5200 vs Screw Holes

[Emouchet]

I would not go with 5200.
You must consider 5200 as permanent, almost impossible to remove once curred.
Most pros will tell you they hate when they have to work with hardware that was mounted with 5200. They will charge 3 times the work time, because it is so hard to remove.

Rather, go with Sikaflex 291 or Life Seal sealent. It is less binding, but as good and this will give you a chance to be able to remove it.

[Suijin]

Having just removed probably around 50 hardware fittings from my deck, all of them bedded with 5200, I can attest to it's virtues and it's sins. My boat is 31 years old and there was not a single instance of bedding failure, other than around the chainplates due to flexing and poor maintenance by the previous owner. If protected from UV, it will last virtually indefinitely.

On the other hand, even with the bolts out it took a car jack and a torch to get the feet of my traveller bracket off the coachroof. 1/4" bolts required a serious dose of impact driver just to get them turning after the nuts were off. DaBond works really well to release 5200 adhesive where the contact area is deep/broad and you can't cut the physical bond. Saturate the edges with the stuff, cover with plastic wrap, and come back 24-48 hours later and it should have released.

In this particular case, to avoid putting down 50 screws, I might advocate for the 5200, provided you can apply it in a fashion that will allow you to remove the panels later on. If these are are flexible panels, only glue them down around the perimeter, no deeper than 3" from the edge. Don't glue them with 5200 in any spot around the edge where you won't be able to maneuver a stiff putty knife in future to cut it free, use 4200 or 4000UV in those areas.

I would not use butyl under z brackets with screws. Butyl works through compression and I'd be concerned that you're not going to get enough of it in this application to ensure that the butyl seal doesn't fail. With 50 screws, this is not something you want to have to disassemble every few years to check on.

Yeah, 5200 has bad rap, and it's a bear to disassemble stuff bedded with it, but it works really really well. A lot of the "5200 has no business on a boat above the waterline" is just people who don't know better parroting what they think is conventional wisdom. If you don't expect to need to take off the panels for 5-10 years, and you use the stuff with some intelligence, it could be an excellent solution depending on the particulars of the installation.

[rwells36]

Originally Posted by thruska

Lots of conjecture here.
But we don't know what you are attaching to what ?
How big and how heavy are your panels ? 50 bolts or screws?
Also consider that depending on your panel , you will have heat generated on the backside of the panel. So if you glue the panel down without venting you could invite early demise of panels or other issues under that panel on your boat.
Pictures are worth a thousand words...

Panels are rigid, about 20lbs each and frames have bolt holes that match up with z bracket(s) mounting. Bolt / Screw holes are 3/8" with 4 places of attachment mounted to fiberglass helm. Off set from the surface is about 1.5 to 2". 4 bolts per z bracket.

[Mainstay]

Originally Posted by davil

here is another way using only adhesives in the absence of backing plates.
5200 provides strength more likely superior to any mechanical fastener ,since you cannot use backing plate I would more likely replace the screws with wooden plugs soaked in epoxy.
Just drill as many holes to your heart's content,the hole just a hair oversize to diameter of plug/dovel,then soak the plug into a container with the epoxy mix,drive it in, it will be waterproof and when cures is structural component,just finish sanding or dremel the tops.

David

Now that is one brilliant idea! Will work on basically anything that needs to be securely fastened to fiberglass. Dave, you immediately solved a heck of a lot of problems for me - Thanks!!

[TacomaSailor]

I think you are over estimating the necessary strength of attachment for your solar panels.

We have four (4) 135-watt Kyocera panels on top of the arch over the aft cockpit in our Caliber 40. There is an 1/8" aluminum plate welded to the top of the arch. Each panel is attached to the aluminum plate with six (6) 3/32" aluminum pop rivets. That is all that attaches each panel while sitting 9' above the water and cantilevered off the back of the boat.

The panels have been up there for 17-years. We've experienced the following weather with the panels in place:

- 65 knots and 10' breaking waves while at anchor
- 52 knot gusts and 10' breaking seas while underway (six times)
- 55 knot gusts and no waves while anchored (24-hour duration)
- 45-knot gusts while at anchor (ten or more times)
- 30+ knot gusts underway in Pacific Ocean (many times)

I just removed and reinstalled the panels. Each panel was rock solid and had no play or movement prior to removal. The rivets had been holding them in place for 12-years. Prior to their removal in lat 2004 (after five years usage) the panels were also still very solidly mounted.

We've done 10,000 miles cruising with the panels in place

[thinwater]

Perhaps the strongest method, short of through bolts, are glue-on studs. These can be either your own custom FRP pads (below) or commercial versions (below that). These are perfect for cored hard tops and decks, since the skin is NOT penetrated, the load is distributed, and they allow for high adjustment, critical for avoiding torque on the panel.

They are quite suitable for heavy items; I've used them to hold down air conditioners on catamaran bridge decks. A solar panel is nothing by comparison.

I discuss both in the book "Keep a Cruising Boat on Peanuts." (in signature block)

[john61ct]

Originally Posted by rwells36

Panels are rigid, about 20lbs each and frames have bolt holes that match up with z bracket(s) mounting. Bolt / Screw holes are 3/8" with 4 places of attachment mounted to fiberglass helm. Off set from the surface is about 1.5 to 2". 4 bolts per z bracket.

Again, stainless Plusnuts bedded in butyl, supporting a generic rack which supports the panels.

Or if you are sure you will replace them with the same size, put the Plusnuts where the Z-brackets will directly bolt in.

[thruska]

Originally Posted by rwells36

Panels are rigid, about 20lbs each and frames have bolt holes that match up with z bracket(s) mounting. Bolt / Screw holes are 3/8" with 4 places of attachment mounted to fiberglass helm. Off set from the surface is about 1.5 to 2". 4 bolts per z bracket.

Ok 20 lbs . Size? Ss or aluminum? Brackets ss ?
3/8 is way overkill I'm sure you know that. But even if you use a smaller diameter fastener, you will require washers .
What's the 'helm' fiberglass thickness? Is it cored ?

[rwells36]

Originally Posted by thruska

Ok 20 lbs . Size? Ss or aluminum? Brackets ss ?

3/8 is way overkill I'm sure you know that. But even if you use a smaller diameter fastener, you will require washers .

What's the 'helm' fiberglass thickness? Is it cored ?

Aluminum 64" x 39". Helm is cored thickness is probably 1/4" maybe a. It more

[Suijin]

I did not realize these were rigid panels. I'd go Thinwater's route, or similar by glueing down blocks with studs. If going with blocks, I would probably mill some out of G10 and paint them. Yes the G10 is overkill in terms of strength, but it takes paint well if properly prepped and won't degrade if the coating fails.

I'd use 5200 to adhere them to the helm roof. They'll be small enough that you can easily get them off if ever needed, but strong enough that you'll never have to worry about the attachment points.

I agree that 3/8" bolts is serious overkill. Even 1/4" is overkill with that number of fasteners.

[Group9]

Originally Posted by UNCIVILIZED

I've seen keels bedded in the stuff not drop off, despite their bolts being removed, due to the adhesive ability of 5200. Quite entertaining!

A friend of mine who owns a boatyard told me a similar story of efforts to get a 10,000 pound keel loose, at the point when it was only being held on by 5200. He finally called the manufacturer, thinking he had missed a keel bolt. He hadn't. He finally had to drive wedges in all around the keel to get it to come loose.

[estarzinger]

Clickbond has about every possible good solution to this sort of question. We used them a lot on Hawk to fasten things to the aluminum (when stainless screws and bolts are not sush a good idea).

They have adhesive studs but also a whole host of other options.

[thruska]

You have 3x6 ridged panels, roughly speaking. Two z channels each. 4 holes per panel holding to 2 holes each to each z channel. Thus 4 holes to attach to hardtop per panel. Your hardtop is not cored with wood or foam, but it's likely reinforced with preformed fiberglass channels forming the cavity which you refer to, thus making access difficult.
You mention 50 bolts ? If that's 8 bolts per panel that's 6 panels?
If this is correct, I wouldn't worry about using adhesive on panel to z channel, use bolts with locknuts, you may want to isolate your aluminum panel from your ss channels , idk. I would follow Thinwaters suggestions of blocks and 'adhesive 'bolts , which will eliminate drilling holes in your hardtop and eliminating any possible leaks.
Mock everything up first, mark your blocks or bolts, then make sure no wax is where you put any adhesive, rough up the surface of the block or bolt and the hardtop where adhesive will be applied.
If you have radar or anything else protruding from your hardtop, it will shadow the panels and affect your solar panel output.
Good luck.

[UNCIVILIZED]

Originally Posted by estarzinger

Clickbond has about every possible good solution to this sort of question. We used them a lot on Hawk to fasten things to the aluminum (when stainless screws and bolts are not sush a good idea).

They have adhesive studs but also a whole host of other options.

Good tip, thanks!