Best Way to Add Solar Panels to a Finished Skoolie (Spray Foam + Ceiling Done)

[OnTheFlyFam]

Hey everyone,

We just picked up a fully converted Blue Bird with an 8.3 Cummins (3606) and are starting to plan out our solar setup. The bus is already spray-foam insulated with the ceiling and interior finished, so unfortunately I don’t have access to the ribs from the inside.

I’ve heard about the Tamarack mounting system and it looks promising, but I’d love to hear from anyone who has installed solar panels after their build-out was already complete. What’s the best approach for mounting? Are you drilling directly into the ribs, using plusnuts, Unistrut, or something like Z-brackets on the roof?

I’m planning a fairly large array (around 2400–2800W), so I’ll need a sturdy system that can handle highway winds and not compromise the roof seal.

PS - bus is already prepped to add solar in terms of wiring - just not to attach to the roof.

Any thoughts, experiences, or product recommendations would be super helpful. Thanks in advance!

 

[s2mikon]

I used unistrut and steel rivet nuts. The advantage of full length unistrut is that it distributes the load over the length of the unistrut. Z brackets don't. Rivnuts need perfect size holes so use a reamer type of drill. Regular twist drills make odd shaped holes in sheet metal. I also left small gaps between the unistrut so water could drain out faster. I used unistrut spring nuts to attach the unistrut L brackets that attached to aluminium angle bolted to the panels. Don't use the solar panel clamps. Someone here already had a panel come off that way.

 

[TheHubbardBus]

Rivnuts need perfect size holes so use a reamer type of drill. Regular twist drills make odd shaped holes in sheet metal.

Thanks so much for this!

 

[Bjorkinman]

Watch this Video of Jonathan install a solar rack. I followed his method (and bought his brackets from him - 352-537-9220 this is the number I have for him) and have been happy with my setup. I used Unirac rails sold in 14' lengths (really reasonable and with free shipping to me in Atlanta!) They sell mounting parts for their system that you need to use but they're reasonable as well. I bought my stuff from City Electric if i remember correctly. I would second The Hubbard Bus and use Rivet nuts, i bought a complete set to install with on Amazon and have been amazed at how useful they are. i would think if you can install two lengths for 28' total and have around 10-14 attachments on each side plus the panels tying it all together you should be fine. Ive put about 700 miles on so far with no issues.

 

[Beeb2]

I faced a similar problem a few years ago. I got solar rails with brackets from a local solar installer, used a couple of small metal pieces to act as shims to account for the curve in the roof, and used 5/16 rivnuts to mount the brackets about every 2' to the roof. Butyl tape under the bracket. Been driving around the country for a few years and haven't had a single issue. Very easy install.

EDIT: Make sure to use good bolts. Grade 8 is ideal. You can get then at Tractor Supply or Ace among other places.

 

[Beeb2]

Thanks so much for this!

I used normal drill bits every time I drilled through metal for rivnuts and never once had a problem. I just tested on a scrap piece of sheet metal first so I knew which size hole fit each size rivnut. I labeled it and still keep that scrap piece around to this day as a reference.

 

[Hooker-SKO]

I'd suggest rivnuts too. I think the guy is nuts myself, but he claimed it's been years now and no problem, but he used some kind of glue and glued brackets to his roof and no drilling, no holes, no possibilityes of leak or starting rust. Sounds great, but I just not sure I could trust it and sleep at night. I guess it could. GM has glued door hinges on trucks for many many years and I don't see their doors falling off.

 

[Beeb2]

I have heard of people using glue as well. I have also heard of their panels coming off while they're driving down the highway, and I know of one story where the panel came off and killed someone driving behind him and the guy went to prison for manslaughter. Don't use glue. I dont care what the Chinese manufacturer on Amazon claims!

 

[Jon1371usmc]

You could try and locate the Tesla glue that they use to glue their frames together. That stuff is strong. They, jerryrigeverything YouTube channel, glued a eyelet to a cyber truck, or maybe it was two cyber trucks, and lifted them high off the ground with a crane. Pretty incredible stuff and no extra holes in the roof allowing water ingress. I would not use that sticky vhb tape I've seen people use before, or some random glue/epoxy. But I would trust the chemicals they use to glue on the rear subframe of a Tesla cybertruck together that is used for towing heavy loads. Would be just fine for a solar panel array.

 

[Jon1371usmc]

 

[Jon1371usmc]

Apparently it's called Fusor 2098, and is a 2 part epoxy

 

[AlphaHare]

You don't need physical access to the ribs, you just have to drill from the top. Snap a chalk line along the existing rivet line and use rivets. They're called blind rivets for a reason.

 

[TheHubbardBus]

I used normal drill bits every time I drilled through metal for rivnuts and never once had a problem. I just tested on a scrap piece of sheet metal first so I knew which size hole fit each size rivnut. I labeled it and still keep that scrap piece around to this day as a reference.

Rivet-nuts should come with the recommended drill size as part of their documentation. That said, the advice given by @s2mikon is sound and appreciated... making a perfectly round hole through sheet metal, particularly with a hand drill, can be a challenge. They have a tendency to oval out to some extent no matter what you do.

I'm not arguing rivnuts can't be used effectively drilling holes with standard bits, but they're going to be more resistant to spin and/or tear-out the 'rounder' and more precisely-dimensioned that hole is.

As far as epoxy goes, we're on the same page for sure! I'm a big fan, and have used various epoxies throughout this build for all sorts of things. But I would never trust epoxy alone for something as safety-critical as securing panels to the roof of a moving vehicle. That interface is going to be subjected to the absolute worst that mother nature has to offer (extreme heat, UV, rain, vibration, flexing, wind, etc).

 

[nikitis]

I will be using bolts straight through the roof and hat channel center for any mounting I do. Not 100% sure on my choice of bracket yet, but bolts will be used in my application. Along with a flex sealant.

 

[Tejon7]

I thought that I had replied to this thread a few days ago, but it turns out I accidentally posted in a different, unistrut-related thread. Whoops. Here's what I wrote, though it's probably a bit late now:

I used closed end rivet nuts through every rib flange (every 18" or so on my bus). Finding the closed end ones with the right grip range was difficult. Put them in "wet" with your favorite sealant. Rivnuts can supposedly loosen up over time, so I check mine before every major trip. About 10k miles now and no issues.

Looking back, I think I'd be tempted to do plus nuts or blind bolts for more pull-out resistance. Back then I was more worried with waterproofness, now I think I lean a little more toward bombproofness.

 

[LargeMarge-TC]

Fasteners need to be GRADE 8.
Avoid stainless-steel, those are equivalent to Grade 2 bolts from the grocery store.

 

[ahibbert]

I thought that I had replied to this thread a few days ago, but it turns out I accidentally posted in a different, unistrut-related thread. Whoops. Here's what I wrote, though it's probably a bit late now:

I used closed end rivet nuts through every rib flange (every 18" or so on my bus). Finding the closed end ones with the right grip range was difficult. Put them in "wet" with your favorite sealant. Rivnuts can supposedly loosen up over time, so I check mine before every major trip. About 10k miles now and no issues.

Looking back, I think I'd be tempted to do plus nuts or blind bolts for more pull-out resistance. Back then I was more worried with waterproofness, now I think I lean a little more toward bombproofness.

 

[ahibbert]

Amen on the plus nuts

 

[AlphaHare]

1/4" structural rivets have shear strength and tensile strength over one ton (2750, 2200 respectively). That means that about 7 rivets would hold the full GVWR of my bus.

I'll have two brackets per hoop rib, each bracket with 4 rivets, 6 hoops in a 5 window bus - a total of 54 rivets. In theory, that would resist a tensile load of 118,800 pounds.

I'm going to worry far more about attaching the panels to the rails than the rails to the bus.

 

[desrtdog]

Fasteners need to be GRADE 8.
Avoid stainless-steel, those are equivalent to Grade 2 bolts from the grocery store.

While it is a fact that plain 18-8 stainless steel fasteners have a similar strength as the so-called “grocery store” grade 2 bolts for a given size (e.g. 1/4-20), what you neglect to point out is that you can increase the effective strength of the attachment by upsizing the SS bolt….so if you were to go with 3/8-16 SS bolts, you can get the same strength as 1/4-20 grade 8 bolts…if you go further and use 304 or 316 SS the strength is about equivalent to a like-sized grade 5 bolt.

…So I don’t really understand the need for grade 8 fasteners…For my rack, I used 3/8-16 bolts as I did not want to worry about bolt corrosion…2 bolts per rack tower, 13 total towers with SS neoprene washers between tower and bolt head, and held by SS washers and nylock nuts….

Bolt Strength