R34 Sports Sedan Build

[rcs_888]

well what a past couple of days its been.... primer sanded, buffed, polished gelcoat doen and coupling coat laid.. wow..

[rcs_888]

So been freaking hectic at work so been struggling to get much time in but have managed to get the bonnet done and the passenger quarter panel. Hopefully soon i will be able to get the rest done i just want to rip it all off and get on with getting the brakes done and actually driving. 

[Unzipped Composites]

Doing well mate! Not a small job, and certainly not an easy job to flange so nice work.

 

Not sure if professional advice is welcome, but I can see you're getting a bit of alligatoring in places, just make sure you are applying the gelcoat thick enough (needs to be 0.7-0.8mm thick minimum), catalysing high enough (2% minimum for gelcoat, mix smaller batches if you don't have enough pot-life), and leaving it to cure for long enough before doing the coupling coat; I like to leave gelcoat overnight, longer if it is colder. It is air inhibited so you can leave it up to 24 hours without issue. Alligatoring causes all sorts of problems later especially if you are planning on infusing, trying to get a good seal on your bagging tape can be a real nightmare.

 

Also just be careful with where you put your backing structure, these tend to print-through onto the surface of the mould over time and cause defects.

 

If you'd like any advice with anything, feel free to PM me, I'm happy to share the knowledge. Otherwise also feel free to tell me to piss off and leave you to it!

[rcs_888]

On 07/05/2020 at 5:27 PM, Unzipped Composites said:

Doing well mate! Not a small job, and certainly not an easy job to flange so nice work.

 

Not sure if professional advice is welcome, but I can see you're getting a bit of alligatoring in places, just make sure you are applying the gelcoat thick enough (needs to be 0.7-0.8mm thick minimum), catalysing high enough (2% minimum for gelcoat, mix smaller batches if you don't have enough pot-life), and leaving it to cure for long enough before doing the coupling coat; I like to leave gelcoat overnight, longer if it is colder. It is air inhibited so you can leave it up to 24 hours without issue. Alligatoring causes all sorts of problems later especially if you are planning on infusing, trying to get a good seal on your bagging tape can be a real nightmare.

 

Also just be careful with where you put your backing structure, these tend to print-through onto the surface of the mould over time and cause defects.

 

If you'd like any advice with anything, feel free to PM me, I'm happy to share the knowledge. Otherwise also feel free to tell me to piss off and leave you to it!

Mate far from telling you to piss off thats been awesome.

I have had some dramas with it frying up in some areas and it looks like the alligatoring is what ive been calling frying.

Anyway i did notice that in the spots it has happened is where the gelcoat is thinner than i would have liked so im guessing that is what has caused it. I have currently filled in the shitty spots with filleting wax so hopefully that will work but im guessing i will just get some styrene and mix up some gelcoat and fix it up eventually. 

Cheers heaps dude gives me something to think about! i will probs mix up the gelcoat for the final part and make it abit thicker than i have been. 

 

[rcs_888]

[Unzipped Composites]

Where are you getting your tooling gelcoat from, do you know if it is brush viscosity or spray viscosity? When you're brushing gelcoat, you really want to just slap it on virtually as thick as you can get it. Watch for pooling in the corners, but you're unlikely to make it too thick on flat sections. Good rule of thumb is if you can no longer see the colour of the pattern or flanges through the gelcoat, then you're probably close. 

 

Mould turned out well though! Are you planning on infusing or wet-laying the component? 

[rcs_888]

I was getting it locally from Adelaide moulding and casting but of late i have been going through Trojan fiberglass as they do free freight over 200 bucks lol. Yeah as you can see in the vids its too thin in alot of places so im going to lay down the white gelcoat abit thicker and then atleast i have the ability to sand out imperfections where currently i cant with the tooling gelcoat

Yeah its going to be just a wet layup. I have been keeping track of the CSM weights as its been going down and keeping to a 2:1 ratio of resin to glass and alot of the time we have been at nearly 1.5:1 so hopefully i will be able to keep the weigh managable. I also have a 2mm layer of Soric Coremat so i have been thinking i will do 2 layers of the 100g a layer of the soric and then a layer of the 300g if its not stiff enough when it comes out the mould i can always add more internally afterwards. Whats your thoughts?

[Unzipped Composites]

Yeh Trojan are great, I get some stuff from them too. When you do your gelcoat, you should be using about 650g per square metre. So if you roughly measure how much surface area you have, then you can calculate how much gelcoat you should be using to coat that area at correct thickness. If you get the area coated and you still have half a kg of gelcoat left, then you know you've left some areas a bit thin. 

 

If you're using CSM, it's going to be heavy, and then it actually needs to be stronger to support it's own weight, meaning it needs to be heavier again. Have you considered using woven/biaxial fibreglass instead? Will be significantly lighter and stronger than the chopped strand, and by using less resin you may find that it doesn't cost much more to do either.

 

For example, if you were doing it that way I would do:

1 layer of 300g twill fibreglass > 1 layer of 450g double-bias fibreglass > 2mm Coremat (only in the flatter areas, leave it out of the contoured areas) > 1 layer of 450g double-bias > 1 layer of 300g twill. Plus an extra layer of the 450g DB in the areas with no core and the mounting points.

That layup would need roughly 1.5kg of resin per square metre of glass, plus about 550g per square metre of Coremat, and I'd expect it to weigh about 4.5kg per square metre. An R34 front end is roughly what, 5.5sqm? That means you would need roughly 12kg of resin, 10kg of fibreglass, and end up with a front end weighing roughly 25kg once you factor in gelcoat. I'm not sure what you're paying for materials, but using average figures, I'd estimate you're looking at about $100 in resin and $300 in fibreglass.

 

If you compare that to chopped strand, I would suggest the layup you mentioned is too light and wouldn't be strong enough to stand up to racing. I would be doing a minimum layup of:

1 layer 225g CSM > 1 layer 450g CSM > 2mm Coremat (again only on the flatter areas, let the geometry do the work for you) > 1 layer 450g > 1 layer 225g. Extra couple of layers of the 225g in the areas with no core, and an extra couple layers of the 450g in the mounting areas.

Then chop strand really does like a 2:1 resin:fibre ratio, otherwise it is a bit too lean and the matrix doesn't take the load well (meaning it will crack and break easily). You could try to aim for your 1.5:1 ratio, but I would stick to 2:1 for longevity. Over a 5.5sqm area, this means you will need roughly 17kg of resin just for the glass, plus about 2.5kg for the Coremat, so about 20kg of resin all up. With about 10kg of fibreglass in there, plus the Coremat and the gelcoat, you're going to be up around 35-40kg total weight. Given the chopped strand is only going to cost you maybe $70 or so, but you're going to need twice the resin, so that's about $200 in resin. So you're 10-15kg heavier, and only saving a bit over $100.

 

 

Not sure if that is helpful or just confusing haha.

 

[rcs_888]

Yeah well my weekends been brought to a complete halt.. just opened up the white gelcoat and its fooked... so now i have the front end in pva and no gelcoat to lay down.. YAY

Can i use tooling gelcoat instead of standard white gelcoat for the final part? i know it will be more of a cost but i live in the middle on nowhere and just want to get this front end done..

 

[timmy_89]

This is awesome

[rcs_888]

20 minutes ago, timmy_89 said:

This is awesome

no no currently its not

[Unzipped Composites]

Yeh that's gone... Sucks man, I know the feels

 

I wouldn't use tooling gelcoat though. Cost aside, it is also more brittle than regular gelcoat, as it's supposed to be used on moulds with very little flex. Using it on a part that is going to have some flex, it will crack in no time. I mean if you really wanted to get it done, there's no reason you can't use it, it will work. But expect it to crack and chip quite quickly.

[timmy_89]

2 hours ago, rcs_888 said:

no no currently its not

Sorry, disregarding the latest post...... just the concept behind all of this is awesome ^_^

[rcs_888]

2 hours ago, timmy_89 said:

Sorry, disregarding the latest post...... just the concept behind all of this is awesome ^_^

haha nah your all good bro i appreciate it!

 

3 hours ago, Unzipped Composites said:

Yeh that's gone... Sucks man, I know the feels

 

I wouldn't use tooling gelcoat though. Cost aside, it is also more brittle than regular gelcoat, as it's supposed to be used on moulds with very little flex. Using it on a part that is going to have some flex, it will crack in no time. I mean if you really wanted to get it done, there's no reason you can't use it, it will work. But expect it to crack and chip quite quickly.

Yeah ive ordered some from adelaide and hopefully have someone bring it up for me so hopefully soon i will be able to get onto it

[Unzipped Composites]

You'll get there man, better not to rush these things - composites are unforgiving when you get it wrong!

 

The PVA might still be ok by the time your gelcoat arrives if you keep it dry, although it may dry out a bit much and pre-release. I would probably wash it off now and let the mould dry off in the mean time.

[rcs_888]

23 minutes ago, Unzipped Composites said:

You'll get there man, better not to rush these things - composites are unforgiving when you get it wrong!

 

The PVA might still be ok by the time your gelcoat arrives if you keep it dry, although it may dry out a bit much and pre-release. I would probably wash it off now and let the mould dry off in the mean time.

Yeah okay i will wash off the pva release tomorrow :( Bugger! Im going to order some of the twill and bi axial glass for the next front end that i try. How will the twill and Bi Axial glass lay up in the front end? will i have issues with the front end and the glass rolling around it?

 

Cheers for your help mate

[Unzipped Composites]

Yeh they are continuous fibres, so they won't break down like CSM. Harder to work with, but what you want to do is get all your fibreglass ready before you mix any resin or even apply the PVA. Lay the glass into the mould, and try to push it into all the corners as tight as you can. Take note of where it tries to 'bridge' the corners as you push it into place. If the fibres won't move to let you get them into place, then cut the fibres where they bridge to give it some relief and let it sit in place. Then use strips of glass with about an inch overlap either side to reinforce the cut sections. Make sure you do all of your glass and have it all ready before starting the layup, you don't want to be messing around with any of that while your resin is going off.

 

 

Kind of like what I was doing here, you want to get all of the protrusions and features covered in glass with no bridging, and then lay up the bigger sections with the protusions cut out of it, if you know what I mean? For fibreglass with a gelcoat, it's not a huge issue to cut strips of material to reinforce tight areas, and put relief cuts where you need them. Then just add a bit of extra material to make up for the loss of strength where the cuts are.

[rcs_888]

11 hours ago, Unzipped Composites said:

Yeh they are continuous fibres, so they won't break down like CSM. Harder to work with, but what you want to do is get all your fibreglass ready before you mix any resin or even apply the PVA. Lay the glass into the mould, and try to push it into all the corners as tight as you can. Take note of where it tries to 'bridge' the corners as you push it into place. If the fibres won't move to let you get them into place, then cut the fibres where they bridge to give it some relief and let it sit in place. Then use strips of glass with about an inch overlap either side to reinforce the cut sections. Make sure you do all of your glass and have it all ready before starting the layup, you don't want to be messing around with any of that while your resin is going off.

 

 

Kind of like what I was doing here, you want to get all of the protrusions and features covered in glass with no bridging, and then lay up the bigger sections with the protusions cut out of it, if you know what I mean? For fibreglass with a gelcoat, it's not a huge issue to cut strips of material to reinforce tight areas, and put relief cuts where you need them. Then just add a bit of extra material to make up for the loss of strength where the cuts are.

Well it doesnt take long to tip the scales on the $200 for free shipping with trojan lol. So ive got 4L of gelcoat and ive got 500ml of Royal Blue pigment aswell so then hopefully it will come out the mould a similar colour to the rest of the car and i can use less paint when i go to paint it. I cant currently get any 300g twill and in fact that have minimal fiberglass twill of anything so am i able to use the 100g CSM and then ive ordered the 400g biaxial glass in between and just replace the twill with CSM? not ideal but rock and a hard place lol. 

Also ive seen a couple of people using foam brushes in place of bristled brushes have you had much to do with them or what is the best method of wetting out the biaxial? I have bristled rollers, the solid ribbed rollers and brushes. 

Sorry to keep nagging you but your have been massively helpfull!! 

[Unzipped Composites]

Excellent. Keep in mind with the pigment, you don't want to add too much. White gelcoat is already pigmented, and you ideally don't want to go over 10% total pigment or you may have cure issues. You can add a bit of the blue to get a very light blue tinge, but I wouldn't add more than 5% by weight in case they had a lot of the white pigment in there to begin with.

 

No issue replacing the twill with the CSM, it wont have much of an effect on weight. In that case, I would do the layup similar to the method you used to make your mould, a layer of the 100g CSM as a single skin making sure to get all the air voids out, and let that cure for a couple of hours before doing the biaxial. That will reduce your print through, and reinforce the gelcoat. Then you can use the biaxial to give the laminate it's strength, and it won't matter as much if you get a bit of bridging as the gelcoat will still have some reinforcement behind it.

 

Alternatively, you don't necessarily need twill fibreglass, you could get a plain weave instead. Will just need more relief cuts to go around corners.

 

Foam brushes are fine, they can be a bit easier to use with woven materials than bristle brushes. Not going to notice much difference working with CSM or biaxial. To be honest, on a job this size I would probably use a 5" short-napp roller (same as the fabric rollers you would use to paint a house) for the bulk work, and a 2" bristle brush for the tighter areas where the roller is too much work.  That will let you get resin on the job and wet out the fibres quickly. Then use a disc roller to consolidate each layer and get the air bubbles out.

[rcs_888]

On 24/05/2020 at 10:35 AM, Unzipped Composites said:

Excellent. Keep in mind with the pigment, you don't want to add too much. White gelcoat is already pigmented, and you ideally don't want to go over 10% total pigment or you may have cure issues. You can add a bit of the blue to get a very light blue tinge, but I wouldn't add more than 5% by weight in case they had a lot of the white pigment in there to begin with.

 

No issue replacing the twill with the CSM, it wont have much of an effect on weight. In that case, I would do the layup similar to the method you used to make your mould, a layer of the 100g CSM as a single skin making sure to get all the air voids out, and let that cure for a couple of hours before doing the biaxial. That will reduce your print through, and reinforce the gelcoat. Then you can use the biaxial to give the laminate it's strength, and it won't matter as much if you get a bit of bridging as the gelcoat will still have some reinforcement behind it.

 

Alternatively, you don't necessarily need twill fibreglass, you could get a plain weave instead. Will just need more relief cuts to go around corners.

 

Foam brushes are fine, they can be a bit easier to use with woven materials than bristle brushes. Not going to notice much difference working with CSM or biaxial. To be honest, on a job this size I would probably use a 5" short-napp roller (same as the fabric rollers you would use to paint a house) for the bulk work, and a 2" bristle brush for the tighter areas where the roller is too much work.  That will let you get resin on the job and wet out the fibres quickly. Then use a disc roller to consolidate each layer and get the air bubbles out.

Yeah on Trojans website they specify 1-10% pigment by weight so i will probs go to around 5-6% just to err on the side of caution. Also looking at the soric data and you said aprox 550g/m2 but its saying it has a resin uptake of 1kg/m2 is that too much of a concern if i stick with the 550-600g? Also what do you recomend for the Double Bias 400g i have seen people saying aprox a 1-1.25:1 ratio of resin so around the 500g of resin per m2? 

My plan is going to be the 100g in the tight areas to make sure i get good key to the gelcoat, Then a full layer of 100g over the whole lot, 400g double bias, soric with double bias in aresa without soric, 400g double then finish off with 100g again does that sound about right?

Sorry for taking up so much of your time but cheers HEAPS