how to mount solar panel brakcets with screws/lag bolts

[wamcneil]

2 hours ago, John C said:

I thought it was 1/2", just looked at again, I believe it is 3/8", that is how I did it on my previous coach.

Maybe a little overkill...

 

A 'little' overkill??? Overkill, btw is my 2nd favorite kind of kill.

Take a look at what's holding the ladder to the fiberglass skin on the outside of the coach...

Somehow that ladder will safely support a big ol' RVer that eats a lot of fried food. 

The solar array just barely needs to be held down. Especially if it's got 50lb of uni-strut underneath it. 

Something like this rooftop deck? Sure... 3/8 bolts in the metal structure would be good:

Edited May 1 by wamcneil

[Benjamin]

If I had to guess, that's a 3/8" hex head with a 3/16" thread.  If that's 3/8" threads, then the hex is 3/4"???   I'd agree that is the appropriate fastener for a metal framed roof if that's what you have (not the 3/4" hex head, the smaller size that I think it is)

[Just Jim]

Back to the original question... If you really want to find the frame then you could invest in this.  It is a pretty cool device to have for seeing into walls. 

https://www.flir.com/products/flir-one-gen-3/?vertical=condition monitoring&segment=solutions

 

On 5/1/2024 at 4:27 PM, wamcneil said:

A 'little' overkill??? Overkill, btw is my 2nd favorite kind of kill.

Take a look at what's holding the ladder to the fiberglass skin on the outside of the coach...

Somehow that ladder will safely support a big ol' RVer that eats a lot of fried food. 

The solar array just barely needs to be held down. Especially if it's got 50lb of uni-strut underneath it. 

Something like this rooftop deck? Sure... 3/8 bolts in the metal structure would be good:

As a NASCAR infield camper guy... I need one of those decks.

[John C]

On 5/2/2024 at 1:43 PM, Just Jim said:

Back to the original question... If you really want to find the frame then you could invest in this.  It is a pretty cool device to have for seeing into walls. 

https://www.flir.com/products/flir-one-gen-3/?vertical=condition monitoring&segment=solutions

 

As a NASCAR infield camper guy... I need one of those decks.

Will call the company tomorrow to see if it can locate the trusses. if so I will definitely buy it.

Thank you!

[John C]

On 5/2/2024 at 1:43 PM, Just Jim said:

Back to the original question... If you really want to find the frame then you could invest in this.  It is a pretty cool device to have for seeing into walls. 

https://www.flir.com/products/flir-one-gen-3/?vertical=condition monitoring&segment=solutions

 

As a NASCAR infield camper guy... I need one of those decks.

@Just Jim Just got this device yesterday at 10am, tried it, nothing,guess it was too late, so I tried it at 8am today, I did see some lines in the first half of the roof(from the first a/c to 2nd ac), I looked at the roof, to my surprise, I did see "dew pattern" @DavidL was talking about, the lines has no dew on it(other areas has dew). I don't know why nothing from the 2nd A/C to the 3rd A/C

Also, the pattern doesn't make sense, there should be a lot of  trusses cross the coach from driver side to passenger side, but I only see a couple next to the two a/c and those are not extended to the edge, also I can't find the trusses from the first a/c to 2nd a/c on Roadmaster chassis diagram in Dynasty's brochure, but the pattern shows two straight lines there from first a/c to 2nd.

 

[cbr046]

Maybe there's a layer of insulation / styrofoam between the skin and the trusses?  Just guessing . . .

Maybe you could pull apart the inside of one of the AC's to see the layers and what those are mounted to?

- bob

Edited May 10 by cbr046

[Tom Cherry]

Thermal Imaging has been used on many “structures” and system (like electrical switch gear).  Don’t know the exact data when the equipment and development started, but a consultant that I hired was a leader in using Thermal Imaging in the roofing industry and held seminars or did presentations and such at major commercial and industrial “roof maintenance” events.

The use in roofing was to show or detect moisture in the insulation of a commercial roof so you could make an intelligent decision as to whether to recoat or add additional plies or to do a complete tearoff.  Water soaked or damaged insulation provides NO R Value so, determining its condition is critical.

It is a “contrast imaging” concept…not Superman’s XRAY vision.  For max resolution, it is done after say 10:00 PM and stops before sunrise.  With the proper equipment and calibration, it can be used…and is very accurate in all climates….and my, now longtime friend, worked on roofs where the wind chill factor was well below zero.  Bottom line….XRAY it ain’t.  Is is also, due to the cost and the evolution of technology, used on large electrical system….laser guided.  But again, it is measuring “thermal contrast” so that a high resistance connection in a high amperage panel or switch gear will be “determined”.  It does NOT trace cables.

That’s the short version.  BTW….there is a concept called “Ground Penetrating Radar”.  It’s use is to detect “masses” or objects like buried drums in fields or even, under the right conditions, a floor.  It would not give the image you want.  Practically, a high class Stud Finder MIGHT….but without then test drilling, a few hits to determine the accuracy, it might not be accurate enough.  IF you need the ceiling joist/“rafter” spacing….then drilling and locating one….could be used.

There may be technology in the reinforced concrete industry that would give an image and locate the rebar.  BUT several years ago, after a cleat on a column failed and the sliding concrete floor caved in on a parking deck.  The consultant cross sectioned the column and cleat and found that the vendor did not follow the design prints….thus a few pieces of rebar were left out.  FAILURE. Check out if there is a “amazon” device that will detect rebar in a floor or column or do some googling. THAT if what you need….a super accurate steel member (stud?) device…a metal rebar or a stud or such ….that’s what you need.

YES…I did my share of construction, demolition and roofing maintenance….

[Ivan K]

My cheap metal detector finds rebar in concrete floor. Not what I have it for but finding a center of a truss may be a challenge. But if there was a specific spacing from a known truss, it might do.

[Benjamin]

For maximum contrast, as Tom said, do it early morning when it's as cool as it will be, before the sun comes up to start heating everything up, and turn the heat on inside to get some conduction through the roof.  I don't know what's going on with those pictures, if the longitudinal lines are gaps in the insulation, or what?  Like Bob said, if there's foam over the top of the framing then it makes the FLIR much less useful, but the foam much more effective, we're reading the thermal bridging, which the foam will greatly reduce if done right, outside metal framing. 

[John C]

2 hours ago, cbr046 said:

Maybe there's a layer of insulation / styrofoam between the skin and the trusses?  Just guessing . . .

Maybe you could pull apart the inside of one of the AC's to see the layers and what those are mounted to?

- bob

There are a lots of insulation, forms on the roof, I was replacing the Fantastic Fan with Maxx Fan last week and measured 7.6" from roof to ceiling, most of those are insulation.

I did open one of the a/c when troubleshooting the a/c problem and I don't believe there are big openings there.

45 minutes ago, Ivan K said:

My cheap metal detector finds rebar in concrete floor. Not what I have it for but finding a center of a truss may be a challenge. But if there was a specific spacing from a known truss, it might do.

I tried with a very good metal detector can detect up to 6" deep rebar in cement, but I couldn't detect anything on this roof.

[Tom Cherry]

56 minutes ago, Ivan K said:

My cheap metal detector finds rebar in concrete floor. Not what I have it for but finding a center of a truss may be a challenge. But if there was a specific spacing from a known truss, it might do.

no doubt....and what I said or tried to say....the consultants that worked on the parking deck floor failure had difficulty in identifying the cleats (cast in when the column was cast), had difficulty in determining if ALL the rebar "network" was inside a cleat.  They removed the cleat and then demolished it and ascertained that the factory, in SC, had two folks working.  ONE did it per the print.  The other did it differently...as in the number or maybe size or length on the design print was critical.  The floor contracted on a cold night.  So, the floor, which was designed due to thermal contraction and expansion, moved TOO FAR OUT on the cleat.  The "moment arm" of the weight, moved from say 6" out to 8" out....sheared off the end of the cleat or destroyed it.  The cleat was NOT to the design print and missing some critical pieces of rebar....thus the failure.  They finally figured out how to inspect or certify all the cleats....maybe 500 or so as it was multideck.  They had to REPAIR or design a secondary cleat to would carry the weight due to the contraction.

BTW...I had to rebuild a building in Brazil that had a THREE PIECE "TRUSS" roofing structure....held together under tension by some 50 steel cables.  Water got into the cables and they corroded and rusted.  Think stretching a rubber band across your thump and first finger.  When the network or bundle of cables started to fail and rust out.....then the three trusses caved in.  THINK of having a rubber band that you could not stretch any tighter and it too ALL your strength to expand and hold your finger and thumb to a certain distance.  THEN the rubber band had a defect...and it POPPED...your fingers would expand...as you were forcing them...

THAT is what happened to the roof.  5 of the 8 trusses failed...  I put STEEL Trusses back up....and reinforced the remaining concrete one.  The roof was NOT being maintained and the caulk that protected or covered the "bands" failed and over the years, the cables rusted and the diameter was reduced.  For those that have use a Tennious Olsen tensile strength tester....the bands became "an HOUR GLASS" profile...and snapped.

THANKS for the comment about using a metal detector.

 

[Happycarz]

Use Z brackets, 4 per panel, and mount them to the panels. Lay the panels on the roof the way it will work for you. Mark the roof using the holes in the Z brackets. Buy a box of 1” long sheet metal screws the fit the holes in the Z bracket, which should be a #6 or #8 if my memory is good.  Take a bracket to the hardware store if unsure. Leave a little wiggle room between the screw and hole.
 

Pre-drill one of the marks you made on the roof.  If not sure what drill to use, practice on a piece of wood. Screw into your test piece to check snugness. Next, without the bracket or panel in place, try your sheet metal screw in your hole. The first 1/4” going in will be firm as the screw makes its way through the fiberglass. Run it all the way in, then back it out. It should back out smoothly. If the pre-drilled hole is too small, you will see tear out on that first 1/4”. If so go up a size drill. Once satisfied, drill all your remaining marks. 
 

Make sure your cables are attached to the solar panels.
 

Put a tiny circle of Dicor lap sealant around each screw hole. Set your panels in place and line up your Z brackets to the holes. It might get smear over the holes and be hard to see them, so take an ice pick, or similar, to probe the hole.  Install the screws about half way so you have wiggle room until all are started. Then tighten them up until firm. Use the Dicor to cover the screw heads. 
 

Now you have secure solar panels and a watertight roof.

[birdshill123]

Somewhere,  maybe FB,O saw poly brackets that hold the panels. They laid some sort of thick sealant/glue and embedded the brackets. Made for this application.

[wamcneil]

There are a number of good and widely accepted ways to attach the panels….
But the original poster has made it very clear that he’s dead set on going waaaaaaasyyyy overboard and using big fasteners down into the steel roof structure. 
I can sympathize… I too am afflicted with a sometimes overwhelming urge to over-engineer things that need to be fixed and fix stuff that’s not broken…😳

Edited May 11 by wamcneil

[Tom Cherry]

28 minutes ago, wamcneil said:

There are a number of good and widely accepted ways to attach the panels….
But the original poster has made it very clear that he’s dead set on going waaaaaaasyyyy overboard and using big fasteners down into the steel roof structure. 
I can sympathize… I too am afflicted with a sometimes overwhelming urge to over-engineer things that need to be fixed and fix stuff that’s not broken…😳

IF we, the staff, were so inclined.....and then required a PERSONALITY POLL with a few questions to determine IF you are so inclined.....BIGGER, TOUGHER, MORE IDIOT PROOF, ETC....is Better...  Then MY GUESS from reading just about every post from March, 2009, I'd be in that....  We would be in GOOD company....maybe 50% (that's MY GUESS...use your own....but above 50%)

THEN we would have to determine just exactly the extent (Mental Illness that causes up to OVERKILL) of such.  My DW says I would rank in the top 1%, UNTIL I laugh at a post or two....and read her the comments or relate some "OFFLINE" examples that many members share with me or a few other "ANAL" engineers come up with.  THEN she lowers my percentile to only 95%.

I could pontificate, in a non judgemental matter...for at least 5 paragraphs of how I FIXED IT FOR LIFE.  My Track Record is good....  RARELY do I have to go back.  MOST OF THE TIME...I DID OVERKILL and OVER Engineer...way beyond the NORMAL "Design Engineering Fudge or Safety Factor".  As an aside,,,I was involved in Manufacturing Engineering and Product Engineering (Design) as both a HANDS ON designer as well as supervising a large contingent.  I NEVER LEARN.. and often times myself and upper management or marketing would "overrule" a 300% safety factor....too costly or unsightly...

BUT, I CRINGE when I do HAVE to pull apart something that I FIXED and should NEVER BREAK.  Example....a Solar Panel goes BAD.  The replacement is no longer available and THAT, per a LOT of reading and talking to some tech, is the NORM for Solar...and the companies come and go or make upgrades.  BUT...in reality...I can't get an exact replacement.  THEN I rue the day when I had installed it for or affixed it down or attached it for a CAT 5 HURRICANE AND a F5 TORNADO, simultaneously hitting the MH  and I have to totally destroy the surface or whatever just to get my Pop Rivets and Double Stick Tape and Epoxy and Lag Bolts LOOSE...  

As you pointed out.  Each of us has our own "safety factor".  SO, whatever the OP wants to achieve....I salute him.  BUT, I know that my single screw, caulked in, solar panel...60 or so watt, is just as rigid as it was from day ONE.  It was installed by CW, GOD FORBID...but they had a LOT FULL of Monaco's and at least 10 Camelots.  They ordered the KIT that Monaco gave to the Assemblers and ran the wires exactly as the FACTORY units were routed.

I also only use 3 M Double Stick tape (Clear VHB) when I fully understand that if I need to "unattach", there will be CONSEQUENCES.

SO... Whatever, as the say, floats your boat....as long as you have, from several approaches, analyzed or calculated or whatever...and accept....IF I OVERKILL, It is gonna be Hades to pay...then you do what you feel meets that particular "Mental Affliction" that possesses....to some degree, the bulk of MH owners...who KNOW that driving a MH is equivalent to having ones house on a fault and there is a perpetual 4.5 quake...

SO....to prevent this turning into a "bashing"... I have left your post...and hope to defuse any ill feelings it might have brought about....

LAUGH WITH ME...and LAUGH at our personalities....but don't sincerely CRITICIZE us.... MOST can take a little ribbing...but not all members...

THANKS...

[Paul J A]

On 5/1/2024 at 2:01 PM, John C said:

I thought it was 1/2", just looked at again, I believe it is 3/8", that is how I did it on my previous coach.

Maybe a little overkill...

That is what I am planning to do if I can't find those trusses.

 

CALL they guys at; https://sourcerv.com/  Jim & Scott worked at Monaco and know the Roadmaster Chassis better than any one. 

[John C]

2 hours ago, Paul J A said:

CALL they guys at; https://sourcerv.com/  Jim & Scott worked at Monaco and know the Roadmaster Chassis better than any one. 

Will do.

Thank you!

[John C]

Thank you all for the help.

The only reason I insist on using lag bolt is because I did it before and it worked, also I want to make 100% sure that the solar panel won't fly down and kill or seriously injure someone, especially  I am installing residential panels and those are really heavy.

In the processing of replacing my Fantastic Fan with Maxx Fan, I saw the whole roof layer, on top is 1/4" fiberglass, followed by tapered bead foam insulation, then 1/4" marine plywood,R7.5 Cel Foam, then Luaun.

The 1/4" fiberglass and 1/4" marine grade plywood look a little thick than I thought, here is what I am going to do:

1) Clean the roof with water, then acetone

1) Lay two aluminum struct channel in parallel (10' or 20' depends on location) and with glue the channels to the roof with 3M tape (that will be much stronger than just glue the bracket), I know I will use much much more 3M tape this way and I am willing to pay for the extra tape.

2) drill pilot hole O.C 16" with small drill bit on the channel through the roof, fill the holes with Dicor 501,

3) Apply 4" #8 screws every pilots holes to secure the channels to the roof. that means the screw is penetrating both the 1/4" fiberglass & 1/4" marine grade plywood

4) Apply Dicor 501 on the screw heads.

5) wait a few days before I venture out, pull the solar panels to make sure they are really secure.

 

 

Right before I click send, I was just made aware that someone drilled his roof, hitting a very important 120v line feeding one of the breaker panels!! so 4" screw is definitely out of question, may be just 1" #8 screws??? can't image Monaco would lay the wire so close to the roof unless it is right next the A/C

Please comment.

Thank you!

 

 

[Ivan K]

Yeah, the wires were my worry when I was installing ours. I used stud finder and did not hit any. I read somewhere that the main wire channels were close to the edge of roof. I used short screws that came with the brackets but my panels are individually mounted and fixed.

[wamcneil]

“Lay two aluminum struct channel in parallel (10' or 20' depends on location) and with glue the channels to the roof with 3M tape (that will be much stronger than just glue the bracket), I know I will use much much more 3M tape this way and I am willing to pay for the extra tape.”

With the long sections of channel, I’d be concerned about different rates of thermal expansion between the AL and the roof fiberglass. 

[John C]

On 5/12/2024 at 1:50 PM, wamcneil said:

“Lay two aluminum struct channel in parallel (10' or 20' depends on location) and with glue the channels to the roof with 3M tape (that will be much stronger than just glue the bracket), I know I will use much much more 3M tape this way and I am willing to pay for the extra tape.”

With the long sections of channel, I’d be concerned about different rates of thermal expansion between the AL and the roof fiberglass. 

Good point, then I will apply the 12" long 3M tape then leave a 2" space, then apply 12" tape, then...

[Gary Cole]

On 5/12/2024 at 1:50 PM, wamcneil said:

“Lay two aluminum struct channel in parallel (10' or 20' depends on location) and with glue the channels to the roof with 3M tape (that will be much stronger than just glue the bracket), I know I will use much much more 3M tape this way and I am willing to pay for the extra tape.”

With the long sections of channel, I’d be concerned about different rates of thermal expansion between the AL and the roof fiberglass. 

Walter that is the method I used. Best to use solid strut rather than the perforated style for increased adhesive contact area. I would highly recommend the expensive 3M pre cleaner. I did some tests and it doubled the adhesive strength of my samples. I was able to clearly identify some roof struts from vent locations.  At those points I used 1/4" X 1/4" X 20 aluminum rivet nuts just in case. I use these on occasion so I invested in the official setting tool. If due to a faulty installation the rivet nut turns before the bolt tightens you are going to have a difficult problem to deal with.

For those who are concerned about the tape adhesive many of the 53' vans on the road use the system to attach outside panels to the trailer structure. Of course this system is better suited for those with a metal roof.

Edited May 14 by Gary Cole

[John C]

33 minutes ago, Gary Cole said:

Walter that is the method I used. Best to use solid strut rather than the perforated style for increased adhesive contact area. I would highly recommend the expensive 3M pre cleaner. I did some tests and it doubled the adhesive strength of my samples. I was able to clearly identify some roof struts from vent locations.  At those points I used 1/4" X 1/4" X 20 aluminum rivet nuts just in case. I use these on occasion so I invested in the official setting tool. If due to a faulty installation the rivet nut turns before the bolt tightens you are going to have a difficult problem to deal with.

For those who are concerned about the tape adhesive many of the 53' vans on the road use the system to attach outside panels to the trailer structure. Of course this system is better suited for those with a metal roof.

Yes, definitely solid strut.

Could you please tell me what 3M Pre Cleaner you used? where did you buy the pre cleaner & 3M Tape? there are so many fake products on Amazon I want to buy genuine 3M.

Could you please elaborate on"Walter that is the method I used", never heard this before.

Thank you.

[wamcneil]

1 hour ago, Gary Cole said:

For those who are concerned about the tape adhesive many of the 53' vans on the road use the system to attach outside panels to the trailer structure. Of course this system is better suited for those with a metal roof.

In general, I have a lot of confidence in the HB tape! That's what I used on the 2"x3" brackets holding my panels to the roof and no fasteners.

My concern is only the differing rates of thermal expansion adding up to something significant over a 20' length.

Take my input with a grain of salt though... I don't have a degree in this discipline, nor do I have any practical experience bonding a 20' piece of metal to fiberglass... 

 

54 minutes ago, John C said:

Could you please tell me what 3M Pre Cleaner you used? where did you buy the pre cleaner & 3M Tape? there are so many fake products on Amazon I want to buy genuine 3M.

I'm sure pre-cleaner can only be a good thing... But I don't trust that'll completely remove 20 years of chalk and sun damage from the gellcoat. Personally, I wet sanded the area with 1200 or 2000 or something like that to remove any chalkiness and wiped down with acetone. Pre-cleaner would probably have been better than the acetone.

Edited May 14 by wamcneil

[Ivan K]

If you want to calculate the expansion effect, maybe this will be a start. Of course internet is always right but this sounds scientific enough for a start:

...fiberglass lay-up will be somewhere around 8 micro inches/inch per deg F.  Correspondingly, for stainless steel it is about 25 percent higher and for aluminum, about 70 percent higher....so stainless steel is much closer

With my non-scientific calculation over a 100F swing, fiberglass might expand 0.19" over 20 feet, stainless 0.24" and aluminum 0.33"...so evaluate the delta from an installation temperature.