Lotus Elan

Bonded screen trim & mastic application

PostPost by: dick+2130/5 » Mon Nov 13, 2017 10:58 pm

Hi, I could do with some help here please !
eg how to get the mastic into the groove in the windscreen trim ?

i am fitting a bonded in screen to my '73 +2. I have formed the trim around the screen OK and now need to bond the trim to the screen.

I have bought 2 tubes of Dinitrol 500 mastic for the job.

What I have found is that the Dinitrol 500 is very viscous ( even warmed to 25C), Using a bathroom sealer type gun I can get it to exude out of the cartridge OK provided no nozzle is fitted. When I fit a nozzle to fit inside the trim groove eg about 6 mm wide, then the load on gun goes up so much that I cannot drive a bead out of the nozzle.

I have tried spreading the mastic into the groove with a knife with very messy results.

So, has anyone had the same experience ? , and if so how did you get round it ?

Any hints or tips will be very gratefully received.

Thanks,

Dick
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PostPost by: vxah » Tue Nov 14, 2017 8:17 am

Are the tubes of mastic "in date"? I usually find that out of date PU adhesives won't come through a nozzle when they are too old..Not sur what Dinitrol is?
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PostPost by: 10kph » Tue Nov 14, 2017 9:45 pm

Stop.....Dont do it.!!!!!
Dinitrol 500 is for bonding modern car screens and is excellent.
Reading the workshop manual will explain and give you your main clue....it mentions that for removal it can be done on a hot day or hot workshop by pushing the top of the screen outwards and cutting the mastic to release the screen. When yo removed your screen you would have ended up with sticky fingers and quite a black mess that will clean up with turps spirit. Dinitrol will not do this because it sets quite rigid so any removal of screen at a later date or if you have not sealed it correctly by the time this sealer sets then you are in big trouble.
What you need is BUTYL sealer....this is available in 10mm round section which is not perfect but will do the job.Butyl is a sealer which remains flexible and sticky and is what was used in the first place.
I have rebonded a few screens and this is how.
Fasten your chrome strip to the glass edge and secure on the outside with masking tape,turn over and work on the inside of the glass.
Use masking tape to stick on the glass to form a perimeter 13mm from the edge of your surround. treat this small glass area with cleaner then with your black Dinitrol primer....this soon dries and gives a nice black edge to your screen like modern cars to hide the sealer.
Use your Dinitrol to form a 5mm bead at the edge of strip and glass and smooth down with a stick to make sure there is no gap..water can not creep round from the inside edge of your surround from the outside.
Take a break for a few hours or the next day.Your strip will not pull off your glass edge now so the next job is to place your screen with surround in your car for a trial fitting.
Make sure it is central,your lower packings give the correct height, then at the top edge stick a strip of masking tape say 10" long upwards from the glass onto the roof to give locating position,cut the tape neatly at the chrome trim outer edge with a sharp blade. Before removing the screen do some measurements inside the car from the glass to the fibreglas lip.....this is not equal all round so take note !
Fit your black trim section up the pillars and across screen top treat the fibreglass with Dinitrol black primer round edge
Run the strip of Butyl sealer round the edge of screen covering partly screen and trim where Dinitrol was previously stuck and use your fingers and a small piece of waxed paper it was supplied with to reshape the round section to a triangulated peak.The top edge will need more and a strip can be applied to the fibreglass.
Warm the sealer with a hot air gun to make sure it is pliable enough and with an assistant place th screen in place and line up to the masking tape. Keep applying presure allround .I used a tie strap across the screen round the pillars and tightened on the inside. Check to make sure no gaps are present, if so you could reshape from the inside with a small stick or add more sealer.
Good luck, I will try to add some photos of an alternative surround I have used which fits flush and does not require corner sections because it can be mitre bonded to give a continuous surround
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PostPost by: dick+2130/5 » Thu Nov 16, 2017 9:33 pm

vxah wrote:Are the tubes of mastic "in date"? I usually find that out of date PU adhesives won't come through a nozzle when they are too old..Not sur what Dinitrol is?


Hi vxah, You are right, I have one tube with Best Before late 2018 and one dated mid 2017. This latter one is very thick compared to the in date one.

All online if you are interested, but Dinitrol 500 is the slowest setting of the windscreen sealers from Dino Gmb, who are best know for their cavity waxes and underbody protection products,

Following other advice I bought an all metal "high ratio" mastic gun from Screwfix (item 4379H P C Cox Sealant & Adhesive Dispensing gun - ?19.99) - and it worked well in forcing the Dinitrol 500 through a narrow nozzle into the trim groove.
Thanks for your useful input.

Dick
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PostPost by: dick+2130/5 » Thu Nov 16, 2017 10:42 pm

p1210324.jpg and
See "Side of Screen RHS"
p1210324.jpg and
See "Side of Screen RHS"
10kph wrote:Stop.....Dont do it.!!!!!
Dinitrol 500 is for bonding modern car screens and is excellent.
Reading the workshop manual will explain and give you your main clue....it mentions that for removal it can be done on a hot day or hot workshop by pushing the top of the screen outwards and cutting the mastic to release the screen. When yo removed your screen you would have ended up with sticky fingers and quite a black mess that will clean up with turps spirit. Dinitrol will not do this because it sets quite rigid so any removal of screen at a later date or if you have not sealed it correctly by the time this sealer sets then you are in big trouble.
What you need is BUTYL sealer....this is available in 10mm round section which is not perfect but will do the job.Butyl is a sealer which remains flexible and sticky and is what was used in the first place.
I have rebonded a few screens and this is how.
Fasten your chrome strip to the glass edge and secure on the outside with masking tape,turn over and work on the inside of the glass.
Use masking tape to stick on the glass to form a perimeter 13mm from the edge of your surround. treat this small glass area with cleaner then with your black Dinitrol primer....this soon dries and gives a nice black edge to your screen like modern cars to hide the sealer.
Use your Dinitrol to form a 5mm bead at the edge of strip and glass and smooth down with a stick to make sure there is no gap..water can not creep round from the inside edge of your surround from the outside.
Take a break for a few hours or the next day.Your strip will not pull off your glass edge now so the next job is to place your screen with surround in your car for a trial fitting.
Make sure it is central,your lower packings give the correct height, then at the top edge stick a strip of masking tape say 10" long upwards from the glass onto the roof to give locating position,cut the tape neatly at the chrome trim outer edge with a sharp blade. Before removing the screen do some measurements inside the car from the glass to the fibreglas lip.....this is not equal all round so take note !
Fit your black trim section up the pillars and across screen top treat the fibreglass with Dinitrol black primer round edge
Run the strip of Butyl sealer round the edge of screen covering partly screen and trim where Dinitrol was previously stuck and use your fingers and a small piece of waxed paper it was supplied with to reshape the round section to a triangulated peak.The top edge will need more and a strip can be applied to the fibreglass.
Warm the sealer with a hot air gun to make sure it is pliable enough and with an assistant place th screen in place and line up to the masking tape. Keep applying presure allround .I used a tie strap across the screen round the pillars and tightened on the inside. Check to make sure no gaps are present, if so you could reshape from the inside with a small stick or add more sealer.
Good luck, I will try to add some photos of an alternative surround I have used which fits flush and does not require corner sections because it can be mitre bonded to give a continuous surround


Hi 10kph, and Thanks ! You got to me in time !

I really like the idea of using butyl strip instead of the Dinitrol 500 to attach the screen assembly to the body.
Apart from enabling future removal, it should be much easier to position the joint line correctly.

It was useful/reassuring to have your detailed description of how to fix the trim to the screen. I have pretty much followed that and trim is now on the screen and the assembly is in position on the body, and fits closely all round. i overdid the mastic in the groove a bit and it exuded out but it has trimmed off OK now set.

3 Questions please:
a) You mention that the butyl strip should overlap onto the glass, not just bond to the trim - is 6 mm enough ?.
( I mention 6mm because that is the figure i got from a very helpful Steve James at SJ Sportscars)

b) Where do you get your butyl strip from ? All the items on eBay are flat strips - which I guess I could use in layers.if necessary.

c) What do you do down the sides of the screen ? On my car the windscreen trim lies over the black U trim that goes round the body opening, Photo of sketch attached.
p1210324.jpg and
See "Side of Screen RHS"


Thanks,

Dick.
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PostPost by: jono » Fri Nov 17, 2017 4:37 pm

There's some good stuff in this thread:

lotuselan-plus2-f51/dundonian-jps-t26714.html
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PostPost by: dick+2130/5 » Tue Nov 21, 2017 11:34 am

jono wrote:There's some good stuff in this thread:

lotuselan-plus2-f51/dundonian-jps-t26714.html


Thanks jono, I very much agree ! Saw it when i first did my search for windscreen advice.

I got some further good advice from vxah on shaping round butyl to a triangle peak on the screen so that it contacts the body in the right place.

The gaps around my screeen (as checked with balls of clay in cling film) vary between 5 and 11 mm so reshaped 10mm round butyl as used by vxah should do it .

Regards,
Dick
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