magnus]

How I have done many times is to:
Coat mould/tube in release agent (I use wax followed by PVA)
Once dry, wrap one layer of glass (440 to 800db) around mould
Once green, slice down length of tube with sharp utility knife and break/release slightly
THEN, continue with remainder of glassing.



Is the mandrel then left in place to support further build up of the shaft once the initial surface tension has been relieved? You did say release slightly, so question answered, the mandrel is left in place.

[ancient kayaker]

No idea if this will work but drapery stores sell plastic sleeving to put over wood closet rails; it pretty's them up and allows the clothes hangers to slide easier. It is not a closed tube, just overlaps itself along its length, so it may need a strip of adhesive tape over the exposed edge. Being PVC I doubt resin would stick to it, and once the glass tube was formed it should be easy to remove by twisting it. Worth a try I'd say.

For larger tubes I would be inclined to make a thin walled wood tube from the lightest wood I can find, wrap the glass around it and just leave the wood in place. But I cheat at cards too . . .

[dinoa]

Try this as described by Jim Marske in his book marskeaircraft.com/workshops

You lay up over a PVC pipe with outside diameter that is close to the inside diameter of the pipe to be fabricated. The PVC pipe can be supported by placing a steel pipe inside to keep things straight and eliminate sag.

The plastic pipe is waxed and 45 deg bias cloth layed up. The cloth wrinkles are worked out with a gloved hand from center out. The 45 bias acting as a Chinese finger trap tightening the cloth.

To seperate the tube the inside of the pipe is heated alternately at both ends with an air gun before it has fully cured thus expanding the pipe. Hold for 15 minutes then allow to cool. The PVC pipe shrinks away from the composite tube facilitating removal.


Dino

[JJ.windspeed]

Something I will be doing soon is to make some f/g epoxy tubes (80D x 400L x 5mm thk.) to be glassed into hulls for aluminium cross spars to sleeve into.

The method is to have a turning mandrel, to buy a cheep wood lathe (eBay) adjust the gearing to slow the rotation speed right down. Set the PVC or aluminium tube mandrel up with 'turned up' wood ends into the tube slightly at incline so as to wedge into the mandrel.

Using methods from above to wrap plastic got from HWH/Bunnings (thinking membrane plastic or those 'warning tape-off area' rolls of plastic tape) and wrapped or wound spiral up the tube and taped down ends, should allow the tape to unwind when mandrel dropped or finished tube counter spun and dropped.

Wet out of cloth is done from a container made to hold a couple of rubber rollers to run the wetted out f/g tape through (much like a couple of disposable paint rollers?) to squeegee excess resin out, working up the tube then back down as the mandrel turns in the lathe. Could be automated with a spiral cogged geared set-up.

Wrap up with peel ply then wrap up in spiral plastic again, tape off, let gel then put into home made oven (mdf boxed up with insulation batting sandwiched and fan heater. let cool and then drop the mandrel to unwind release tape and release tube.

Hope it works, as a carbon tube spar company in Sydney quoted $300 p/lm to do this in f/g or c/f pretty much the same cost!

p.s. this system of turning mandrel reminds me of the big A1 plan printers and how they have paper rolls on tubes with end plugs for different size paper rolls.

[jim lee]

So, we think we're getting close to perfecting an infused carbon tubing process. Here's an example of 3 1/2" tube we made. Its 45/45 UNi 45/45 sandwich.

Have a look.
http://a3.sphotos.ak.fbcdn.net/hphotos-ak-ash4/386034_10150412035571290_184959066289_8786226_157617956_n.jpg

Once we get this down, we'll see about doing different lengths, shapes and fabric loadings.

-jim lee

[tunnels]

So, we think we're getting close to perfecting an infused carbon tubing process. Here's an example of 3 1/2" tube we made. Its 45/45 UNi 45/45 sandwich.

Have a look.
http://a3.sphotos.ak.fbcdn.net/hphotos-ak-ash4/386034_10150412035571290_184959066289_8786226_157617956_n.jpg

Once we get this down, we'll see about doing different lengths, shapes and fabric loadings.

-jim lee

Thats really nice !! :D

[Frosty]

I am pretty sure Im going to have to do something on these lines . I priced up a 6 meter length of 304 stainless at 2800 baht (thats 30 to the dollar)

A local gate maker wanted 7000 baht to make two 3 meter lengths with a 90 degree welded on the end and a meter on that,-- a L shape.

The 90 degree elbows are only 2 dollars--in 2 inch.

[magnus]

Back when this thread was hot I ran a thermal test on tubes, all close to 3/4"diameter. I was going to post it but did not because nothing was surprising. I warmed PVC , aluminum (.058" wall), aluminum rod stock, steel tubing, and HDPE rod stock. The measurement was the difference between 70 degrees F and 170 degrees F. With 100 degrees F difference I got almost no change in dimension from the metals (maybe .0005" from aluminum). Plastic was good for 2 to 4/1000 of an inch. Solid stock had less change than tubing/pipe. My conclusion was that the introduction of heat can certainlly be a help with plastic mandrels.

[Frosty]

Thats good information . Using heat is a good idea and now makes this thread hot again.

I am nearly at the point to start to make some, I only need 8 meters but running through the whole process in my head I am stuck at how to keep a 4 meter PVC pipe mandrel straight as it hardens. All I can come up with is a line of house bricks leveled up on the drive way.

How did you anticipate putting heat into the mandrel --a hair dryer ?

Oh Oh I just though of maybe 4 of 5 gallon cans with the lip being less damaging to the hardening resin.

[ancient kayaker]

Some thoughts:

PVC pipe is prbably the best of the plastic pipes for long unsupported lengths.
Schedule 80 PVC pipe would be a lot stiffer than schedule 40
8 m sounds kinda long, if supported only at the ends sag would depend on the diameter
Your first post said 2/3" (as in 0.667") I assme you meant 2 to 3", maybe more for a 8 m mast
Try a shorter length first to estimate sag; mid-span sag is proportional to L^4
You could fill it with water to increase the weight and sag for a more sensitive measurment
If you extend the length of pipe and weight the ends it will reduce mid-span sag
Ensure you can extract the mandrel with a shorter practice length!
This link has a table of recommended support spacing for pipes of various sizes when they are full of water http://www.engineeringtoolbox.com/support-spacing-pvc-pipings-d_783.html

Theoretically pressurizing the pipe should stiffen it: allowable pressure depends on schedule and diameter but it is good to at least 125 psi, provided the end caps are rated to the same. It is safest to fill the pipe with water first before pressure testing it any higher.

[Frosty]

I need 8 meters in 2x 4 meter lengths for transportation. I need the finished product to have 2 x 90 degree bends which I intend to use PVC water pipe bends inserted internally to give me room to glass over then and leave them in there.

I am un shure how to do the lay up,--ie shall I just cut a 4 meter length and wrap the pipe dry possible hold in place with elastic bands and then wet out , or --cut strips of matt to say 4 inch and wrap spirally around then wet out --Or wet out either way and wrap wet.


Ive a feeling im going to end up with a soggy mess either way

[hoytedow]

Fanie did something similar on the http://www.boatdesign.net/forums/multihulls/boxy-fisher-catamaran-26429-3.html thread. Maybe some of his technique would be valuable in this endeavor.

[ancient kayaker]

I doubt there'd be much sag for a 4 m length of PVC pipe with no water in it. I just noticed that table has a column for fiberglass pipe which can handlea much longer span than PVC; if you can get some of that it would be a better mandrel, might even make an adequate mast . . .

[BobBill]

Have comments on using glass or carbon sleeves, rolled back on itself. like rolled socks, and rolling out on prepared mandrel?

I am planning to use a windsurfer mast above a aluminum Force 5 base, and intend to stiffen the windsurfer mast with carbon sleeves. I thought rolling the carbon out would be easier than pulling on to mandrel...

[P Flados]

I am stuck at how to keep a 4 meter PVC pipe mandrel straight as it hardens. All I can come up with is a line of house bricks leveled up on the drive way.

Two very straight pieces of wood can make a quick temporary cradle to rest the tube in. You want to support it with two 45 degree surfaces that act like the vee blocks that machinist use to check shaft straightness. Build the cradle and use tight strings to check straightness. Shims can be used for vertical adjustments, 5 gallon buckets full of water can be set on the ground and pushed up against the sides for horizontal truing.

[michael pierzga]

Note sure if anyone gave the Gougeon Brothers link for composite tube building

http://www.westsystem.com/ss/building-composite-tubes-with-west-system-epoxy-and-braided-fibers/

[Frosty]

Well-- wrapped a 2 inch PVC pipe in glass and a small 1 inch strip on the join. Only 40 inches more of an experiment .

Now then who of you said it separates easily,-- you gotta be joking. I cant get it off banged it ,hit it ,prized at it. Yes coated it with boot wax.

No way in hell is that coming off. Will have to rethink and glass over a PVC pipe and leave it. Incidentally one layer of glass makes for a surprisingly rigid tube and satisfactory with one layer.

So--new plan is thin PVC pipe with a layer of glass only, actually lighter than the glass pipe.

[michael pierzga]

Slit with a razor knife and remove glass from PVC when the glass is in the rubbery stage. It will peel off the tube . Ive not used pvc as a form , i used mylar boxing tape covered steel pipe. My finished glass tubes were about 200 mm long. Once the glass is free of tube gently squezze back into shape and hold in shape with a few pieces of tape until it cures hard.

[sabahcat]

as Michael said
How I have done many times is to:
Coat mould/tube in release agent (I use wax followed by PVA)
Once dry, wrap one layer of glass (440 to 800db) around mould
Once green, slice down length of tube with sharp utility knife and break/release slightly
THEN, continue with remainder of glassing.

Roger Simpson, an Australian Multihull designer, suggested for rudder tubes, doing multiple coats of epoxy thickened with graphite powder first, then 1 layer of glass.
When green, follow steps above, end result is a rudder tube with graphite bearing.

[michael pierzga]

I have good luck using Brown Mylar tape as a mold release. Obviously its not suitable for some shapes and highly finished surfaces.

[CatBuilder]

This may work a little better...

Instead of using the pvc surface to glass on, tightly wrap a long length of line around the pvc, then cover that line with plastic film.

Wrap entirely in glass and let cure.

Now, pull the line out of the tube and slide the pvc out from your new tube.

This is how Richard Woods suggested I make my dagger board trunk and may work just as well here.

[hoytedow]

This may work a little better...

Instead of using the pvc surface to glass on, tightly wrap a long length of line around the pvc, then cover that line with plastic film.

Wrap entirely in glass and let cure.

Now, pull the line out of the tube and slide the pvc out from your new tube.

This is how Richard Woods suggested I make my dagger board trunk and may work just as well here.This sounds logical. I am going to try this for my cross-beams.

[tunnels]

Well-- wrapped a 2 inch PVC pipe in glass and a small 1 inch strip on the join. Only 40 inches more of an experiment .

Now then who of you said it separates easily,-- you gotta be joking. I cant get it off banged it ,hit it ,prized at it. Yes coated it with boot wax.

No way in hell is that coming off. Will have to rethink and glass over a PVC pipe and leave it. Incidentally one layer of glass makes for a surprisingly rigid tube and satisfactory with one layer.

So--new plan is thin PVC pipe with a layer of glass only, actually lighter than the glass pipe.

Why are you wasting time wth all thoses things Pvc tube abs smear with petrolium jelly (vasoline ) wrap 2 layers of mylar round the tube and use the vacoline to hold the mylar wraps and then wind a layer of tissue and one of csm and wet it out !when wet and rolled then carry on with the rest of the layers you want to put on leave a space on the pvc tube to pass a steel rod at the opposite end of the glass tube glass on a piece of stout rope with a loop when is all hard then attach one end to a imovable object and the other end you might be able to pull by hand or simply attach to the back of your car and gentle pull !,it will slide off and when you take the mylar out from inside you have a shiney glossy tube
The outside peel ply it or use a braided sleeve as the finished layer . Used to make 4 to 6 ,6 metre long tubes every day som off pl astis and some off steel . all came off quite easly !!

[Frosty]

To be honest the PVC pipe wrapped with glass is perfectly suitable for the job. There is no need to remove the PVC pipe for my application and that is as supports for a rigid awning on the fly bridge.

It will look like fibre glass and will be painted with urethane after fairing,I see no reason any more to remove a perfectly good inner pipe.

[ancient kayaker]

Something here on using Al tubing mandrel and dissolving it with swimming pool (muriatic, hydrochloric) acid. Other posts decribe using balloons and caution about mercury content when using fluorescent tubes.

http://www.homebuiltairplanes.com/forums/composites/6038-composite-tube-fabrication-methods-work.html#post50073

I wonder about using PVC pipe, cutting a longitudinal slit in it, expanding the slit slightly with wedges then filling it with wax would work as a mandrel. Heating it up after forming the composite pipe should dissolve the wax, shrink the tube and make it a lot easier to remove. Anyone tried something like that? Possibly the slit could be held open with a rope that could be pulled out later; it would also provide support to the wax while it is setting.

[PAR]

I wonder how much the epoxy exotherm would affect the wax during the cure.

[ancient kayaker]

I wonder how much the epoxy exotherm would affect the wax during the cure.

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.

[PAR]

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

[Frosty]

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

[P Flados]

I wonder about using PVC pipe, cutting a longitudinal slit in it, expanding the slit slightly with wedges then filling it with wax would work as a mandrel. Heating it up after forming the composite pipe should dissolve the wax, shrink the tube and make it a lot easier to remove. Anyone tried something like that? Possibly the slit could be held open with a rope that could be pulled out later; it would also provide support to the wax while it is setting.

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.

[ancient kayaker]

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.

[magnus]

So--new plan is thin PVC pipe with a layer of glass only, actually lighter than the glass pipe.

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.

[Frosty]

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.

[PAR]

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.

[Frosty]

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.

[Silver Raven]

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.

[DaEdster]

Building a boat company from scratch
-jim lee

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

[Silver Raven]

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.

[Frosty]

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.

[FishStretcher]

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!

[Frosty]

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.