That was a year that was..

[Ian Vincent]

I know my name’s not Stuart, but I have had success with polyurethane water activated adhesive - it hardens when exposed to the water in the atmosphere. 

Rgds Ian

[Bfg]

50 minutes ago, Mk2 Chopper said:

Sounds like it's all come to plan for you, well mostly. You'd have thought the rear glass would slip out with the air flow at 70mph, so whatever you managed to do sounds like it's worked. 

Looking forward to your pictures from the Sandringham pageant of motoring. 

Gareth

Thanks Gareth,  yes, we're definitely moving forward here n' there rather than constantly fight-fighting, so to speak, in every dark corner. The plan is ongoing and although I'm sure not to everyone's or the purist's approval - her present middle aged style certainly seems to please passer's by, from schoolboys to thumbs up from lorry drivers. 

I'm not sure how much a low pressure there is behind a backlight, with or without the top on.  Previously experienced backwash-airflow might imply the rear window is being slightly pushed in / forward (..at the speeds I drive).  Tbh., I was very much more concerned around the streets, roundabouts and over speed-bumps ..what with the body twist, shaking and lateral forces all at play.  The friction which restrains it would of course be very much less when rain water seeps in between the glass and the rubber. I'm keen to seal it as soon as I know what to use.  I asked the windscreen replacement centre and I couldn't understand the answer, but I've just looked it up and I'm sure he must have been saying Arbo < here > 

Heating the rubber and pushing up n' down on the glass is all I've presently used.  And I didn't use soap or anything else to help get it in. 

I'm also keen to replace the rubber's sealing chrome bead, which is a poor fit. Very seems as if the round bulb part of the section is way too small . . .

 

Pete

 

[Bfg]

2 minutes ago, Quicksilver said:

 

It is also possible to secure the rear window with metal/aluminium plates, so that it stays in place. see example on TR3

Marcel

Thanks Marcel, That's a good suggestion and may well be the way to go.  Personally i don't think it looks out of character on a old car either.  I wouldn't want to try and drill a toughened glass window but just fastening through the backlight's fibreglass would still work.   I'll wait to see if it turns out to be necessary, for how I use the car, but it's certainly worth keeping in the back of my mind.     Cheers, Pete

[Bfg]

7 minutes ago, Ian Vincent said:

I know my name’s not Stuart, but I have had success with polyurethane water activated adhesive - it hardens when exposed to the water in the atmosphere. 

Rgds Ian

And who are you ?

 

Thanks Ian, I'll look it up.  We have plenty of fresh rain water to harden the stuff at the moment !

[stuart]

2 hours ago, Bfg said:

i agree. for both water sealing and peace of mind when I get used to things and start driving a lot harder.   Might I ask, what do you use Stuart.?

nb. I'd prefer not to use silicon because of plans to spray paint.

Pete

I would use what I recommended earlier https://www.ebay.co.uk/itm/360390006441

Stuart.

[stuart]

1 hour ago, Bfg said:

Thanks Gareth,  yes, we're definitely moving forward here n' there rather than constantly fight-fighting, so to speak, in every dark corner. The plan is ongoing and although I'm sure not to everyone's or the purist's approval - her present middle aged style certainly seems to please passer's by, from schoolboys to thumbs up from lorry drivers. 

I'm not sure how much a low pressure there is behind a backlight, with or without the top on.  Previously experienced backwash-airflow might imply the rear window is being slightly pushed in / forward (..at the speeds I drive).  Tbh., I was very much more concerned around the streets, roundabouts and over speed-bumps ..what with the body twist, shaking and lateral forces all at play.  The friction which restrains it would of course be very much less when rain water seeps in between the glass and the rubber. I'm keen to seal it as soon as I know what to use.  I asked the windscreen replacement centre and I couldn't understand the answer, but I've just looked it up and I'm sure he must have been saying Arbo < here > 

Heating the rubber and pushing up n' down on the glass is all I've presently used.  And I didn't use soap or anything else to help get it in. 

I'm also keen to replace the rubber's sealing chrome bead, which is a poor fit. Very seems as if the round bulb part of the section is way too small . . .

 

Pete

 

That Arbo quoted is a non setting sealer like I use for panel fitting, it doesnt hold anything in place. Best use the Sikafex one I recommended earlier.

Stuart.

[Hamish]

I lightly bonded the rear hardtop screen to to the rubber and rubber to hardtop as I feared it popping/blowing out at speed. 
seemed to work. 

 

[Bfg]

1 hour ago, stuart said:

I would use what I recommended earlier https://www.ebay.co.uk/itm/360390006441

Stuart.

Sorry I missed the early recommendation, but thanks, I'll use Sikaflex.  I've used their products on my own boat to bond all around new poly-carbonate windows in (without any screw fastenings because of their long length) so I am now obliged so to trust it.   I may have some tubes (now old stock) which I'm sure will do for this window.

Pete

[Bfg]

Thanks Hamish, I didn't know the needle in the rev counter actually went that far around ! 

But yes I can see why you've bonded it together. I should think without sidescreens it might get a bit blustery inside there.  The helmet to keep your hair on is also a good idea. 

Pete

[Bfg]

The backlight is Okay to live with, having now tried it on the road.  It being an inch higher would have helped a lot (..in getting it away from the top of my head) but for the time being it is what it is ..and the studs are too short to fit some sort of packer under it. 

Regarding the gap (..rain scoop !) inbetween that and the windscreen,  and my head being in conflict with the fabric-Surrey-top's frame,  I've now considered the options, and I've decided to try and make a lightweight grp hard-top lid.  And I'll use the car without weather protection for the time being, or else refit its existing rag-top.. until I get the new hard-top-lid made. 

With HUGE THANKs to Roger-H,  I have an old steel hard-top-lid to work from.  It's been hand painted, is dented, has rust holes through it ..and fraying gutter flanges. It's been poorly welded / brazed (?) with a weird brittle aluminium-like filler, and the lid's inside structure and flanges are half intact  ie., the other half have rotted away ! ..so it's perfect for my needs

^ As Roger assured me.. at first glance - it looks better than it is.  Still, these original hard-top-lids have a pleasing line, and is (relatively) spacious inside. The rest of it (inside structure, flanges, fixtures and fixings, seals, etc) will for my purposes be redesigned anyway. 

Starting off then. . .

  

^ This lid is a great starting point, for me to take a flash mould, and to make a new outer-skin panel in lightweight grp, onto which I'll graft simple grp flanges for the weather seals. 

  

^ someone had real issues with paint blisters.  The thick hand-painted black that tried to cover those was really hard to cut back, but in time I won over. 

  

^ the 'welded repair'  (rear RHS corner) ..which split open again as soon as I tapped it with the dressing hammer.   ^^ Oh well, there's always bondo !  glass reinforced filler in this case.

^ second coat, and already a fairer shape.

Wishing you great holiday celebrations. 

Pete

 

 

[Bfg]

Yesterday Katie  finally made it to her first local (East Saxons) TR group meeting, albeit an informal breakfast meet at The Alma, Copford Green, Essex . . .

^ Katie ~ TR4A, parked up with Rich's TR4, Bob's TR2 and Tim's black TR6. Chris turned up in his thirsty Covette Stingray a little later.  Good conversation, perfectly acceptable weather for having the top off, and good food and beverages served by our hosts, what more could you ask for.  The A12 was 40mph around Colchester which doesn't make much sense when the road is only being worked on at night ..and even single track country lanes are 60mph, but on the other hand 40mph is very good for fuel economy. !

In conversation I asked Rich if had, and whether I might borrow a TR4 Surrey-top windscreen capping, until at least I get a lid made in GRP.. Part of my motivation was that I was booked to go to Sandringham's Pageant of Motoring this morning and the weather forecast was not good, but seemed to be becoming more favourable with each Met-Office update. The hope was that if I could fit and drive with the fabric Surrey top, even if a little uncomfortable in terms of headroom, then I could go.  Otherwise I'd have to remove the backlight again to fit the rag-top.  Rich did, and very kindly offered to lend it to me, and so we went off to his home and with cordless drill removed the cap rail's rivets off one of his projects.  

Further good conversation and hospitality, before I headed home to try and fit it. . .

  

^ Katie has had a TR6 windscreen frame and cap rail, as is evident by the toggle's keeper for the hood frame. Its aluminium cap-rail has an indent above those, and like the non Surrey-top cap-rail for the TR4, its flusher fitting without the front overhanging rim.  The TR6 cap-rail also doesn't have the end (outside top corner of the A-post) plate and hole for the fabric Surrey-top's press stud.  Amazing then that all but the two rivet holes next to the Surrey-top H-frame's bracket holes were in the same position.  Katie's cap rail had been fitted with self tappers instead of 1/8" rivets, but still no second-guess drilling was necessary to fit the TR4 cap rail onto a TR6 windscreen frame.

 

^ Katie's cap-rail had been fitted over a bead of what looks to be clear silicon sealer, whereas the TR4 cap-rail was bedded on black dum-dun sealer.  I've removed those and instead used sticky back neoprene to set rail on.

^ First impressions were very encouraging. The front rail of this vinyl hood needed a little motivation to sit under the cap rail's front lip but I think that's probably quite usual. Clearly the vinyl needs a thorough warming in the sun to stretch it, as intended.. as it's width across the front is 1-1/4" short of that top corner press-stud on the passenger side and 3/4" short on the driver's side.  But even as it is it looks to be workable for low cruising speeds.

The side press studs pulled on, although the driver's side needed to be done first. And similarly the fabric's sewn in tubular-bow ..which is to pull down across the back edge of the backlight, and the two rear press-stud did go on. 

    

^ I presently only have one of the four hook-brackets fitted. These are used to tension the door window's draft-flaps.  However as it holds the glass away from the B-post's weather seal, I feel they might well be left off / an alternative used.   

  

^ Otherwise looking even better from the rear three quarter view.   ..well aside from the width being way too tight.

 

^ regarding interior headroom and the hood's H-frame being against the side of my head ..I lessened the problem by bending the rear legs of that frame into a bowed curve.  There's not much space in these cars for someone of my size, but as the top is not intended to be used unless really necessary, then a little compromise is to be expected and so acceptable.

So far so good huh, with a bit of heat and use - this fabric top ought to serve its purpose..  Well yes, but also not quite yet.  More modifications will need to be done, because as I tensioned the stays - the back window popped out of its top edge seal.     

^ As illustrated by the screwdriver, the top of the backlight has pulled up. The hood stay's adjustment was only by finger, no spanner or grips.   

That put paid to my going to Sandringham this morning, because it was already 6:30pm ..and tbh I couldn't be arzed to then pull the backlight off (necessitating removing the trim around the back shelf ..to get to the fastenings), to change the header rail back to the TR6 one, and to then fit the TR6 rag top again ..ready to drive off at 7am on a Sunday morning in the rain.  No thank you - I'll return to base camp and wait.. to come back again soon. 

What happened ?  well . . .

 

^ The fabric Surrey-top's H-frame (bowed rather than straight to give a little more clearance for my bonce), with the beautifully hand-crafted brass tensioning nut made by Roger-H. *  Thank you Roger - I recommend   . . .  The illustrations reflect what has happened.  In short ; although the tubular stays push back against the backlight, as one does so ..the tension in the vinyl hood pulls and twists the top rail of the grp backlight.  The bowed roof shape across the car adds leverage to this because the height of the tensioned fabric on the car's centreline is approximately 1-1/2" higher than the locating pin of the stays, positioned just outside the driver's head.  And that leverage twists the lightweight grp backlight enough to pull the seal away from the glass.         

It's not insurmountable though..  to rectify the problem I could remove the backlight, it's glass, and the vinyl trim on it's inside, and then clean that up and abrade the inside of the fibreglass as a key to add further resistant to torsion structure (ie., to bond in as large a diameter tube as will fit).  or else..  I make and fit (perhaps removable if so desired) a T-bar between the windscreen and the top face of the backlight ..on the car's centreline to counter the tension of the hood material.

For anyone buying / about to fit a grp backlight - either or both of these may be worthwhile to check for &/or consider.

Hey ho,  a most enjoyable morning, and then very positive progress ..so we can cope with a little setback now & again. 

Bidding you a pleasantly warm and comfortably dry evening.

Pete.

 

* NB. How anyone instead manages to tighten a plain nut on the end of the rear frame stays I don't know.  It looks easy enough with the fabric off, but with the furflex weather seal below and the hood material above, I should think it rather awkward.  In comparison Roger's screw adjuster can be tightened sufficiently with ones fingers, and the final tensioning done after the Surrey-top is fitted.   

 

p.s. the weather in Sandringham did start with light rain, but as we'd hoped it soon dried up until around 3pm when it drizzled for a while, then dry again until anytime now (5:30 - 6pm) when heaver rain is due for the drive home. It's also a chilly day for summer !

 

Edited June 5, 2022 by Bfg

[stuart]

The problem with the frame pulling up across the top is more likely to happen when you trim the edge lip to take the glass, thats why I said about bonding a bit of wood in right across between the two roof bolt holes (Which is what Ive done with mine ) and also bonding the screen in as I suggested earlier, this would stiffen it up no end. I didnt have much success with a new laminated glass as theyre too fragile to allow any pushing and shoving hence why I just went with the perspex/acrylic window.

Stuart.

[Bfg]

On 6/3/2022 at 8:11 PM, Bfg said:

^ second coat, and already a fairer shape.

 

This afternoon I moved on with filling the through holes and fairing the dents. . .

^ Starting off with lightly sanding coarse paper on a flat board, so the scratch marks give a clear picture of high points and troughs.  These I then filled and faired. To cut to the chase after a long afternoon's work, including bridging the frayed edge flanges.. and we now have . . .

^ the green filler with white over is my 'handiwork' to fair over the welded (and split open again) repaired back corner on the RHS.   The blistered paint encountered by some unfortunate soul was in the cream undercoat and then again in the red top-coat (..that was under the hand painted black when I started). Apparently this Surrey-top's metal lid was originally the very nice hue of light sky blue.

 

^ viewed from the rear corner of the LHS, shiny only because it's just been hand flatted with 320 grit wet n' dry, washed off and not yet dried.   That grit of finish will do fine for taking a mould off.  Perhaps tomorrow afternoon I'll get it waxed and a couple of coats of PVA release agent, and perhaps even a gel coat on it.

A constructive afternoon  (..that's heading in the right direction ! )

Pete

Edited June 6, 2022 by Bfg

[Bfg]

Just a few hours on the job this afternoon, but hopefully (if things go well !) then useful progress made. . .

^ Three polishing coats of Mirrorglaze bee's wax, which I've long used as a release agent when making moulds and with mouldings.  There's no additives and nothing to chemically react with, just bee's wax, which together with elbow grease to really rub the wax into the surface, all the corners, and of course any scratchmarks, pin holes, etc. The wax is equally vigorously rubbed off again, inbetween coats, so as to minimise surface build up.  

^ next up I applied two coats of PVA release agent, using a small pad of soft cloth.  The PVA is applied as thinly and smoothly as can practically be done (so as to avoid brush and dab marks.  I focused on making sure the PVA really brushed into the crease of the folded-double front edge, as well as onto the vertical sides of the rain gutters.  Once the first coat has air dried then I similarly applied a second coat at 90 degrees to the first. This helps build an even thickness film of PVA (micron when dry) and of course to ensure that nowhere gets missed. 

You'll note that the pattern's surface reflections have gone from matt (320 grit wet n' dry) to a waxed sheen, to a PVA'ed satin .   

After that had also dried then I moved on to gel coating the surface. . .

  

Gel coat being hand-painted on is thickened polyester resin (setting when catalyst is mixed in with it), often with a colour pigment (in this case white as it's left over materials from my making new cockpit hatches for the boat). The second photo simply shows that I started painting along the edges and worked my way in as a spiral  so as to maintain a 'wet-edge' to the coating. 

The gel-coat is the surface / skin layer of a mould or moulding (panel) which ought to be mostly devoid of visible air bubbles / pin-holes.  Its thickness is necessary to help prevent 'print-through' of glass fibres showing ..and to a large extent because it may be considered a sacrificial that may be sanded and polished smooth.  It has next to no strength, so its thickness needs to just thick enough to cover the surface. Too thick and the edges will easily chip and stressed surface areas will show cracks / craze. 

Neither the gelcoat, nor fibrglass laminates, are absolutely water-proof. They are in fact hydroscopic, insomuch as they will absorb moisture from the atmosphere and similarly it will allow moisture within the fibreglass to (very slowly) pass through it so to dry out.  This is common practice with racing grp sailing boats which are removed from the water to dry out, and therefore be lighter.  Wax and other surface finishes (including some paints and most epoxy coatings) will seal the surface.  Epoxy is pretty close to being water-tight.

My need, for this flash mould, is a gel-coated surface that can be lightly sanded (..on its presently unseen underside surface) to get rid of, or at least lessen, surface blemishes that were in the pattern. Any scratches, pin-holes, and even the hollows of paint blisters on the panel will be raised ridges, blips, etc in the mould and so are easy to sand back to the mean-surface. 

  

^ The visibly hand-painted finish will be covered with fibreglass impregnated with polyester resin, so it's not super critical. I simply sought an even-thickness and unbroken  covering.  

Job done.  

 

It's old stock materials so I just have to trust that it still goes off (and also that I guessed the right amount of catalyst to add).  Although gel-coat sets, its surface remains tacky until the air is excluded. On the inside the original steel panel is doing that. On it's outside I'll be covering it (..within a day or two) with fibreglass impregnated with polyester resin. That then cures the gel-coat's surface and its own outside surface dries tack-free.  

In a few days time we'll see.

In the meantime, have a good evening.  I'm off to supper and the TSSC club meet at the Sorrel Horse, Barham. 

Pete.

 

[Mk2 Chopper]

This is fascinating stuff, really enjoying the step by step process you are going through to make a new mould and eventually from that a copy of the Surrey top metal roof. 

Looking forward to the next instalment. 

Gareth

[Charlie D]

Pete,

It’s been a long time since I did it, but…

I thought that the PVA went on first, and then the wax.

(That's what I recomended to Richard last week.)

Thinking about it there is more chance to disturb the PVA skin when you put on the wax, but then again if the wax goes on first then the PVA does not brush on smoothly. (Water on wax ).

It is really a black art though, isn't it.

Charlie.

 

[Bfg]

Charlie,  I know what you mean "It’s been a long time since"  but I sorta have to go through a refresher experience now n' then when making things for the boats &/or trailer tent.   

The quick answer is ; wax and then PVA,  but for others who are interested to know more or have insomnia . . .

The release agents, in this instance* bees wax and PVA, are a barrier and a skin (..each just microns thick) to prevent adhesion between the fibreglass resins being applied and the keyed surface (clean, dry, finely scratched and with pin holes) of the pattern or mould.   On new jobs, they also help seal the release of styrene vapours which contribute to the chemical bond between body-filler and any new fibreglass.      * NB. other layer barriers are commonly used, including of course various types of tape &/or plastic sheet.

For application like this Surrey-top lid and in making new cockpit hatches for my boat - I'd generally use applications of wax rubbed into the surface first, to fill micro pin-holes etc (that are in any surface ..even window glass).  The excess wax is polished off again and then the PVA is wiped on.  As you say ; the other way around wouldn't work because the PVA would peel away by the cloth when wax is vigorously rubbed into the surface and polished off again.  

To then apply the PVA ;  I find a soft cloth old-T-shirt pad (ideally lint free but that's rare in the real world) which is dipped into a shallow tub of PVA, so it's well-wetted, works best.  Liberally wipe / smear the PVA on and then, using the rolled edge of the same wet cloth pad, lightly and evenly squeegee the excess off.  It is important to let the coats dry before applying the next otherwise., when wet - the PVA just wipes off again.  Use a brush to apply the PVA is indeed be like painting water-on-a waxed surface.  Thankfully the PVA is much stickier and so like warmed honey it spreads well enough.  A sponge can be used to apply the PVA over a larger surface faster. But again if you want a decent finish then the excess still needs to be gently squeegeed off, and I prefer the rolled edge of a wet with PVA soft cloth to do that. 

Both the wax and the PVA can be used without the other, but fresh filler (which is also also polyester resin) will continue to release its vapours for some time (..depending on temperatures that can be days or weeks) after it has apparently fully cured, and so a chemical bond between the filler and gel-coat / fibrgalss is a big risk.  That's when I use PVA as well. ie., both when fibreglassing over new filler and also when taking the first few mouldings out of a new mould (which likewise continues to release its vapours for months or until cooked from use). 

For other porous materials like plywood or card (which may be a positioned to create a temporary wall / an upstand ..such as I'll use when making the hard-top lid's weather-seal flanges) ...when you do not want your fibreglass to stick - then I'd first use PVA to soak into the fibres.  I'd then use wax, and then top that again with layers of PVA, which form a peelabe skin. 

PVA used to be commonly used for 'industrial mouldings'  ..like water tanks and bus panels, where an excellent finish is not necessary (..in the latter case because the panels were to be heavily painted). Primarily because PVA is quicker and much less work to apply (ie., cheaper), and because there was no wax transfer to upset the paint shop. 

But where the finished panels are to be coloured and polished smooth, such as the self-coloured car panels we made for Lomax and Falcon kit cars, as well as for things like motorcycle top boxes, then multiple applications of wax - to a polished finish was necessary ..no PVA and therefore no brush marks.

Pete.   

[Bfg]

  

19 hours ago, Bfg said:

It's old stock materials so I just have to trust that it still goes off (and also that I guessed the right amount of catalyst to add).  Although gel-coat sets, its surface remains tacky until the air is excluded.

After a couple of hours the gel coat was still wet !  ..and the day (not particularly warm anyway) was fast turning to dusk, and so the temperature was likely to drop more. 

Panic ?  ..or go to the pub ! ??  

.. quickly build a tent under the lid / around the two 'Workmates' it is sitting on, with an electric oil-filled radiator inside..  and then go to the pub. . .

 

   

TSSC club meeting at The Sorrel Horse Inn, with Katie  parked in alongside Russel's wonderful 2ltr estate.

Pete

p.s. when I got home.. the steady low warmth from the radiator had done its deed, and the gel coat was setting and tacky.  Not quite enough but its 'kicking off' was underway., so I left the radiator on low until the early hours of this morning.  That worked, and now within the sun-warmed polytunnel, the gelcoat is reassuringly set but still surface tacky.   Phew .. I really didn't want to clean all that off and start again !  

 

[john.r.davies]

What a full account of using GRP!   I can only add that while resin filler may be needed for some situations, to smooth out defects in the original part Plasticene, that clay-like substance from school days, is excellent for defects in the original part.   Rubbed into the surface, it can be smoothed, and polished to prevent adhesion.  No need to wait for curing.

John

[Bfg]

2 hours ago, john.r.davies said:

What a full account of using GRP!   I can only add that while resin filler may be needed for some situations, to smooth out defects in the original part Plasticene, that clay-like substance from school days, is excellent for defects in the original part.   Rubbed into the surface, it can be smoothed, and polished to prevent adhesion.  No need to wait for curing.

John

Agreed, and very useful for quickly filleting (putting a radius) into sharp corners and for sealing cracks and undercuts where panels have an overlap or parts of a split mould are joined. 

Full account only this time, because some appear interested in the lost science of making things from raw materials.  Next time I do fibreglassing I'll skip the explanation.!

Pete.

 

[Bfg]

But in the meantime  . . .

  

^  'Surfacing tissue' .. is glassfibre on a very fine level. It is particularly useful for working into tight corners as well as for preventing print-through of coarser glass fibres showing through on the finished (generally outside) surface.  As you can see it literally has the thickness of a single thin layer of tissue, but as I say those are glass fibres rather than paper or cotton.  Do NOT use as toilet paper !!!

 

^ I've only a small amount of this tissue left over from previous jobs, so I'm using it as a first layer in the rain gutters and all around the edge. It's fineness helps avoid air bubbles in such awkwardly tight corners.  I used a mix of catalyst in the resin which, within the warmth of the polytunnel, cured quickly.  This in turn meant I could get on with the next layer without that being disturbed . . .

   

^ Like the surfacing-tissue, chopped-strand-mat is also made up of fine filaments (drawn fibres) of glass.  And likewise they are each held together (for ease of handling as a sheet) by starch. This goes soft and washes away in the resin - so the glass filaments laid on the job can take to the required shape even if like this Surrey top lid the shape is a compound surface (it doesn't matter whether that is convex or concave, conical or a tube).  For ease of handling I chose to fibreglass the mould in three strips, with a hard cut straight edge first aligned into the rain gutter, but with it not long enough to come up the other side yet. 

  

^ The surfacing tissue, because it's so thin, can easily be wetted out with the resin from the outside. However as thicker glassfibre is used.. then it's usually quicker and easier to paint the wet resin onto the surface first, and then lay the glassfibre mat onto that, and then to apply more resin on top.   Once laid - the important task is to squeeze the air out from inbetween all those glass fibres.  The brush action is one of stippling ..so as to not drag and displace the fibres.  On flatter surfaces I apply the resin with a brush, but then prefer to use a paddle wheel ..which rolls across the wetted surface. This pushes the resin into the glass mat.. which at the same time displaces the air.  The action is light ..rather than a lot of pressure.  Many amateurs try too hard, but if you watch someone with experience they'll wet the surface out and then move on to the next patch, and then return to the first area of work ..when the resin has by itself mostly soaked in. 

The thoroughly wetted-out glassfibre becomes more translucent and takes on the hue of the catalyzed but uncured polyester resin. In this case the resin is tinted blue, so it's easier to see what your doing.  I have in the past used (and generally prefer) green tinted resin, and even pinkish coloured resin which was specifically intended for mould making.  As it cures, the colour will change to a sort of cardboard colour.  Opaque pigment can be added to the resin but that just makes seeing what you are doing all the more difficult.

   

^ a strip of glassfibre to run up the outside flange of the gutters ..and the job for today is done.

Yes.,  just a single layer for today. I don't want the mould to pre-release from the pattern which can happen if too much fibreglassing is done too soon.  This type of fibreglass resin will want to shrink by 1 - 2% as it cures, and so letting this thin layer cure first means that it internal stresses are too small to pull it away.  Too thick a layer of fibreglass will cause the panel to misshape, as its exotherm (byproduct of the curing process) warms everything up too much.  No, I'll let it cure overnight and then apply some more when this polyester resin well set and more stable. 

Pete

 

 

Edited June 8, 2022 by Bfg

[Mk2 Chopper]

How many further layers will it need, I guess I'll stay tuned to find out! Looks like a very satisfying thing to do though... and after watching the jubilee parade and seeing the Daleks, I couldn't help wandering on to their website and seeing the mould for constructing parts of the body, now that would be a fun use of this technique!

Gareth

Edited June 9, 2022 by Mk2 Chopper

[rcreweread]

13 hours ago, Bfg said:

But in the meantime  . . .

  

^  'Surfacing tissue' .. is glassfibre on a very fine level. It is particularly useful for working into tight corners as well as for preventing print-through of coarser glass fibres showing through on the finished (generally outside) surface.  As you can see it literally has the thickness of a single thin layer of tissue, but as I say those are glass fibres rather than paper or cotton.  Do NOT use as toilet paper !!!

 

^ I've only a small amount of this tissue left over from previous jobs, so I'm using it as a first layer in the rain gutters and all around the edge. It's fineness helps avoid air bubbles in such awkwardly tight corners.  I used a mix of catalyst in the resin which, within the warmth of the polytunnel, cured quickly.  This in turn meant I could get on with the next layer without that being disturbed . . .

   

^ Like the surfacing-tissue, chopped-strand-mat is also made up of fine filaments (drawn fibres) of glass.  And likewise they are each held together (for ease of handling as a sheet) by starch. This goes soft and washes away in the resin - so the glass filaments laid on the job can take to the required shape even if like this Surrey top lid the shape is a compound surface (it doesn't matter whether that is convex or concave, conical or a tube).  For ease of handling I chose to fibreglass the mould in three strips, with a hard cut straight edge first aligned into the rain gutter, but with it not long enough to come up the other side yet. 

  

^ The surfacing tissue, because it's so thin, can easily be wetted out with the resin from the outside. However as thicker glassfibre is used.. then it's usually quicker and easier to paint the wet resin onto the surface first, and then lay the glassfibre mat onto that, and then to apply more resin on top.   Once laid - the important task is to squeeze the air out from inbetween all those glass fibres.  The brush action is one of stippling ..so as to not drag and displace the fibres.  On flatter surfaces I apply the resin with a brush, but then prefer to use a paddle wheel ..which rolls across the wetted surface. This pushes the resin into the glass mat.. which at the same time displaces the air.  The action is light ..rather than a lot of pressure.  Many amateurs try too hard, but if you watch someone with experience they'll wet the surface out and then move on to the next patch, and then return to the first area of work ..when the resin has by itself mostly soaked in. 

The thoroughly wetted-out glassfibre becomes more translucent and takes on the hue of the catalyzed but uncured polyester resin. In this case the resin is tinted blue, so it's easier to see what your doing.  I have in the past used (and generally prefer) green tinted resin, and even pinkish coloured resin which was specifically intended for mould making.  As it cures, the colour will change to a sort of cardboard colour.  Opaque pigment can be added to the resin but that just makes seeing what you are doing all the more difficult.

   

^ a strip of glassfibre to run up the outside flange of the gutters ..and the job for today is done.

Yes.,  just a single layer for today. I don't want the mould to pre-release from the pattern which can happen if too much fibreglassing is done too soon.  This type of fibreglass resin will want to shrink by 1 - 2% as it cures, and so letting this thin layer cure first means that it internal stresses are too small to pull it away.  Too thick a layer of fibreglass will cause the panel to misshape, as its exotherm (byproduct of the curing process) warms everything up too much.  No, I'll let it cure overnight and then apply some more when this polyester resin well set and more stable. 

Pete

 

 

Pete - why don't you make some spares ones? I'm sure they would go like hotcakes and make you a few bob as well - if you do, can I be first in the queue?

Cheers Rich

[Bfg]

10 hours ago, Mk2 Chopper said:

How many further layers will it need, I guess I'll stay tuned to find out! Looks like a very satisfying thing to do though... and after watching the jubilee parade and seeing the Daleks, I couldn't help wandering on to their website and seeing the mould for constructing parts of the body, now that would be a fun use of this technique!

Gareth

There's lots of fun &/or interesting things that can be made in fibreglass, 

Layers ?   ..just two more layers, which I did this morning before going out (in Katie ) to lunch at the Maybush Inn, Waldringfield nr Woodbridge – on the banks of the picturesque River Deben < here >. 

I was asked by my friend Mathew about adding timber reinforcement to strengthen / stiffen it as a mould, to which I replied . . .

" For a flash mould where I just require the top skin ..and the moulding's exact width, length or curvature is not essential - that stiffening will not be necessary.  I'm about to give the mould just two more layers of the lightweight (450g/m csm) glass mat and that'll do.  This mould will probably be no thicker than the final moulding taken out of it.  

I'll then most likely keep it 'in the loft' ..just in case I loose or damage one part of the lid I make, so it remaining compact will be an advantage.  If I were to bond-on a base structure, then the mould's skin would have to be thicker and allowed to cure for a good while before any timber was added ..so as to prevent localised sinkage under the timber (caused by shrinkage of its attaching grp).   An alternative would be a deep perimeter flange,  ie., four sides of a box around (under) the mould, which would only require local-to-the-perimeter extra mould thickness, but still the additional time to cure.  And although a base / cradle for the mould to sit and be worked upon would be convenient - for the just a one-off moulding - it's more work and time than reward. 

If I were making a mould for series production, then it would be three or four times as thick, and allowed to cure for a month or two, and then I'd build an egg box type plywood base box to keep it in shape and as a table base. Someone else can do that if they want to take over from where I leave off. "

. . .

^ I did those two additional layers this morning, so aside from trimming and a quick-sanding (to prevent splinters when handled) ..assuming it releases OK.,  that'll serve the purpose of my taking a single moulding from it.   I'll then cut that moulding, so its (smaller) parts are easy to carry on a boot-rack (yet to be acquired and fitted).  I'll also have to add flanges for weather seals and its attachment to the car ..so still much work to do.  Although this mould has now cured in the sun-heated polytunnel all day and feels hard, it'll be best to leave it a week or two for fully-cure ..which is when most of the styrene vapours have dissipated, before using it.    

9 hours ago, rcreweread said:

Pete - why don't you make some spares ones? I'm sure they would go like hotcakes and make you a few bob as well - if you do, can I be first in the queue?

Cheers Rich

I'm very sorry Rich, but I'm desperately  trying to retire and to enjoy a quiet life  ..and the car,  before my size-12's turn to push up daisies.  In the meantime I'm not looking for another business opportunity.  Been there, done that, paid the taxes, and remember it all.!

Pete

 

[stuart]

And Honeybourne mouldings already do a very good fibre roof anyway so no point in competing with them.

Stuart.