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Thought I would start a separate thread for this repair and hope you Dub or someone has a few comments or criticisms prior to mixing up the fiberglass. Dub thanks so much for the offer to call you which I will do at some time but just want to keep my questions to a minimum for your sake as I know I have so much to learn but much you have already covered in other threads.
I need to add about 1/2" to 1" of material to the right side of the heater cutout as someone made a mess when replacing the heater core.
Hopefully, I can fix this without removing the heater box in the cockpit as I am trying to limit the amount of parts I remove to a "manageable amount"
In other words, is it acceptable to repair this from just one side since the other side will never be seen but just needs to be structurally sound.
My process was:
1. Sand using 36 grit and feather the edges somewhat
2. clean using a cleaner/solvent for painting
3.build a plastic backing and cover with masking tape
4. cut a piece of fibreglass mat just slightly larger than the area to be prepared.
1. Sand using 36 grit and feather the edges somewhat
Do not feather the edges 'somewhat' .... Feather them well. You grinding a taper is the beginning stage of good successful lamination.
Even though I see you prepped the area back a good inch or so...make sure that your taper of your grind is good taper. And you not just running the grinding disc on the panel to make it look sanded. The inside edge of your repair should be razor thing and weak...and the angle of your taper go back about an inch or so.
2. clean using a cleaner/solvent for painting
NO...IF you are wanting to clean the area that you ground on.. Either use clean dry compressed air or acetone and still blow it off. The problem can be is that IF you have good grind on it...wiping it with a paper towel can leave lint behind and thus need to be blown off. Where this repair is...is it not an exterior repair that will ever be seen. So If it were me I would use compressed air and not think twice about it.
And why I use a paper towel a vast majority of the time when I am wiping things during the prepping stage. I do not trust cotton towels and I do not care if they have been laundered. I want a VIRGIN clean wiper that has never had anything on it.
DO NOT use the prep solvent that is used to wipe the primer/paint down before a paint job.
3.build a plastic backing and cover with masking tape
Doing it that way can cause for resin to get inside the car unless you seal it off with something like modeling clay....if you are concerned about that.
4. cut a piece of fibreglass mat just slightly larger than the area to be prepared.
Your mat needs to go the inside edge of the tape outline you show in your last photo you posted. Which is why how you prep and taper it matters. Having your mat be on about one inch of the good panel is a smart thing to do. More strength due to over lap.
Thanks Dub, I will try it again before I glass it. The plastic backing was just to hold the piece which should come out easily once it is fibreglassed. (may try a bit of modelling clay as you suggest to keep the mess to a minimum) Will post again before I mix up the resin. Everything you said makes sense, why didn't I think of all that!
Pete
Round Two Dub,
Hoping to get this first one spot on and then build a little confidence for much more difficult repairs I will eventually have to tackle regarding the front clip.
1. Resanded with 36 grit to a larger area with the bevel starting about 1 inch back and tapering to nothing (just a few fibres)
2. Used compressed air and nothing else to clean area
3. Cut a larger piece of cloth the overlaps the sanded area to the end of the bevel, (not the beginning like before)
4. If all well plan to glass it in a warm 70 degree garage
All looks good but you changed something from when you first posted photos to the last photo session.
In your first series of photos the edge of the fiberglass mat that is on the right side. You had frayed/torn edges. BUT in this session of photos you cut it with scissors and it is NOT frayed.
I know it is a small thing but the frayed edge will not be so abrupt of and edge...especially if you apply three layers and the cut edge all stop in the same spot.
SO...frayed edges is what I use unless it is like the left side...where it does not matter due to you are cutting it off anyway.
Thanks Dub,
Will fray the edges as you say more like the smaller piece originally that didn't overlap and then have a go with the fiberglass. I appreciate your taking the time to respond!
Just want to get started on the right foot so to speak
Hey Dub,
I am pretty happy with the look of this repair. As you mentioned I pulled the edges so I had no "cut edges" on the fibreglass mat (see first pic). I mixed up the fibreglass and made my first mistake (I think). I only had enough fiberglass resin for two layer thick of the mat as I clearly had not thought the entire process through. So I just went with two layers (very thin). Anyway, I let it dry overnight then carefully removed the backing and it seemed very solid. I then glassed on top approx 10 more layers the next day.
My other mistake was making the repair just a bit to big and butting up against the two bolts (top and bottom) and the rubber grommet on the right. (I am thinking I should be able to cope with that when I sand). I really didn't want to remove the heater from the inside so in this case I didn't have a lot of choice.
Overall though, I am very happy with the repair so far. Just a couple of quick questions.
1. Normally should I be able to sand this the next day if I have the correct amount of hardener added to the resin or should I wait longer
2. Is about 10-12 layers of the fibreglass about the correct amount for this type of repair (my repair pieces were all small irregular shapes, not the exact size of the repair like the first one)
3. Is my next step to sand with 36 grit with the tape in place or what do I do now? I was planning to cut and shape it to the correct size after the surface was sanded.
4. Do you normally us a DA sander or should I tackle this one by hand.
5. Is there any obvious mistakes that I have made based on the look of this repair?
I just want to get through this repair so I can really get the fundamentals correct right from the beginning.
Hey Dub,
I am pretty happy with the look of this repair. As you mentioned I pulled the edges so I had no "cut edges" on the fibreglass mat (see first pic). I mixed up the fibreglass and made my first mistake (I think). I only had enough fiberglass resin for two layer thick of the mat as I clearly had not thought the entire process through. So I just went with two layers (very thin). Anyway, I let it dry overnight then carefully removed the backing and it seemed very solid. I then glassed on top approx 10 more layers the next day.
My other mistake was making the repair just a bit to big and butting up against the two bolts (top and bottom) and the rubber grommet on the right. (I am thinking I should be able to cope with that when I sand). I really didn't want to remove the heater from the inside so in this case I didn't have a lot of choice.
Overall though, I am very happy with the repair so far. Just a couple of quick questions.
1. Normally should I be able to sand this the next day if I have the correct amount of hardener added to the resin or should I wait longer YES 24 hours at ambient air tempos (70-85F)
is a giood gauge to go by.
2. Is about 10-12 layers of the fibreglass about the correct amount for this type of repair (my repair pieces were all small irregular shapes, not the exact size of the repair like the first one) 10-12 layers will way too thick. You can more than likely get by with 4-5 layers in total and then grind to get flat so you get a good sealing surface.
3. Is my next step to sand with 36 grit with the tape in place or what do I do now? I was planning to cut and shape it to the correct size after the surface was sanded. YES...36 grit to get the mat/resin you just applied prepped for your next 2-3 layers. THEN...grind that flat. Then make your cut-out as you need so it looks like a factory opening for this area of the dash like what Roger posted a photo of.
4. Do you normally us a DA sander or should I tackle this one by hand. I use my angle grinder with 36 grit Rolloc discs and then I will finish up with my D/A sander and take it to at least 180 grit so it is smooth for my primer and black paint.
5. Is there any obvious mistakes that I have made based on the look of this repair? None that I can see that would cause me concern. The only thing I see is on teh left side of your repair where the fiberglass mat stops on the vertical straight edge. You did not need to fray the edge of the mat here. it could have stayed straight like as if you cut it with scissors....because you know you are going to cut it anyway. but...it is no big deal.
I just want to get through this repair so I can really get the fundamentals correct right from the beginning.
Again Dub, Thanks in advance
This is a good beginning repair to learn off of. but when other areas are found that need repair..some of these principles and procedures will transfer over to that repair...and that 'new' repair may take another series of steps and procedures...becasue not ALL laminations are treated the same and how you will learn that learning tricks on what you can make the mat do...will be very useful. Because you laminated on a flat surface with no contours in it.
Didn't know what Roloc Disks were and certainly had never used an angle grinder before today although I have one which I inherited somewhere along the way. Spent today getting those Roloc disks/2" cut off disks and working on my air dryer system that I will need more and more as I progress. I couldn't sand the repair properly in the confined space with a DA so I see the benefit and requirement for these small tools.
Without proper tools, these jobs are next to impossible!
Thanks Dub.
Moving along with this repair Dub, I hope you can steer me in the right direction to finish this up and move on to some other tasks.
I sanded with the Roloc. 40 grit then just as I began to hit the edges of the sandpaper with the sander, I moved to sanding it by hand with 60 grit.
These are the results and I was now planning to cut it to the correct shape.
Overall, it is very very strong and I am very happy with the results. I can't imagine this repair ever coming back to haunt me.
So my questions are;
1. Shall I finish sanding it with 100 and then 180 grit by hand
2. Is the VPA Vette Panel Adhesive required for this type of repair? I do have some so I suppose it is a good place to use it for the small pinholes from the air bubbles even though almost none of the repair will ever by seen.
3. Shall I clean it with solvent cleaner I have for automotive paint prep or this type of a product a NO NO when getting close to adding paint. I remember you said clean the dust with compressed air only for the fibreglassing portion.
4. What type of black paint would I use to blend it in to the rest of the firewall. I don't plan on removing everything from the firewall to paint and prep it all so I was just hoping to blend it in to the rest of the firewall. Is this possible? Is there a paint that would be acceptable to put over the bare fibreglass for the firewall or is it always best to use a primer first.
1. Shall I finish sanding it with 100 and then 180 grit by hand
It depends on what you plan on putting on this repair. if you are going to prime and block it and make it super nice. You might want to stop at 180 grit and prime it...sand it and paint it.
2. Is the VPA Vette Panel Adhesive required for this type of repair? I do have some so I suppose it is a good place to use it for the small pinholes from the air bubbles even though almost none of the repair will ever by seen.
YES...If you have not already...Look at this thread.
Look at POST 4 ,11 and #63
3. Shall I clean it with solvent cleaner I have for automotive paint prep or this type of a product a NO NO when getting close to adding paint. I remember you said clean the dust with compressed air only for the fiberglass portion.
IF you wipe the fiberglass with anything ...use acetone in a VERY WELL VENTILATED AREA WITH NOTHING THAT CAN CAUSE A SPARK or IGNITE the FUMES/VAPORS. I am NOT responsible for someone who does not practice common sense and safety when it comes to products that are flammable. Just saying.
But like you already know.,..most of the time compressed air will do the trick...and my shop conditions do not promote oil, grease or floating crap in the air that can land on sanded panels and cause them to fish-eye. So your shop condition is a huge variable.
4. What type of black paint would I use to blend it in to the rest of the firewall. I don't plan on removing everything from the firewall to paint and prep it all so I was just hoping to blend it in to the rest of the firewall. Is this possible? Is there a paint that would be acceptable to put over the bare fibreglass for the firewall or is it always best to use a primer first.
SEM sells a black primer....so it all depends on how well you want this to work. It is not always necessary to prime the fiberglass. Especially in an area like this that is really not exposed to the environment...and it is not easily seen..and hidden by other items that can 'trick your eye'....you can paint it and move on if you choose. But it does depend on how well you get the surface and IF you are happy with it...which is all that matters.
I personally like the SEM TRIM BLACK. It has basically the right luster to it. But...once again...it depends on if that will match what you have. And i am not flooding the stuff on the panel. Light/thin coats flash off and dry faster than pounding coat on expecting tit to turn out as you want. Also...light coats are less likely to fish-eye.
Thanks so much for the help DUB,
Just used one quick coat of the VPA and quickly realized that because I was only doing parts of the firewall I didn't want it perfectly smooth but wanted it to mimic the factory finish with the fibers exposed like the rest of the firewall. I presume this really is not possible or very very difficult?
Anyway, just wanted to say thank you for going out of your way to help me on this repair! I am very happy with this repair and will call it done as it is an area that will be mostly hidden by the engine. I now see how hard it is to balance restoring things to factory correct vs over restoring them.
One quick question, does anyone know what the small square hole in the middle of the heater box is for? I don't show anything in the AIM.
Funny how fixing one thing that was once the worst part of the firewall just moves your eyes to the next worst thing. I will resist the temptation to do the entire firewall as its functionally original and correct for the most part from what I can tell. A little cleaning on the original part and some dust on the new part should blend it all together. On to the tunnel and shifter.
Last edited by VancouverL71; 04-02-2018 at 10:47 AM.
Thanks so much for the help DUB,
Just used one quick coat of the VPA and quickly realized that because I was only doing parts of the firewall I didn't want it perfectly smooth but wanted it to mimic the factory finish with the fibers exposed like the rest of the firewall. I presume this really is not possible or very very difficult?
Anyway, just wanted to say thank you for going out of your way to help me on this repair! I am very happy with this repair and will call it done as it is an area that will be mostly hidden by the engine. I now see how hard it is to balance restoring things to factory correct vs over restoring them.
I am glad that I was of some help. Putting the texture in the VPA is possible. And honesty..I doubt that anyone will call you out on your repair and say that you did it incorrectly.
When that happens to me from time to time...I always ask them to show me what they have done with their own hands and not just their wallet.
One quick question, does anyone know what the small square hole in the middle of the heater box is for? I don't show anything in the AIM.
That square hole is where the special heater hose clamp goes. IF you plan on putting it in there. You WILL need to remove the heater box cover so you can really cage this special heater hose clip.
Funny how fixing one thing that was once the worst part of the firewall just moves your eyes to the next worst thing. I will resist the temptation to do the entire firewall as its functionally original and correct for the most part from what I can tell. A little cleaning on the original part and some dust on the new part should blend it all together. On to the tunnel and shifter.
Knowing when to stop is a very good trait to have. Because it can get totally out of control.
02-27-2018, 10:55 PM
Firewall Heater cutout repair 1969
