Not installing a window was a mistake on FarOutVan#1, because we lacked an intake for the Maxxfan to properly exchange air in the van. So here is our redemption on FarOutVan#2! It’s our very first time installing a window, and we chose a 300x700mm Tern Overland’s Arctic Tern window (new “Flat” style). We documented the whole process below, hope this helps!
Table Of Content
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Why we chose Arctic Tern Window
- Unlike slider windows, the window opens through its entire width, for maximum ventilation.
- Opens 10 and 35 degrees (300mm size), or 20, 40, 60 degrees (all other sizes).
- Semi-lock position that allows air in during stormy conditions.
- Double pane acrylic glazing, for better insulation.
- The included blind/bug screen is VERY neat.
- We like the installation method (clamped instead of bonded).
Built-in Blind and Bug Screen:
Flat vs Classic Style
Tern Overland just released the “Flat” style windows. We really like that style and waited quite a while to get them! The tint and look match the van very well, it almost looks OEM.
Considerations for Installation
cut hole & clearances
Cut hole dimensions
Tern Overland recommends to cut a hole as follows:
- 3mm clearance on each side.
- 70mm corner radius.
For example we are installing a 300x700mm window, so our cutout is 303x703mm with 70mm corner radius.
Unsupported sheet metal
As a general guideline, for curved surfaces, Tern Overland recommends 3 inches of unsupported sheet metal on all 4 sides of the cut hole. This allows the van’s sheet metal to deform during the installation (from curved to flat), and provide the required flat surface for the window to be waterproof (flat surface = uniform seal compression). If the window was installed on a perfectly flat surface (that is NOT the case for vans generally), the 3 inch clearance wouldn’t be required.
blind & screen Clearance
Inside the van, you need at least 50mm clearance above and below the cut hole, and 25mm on each side. This is to prevent interference during the blind & screen installation.
wall thickness & spacer frame
Arctic Tern windows are secured by clamping. The van’s wall is sandwiched between the Outer Window and the Inner Frame Ring, and fastening the screws clamps the window to the wall and compresses the seal; no adhesive or sealant is required:
To ensure a waterproof installation, the wall must be flat and at least 24mm thick. Most walls on vans are around 1mm thick and curved, and therefore a Spacer Frame must be fabricated. The Spacer Frame provides a flat mounting surface and the correct wall thickness.
When ordering your window, you must specify the wall thickness in order to get the correct Inner Ring and screws with the correct length.
Tern Overland recommends fabricating the Spacer Frame out of hardwood or metal. Our spacer frame is comprised of an “inner” and “outer” frame, bonded together:
OUTER FRAME
18mm Russian Birch
Mates with the van sheet metal. Round corners for a smooth sheet metal deformation. Helps to clear the structure inside the van.
INNER FRAME
12mm Russian Birch
Mates with the window’s inner ring and blind. Protrudes 3/8″ around the blind, to eventually attach a frame to it (decorative frame from finished wall to window).
We’ve seen people fabricate their Spacer Frame out of 10-Series (1″ thick) 80/20 aluminum or wood. Definitely easier! Our only concern: with the square corners, we are thinking that maybe the sheet metal deformation wouldn’t be as “smooth” and the transition from curved to flat could be more apparent outside? Maybe it’s fine too and we’re just overthinking this:
Blind & Bug Screen
Most installers choose to fit the blind & bug screen outside of the finished walls. It makes the installation a bit easier:
But we rarely choose the easy path (why oh why) and decided that, for aesthetic reasons, we want the blind & screen to be recessed inside the wall. So we fabricated our spacer frame to accept the blind & bug screen assembly on it:
We still don’t know how we will fabricate the “decorative” frame to join the finished walls and the window frame; we’ll cross that bridge when we get there!
Slider Door Interference
Keep in mind that awning-style windows can interfere with the slider door.
In our case, the slider door doesn’t go all the way back on the extended-length Transit, so we’re good!
But consider this when choosing a window for your van…
Installation
Time
6 hours
Cost
$700 USD
Weight
12 lbs
Material
| ITEM | QTY | DESCRIPTION | BUY |
|---|---|---|---|
| 300x700mm – Arctic Tern Flat Window (24-34mm Wall Thickness) | 1 | Dual-pane acrylic with included blind and screen. | Campervan-HQ |
| Spacer Frame for Arctic Tern Window | 1 | Arctic Tern windows need at least 24mm wall thickness; thus, a spacer is required. | DIY or SatsangVanWorks |
| Sikaflex-252 | 1 | To bond the spacer frame to the van. | Amazon |
| Rust-Preventative Paint | 1 | To touch-up the edges. | Amazon |
| Anti-Seize (non-Teflon) | 1 | To apply on inner ring screws | Amazon |
| Mineral Spirit | 1 | To remove the adhesive residues (from noise deadening) | Amazon |
Tools
| ITEM | DESCRIPTION | LINK |
|---|---|---|
| Permanent Marker (Silver) | To trace our cut lines. | Amazon |
| Oscillating Multitool with flush-trim blade | To remove the support ribs. | Amazon |
| Heat Gun | To remove sound deadening. | Amazon |
| Scraper | To remove sound deadening. | Amazon |
| Painter Tape | To protect the paint from damage. | Amazon |
| Power Drill | To drill a starter hole for the jigsaw blade. | Amazon |
| Pneumatic Jigsaw (preferred) “Normal” Jigsaw (no air compressor) | The pneumatic jigsaw allows to cut from the inside of the van, which is easier. | Amazon |
| Shop Vac (Wet/Dry Vacuum) | To remove the metal chips everywhere! (The new Dewalt StealthSonic is insanely quiet, love it!) | Amazon |
| Debur Tool | Amazon | |
| File | Amazon | |
| Sanding Paper | ||
| Daubers | To touch up the edges. | Amazon |
| Clamps | To secure the spacer frame to the van during bonding. | Amazon |
| Screwdriver | To torque the inner ring screws by hand. | Amazon |
Resources
- Arctic Tern Window Tech Resources (installation guide, considerations for fitment, etc.) – ternoverland.com.
- How To Cut and Install Windows – AVC RIG YouTube.
1. Fabricate the spacer frame
The Spacer Frame can be as simple as 4 straight edges (aluminum, wood) around the cutout as seen in Considerations section. But I recently received a gift from me, to me: a 4’x4′ Shapeoko 5 Pro CNC. So I’m in charge of making the design, and the machine is in charge of making the cuts (well it’s much more complicated than that, but let’s pretend it’s simple):
The Spacer frame is comprised of two parts (inner and outer frame) bonded together with Titebond III glue. The total thickness is 30mm and the frame is sealed with Spar Varnish:
OUTER FRAME
18mm Russian Birch
Mates with the van sheet metal. Round corners for a smooth sheet metal deformation. Helps to clear the structure inside the van.
INNER FRAME
12mm Russian Birch
Mates with the window’s inner ring and blind. Protrudes 3/8″ around the blind, to eventually attach a frame to it (decorative frame from finished wall to window).
2. remove the support ribs
With the 300x700mm Arctic Tern window at the very back of our Ford Transit, we need to remove two support ribs. Don’t worry, these can be removed; a Transit with the factory windows wouldn’t have these ribs!
Use a straight edge to trace the top trim lines:
Trace the bottom trim lines. With the 300x700mm window, our trim line is 16.5in lower than the top line (that leaves about 3in of unsupported sheet metal around the cutout):
Use an oscillating multitool to trim the ribs (wear ear protection, it’s loud!):
Use the multitool to trim the adhesive at the back of the support ribs (a scraper blade without teeth works well, if you got one):
The ribs can then be removed:
Remove the OEM sound deadening with a heat gun and a scraper:
The adhesive residues can be removed with Mineral Spirit (we did that a bit later):
3. Make the window’s cutout
Leveling the window
Our goal is to install the window parallel to the edge just above it, outside the van, so that it’s not shocking to the eye:
But remember, we are working inside the van, so we need to find a common reference. Surprisingly the edge inside is not exactly parallel to the outside edge, so we 3D printed shims to make it work (and to ensure some clearance between the edge and the spacer frame). The shim in the back is 4mm thick, and the shim in the front is 6mm thick:
Cutting from outside or inside
Most people cut from the outside of the van. One way to do this is to transfer the cutout line to the outside by drilling a series of tiny holes all around the line, and then cut by following the holes.
It can be done, but there are more risks of damages/errors. We’ll follow AVC RIG’s advice here and cut from the inside. A normal jigsaw doesn’t fit, but the Astro Pneumatic Mini Reciprocating Air Saw does. The downside is that an air compressor is required… Luckily we have one, and spending a few bucks on the air saw seems like a good investment to protect our van!
Push the frame/shims UP against the edge and trace the cutout line by using the Spacer Frame (or make a template by tracing the contour of the window on a cardboard box):
Before cutting, we need to protect the van on the outside:
We also added painter’s tape inside. Now we can drill a starter hole (a step bit works great on sheet metal):
Get the shop vac ready and trim!
Before completing the cut, add painter’s tape (inside & outside) to prevent the sheet metal from falling and making damages:
The moment you realize you just added a giant hole in your van:
When cutting a hole in your van, you must put your face in it IT’S THE LAW:
Dry-fit the window and remove more material as needed:
Debur and smooth the edges:
Apply rust preventative paint and let cure per manufacturer instructions:
4. Install the spacer frame
Apply Sikaflex 252 to the spacer frame (I could have added a bit more, to get a nice uniform oozing at installation):
Align the spacer frame with the cutout and add clamps:
Do not apply too much clamping force if using trigger or any other types of clamps, or this will create dimples on the outside sheet metal! These spring clamps worked just fine (we added some padding just in case, but this proved unnecessary):
Let the Sikaflex 252 cure (per instructions) and remove the clamps:
Inside:
5. Install the window
Choosing the correct screw length
Arctic Tern windows ship with 2 different screw lengths; it is important to select the correct screw length. Too long and the screws will bottom out into the window during the installation, preventing the seal to compress (50-75%) and damaging the window. Use the chart below (wall thickness = spacer frame + sheet metal):
| WALL THICKNESS | SCREW LENGTH |
|---|---|
| 24-30mm | M4x14 |
| 30-34mm | M4x20 |
| 34-39mm | M4x14 |
| 39-44mm | M4x20 |
| 44-49mm | M4x14 |
| 49-54mm | M4x20 |
| 64-69mm | M4x14 |
| 69-74mm | M4x20 |
Insert the window through the cut hole from the outside (with the two center holes UP). Insert the inner ring from the inside (with the metal brackets UP):
Apply anti-seize and loosely insert all the screws (do not tighten at this moment):
With the screws still loose, measure the gaps around the window and the van:
Using a hand screwdriver, equally tighten all the screws in a crisscross pattern:
Measure the gaps again. The goal is to have 50-75% seal compression in order to get a waterproof installation. In our case we started with a ~4mm gap, so we’re aiming for ~ 1.5-2.0mm gap:
Tighten, measure, repeat, until 50-75% seal compression is achieved:
Remove the protective film inside:
Guys, we’re getting close!
At last, test for leaks:
6. Install the blind/screen
Blind & Screen Orientation
The blind & screen can be mounted with the bug screen on top and shade on the bottom, or vice versa!
Position the blind & bug screen assembly over the metal brackets on the inner frame ring:
Open the top and bottom blind roller covers:
Center the blind & screen assembly (front/rear position), pilot all four holes and hand-screw using the provided screws (do not overtighten):
7. Install the window/wall frame
This is the part where we make a decorative frame to join the finished walls to the window frame… we’re not there yet, so wait for it!
On Second Thought…
We were quite nervous about installing the window, because we had a few concerns:
- Making the cut hole too large.
- Dimples resulting from the clamps when bonding the spacer frame to the van.
- Apparent sheet metal deformation.
- Water leak.
- etc…
Fortunately, everything went for the best! So nothing to report here so far 🙂
It looks like with the extended length Transit and your window placement, you don’t have to worry about the sliding door hitting an open awning style window. Is that right?
That’s correct!
With the non-extended, this may be an issue.
Thanks once again for your superb tutorials. I also purchased your wiring helps and they have been very informative. I only wish i would have found this specific article last week. I used square framing and overtightened the clamps. The results were heartbreaking. So I am now ordering a larger Artic Tern unit to cover my sins and (hopefully) get the job done. I wish the extra precautions were in the installations document but alas…
Thanks for the feedback.
Sorry to hear, I’m sure the second try will work just fine… Good luck!
The Timing of this, I was just looking for information on this and going to order my window tomorrow!
Perfect!
Good luck 🙂