Solar Mounting - rail mounts or adhesive on hdpe blocks?

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huruta

Senior Member
Joined
Jan 9, 2022
Messages
125
Vessel Make
2006 Nordic Tug 32
Hi. We have a NT 32 and are needing solar as our boat will be on a mooring buoy all summer. We are mounting them ourselves and have an electrician who will do the set up. My question is whether to create a railing system to hold the panels, which many NT owners have done across the top of their pilot house, or to adhere 6 hdpe blocks with hinges screwed into the blocks to hold each panel (2 300 watt panels, ~35" x 60").

My electrician mentioned that 3m 5200 adhesive is a bear to get off and can damage the roof if we ever changed our minds. He didn't have concerns about it holding. And an adhesive approach is more appealing due to cost. It's a bit more minimalist and cleaner. Could a 4200 work and be removable yet secure? I've seen an example so others have done this.

Railings are more $ but if we ever needed to change our solar panels it could accommodate different sizes. It is also what I've seen on most Nordic Tugs and I haven't heard anyone complain about this approach.

Thoughts?
 
I wouldn't try to glue HDPE blocks to the deck, not a lot will actually stick. Personally, I mounted mine on C shaped aluminum brackets (2 pieces of angle bolted together) glued to the deck with 4000UV. 3 years in and they're doing fine.

Either something like that or rails would be fine. Or bolted brackets would work too. I went for glued brackets only because of poor access to the underside of the deck where I put my panels, so through bolting would have required a lot of interior surgery.
 
On my NT 37, I installed 2 SS cross rails using the handrails that were already on the Pilothouse. For a centre support (due to the span and flexing), I used Sikaflex as the adhesive. No screw holes to later leak! It held great, and is relatively easy to remove (if in future you decided to remove the solar). The straps shown in the photo were temporarily used as a "extra" hold down measure and proved to be unnecessary. :dance:
All of the parts were available at a local chandlery, except the SS pipes that I bought at a local metal supply company.
It was not cheap, but not crazy expensive either, and I wanted something that would work well, stand up to the rigors of boating, not result in future leaks and damage, and last a long time. This met all points.
Good luck.
 

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Hi. We have a NT 32 and are needing solar as our boat will be on a mooring buoy all summer. We are mounting them ourselves and have an electrician who will do the set up. My question is whether to create a railing system to hold the panels, which many NT owners have done across the top of their pilot house, or to adhere 6 hdpe blocks with hinges screwed into the blocks to hold each panel (2 300 watt panels, ~35" x 60").

My electrician mentioned that 3m 5200 adhesive is a bear to get off and can damage the roof if we ever changed our minds. He didn't have concerns about it holding. And an adhesive approach is more appealing due to cost. It's a bit more minimalist and cleaner. Could a 4200 work and be removable yet secure? I've seen an example so others have done this.

Railings are more $ but if we ever needed to change our solar panels it could accommodate different sizes. It is also what I've seen on most Nordic Tugs and I haven't heard anyone complain about this approach.

Thoughts?

Firehoser’s system looks solid and seems like a good option.

I have successfully used mounting blocks and like that approach. HDPE won’t hold adhesive, but other materials will. Both systems that I set up, I made plywood blocks from 2 layers of 3/4” ply. You can fully waterproof them with a couple of coats of resin, and include a layer of FRP cloth or mat if you feel inclined. A couple coats of either polyester resin/gelcoat or epoxy resin will seal them up without any cloth. If you use epoxy, paint the visible sides of the blocks (everything but the bottom) to match your gelcoat and protect the epoxy from UV.

In both cases, they were positioned under the edges of the panels. The latest round, I’m using tilt brackets between the blocks and the panels. You can skip the tilt brackets if you wan’t the panels down closer to the roof. Use lag bolts through the brackets and into the blocks, and seal those penetrations with sealant (4000UV preferred) or the epoxy close-out method if you want extra work.

3M 4000UV has bonding strength similar to 4200, and both are plenty strong enough for a permanent bond between the blocks and PH roof. The 4000UV will hold up better to sunlight over time.

This system avoids any penetrations into the PH roof, which is an important point in my book. My setup has 390w panels and made it through 3+ years so far and lots of wind, including at least one round of 50kts, with no issues.
 
3M 4000UV has bonding strength similar to 4200, and both are plenty strong enough for a permanent bond between the blocks and PH roof. The 4000UV will hold up better to sunlight over time.

I used 4000UV both for that reason and because my mounts are aluminum. Based on the specs, 4000UV has a stronger bond to metal than either 4200 or 5200 does.
 
If you are limited on how many panels you are going to mount because of flat space.... I had 2 mounted to the flybridge hand rails that hung down when traveling and had multi-position bars to angle them from hanging to slightly past horizontal if the suns position dictated and angle. I also had 2 lightweight flex panels that I moved all over the boat when anchored to get the best angle of the sun.

I had several times where the conditions were perfect (cold/clear, etc) and the panels that were facing the sun till sunset were producing near max amps until the sun started to get blocked by obstruction on the horizon.

Flat mounted on the roof without flexible angling to me is a huge waste of a resource....unless you have done all the calculations to see if max output for only a couple hours a day and the increasing and declining output from sunrise to sunset will satisfy your needs.
 
I used flex panels, that I bolted to plastic corrugated sheets I got at HD, about $30 each. This allows the panel to breath underneath and stay cool, vs direct mount to the gel coat. In addition, I used VHB tape to mount them, extremely strong and durable, yet if you want to remove it’s not a big chore. Routed my 175 Watt Renogy panels down the inside of the eisenglass, and into the bilge, then thru the house. 2 day project, with fantastic results!
 

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Huruta: your electrician is correct about 3M 5200. I think it would be overkill. I got eight years on 3M 4200. The adhesive failed on 2 of the supports, but examination of these revealed I didn’t roughen up the aluminum which was afixed with the 4200. So it was probably a mistake on my part.

I proceeded to disassemble, clean up and reattach all of the supports for my three solar panels. It was a lot of work to remove it all, and I probably only needed to reattach the two that failed. There was no evidence that the 4200 had failed on the other 10 supports.

I used aluminum angle bar, and made my own brackets. It was a very cheap solution, held together with stainless bolts with locknuts and washers. It worked well and everything could be removed, allbeit was a bit of difficulty in order to clean underneath the solar panels, which I did once a year. I didn’t hesitate to reuse the brackets and the 4200 in my case it worked fine. I recommend it. It’s an inexpensive solution.

Everyone’s vessel is different and will require different methods. I used the simplest solution that was within my capabilities.

Jim
 
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Thanks for al l the responses and pics! After a lot of thought I think the railing approach makes the most sense given my skill level and future flexibility for modifications.
 
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I like to use starboard to mount things like electronics too because it doesn't rot. But as noted gluing stuff to it works poorly. What I've done in a bunch of instances is take a dovetail router bit and run some grooves across the back of the panel. Or, I've set my tablesaw at 45 degrees and run a bunch of horizontal grooves through the back.

Then when you cover it with 4200 it has a mechanical keyed in joint with the grooves you added.

It's worked well.
 
I recommend rails of some kind, because later when you go to replace the solar, you will find that the panel sized have changed. There is no standard, and the dimensions change with the latest fashion in wafer size. Rails can accommodate any change. I used Seadog plastic rail clamps to mount the panels to the rails. I made the rails myself, buy any store bought hand grasp will likely work. To put them on the deck, I made G10 pads, and bonded them down with VHB 3M tape. This grabs pretty well even on the non skid, if you get a thickish version (that can sink into the non skid pattern). Inset the tape a little from the edge, and seal the edge with 4000UV. This will be removable without damage should plans later change.

I would not use flexible panels unless your expectations of longevity are low. They delaminate and fail much quicker than rigid ones.

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I would not use HDPE to secure the panels to the roof. I used to work with and sell HDPE and it is slippery and a POOR fastening substrate.
We used to sell it for wear resistance, chemical resistance and it performed WELL but as a glue or tape securing spot I don't see it for long term.
 
I had a NT32 and had 2 SS rails built and I installed them athartship. They were curved to match the contour of the boat and looked great. I mounted kayaks on them, but you could mount anything. It wasn't that much money, and added value to the boat. I would do that again in a heartbeat. That was before solar was as accessible, but I'm sure I would have mounted solar on by now if I still owned the boat.
 
Thanks to all for input. Going to do rails with mono rigid panels, within my skill level, modifiable and less technical for someone not especially handy!
 
Hi. We have a NT 32 and are needing solar as our boat will be on a mooring buoy all summer. We are mounting them ourselves and have an electrician who will do the set up. My question is whether to create a railing system to hold the panels, which many NT owners have done across the top of their pilot house, or to adhere 6 hdpe blocks with hinges screwed into the blocks to hold each panel (2 300 watt panels, ~35" x 60").

My electrician mentioned that 3m 5200 adhesive is a bear to get off and can damage the roof if we ever changed our minds. He didn't have concerns about it holding. And an adhesive approach is more appealing due to cost. It's a bit more minimalist and cleaner. Could a 4200 work and be removable yet secure? I've seen an example so others have done this.

Railings are more $ but if we ever needed to change our solar panels it could accommodate different sizes. It is also what I've seen on most Nordic Tugs and I haven't heard anyone complain about this approach.

Thoughts?
3M 5200 is "forever" and 4200 is "for a long time". choose wisely. I have had to remove window bonded with 5200 and although I eventually won, it was a Bi%@#!
 
I used 4200 and some aluminum angle brackets to mount my panel. It has worked well and is still solidly attacked to my pilothouse roof. The old thread is here.

Post in thread 'More solar questions....' More solar questions....
 
Used SS rails mounted port to stb using stanchion bases with short stubs, 90 deg. connectors. Center was supported by a tee, short stub, and another base just resting on a bed of butyl. Zarcor makes some good clamps to mount the panels to the tubing.
 
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Got it done. Has been working great on the buoy. The structure was harder to secure than anticipated. Had 1.25” rails and getting vertical pieces to start was challenging. Have been secured and working for 6 weeks with no problems. Yeah!
 
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