Requesting Details of Roof (with AC) Construction - Now, Solar Install Discussion

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Gordon2
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Requesting Details of Roof (with AC) Construction - Now, Solar Install Discussion

Here's hoping someone (Greg?) is familiar with the internal construction of a Scamp 16 with roof support for a AC unit:

I'm in the planning stages of a roof top solar install and will likely go into more detail on that subject at a later time, however my immediate question is related to the mounting options.

Mounting options for the brackets include epoxy, VHB tape and mechanical fasteners (including rivets or bolts) or some combination of these. 

I am leaning toward using VHB tape but the curvature of the roof makes it a little more difficult to get a lot of surface area bonded to whatever brackets I end up using. The most likely location for a single panel is on the raised portion of the roof's front center, ahead of the AC unit.

More importantly, while VHB tape has good resistance to pulling apart, it is somewhat susceptible to sustained sheer forces, therefore it might be prudent to also use a very limited number of mechanical fasteners to prevent the panel from trying to slid backwards along the top of the roof at highway speeds, which would weaken the VHB tape bond over time (as I understand it).

The benefit is using VHP tape is that there are no holes required in the roof and I would like to retain that benefit even if using fasteners also. Since the fasteners used in conjunction with VHB tape will only be used to prevent "creep" they might not need to go through the body of the trailer.

So with all this preamble, I can finally get to my question...

How is the roof in my 2015 Scamp 16 (#4) constructed in regards to support for the air conditioner?  Is there wood reinforcement that I could utilize to anchor screws to hold a solar panel bracket in place? Would a stud finder reveal the location of the reinforcement? 

Note that brackets could extend on the roof along the sides on the AC unit if needed.

Below is a photo of my trailer's roof with added colored lines which I am using for reference to measurements.  Feel free to refer to the photo to describe the internal construction.

Gordon2
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RE: Requesting Details of Roof (with AC) Construction

PS.. anyone planning on putting a solar panel on the roof of a fiberglass trailer should read this post from the Escape Trailer company rep (and maybe read the entire thread also).

After reading that, I am reconsidering my approach. Another option might be to mount the panel with the longer side perpendicular to the trailer’s sides (and direction of travel) using four “through the shell” bolts.  While this would increase the wind load slightly, it would avoid the problem of the AC unit shading the panel since it could be (and would have to be) mounted a distance from the AC.

In this case I would use mounting brackets on the more flat side of the roof nearer the trailer's sides, in the area forward of the fridge and bathroom vents (where the red line is in the photo). This area of the roof is flat but the brackets would need to be designed to get the panel up over the raised section of the roof, along with an air gap to keep them ventilated. Thats about four inches minimum at the rear end.

Inside the trailer, I am pretty sure I could peel off the rat fur trim and a little of the rat fur under the mounting area to get backing plates installed.  The rat fur then could be reglued and no hardware from the solar panel mount would show in the interior.

But I wonder how strong the fiberglass is in this area of the roof.  Any comments?

ELongest
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Roof Support

This is a picture of a S-13 DX A/C support. The tabbing is for the front bath wall. Usually the support is about as long as the A/C unit. On some trailers you can see the see or feel the support under the rat fur. The support is only on the underside of the trolly top. The roof thickness can vary in the non-supported area of the roof, I would say on average the roof is about 1/8"- 3/16" thick.

 

Eddie

Greg A
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Roof Solar Mount

Roof solar mounting has been done with bolt through, VHB, and glue combinations. Escape did go to a bonding process a few years back and did not bolt through but had a couple of units fail so they now bolt through at manufacture. Escape also sent out bolt through retrofit kits to any owners who had the solar bonded to the roof.

There is a solar outfit in Oregon, AM Solar, is using a VHB tape and bonding now for years and they claim to have no failures. This company comes highly recommended for solar installs and accessories. I recommend taking a look at their mounting systems, tilt racks, etc. which are available for purchase.

I personally ordered solar on our new Escape after they reverted to manufacturing with bolt through solar mounts. I would do some type of VHB, bolt through, or rivet combination so there is peace of mind that it will be unlikely to fail.

Our Trailers:
2015 19 Escape

Buying or Selling Molded FG Trailers:

Fiberglass-RV-4Sale

Gordon2
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RE: Roof Solar Mount

Greg.., I spend most of yesterday reading the over forty pages at the Escape forum thread that I referred to in my second post and other threads there as well on the subject.  

You synopsis is spot on, well said!  Even with AM Solar's claim (and 3M's marketing), I do agree now, that VHB alone is not to be trusted with such a high liability install (flying panels could cost you a million dollars in a lawsuit). At least for traditional glass panels.

But if putting holes in the roof, why use tape at all.  Four through bolts with backing plates should be sufficient, no?

But will the 1/8 inch thick  fiberglass itself be too stressed, not that the panel would come flying off but the fiberglass might crack from the high wind forces on the panel?    Yesterdays's post about the cracked fiberglass by the door on a 2014 unit has me worried.

What about  sanding off the gel coat and using some 5200 to attach some sort of mounting blocks of some sort?  You might never get the blocks off but the brackets could be made removable and the blocks on the roof would not be that bad (should one decide to do away with the solar panel).

 

ELongest
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Mounting panels

FWIW

I really don't trust VHB tape for panel mounting. (Just old school I guess.) Most awning brackets and doors are held on with 1/4" through bolts and washers and they do OK. I was looking at using 1/4" stainless hardware with 1"-1 1/2" fender washers inside the trailer under the rat fur. If  the panel is mounted front to back I was also thinking of adding a wind deflector to the nose of the panel to cut down on the lifting forces while on the road. I currently have a portable 100W panel but  looking at placing a 100W panel on top of the trailer. My only hold back is trying to decide where to also mount a Jack TV antenna.

Eddie

 

 

Greg A
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Solar mounting

I did what Eddie refers to on our 13 awning rail and used fender washers front and rear with rivets down the remainder. After years of the stress of the bag awning there were never any issues. I would think if you use a combo of the vhb and bolt or rivet through with backing washers it would not create much stress on the glass. You could then 5200 each foot to seal and also add more strength. Just thoughts, anything similar would probably work fine once you find a workable location.

Escape glasses in wood blocks during manufacture on the interior of the roof the solar bolts through, but don't know that you'd have good access to do similar.

Our Trailers:
2015 19 Escape

Buying or Selling Molded FG Trailers:

Fiberglass-RV-4Sale

Flyboyscamp
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Best to contact Scamp

Best to contact Scamp directly for your answers to such questions.

<p>Doug Allen 2016 Ford F-150 2018 Lance 1575</p>

Gordon2
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Solar Mounting

Well Eddie, you and I are in about the same stages in the project so let me expound on my thoughts and research.  I will be discussing a 2015 Scamp 16 with roof air conditioning and the following is mostly opinion and just thinking out loud, so don’t assume I know what is best.

PV Panel selection:

The curved roof and raised center section makes it harder to mount a rigid panel and while it is tempting to consider some sort of flexible panel that might be mounted flat on the roof, IMHO we should rule out flexible panels until the technology is improved.  Most people will want at least a 100 watt monocrystallin​e or polycrystallin​e glass panel, and that means a physical size in the general area of 47 x 21 or 42 x 27 inches and about 20 pounds.

Panel placement:

It might be possible to fit a PV panel on the 35-36 inch-wide raised center section of the roof with the shorter edge parallel with the trailers front (leading) edge and this would result in a little less air resistance while driving than if the panel were turned 90 degrees.  However this would require that the panel be near (or up against) the AC unit and/or extend too far over the front of the trailer. In the first case, the AC unit would sometimes shade part of the panel making it less efficient.  In the latter case, it would create an air dam and the uplift on the panel from the airflow while driving would be substantially increased. It seems that, for a typical 100 watt PV panel on the roof of a Scamp 16 with AC, the dimensions dictate that it would perform better if it were mounted lengthwise across the front.  The ends would then be over the non-raised sections, in front of the bath vent and fridge vent on my trailer.

Panel Mounting:

The primary concern with placement and mounting has to be the wind load, both from traveling at highway speeds and cross winds from passing trucks and storms. It would be nice to have access to wind tunnel testing but for now we can estimate the effects.

PV panels drop in efficiency as they heat up, therefore they should be mounted with an air space underneath that provides adequate ventilation. This means that a panel on the trailers roof is going to act like an airfoil. Lifting forces (both up and down) will be minimized by having the same amount of air traveling on both sides of the panel (or more precisely, the same pressure). I would expect on a flat roof, a panel which is mounted equidistant from the roof (say an inch or so off the roof) would have very little in the way of airfoil effect.  However, on the curved surfaces of the Scamp, things are a little different and this is also different than mounting an awning or other item that has little frontal area.  My concern is that there will be a concentrated flow of air that follows the curve of the roof and goes under the panel, creating a good deal of lifting force at higher speeds.  This force will be variable with speed so there will be frequent pulling and pushing on the mounting surfaces. Wind from weather only adds to the effects. I don’t know how the thin fiberglass roof will hold up to these repeated stresses.

Unless there is some part of the roof in the right place that is stronger than the rest, I think the best option is to use the flat area near the roof’s edges.  On the interior, the rat fur trim is basically along the edge of this raised portion. It appears that the trim could be removed, and then some of the rat fur and insulation pulled away from the roof under the side flat portions of the roof in order to install fairly large (and hidden) backing plates. In fact, when I get into it, I might even try to install a continuous piece of sheet metal that is a little longer than the mounting brackets. Flat head bolts facing up from the interior (through the backing plates) would then be well hidden when the rat fur and insulation were re-glued.  This should provide as strong a mount as is possible, and I don’t see any advantage to adding VHB tape, 5200 or anything else because the thing that will fail first is the fiberglass body itself or the attachment to the panel (and that might take a tornado). This idea will likely require custom made mounts that follow the rise in the center roof from the front toward the rear in order to have the required space for ventilation. It is about three inches higher near the AC unit. 

Another idea is to mount the panel so it actually lies flat on the front leading edge while also raising the rear to about one to two inches over the roof (a total rise of 4-5 inches over the entire width).  This would in effect create a shallow-angle wind deflector which, at highway speeds, results in a downward and backward force but almost no lifting force. Since the panel is wider than the AC unit I expect the total air drag would still be increased.  While parked, the ventilation at the edge might be reduced but it should be good for most of the panel. You would want to park the trailer facing the sun.

Maybe something like this would work:

http://www.windynation.com/Mounting-Hardware/Windy-Nation/Adjustable-Solar-Panel-Mount-Mounting-Rack-Bracket-Boat-RV-Roof-Off-Grid/-/932?p=YzE9NDk=

This mount is intended to be put in the lowered position while underway but I wonder if it would work OK with one side raised a few inches as I just described. The one in the link would require simple modification and perhaps a third support arm would be a good idea.

Wiring is easier.  I foresee running the wires from the panel through my roof mounted fridge vent, then (in conduit) along one of two routes to the controller and battery. (If you don't have a roof fridge vent then I would bite the bullet and drill a hole for a passthrough.) The first idea is straight down and over to the sink cabinet area, then down and through the floor, under the trailer to the front sofa area. The second idea is, from the roof fridge vent, to the top of the screen door and then along the front screen door frame down into the sofa storage area.  The latter route would involve exposed conduit but it is a shorter route so the voltage loss would be a little less.

Regarding this project in general, my initial thought was to do a roof install and supplement that with a portable panel when, and if, needed.  This was for a few different reasons including the fact that I might not be good about deploying a portable panel often enough; I like the idea of charging the battery while driving (without using the tug’s alternator); portable panels are easier to steal; and the tax credit that expires the end of this year (and I am guessing would not be available for a portable unit). But with the unknowns involved and the fact that my trailer is still under warranty until September, I am considering forgoing the roof install for now and starting with a portable panel.  Then perhaps I could add the roof panel in the fall and get it all done in time to claim the tax deduction for the entire setup.

As for the Jack Antenna, I am out of room on the roof if I add a solar panel.  I plan on a TV antenna on a mast using the rear hitch, set up only when I have set up camp and bored. If you have a hitch on the back that is one option.  With the Jack Antenna, you could rotate the entire mast by sticking your arm out the back window, but since TV is for rainy days, who wants to do that. My antenna is omnidirectional.  If I can't get an interesting station, I still have a terabyte of videos to fall back on.

Gordon2
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Solar Install Planning Update

I have decided to NOT mount a panel to the roof of the Scamp at this time and instead try a portable unit at first. I was tempted to buy the Renogy 100 Watts 12 Volts Monocrystalline Foldable Solar Suitcase and that would still be a good option for someone who wanted a convenient, compact and more transportable option.  I might well end up with it to supplement a future roof mount.

In order to get the most use out of your battery or battery array, you need a meter that measures and tracks usage (amps in and out). The TriMetric meters from Bogart Engineering are very popular and well regarded.  Their latest model (TM-2030) interfaces with a companion PWM charge controller (SC-2030). Their brochure describes the charge controller this way, “Designed to work with the TM-2030 TriMetric monitor for unusually precise charging in accordance with battery manufacturer recommendations.”

For a larger or higher voltage set-up one would likely want a MPPT type of charge controller, but for all practical purposes, for a small trailer and under 400 or so watts of solar panels, the 30 amp SC-2030 charger should be just as effective.  Add in the advantages of pairing it with the TriMetric meter and it became my choice.

The Renogy solar Suitcase comes with or with a controller.  Since the controller only adds $20 I would buy it with the controller so I could use it anywhere I wanted, but while using it with the trailer mounted charge controller, I would remove the controller from the back of the panels.  The controller is a very basic model and not waterproof. However, instead of the suitcase, I decided to start with the Renogy RNG-100P single panel. This polycrystalline panel is a little less than 40 x 27 inches so it is easy to handle. And if I decide to roof mount it in the future, it will fit on the roof of the Scamp much better than the moncrystalline version which is longer and narrower. It will also help me avoid shading from the AC unit (which can really kill the power output). The polycrystalline version has a surface area of 1060 square inches while the mono one is a little less (987 sq in.). Other than that difference, the specs such as power output are almost identical. The poly panel is less than half the cost of the foldable suitcase with charge controller (with the same wattage) and only 16.5 lbs vs. 27.7 for the suitcase model.  Lastly, the single panel has 36 cells which make it a slightly better match to the rest of the system.

Of course I have to provide some wire (using MC4 connectors ) from the panel whereas the suitcase model comes with wire and clips to go on the battery.  However, the wire with the suitcase is just barely adequate so I was planning on replacing it anyway.  Also i will need to custom make some legs to prop it up. I will use a marine trolling motor plug on the other end and the matching jack (with 8 gauge pigtails) on the trailer’s body, wired to a breaker.

Also a shunt and additional wire will be needed, some of which I have already. I also ordered the optional  temperature sensor for the charger to get improved performance.

The charge controller will go in the storage area under the front sofa (where the battery wire and tug connection wiring bundle enter the trailer). I will replace the cheap 10 g wire from battery that Scamp used with 4 g from battery to shunt (neg side) and circuit breaker (pos) in this storage compartment. The charge controller is supposed to be in “a well ventilated area.”  I talked to Tech support at Bogart Engineering about the space under the sofa and they feel that as long as my charge controller is at 20 amps or less it will not be a concern, and even at higher current it might be OK but it’s depends on other variables.  This will be one part of the installation I will have to investigate further by monitoring the temperature and current, but since I will be well under 20 amps it should be OK. If not, I might have to ventilate this space somehow.

Admittedly, this is a very minimal solar charging set up (or at least it is to start with) but my power use is only LED lights, occasional water pump and fan,  cell phone charging, and if power is sufficient, laptop computer use and charging.

All the gear will be here this week and I will breadboard it inside my nice warm house to test it out and get familiar with the operation.  Any comments, criticism, suggestions, warnings, or tips are welcome since I can still return the items.

enigma1083
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a question

How do you power your laptop from 12 volts?

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