DIY T1N window flares

My 2005 Sprinter 140 conversion has slowly been progressing. I spent much of my spare time last winter designing and building a motorcycle-carrying bumper (I'll post more on that another time), but recently I've been making a set of fiberglass window flares for the van. I was inspired a while back by Midwestdrifter's window flare post and decided to tackle the project and develop some fiberglassing skills.

I considered purchasing a pair of window flares from Flarespace, and now, knowing the time and expense involved, the Flarespace option seems to be a fair price and it would have been way easier to go that route. But there are a few reasons that I didn't think the Flarespace product would work for me. They don't offer an extra deep flare for the T1N, so I don't think they would provide enough width for me. I am 6'2" and like a little extra space above my head and below my feet. Also, I will be installing a Tern Overland window in the passenger side flare, and the privacy shade/insect screen mechanism takes up almost 2" of interior space, so the flares had to be extra deep. I wanted more defined edges and corners on my flares to match the style of the T1N rather than the soft edges of a larger radius. Also, it looks like the Flarespace flares are really designed for the rear panels of a 170 and can be modified to fit the longer rear panel of a 140. This means adding a spacer in the channel around the panel to make the forward lip of the flare sit flush onto the panel itself where it needs to. This to me is a compromise that has an unfinished look.

So, I read through Midwestdrifter's excellent DIY Flare post, watched lots of youtube videos on fiberglass work (mainly from the boatbuilding community), and ordered materials. The rough plan was 1) Create plug in the shape of the flare 2) Prep the plug for the molding process 3) Form the mold over the plug 4) Use the mold to create the finished fiberglass piece. I started with the passenger side flare because it is the smaller of the two, limited in size by the sliding passenger door. I repeated the process for the driver side, having made many mistakes and learned a lot on the first go around. Below I use photos from both flares to illustrate the process.


This step proved to be the most challenging and by far the most time consuming. I think Midwestdrifter knows what I'm talking about here. The design of my flares is similar to that of the flares on the Winnebago Revel. I like the sharp curved lines, which not only look good but provide more stability to the flare, rather than a flat panel.

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I was planning on adding a wide window to the passenger flare, so I kept the horizontal dimension of the panel face flat. It only curves on the vertical. The driver side panel curves in both dimensions.

I used styrofoam as the foundation for the plug shape. To help guide the cutting of the styrofoam and insure a uniform curve to the flare, I cut 1/4" masonite spacers between the layers of styrofoam. The width of the masonite decreases as you move towards the top of the flare, creating a uniform curve. The top edge of the masonite is curved on the driver flare.


I used a plywood blade on the table saw to make the initial cuts on the styrofoam and glued them together with spray adhesive. One the second flare, I glued them with wood glue, and it worked just as well. On the first flare, I cut along the guides with a hacksaw blade, which worked fairly well but made a mess and left some voids in the foam. For the second flare, I made a foam cutter with a 22 gauge nichrome wire attached to a car battery. A lot faster. A lot cleaner.

I also made a template of the curvature of the panel surface and glued up the styrofoam/masonite sandwich with the pieces seated on the template so the plug would sit flush onto the panel, important for the next step.



Next was to create the flanges on the perimeter of the flare that will seat into the channels around the van panel. Continued in the next post. . .
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I taped off the channel around the panel and created a vertical channel with 1/4" masonite (hot-glued onto the panel) for the front flange (driver side pictured). The awkward step-up from the channel depression onto the panel surface was a challenge, but I wanted this edge to look good and be of uniform thickness because it's the only part of the flange that will be in full view.


Next, I waxed and buffed the entire channel area and the masonite 3-4 times with a mold release wax that has NO SILICONE. The silicone can create irregularities in PVA coats. I then painted on three layers of PVA, allowing to dry for about 30-45 minutes in between. The PolyVinylAlchohol creates a film, almost like a layer of plastic, between the waxed surface and the resin, helping insure the fiberglass piece will release easily.

I then brushed epoxy resin into the channel around the panel multiple times, allowing to firm up in between coats. I cut strips of fiberglass mat and laid them into the channels, adding more resin to thicken the flange. This was a messy process, requiring plenty of masking tape, acetone and paper towels to catch the resin running down the side of the van. I then propped the styrofoam plug against the panel in it's final position and fiberglassed the flange to the plug. I am using epoxy resin rather than polyester resin for this stage (and the next) because polyester resin melts styrofoam on contact.



The plug popped off of the van with ease. And now begins the process of finishing the plug. A couple layers of epoxy resin and fiberglass over the styrofoam base, then layers and layers and layers of body putty, each followed by lots of sanding.


Coming up . . . the finished plug.
Days later . . .

I have smoothed out the plug, primed it, and sanded it down to 220 grit. Now it's time to lay fiberglass over the plug to create the mold. Here I'm making a flange around the perimeter of the plug so the fiberglass layup can continue seamlessly beyond the edge of the plug. The excess will be trimmed off later. 1/4" masonite is hot-glued to the bottom surface of the plug flange all the way around. I then ran a bead of silicone around to fill in the gap between the masonite and the flange. If any resin during the molding process were to creep into that gap, it would be very hard to remove the mold from the plug.

Note that I sanded the edges of the plug flange to slightly less than vertical so it will pull free from the mold. If they were angled outward, like they were when removed from the channel on the van, they would be locked into place in the mold and the plug probably could not be removed.



Now to create the release surface on the plug: 5 layers of buffed wax and 3-4 layers of PVA, on both the plug and the masonite flange.

For the mold and final piece processes, I used a polyester laminating resin. From my googling and youtube binging: Polyester resin cures completely only in the absence of oxygen. A FINISHING resin has a wax additive, which rises to the surface during the curing process and deprives the resin below of oxygen, allowing it to cure completely. Once it is cured you cannot add more resin and fiberglass since the wax additive will prohibit bonding. The finishing resin must be wiped with acetone and/or sanded before the next layer can go on. A LAMINATING resin, however, does not have the wax additive, so it will never fully cure until wax is added to the mix or the final layer is sprayed with a coating (PVA works well for this) to deprive the resin of oxygen. So one of the great advantages of a laminating resin is that you can add more layers (even days later) with minimal prep and ensure a good chemical bond with the previous layer.

A gelcoat layer, similar to polyester resin and tinted white, is the standard for the mold surface and also, later on, for the surface of the finished piece. Gelcoat can also be laminating (without wax) or finishing (with wax added). I wanted to brush on at least two coats of gelcoat, so I chose the laminating gelcoat for this process. On the first attempt, I brushed the plug and the masonite flange and allowed the gelcoat to cure for about 4 hours before adding the next layer. When I started to brush on the next layer, irregularities began to appear (photo below). Since this would be the finished molding surface, I knew it would be an issue. I waited until the next day to continue with the second coat, but had the same results. Very disappointing. I was told that the styrene in the gelcoat can cause this problem, and my gelcoat was about a year old, so maybe the 6-month shelf life contributed to the problem. Any way, I quickly put a layer of fiberglass over the whole thing, peeled off the failed mold, and started over with a freshly waxed and sprayed plug.


On the second try, I painted the plug and masonite flange with the first layer of gelcoat and sprayed it with PVA so it would cure completely before adding the next layer of gelcoat. The next day, I peeled and washed off the PVA layer (with soap and water) and brushed on the second layer of gelcoat. This time there were very few irregularities.

Next comes the laminating resin and fiberglass mat. I used different weights of mat (6 oz. and 12 oz.) to negotiate the sharp corners, ending up with about 4 layers of fiberglass.


The mold separated with ease from the plug. Whew! There were a few voids and imperfections in the mold surface, mainly due to air bubbles between my fiberglass layers, that I repaired with body putty. I haven't gotten to this stage for the driver side yet, but rather than using body putty here, I will use a fairing compound formulated for making repairs in gelcoat.

I built a 3/4" plywood box around the mold and glassed it to the underside of the flange. I also glassed in some plywood ribs to the underside of the mold for extra support.


Coming up . . . the finished piece
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Now I FINALLY get to lay up the finished piece.

So again, 5 or so layers of buffed wax, 3-4 layers of sprayed PVA onto the entire mold surface, flanges included. By now I know the importance of making sure there are no bubbles between layers of fiberglass, so I'm being very careful to eliminate all of them, poking at them with a brush or rolling them out with an aluminum fiberglass roller. Because I am anticipating a struggle to get the piece to release from the mold, I glass in a couple nylon straps to the corners just in case. I'm ready to do some prying if necessary. After 4-5 layers of glass, I spray on a couple layers of PVA and let the piece cure over night.



The next morning. . .

I take a putty knife and carefully run it in between the mold and the piece all the way around the flange to make sure nothing is stuck, and . . .

VOILA! The piece lifts out of the mold with no effort at all. I'm sure if I hadn't attached those nylon straps I would've been prying at it all day.


Very happy with the results. The pink is the layer of PVA on the surface of the piece. It peels and washes off easily. Now it's just a matter of trimming the edges, touching up the surface, and smoothing out the underside of the flange, where it will be attached to the van skin.

And then do it all over again for the driver's side.
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Very nice work there, Marcusbest. That foam form glue up looks a lot like a surfboard blank.

I am 6' and when I put a futon frame and mattress in the rear area by the doors in my 06 T1N, I can sleep somewhat diagonally. The extra width would be even nicer.

I would think a metal flange would be more secure, but apparently that has not been an issue with anyone with the fiberglass flares.

Thanks for showing the process of making your own. Good on you.
Yes, when my pieces are finished, I plan on passing the molds along to the next DIYer if anyone wants to use them. I may make one more set of flares with a detailed instructional video. There are lots of tricks I've learned, even specific to these molds, that would save a lot of headaches.
The passenger side flare came out looking good and only required filling a few small voids and irregularities. The head of the bed is toward the passenger side, so I'll be putting an Arctic Tern window in the flare. I cut the window hole in the flare, made a wooden frame to accommodate the window bracket and fiberglassed it onto the inside of the flare.



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Now the passenger side flare is ready for primer and to be attached to the van panel. I cut the hole in the van wall and removed the paint where the flare will attach. I will be using urethane window weld to attach the flares.
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I've also made progress with the larger driver side flare. I'm working on completing the mold this weekend. I'm also in the process of prepping my van for a full paint job, so I've been removing lots of bits and pieces and will start minor body work and sanding next week. I bought my van in Phoenix, so there's hardly any rust anywhere and the paint has held up very well for Sprinter paint.




The passenger side flare is finished, primed, and installed. I'm about halfway through the sanding and prep for a full paint job and hope to have the driver side flare completed this week.


COLOR! I'm very happy with the paint job and the color.

Newer Subaru Crosstreks come in this color (paint code PAF). They call it "cool gray khaki" but it's more like a light gray/blue.

Also got a new windshield and cleaned and painted the bumper and all the trim pieces. Now I'm working on putting it all back together.

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Well-known member
Nice... Looks similar to the new 'silver gray' on the 2020.

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