Cap Vent Fan

I have searched hi and low for a perfect window vent fan for a topper and they don't seem to exist, so I'm going to make one. For my cap, I'm envisioning a custom molded piece of plastic that covers the popout section of my side windows that has a large 12v fan mounted with variable speed control.

I found the fans I want to use: https://www.ebay.com/itm/2x-8inch-E...wVctY5IbY:sc:USPSPriority!21122!US!-1&vxp=mtr

And the rest should be electrical parts and then sheets of moldable plastic. My question for the forum is, who has DIY molded plastic before and what type of plastics did you use and technique. I found this article: https://www.wikihow.com/Easily-Mold-Acrylic-Plastic-Sheets. It seems pretty simple, make a wood form, heat up the plastic, and press it over or inside the mold. In my case I plan to make a wooden form that matches the shape of the interior window frame, then cutout the hole for the fan and window crank knob. If this goes as planned I can see a market for these, especially for those that put their dogs in the back like I do. The theory is to create a vacuum inside the cap, then crack open the front sliding window if necessary to get some air flow. The cap itself might leak enough air just leave it closed, time will tell...

Anyone with plastic molding experience that has some pointers would be greatly appreciated.

 

I've messed around with Kydex making some knife sheaths, it's pretty easy to mold and it's also pretty forgiving. You can use a heat gun for finer tuning after you've done your pressing.

Have you thought about using computer fans for cooling instead of 12V fans? Less amperage draw and typically a lot quieter if you plan on sleeping back there. They won't move as much air as the radiator fans but it's not a huge space to vent. When I'm camping in hot weather I use a small fan that runs on 4D cell batteries; I open both windows and put the fan on top of the side cabinet. I can get a couple of nights out of a set of batteries when running it on low or I can plug it into my marine battery using an adapter.

 

I did some additional research after my post about fan design and what properties yield the quietest fan. My original proposed fan is not a good choice, but I think I’ve found others that are. I considered a comp fan, but like you said they just don’t push enough air. I’m still in the thinking phase and hope to have a solid design plan in a few weeks.

Is Kydex acrylic or some other polymer? I think the key here is obviously workability and enough strength to support the fan.

 

https://en.wikipedia.org/wiki/Kydex

You can get it in different thickness as well as different textures and colors. It's become very popular for sheaths and holsters and there are a ton of videos on youtube showing how to mold it (if they haven't pulled them for being weapons related since youtube seems to have gone full retard recently). The heaviest item I've used it with is my old Prolink netbook; I made a tray with a lip that I mounted to a Ram stalk mount to use in my truck. No problems with the Kydex but the Ram mount wasn't quite as vibration free as I'd have liked and my tablet works better.

The last stuff I ordered came from either Knifekits.com (https://www.knifekits.com/vcom/index.php) or Texas Knifemakers Supply https://www.knifekits.com/vcom/kydex-kydex-sheet-material-c-41_54_136.html , I can't remember which.

The back is such a small area that you may be OK with like two computer fans, the single fan I use has a blade diameter of maybe 4" and even though it's not actually in the window, just sitting in front of it, if moves enough for me to be comfortable- or as comfortable as one can be without actual A/C in the high heat and humidity here.

 

Parts ordered, we'll see how this thing turns out. I did heed your advice @Bajatacoma and ordered a large 140mm PC fan. Did way too much research on it too, haha, but I think the one I have coming should work awesome. Depending on how this one turns out, and if I need more airflow, I might make another one for the other side window.

$18 Noctua NF-P14r redux-1500 PWM, High Performance Cooling Fan, 4-Pin, 1500 RPM (140mm Grey)

https://www.amazon.com/Bearing-Cooling-NF-P14r-redux-1500-PWM/dp/B00KF7QO2G#customerReviews

Aweking DC10-60V 12V 24V 36V 48V 30A Motor Speed Controller,PWM,Adjustable Driver,Max500W,LED Indicator,Reversing Switch,0%-100% Speed Controlling,Brush Motor

https://www.amazon.com/gp/product/B071ZKGMGN/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

$41 KYDEX® V Sheet - .118" Thick, Black, 24" x 48" Nominal

https://www.amazon.com/gp/product/B0051WCGU4/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

Completed pics forthcoming...

 

I'm interested in how this turns out, please don't forget about posting the project details.

 

I will do my best. I have a feeling there will be a lot of steps and trial and error here. That’s part of the reason I bought such a huge sheet of Kydex.

 

Sub’d i don’t think there’s a limit on how long a post can be! Post away

 

Whew, slow start but it's coming together. Nearly finished the molding process, just need to fine tune a few things and then start making the cutouts. After heeding warnings from my wife not to use the oven, I resorted to the grill which made this process so much harder.

Here is the side window I'm covering. Obviously I'll need a cutout for the knob, which cranks the window out at a angle.



Every good project starts with a plan. I've designed this to accommodate two fans, but we'll see how the first one performs. It should be a simple mod down the road to add the second fan. There are two tiers, one for the knob cutout, the other for accommodate the fan and speed controller. The controller, switch, and speed knob will all be mounted approximately where shown, and installed behind the shroud I'm molding. To keep water away from the electrical I'm going to mold a back cover.



I made the mold using 2x4x and 5/8 sheathing I had laying around. I ended up mounting the mold to another piece of leftover material that keeps the whole thing secure. I found this extremely helpful during the molding process.



After much trial and error getting the temp right and eliminating as many hot spots as possible with tinfoil, in she goes. It barely fit in my grill, but I'm pretty sure it would have made it into the oven. Supposedly this stuff smells, but I didn't notice any odor until the wood blocks I had holding it up started to catch fire, haha.



As you can see I got some burnt ends and the initial finished product looks pretty rough. Many improvements could have been made here.





Here's where I'm at at the end of the day. Like all one-off projects I could have done this in less than half the time I spent today doing it again, but this is about 6 hours deep. I've been using my heat gun to fine tune all the corners, and I think I could have just used the heat gun for the entire project. My biggest issue is the Kydek I'm using is about as thick as you can get, so it's not easy to begin with. With a little more time I should have this looking really good, then the fun part begins.

 

Some random suggestions; not criticizing as I made a mess of a few pieces when I first tried the stuff- use an oven, not a grill, for more even heating. Look online for temp and time requirements, they vary by user, thickness, project, etc but should give you a good starting point. If it starts getting shiny it's too hot. You're using a larger piece than I have but you need to either use a press or what would probably work best for you, a vacuum press or possibly vacuum bagging it. You have to work quickly as it starts cooling quickly and won't mold as well. A hacksaw or coping saw works well for trimming then sand the edges then burnish them with a dry buffing wheel. Use a heat gun to fix small areas but keep it moving or you'll get shiny spots.

I do mostly small projects so I grabbed a used but really clean toaster oven from the local Goodwill for I think $7. You can pick up some cheap cookie sheets there as well but I just bought a cheapy from Wally world.

 

Trust me, I know it looks rough, haha. That’s why I bought the big piece figuring my first or second attempt might be a flop. I was surprised how well it cleaned up though, and I’m not convinced I can’t make this first piece work. As I said before, temperature control was my number one problem and the grill is probably the worst appliance to try this on, but it’s the only thing big enough my wife will let me use. For some of my future projects I’ve got a big toaster oven that will work perfect.

I watched many videos on vacuuming and pressing, but again comes the issue of size. A big comforter vacuum bag might work, but for a one off piece I’ve decided to struggle through it after seeing what I can do with my bonehead methods. For some other projects I have in mind I definitely plan to go another route.

I really appreciate your constructive criticism and after some more experience, I’m pretty sure I can make some nice stuff. If you ever decide on a larger project, an oscillating saw is your friend for trimming up edges. Cuts through like butter.

 

Any progress?

 

Yea, still need to clean a few things up and install in the cap. I’ve been fishing a lot recently and building a new front porch, so time has been limited. Should have a finished product post at the latest next week.

EDIT: maybe the month of June, haha. It's prime fishing season still.

 

Finally had a free weekend to finish this up. It works well as-is, but I might add the second fan depending on the first camping trip. I think after I seal a couple gaps it will work fine. On full blast it really isn't much louder than on low, and with the front window cracked there is a noticeable breeze coming through. The fan is controlled by the switch and speed knob. I was hoping to have the fan reversible with that switch, but found out most fans only work in one direction. In this case exhaust. This project was cheap, less than $100, but man it was a lot of work.

 

That turned out awesome. Nice work @silasvirus82!

 

very nice! I have the same windows on my cover and was wanting to do a similar install. Would you do it again? Any thing you would change to make it better easier?

 

I would definitely do a lot different with the moulding process, mainly making it easier, but as for the design and function of the fan, the only thing I'd change is adding the second fan. It's pretty simple to do even after the fact, which I plan on if needed. Also, if you can find a similar fan that has reverse, that might be nice to have, but I believe working as an exhaust is way more efficient.

 

How’s the testing going? Is this seeming to be effective? I travel with my dogs in their wire kennel in the shell and I’m always looking for ways to keep them cooler. Currently I just keep the back window open and run a 20” box fan on top of the kennel pointing down

 

I haven't done any in depth testing, but my dog rode back there this morning on the way to the vet and it stayed what seemed to be air temp back there. Like I said before, there is a noticeable breeze coming through the front window when I was sitting inside the cap with the fan on. For a dog specific setup I would recommend the much larger radiator fans I was originally considering since noise is not a concern. Since I'm planning to sleep with mine on, I choose the quietest fan with the highest flow specs. My next fishing trip in two weeks will be the real trial run with me sleeping back there in the summer weather. If the one fan doesn't do the trick I plan to add a second identical fan for which I left room for.

 

@jpereira2
Assuming you saw this?