ventilation fan - preliminary version

This is a iterative step in the making of a ventilation fan for Tatyana. The purpose of the fan is to reduce the cabin temperature from solar gain when the vehicle is parked in the sun.

The three previous posts related to this:
james cook enhancement - part 3
the proof is in the pudding
intelligent venting fan

A lot of owners of this camper replaced the stock bath skylight with the very popular Fan-Tastic Vent. I personally like the stock skylight. I see no downside with it's non-motorized design. I also like the retractable fly screen as well as the high quality design and construction.

The goals of my home-made ventilation fan are:

• very low power consumption
• very low noise
• does not involve permanent alteration
• easy to deploy and stowable when not in use

In this iteration I created the fan assembly which consists of a low-power 4.5" diameter computer fan mounted onto a 1/4" thick foam board.

i plunge-cut a 4 1/2" diameter hole with an e-xacto knife

the fan is mounted to suck in air from the outdoors; the cabin air exhausts through the bath skylight

Finding fasteners to mount the fan to the foam board can be challenging. Fortunately I am a pack rat and I saved these elastic silicon rubber fasteners years ago for the rainy days.

silicon rubber fan fasteners - they are designed to also function as vibration isolators

the head is big enough so it does not pull through the delicate foam board - how nice is that!

finger guard for inside - i decided not to use it to keep the noise level low

One technique for designing quiet forced air ventilation is to select fan with biggest diameter to keep the RPM low. I chose this low power 4.5" diameter fan for this reason. It consumes only 320mA and owing to the low power it is very hard to cut yourself even if you try. However for installation where it can be accessed by young child a finger guard is highly recommended.

At only 320mA (that is 0.32A) the fan can probably runs a month before depleting the coach batteries. Yet it circulates enough air to keep the cabin cool when the vehicle is parked and locked.

I have considered mounting 2 fans side by side for doubling the CFM but decided against the idea. 2 fan would cause annoying beating acoustics as they do not rotate at a synchronized speed.

Designing the outline of the foam board requires some careful planning and thinking. I want the assembly to be just pop into one of the winged-skylight on the side, without the need to make any permanent alteration to the vehicle.

trimmed for used on passenger side skylight

In the above photo the notch on the top left hand corner is to clear the strut that keep the skylight. open. To make it usable on either skylights, I just simply add an identical notch to the top right corner. When the fan is deployed, the notch is obscured by the skylight inside trim.

you just slide it upwards and then push the bottom edge in; the bottom edge of the foam boards rests on top of the roller blind frame

The power cord tucks neatly under the upper berth mattress and is plugged into the DC power receptacle on the side of the kitchen upper cabinet. When not in use the entire assembly stores in the space between the upper "bed frame" and the fiberglass high top just in front of the winded skylight. It weight about 0.5 lb including the power cord.

view from outside - clean and understated appearance

I am very happy with the result. Removing the finger guard made a marked difference in the sound level. Now outside the vehicle in a quiet neighborhood I have to walk up to directly under the fan to tell it is running.


another view from the outside - i always keep the sunny side one closed