New Hightop Option

[DuncanS]

[DuncanS]

https://multimedia.3m.com/mws/media/576967O/3mtm-marine-adhesive-sealant-fast-cure-5200.pdf
https://technicaldatasheets.3m.com/en_US?pif=000890

These are the data sheets for both 5200 and 4200. 4200 is not as strong but is removable--with difficulty--unlike 5200 which can not be removed. Check the data sheets, for 4200, it has a psi of 125 on steel and 20 on fiberglass. 5200 is much stronger with its bond. If you remove it from fiberglass, it will tear apart the laminations at it is stronger than the fiberglass resins. I found this out the hard way on my boat. It is NOT a bedding compound, it is a bonding agent.

Although they don't mention it, 5200 comes in three colors--white, black and mahogany.

I didn't check it out, but assume slow cure is stronger. That may not be correct.

Duncan

[tim_ha]

Here are results from a Sikaflex 221 metal to fiberglass bond test.

I did the exact same surface prep as I did for the Evercoat Maxim. According to the tech sheet, this ~3mm thick application cures in ~2 days. I gave it 3. I am not convinced it was fully cured because I smelled it as soon as the failure occurred (and quickly put on my ventilator). Note that the Sikaflex had no problem bonding to the same surface prep. As can be seen in the video, I was pulling on it hard enough to nearly damage the fiberglass. The failure was as I pulled on the edge so that there was only stress along the edge of the bond. This type of stress would be impossible on a hightop. Also, look at how much the ~3mm thick bond is able to flex! I wouldn't hesitate to use this adhesive.

Failure testing:

Link


Comparing the data sheet for the Sikaflex 221 to 3M 5200...
Sika has tensile strength of 1.8 MPa = 261 psi
3m 5200 overlap sheer strength is reported to be 530 lb/in2 for cold rolled steel and 360 lb/in2 for Fiber-Reinforced Plastic.
I am not sure if this is an apples to apples comparison.

I also set up another test of the Evercoat Maxim with suggested improved surface prep. I will post results when I have them.

Based on testing thus far, I am considering breaking the Evercoat Maxim bond and cleaning all of it off of the fiberglass and as much off of the metal as is reasonable. Then I can improve my surface prep of the fiberglass and use either Sikaflex 221 or the 3M 5200 Fast Cure that I have on hand to completely redo the bond.
_________________
1986 Syncro Sunroof EJ22
www.subagonsouth.com

[dobryan]

Fiberglass itself does not cure. The adhesive, in this case epoxy, is what cures.

As Duncan said try the test again but really sand off that shiny surface layer from the epoxy.

I used an angle grinder on my euroBus top and have no doubt it is bonded.

That being said I will use 3M5200 on my next one for the ease of working time. As Duncan said you must wait many days for it to cure.
_________________
Dave O
'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD

"To travel hopefully is a better thing than to arrive." Robert Louis Stevenson

MD>Canada>AK>WA>OR>CA>AZ>UT>WY>SD
https://www.thesamba.com/vw/forum/viewtopic.php?t=620646

Building a bus for travel in Europe (euroBus)
https://www.thesamba.com/vw/forum/viewtopic.php?t=695371

The Western Syncro build
https://www.thesamba.com/vw/forum/viewtopic.php?t=746794

[DuncanS]

[J Charlton]

When fibreglass cures there is a thin layer of wax that is released to the surface of the wet resin/hardener mix - this is deliberate to limit the contact with the air and slow the curing rate of the mix. The first step of any install is to put several pails of warm soapy water into the inverted top and give the inside a thorough scrub, wash and rinse. nothing will bond well with the fibreglass if this is not done - the waxy surface residue has to be removed.
_________________
NAHT hightop availability May 18 2023 -
Bend Oregon - for Oregon, California- (7 tot , 3 available), Kennewick Wa (6 tot, 1 available), Small Car Performance Fife Wa. (7 tot 4 avail ), Fairbanks Alaska (1 tot 0 avail)
Future availability TBD : Springfield Mass. Staunton Va, Florida, Colorado, Grand Junction Co., SLC probably late 2024

[dobryan]

[jimf909]

^^^ <Like>

Agreed.
_________________
- Jim

[calsurf]

Looks great, congrats. I wish there was a "Like" button for each post on this forum

[DuncanS]

Thanks for the update, Tim. This will head off potential users of the 813/15 in the future. Unfortunately, once an item gets listed, it becomes very difficult to get a mistake removed. I recommend that one of the administrators put this information in a sticky so future high toppers will get decent advice.

Went to FAQs and found this topic: https://www.thesamba.com/vw/forum/viewtopic.php?t=...p;start=20 On page 2 Hodakaguy mentions he used 813. He also put ropes over the top to help hold it down until the epoxy had cured. My guess is that since he did this after cleaning the outside and putting more 813 inside and cleaning that too, the epoxy had already set and the ropes probably didn't do much. With 5200 you have all day to do the job. BUT 5200 TAKES SEVERAL DAYS TO CURE SO DON'T EXPECT TO DRIVE OFF THE NEXT MORNING. Since it draws moisture out of the air to fully cure, in a dry climate--'Zona, Baja etc., you might need to wet the joint periodically. 5200 cures under water, so no problem there. Also a warning: 5200 once cured is irreversible without destruction to either the metal or fiberglass. It is permanent.

4200 fast cure would work too. Tack free in an hour and cures in 48. https://www.3m.com/3M/en_US/p/d/b40066971/

Duncan

[tim_ha]

PSA to those Do-It-Yourself installers: I would strongly recommend against using Evercoat Maxim epoxy to adhere the hightop to your van.

I mocked up a overlap joint similar to that between the hightop and the van using some scrap angle iron and a chunk of fiberglass from one of my window cutouts. I prepped the metal using the same wire wheel that I used to remove paint on the van and scuffed the fiberglass using 80 grit sandpaper. The metal was cleaned with acetone and the fiberglass was cleaned with alcohol. Then, I bonded them together using leftover Evercoat Maxim 815.

After the 24 hour cure time, I tested the strength of my mock bond and was sorely disappointed. With with surprisingly little force, the epoxy stripped right off of the fiberglass leaving almost no residue. It did appear to have good adhesion to the metal. I tested it with a chisel and could not get the epoxy to break cleanly off of the metal like it did on the fiberglass side. The only thing that I can think I may have done wrong in surface prep would be that I didn't sand the fiberglass aggressively enough. One other comment on the epoxy... It cures very hard with no flexibility. This is another reason I would advise against its use. It will not allow for different expansion/contraction rates of the fiberglass and metal nor will it handle vibration very well.

I currently have a similar mock up using Sikaflex 221 curing and plan to do the same with 3M 5200. To save my situation and give me confidence in my hightop bond, I plan to squeeze a bunch of 3M 5200 down into the void between the roof and the hightop. I believe there is sufficient surface area down there to save my situation without trying to de-bond the Evercoat Maxim and potentially damaging the fiberglass.
_________________
1986 Syncro Sunroof EJ22
www.subagonsouth.com

[DuncanS]

If the track were continuously bonded with 5200, you avoid the point loading of fasteners which is exactly why it is used to secure the deck to the hull of a sailing yacht.

Duncan

[J Charlton]

The issue of having racking mounted directly on the fibreglass involves more than weight. No matter what the weight anything mounted on the outside will vibrate due to the movement of it through the air at speed. This vibration will be passed to the through fasteners that afix the track to the fibreglass and will ultimately result in cracking in the fibreglass. I discourage ANY through fasteners in a fibreglass top, especially to secure racking.
JC
_________________
NAHT hightop availability May 18 2023 -
Bend Oregon - for Oregon, California- (7 tot , 3 available), Kennewick Wa (6 tot, 1 available), Small Car Performance Fife Wa. (7 tot 4 avail ), Fairbanks Alaska (1 tot 0 avail)
Future availability TBD : Springfield Mass. Staunton Va, Florida, Colorado, Grand Junction Co., SLC probably late 2024

[tim_ha]

[pnwkayaker]

This is a very nice top! Could you please indicate how you are planning to use the single airplane track on the side? Usually I see them in pairs..

[J Charlton]

I suggest that you run a liberal amount of the 221 applied from the inside and run down into the cavity between the top and the van along the sides as well as what you plan to do across the front and rear.
_________________
NAHT hightop availability May 18 2023 -
Bend Oregon - for Oregon, California- (7 tot , 3 available), Kennewick Wa (6 tot, 1 available), Small Car Performance Fife Wa. (7 tot 4 avail ), Fairbanks Alaska (1 tot 0 avail)
Future availability TBD : Springfield Mass. Staunton Va, Florida, Colorado, Grand Junction Co., SLC probably late 2024

[DuncanS]

Congratulations--Very well done. You certainly followed the most important rule of all--the six Ps.

Duncan

[jimf909]

Super sweet. There are so many things to like about your van. Thanks for posting the post-game report.
_________________
- Jim

[dobryan]

Great job. Nice techniques.

I think I will copy some of them on my next one.
_________________
Dave O
'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD

"To travel hopefully is a better thing than to arrive." Robert Louis Stevenson

MD>Canada>AK>WA>OR>CA>AZ>UT>WY>SD
https://www.thesamba.com/vw/forum/viewtopic.php?t=620646

Building a bus for travel in Europe (euroBus)
https://www.thesamba.com/vw/forum/viewtopic.php?t=695371

The Western Syncro build
https://www.thesamba.com/vw/forum/viewtopic.php?t=746794

[mikemtnbike]

Looks amazing, great color choice and I think the Maxxair fan actually soothes the lines a little bit.
_________________
1991 Vanagon GL 2.1 AT Westfauxlia. "Frankie" Totaled https://www.thesamba.com/vw/forum/viewtopic.php?t=764510&highlight=carnage
1995 Eurovan Camper "Marzivan"
2020 GTI SE manual