Flexible Solar Panel Install Guide for a 4WD, Caravan, Camper or Boat

Flexible Solar Panel Install Guide for a 4WD, Caravan, Camper or Boat

Flexible solar panels are a great way to add useful solar capacity without the weight and height of a conventional framed panel. They're well suited to 4WDs, caravans, camper trailers and marine applications where roof space is limited, weight matters or the mounting surface has a gentle curve.

But while installing one can look as simple as sticking it down and running the cable inside, the way a flexible solar panel is mounted has a big influence on how well it performs and how long it lasts.

Flexible panels still need to deal with heat, expansion and contraction, vibration, movement and the occasional rough road or rough sea. The panel also needs to remain properly supported without being placed under unnecessary stress.

For most of the current Sunman eArc panels being mounted to a smooth, rigid surface, our preferred method is the 4.6mm high-bond tape. It provides a strong bond while also maintaining a small gap between the panel and the surface underneath, rather than bonding the entire panel completely flat to the roof. There are a few important things to get right though, so it's worth reading through this guide before getting started.

Preparation

Solar panels generate electricity whenever they're exposed to light, so ideally carry out the installation inside or in the shade and keep the panel covered with a towel or blanket while you're working.

Avoid installing in strong or gusty wind. Sunman eArc panels are extremely light for their size and can become difficult to handle once wind gets underneath them. It's also worth avoiding very hot days. Apart from being more pleasant to work in, hot panels, roof surfaces and adhesives can make the installation harder to control.

We would also recommend avoiding sharp jewellery, not stacking objects on top of the panel, keeping the panel fully supported and protecting both its front and rear surfaces during installation. Most importantly, don't treat the panel like a sheet of rubber just because it's flexible. The solar cells and electrical connections still need to be protected from excessive bending, twisting and concentrated pressure.

How Much Can a Sunman Flexible Panel Bend?

Flexible panels can follow a gentle curve, which makes them useful on slightly curved caravan, camper and boat roofs. The important part is that the panel should bend in one direction only. It can follow a longitudinal curve or a transverse curve, but it shouldn't be twisted or forced to follow a compound surface that curves in multiple directions at once. As a general guide the panel can withstand approximately 100mm of midpoint deflection over a 1.5m panel length. 

If the roof has pronounced ridges, multiple curves or abrupt changes in shape, don't force the panel to conform to them. Find a flatter mounting area or use a mounting arrangement that supports the panel properly.

Handle the Panel Carefully

One of the easiest times to damage a flexible solar panel is before it's even installed. Larger panels shouldn't be carried horizontally like a tray because their own weight can allow the centre to sag. Carry the panel vertically along the long edge and support it without gripping or pressing directly onto the cells.

When lowering a large panel into position, support both sides or carefully slide one edge onto the surface rather than allowing the centre to droop. The junction box and solar leads are not handles. Once the panel is lying down, make sure the whole panel is supported. Leaving one end hanging over the side of a roof or workbench can create a concentrated bend through the cells.

Check the Mounting Surface First

Before even reaching for the tape, have a proper look at what you're actually mounting the panel onto. A suitable surface should be rigid, stable and capable of continuously supporting the panel. Suitable surfaces can include:

• Aluminium
• Steel
• Sealed marine plywood
• Fibreglass
• Checker plate, when installed using an appropriate intermediate mounting method

Surfaces we would consider unsuitable would be twin-wall polycarbonate, Corflute and HDPE  direct mounting substrates, along with any surface that is damaged, unstable, heat-sensitive or likely to trap moisture. Flexible solar panels can become very hot in operation. Panel temperatures may exceed 85°C, so the surface underneath also needs to tolerate that heat.

Method 1 - 4.6mm High-Bond Tape

For current generation Sunman eArc flexible panels installed onto a suitable smooth, rigid surface, this is generally the method we'd recommend. It secures the panel, but its thickness also creates separation between the panel and the mounting surface.

That means the entire rear surface isn't bonded hard against the roof, and there is some space beneath the panel rather than creating a completely trapped interface. The foam tape also has some ability to accommodate small differences in thermal expansion between the panel and the surface underneath.

Step 1: Clean and Degrease the Surface

Even the strongest tape available won't bond properly to dirt, wax, polish, silicone residue, oils or poorly adhered paint. Start by washing the area with mildly soapy water to remove dirt and grime, allow it to dry completely, then inspect the surface for loose paint or coatings.

Finally, clean both the mounting surface and the rear of the panel with a suitable degreaser such as isopropyl alcohol or industrial alcohol and allow it to evaporate before applying the tape. 

Step 2: Position Everything Before Removing the Backing

Place the panel in its intended position first. Check that it's straight, isn't overlapping another panel and won't interfere with roof joins, drainage paths, roof vents or anything you may need to access later.This is also the time to plan your cable route and roof entry. Mark the panel position using masking tape or another removable reference. Once high-bond tape touches a properly prepared surface, repositioning it becomes much harder. Measure twice. Stick once!

Step 3: Apply the 4.6mm High-Bond Tape

Lay the panel face-down on a clean, soft surface.

The tape should run across the width of the panel, positioned between the cell rows so the panel remains evenly supported.

The manufacturer mounting layout suggests support points at approximately 160mm intervals, with additional support at the ends of the panel. The exact location will vary depending on the panel size and cell layout. 

Apply firm finger pressure along the full length of each strip so the adhesive properly wets into the surface. Leave the outer backing in place until you're ready to install the panel.

Step 4: Install the Panel

Carefully align the panel with the marks you made earlier. Where practical, remove the backing progressively rather than peeling everything off and dropping the whole panel into place at once.

Once positioned, apply gentle, even pressure over the taped areas. A roller can be useful, but only roll over areas that are properly supported underneath. Avoid pressing heavily onto cells where there is no tape directly behind them. The aim is good adhesive contact, not maximum force.

Give the Tape Time to Reach Full Bond Strength

High-bond tape doesn't reach maximum strength immediately.

• 20 minutes — 50% strength
• 1 hour — 75% strength
• 24 hours — 90% strength
• 72 hours — 100% strength

Don't install the panel and immediately head down the highway. Where possible, plan the job so the vehicle, caravan or boat can remain stationary while the adhesive develops its bond.

Don't Seal Around the Entire Panel

It can be tempting to finish the installation with a neat bead of sealant around the perimeter, but completely sealing the panel can trap air and moisture underneath it. As that air heats and expands, it can place unnecessary stress on both the panel and mounting surface. Any water that does get underneath also needs a path to drain.

What About Sikaflex?

Sikaflex is used for plenty of jobs on caravans and 4WDs, but that doesn't make it the right adhesive for every application. Polyurethane adhesives such as Sikaflex and MS Polymer products such as Fix15 are unsuitable for directly adhering these flexible solar panels.

Approved silicone-based products such as SG20 or Fix8 can be used in appropriate applications, but they should be installed in strips rather than as a full bed of adhesive.

For current Sunman panels on a suitable smooth rigid surface, we'd generally use the 4.6mm high-bond tape method unless the particular installation calls for something different.

When Would We Use Silicone-Based Adhesive?

There are still situations where a suitable silicone-based adhesive makes sense. If using a Silicone based adhesive such as SG20 or Fix8, apply the product in strips running the width of the panel underneath each cell gap or no more than approx. 180mm apart using lines of minimum 15 mm² contact area.

Again, do not seal around the edge of the panel as this will trap air under the panel which will expand as the panel heats up, causing damage to both the panel & mounting surface. The panel should still maintain approximately 2–5mm of clearance from the mounting surface, which can be achieved using temporary spacers.

What About the Vented Gap Kit?

The vented-gap system still has a place, particularly where additional clearance is required or where a particular panel or junction-box position makes it useful.

The system uses lightweight strips underneath the panel, with high-bond tape on either side, to provide support and create additional clearance. The 4.6mm tape gives us the spacing we want with a much simpler installation, and is the current manufacturer recommendation. 

Mounting to Checker Plate

High-bond tape works best when it has plenty of smooth surface area to contact. Some adhesives may appear to bond well to checkerplate initially, but then lose adhesion over time. The raised checker pattern reduces that contact area substantially. So, instead of adding more tape, we need to create a smooth mounting surface first. We recommend that another medium such as aluminium composite (as a sheet or cut into strips) be used in between the checker plate and tape. Attach the aluminium to the checker plate with screws, pot rivets or a suitable adhesive then use of one of our standard mounting methods to mount the panel to the aluminium.

The solar panel can then be installed onto those smooth strips using the usual high-bond tape arrangement. The area also needs to drain properly. Don't mount the panel in a depression where water can continually pool underneath it.

Mounting a Flexible Panel to a Roof Rack

A flexible panel still needs support. Sunman eArc panels can be stiffened using aluminium C-channel along the edges and flat-bar supports running underneath the panel. The aluminium support structure can then be mechanically mounted to the roof rack instead of drilling through the panel itself. The objective is to prevent continuous flapping, vibration and concentrated bending while the vehicle is moving.

Marine and Canvas Installations

These panels can work extremely well on boats, biminis, camper trailers, pop-tops and other canvas structures, but the mounting requirements are different to those of a rigid roof.

Essentially, the canvas needs to support the entire panel. Don't install the panel across tubes, rails, beams or structural ridges underneath the canvas. Those hard points can create a concentrated crease through the solar cells every time the canvas moves. The canvas should remain taut and so the panels are not flexing in multiple directions. 

In marine applications, it's also worth positioning connectors where they're protected from direct seawater and rain exposure wherever practical. Cables should sit neatly with gentle bends and should never pull or twist against the junction box.

Zipper Mounting

Zippers can be sewn along each long edge of the panel, with the zipper material positioned so it also provides some cushioning between the panel edge and canvas. We recommend:

• YKK marine-rated UV-resistant zippers
• Auto-locking sliders
• Polyester or PTFE thread
• A coarse stitch of no more than approximately 5–6 stitches per inch
• Zippers installed in opposite directions so the sliders finish at opposing corners

A marine trimmer or canvas maker should generally be able to carry out this type of installation.

Velcro / Hook-and-Loop Mounting

Marine-grade UV-resistant hook-and-loop can also be used. The recommended arrangement sandwiches the panel between hook-and-loop material above and below it. However, removing a large panel from Velcro can require quite a bit of force, and that pulling force can flex the panel more than removing a zipper-mounted panel. For that reason, zippers are generally the preferable removable method where practical.

Eyelet Mounting

Stainless steel eyelets can also be incorporated around the perimeter of a flexible panel. Rope, cord or another appropriate fixing can then be used to secure the panel to a continuously supported surface.

But a couple of eyelets at the corners isn't enough if the middle of the panel is free to flap or bend. The required number will depend on the size of the panel and the application.

 

Cable Management

A perfectly mounted solar panel can still be damaged by poor cable management. The solar leads should follow a smooth route without tight bends, rubbing or unnecessary tension.

Most importantly, the cable shouldn't be supporting its own weight from the junction box. Secure it independently so vibration, wind and vehicle or boat movement aren't transferred directly into the junction box. Any roof or deck penetration also needs to be sealed with an appropriate cable gland or entry system. An example on a bimini shown below.

Cable Sizing and Solar Regulator Capacity

Before connecting a new panel or increasing the size of an existing solar array, check that the cabling, connectors, solar regulator and battery-side wiring are capable of handling the system. Solar cable needs to be sized according to both the current it will carry and the length of the cable run. Cable that is too small can create excessive voltage drop, reducing the amount of solar energy that actually reaches the regulator. Longer runs will generally require heavier cable, particularly in 12V installations where voltage drop becomes significant quite quickly.

If multiple panels are being installed, also consider how they're connected. Series connections increase voltage, while parallel connections increase current, and both configurations affect the requirements of the wiring and solar regulator. The solar regulator also needs to be appropriately matched to the complete panel array. Check the regulator manufacturer's limits for:

• Maximum solar input voltage

• Maximum PV current

• Maximum recommended solar wattage

• Maximum charging current

• Battery voltage compatibility

The wiring between the solar regulator and battery is just as important. An MPPT regulator may receive a relatively high panel voltage and lower current on its solar input, then convert that power into a lower voltage and considerably higher charging current on the battery side.

If you're upgrading an existing solar system, it's worth checking the complete installation rather than only the panel itself. The panel, cabling, connectors, circuit protection, solar regulator and battery should all be considered as part of the same system. We'll cover cable sizing, voltage drop, series and parallel wiring, regulator selection and system protection in more detail in our Solar Panel Wiring Guide, coming soon.

Marine and Coastal Maintenance

If the panel is regularly exposed to marine, coastal or high-salt environments, rinse the panel and connectors more frequently with fresh water to reduce salt and contaminant build-up.

For general cleaning, use fresh water, neutral soap and a soft cloth or sponge. Avoid harsh chemicals, abrasive pads and pressure washers unless they're specifically approved for the panel.

Some Examples of Bad Installs

In this example, the bending over the tube led to fracturing of the cells and produced a hot spot within months of installation. Panels have an obvious crease which will cause stress on the cells, and the plastic cover over panels traps excess heat and moisture

In this example, panels are flexing in multiple directions causing increased stress on the cells. They also have an obvious crease which will cause stress on the cells.

Some Examples of Good Installs

In this example, the end of panel is well clear of the sharp roll-off at the side of the bimini, and the canvas is taut which is essential to avoid “flapping” induced mechanical stress on the panel.

This example ticks a lot of boxes!

• Panels are well supported by the canvas over the entire back surface of the panel
• Panels are well clear of the transverse beams
• Slight bending of panel in one axis
• Similar sun strength on all cells
• Cables are not applying any lifting, shear or twisting force on the junction box, i.e.
• Cables are laid neatly, level and are gently radiused.
• Custom “sewn-in conduit” keeps cables neat

Pre-Installation Checklist

Panel

• Have you confirmed the correct panel model and mounting requirements?
• Have you checked the panel for any transport or handling damage?
• Will the panel remain fully supported once installed?
• Will it stay within the permitted bend radius?
• Is it only bending in one direction rather than following a compound curve?

Mounting Surface

• Is the surface rigid, stable and structurally sound?
• Is it suitable for the mounting method you're planning to use?
• Can it tolerate the heat produced by the panel?
• Is it clean and completely dry?
• Is the paint or coating itself securely bonded?
• Can water drain away rather than pooling underneath the panel?
• Have both the roof and rear of the panel been cleaned and degreased?

Mounting Method

• Is the tape, adhesive or mounting system compatible with both surfaces?
• If you're using tape, have you allowed for the manufacturer's bond-development time before travelling?
• Is the panel supported at appropriate intervals?
• Have you avoided full-surface adhesive bonding?
• Have you avoided sealing around the perimeter of the panel?

Cable Routing

• Are the cables free from pulling or twisting forces?
• Is the junction box free from cable strain?
• Are cables protected against rubbing and sharp edges?
• Are cable entries properly protected from water?
• Are connectors located somewhere reasonably protected?

Vehicle, Caravan or Boat

• Have you considered highway-speed/wind load?
• Have you considered road vibration or wave movement?
• Have you considered expected heat exposure?
• Is the installation appropriate for the surface curvature?
• Does the installation comply with applicable vehicle, marine and local requirements?

Before Finishing

• Has the complete mounting system been checked for security?
• Have you taken photos of the tape layout, cable routing and completed installation?
• Has the adhesive had enough time to develop adequate bond strength before the vehicle or boat is used?

Check the Installation Again After Use

The installation shouldn't be forgotten once the job is finished. Inspect it:

• After the first trip
• After the first month
• At least once every 12 months
• After particularly rough off-road travel
• After storms or extreme heat
• After impact or anything else that may have affected the installation

Look for lifting edges, failed tape or adhesive, movement, cracks, creases, delamination, bubbling, water pooling, cable rubbing, junction-box strain and damaged or corroded connectors. If something has moved, don't just stick it back down and keep going, work out why it moved first.

Still got questions we didn't cover? Hit us up, we're 4WDers too and happy to help.