One of the fundamental requirements for an off road camper trailer is to travel comfortably in fine bull dust or mud. This means when you break for camp, you can get straight into the cooking or into bed without having to clean up dust and mud that has got in through the seals.
This blog will describe how seals work, the most common mistakes with sealing and finally how to test a seal for the right compression!
The photo on the left is a Kimberley Kamper Platinum Model after travelling to Cape York in 2014. The Gullwing lid on the kitchen side is opened up and photographed by a happy customer.
The way seals work for an off-road caravan or camper trailer is that they are semi-pneumatic. In otherwords, they are a round “tyre” like profile and this presses against a clean and smooth surface. They will also have a pneumatic property as the air inside will be captured with very small controlled drain holes.
In off-road conditions, when vibration travels through the seal, the seal will flex its profile shape. If the sealing is the correct design, with the correct seal and fitted in the right way, even when flexing the seal will will maintain contact with the sealing surface and isolate the inside from the dust and or rain or mud.
The size of the seal used and the type of seal depends on the amount of flexing required. As you may know the secret to off road design is to have a flex in the chassis and the whole suspension system for the extreme off road conditions. The same applies to lids and seals. Kimberley have a 5 Year Warranty on their chassis and suspension arms and it is transferrable to the next purchaser on resale within that time period.
At Kimberley we DO NOT USE closed cell or open cell rubber strips as primary seals. These have no “flex’. This type of seal is useless as a primary seal as they have no semi-pneumatic compression. These can be used as secondary seals is some special applications.
We have a famous customer “Phil” who hates bull dust. He claims it is so fine, it will “get into your salt and pepper shakers”; BUT it doesnt get into his Kimberley. One thing that Phil does though is keep the seals and the surfaces they press on immacualately clean. As you can imagine if there is some “stuff” that falls on the sealing surface whilst in camp and it is not cleaned off, there will not be a perfect seal when the camper or the gullwing lid is closed. This is the most common cause for poor sealing in a Kimberley.
The key to good sealing is:
- The design has to have the right type of compression seals on smoothly painted or poly-urethane coated surfaces. You cant seal on a galvanised surface or a rough stainless steel surface. It is difficult to seal on plastic or polypropelene surfaces for off road use.
- The design has to have a sufficent recessed gap between the 2 surfaces to match the seal size. So for large seals, generally, a recessed retainer plate is required for sufficent compression volume because of their size.
- The compression latch “travel” has to be precise to match the seal profile.
- The type and quality of the seals. There is a big difference between using EDPM, natural rubber and a rubber mix. Natural rubber wears too easily for camper trailer lids that expose this rubber at the floor when walking in and out. Camper trailer lids need an extremely high quality EDPM seal with a large compression profile.
- The design of the seals may require additional fine rib lines or lips. This is one of the secrets to keeping out bull dust.
- Maintaining clean surfaces for the seal to make 100% clean contact with the painted or highly polished surface.
The reasons a seal may not work assuming it originally DID are:
- Build up of grime and dirt: Run a cloth around and make doubly sure the sealing surface and the seal is clean of grime and other material. If it isnt perfectly clean, the seal may not work.
- Paint or surface is chipped where the seal sits on.
- Corrosion of some type on the surface where the seal sits on
- The seal has been closed and tight for a long time and it has “lost its ability to rebound” to normal shape. This occurs commonly while the camper trailer is in storage, so relax all the doors and open the lids to take all the pressure off the seals.
- The seal has cracked. This generally occurs with older high quality seals or poorer quality Asian seals that dont have sufficent UV protection.
- The seal has a tear. A sharp object has punctured the surface and the seal is no longer completely pneumatic.
- The seal has a rough and raspy feel to it: Something has grazed the surface and the seal is no longer completely smooth.
- Water has entered the seal producing a hydraulic “lock”
- The seal is not joined professionally and the joint has a ridged and inconsistent surface at the join
- The join is not at the furtherest point of the seal away from the hinge point where control on the compression is easier to achieve.
- The sealing latches are not adjustable within the required range. The latches that hold the door or lid or roof of the camper trailer must be adjustable to set the right compression.
The way to test for the right compression on a perfect seal is:
- Take a piece of clean copy paper (80 GSM approx)
- Place the copy paper midway on the sealing surface and close the lid/door/roof.
- Close the compression latch to the normal setting you are wanting to test.
- Jerk the piece of paper by pulling about 40-50mm
- If the paper tears, the compression setting is too tight
- If the paper pulls through and doesn’t stop at the end of the jerk, the compression setting is too loose.
- Keep adjusting the compression setting until this works at all points in the seal.
- The most common mistake by manufacturers is to make the hinge side too tight so the latching side is good but there is poor compression on the hinge side. There is not a lot you can do about this. This is in their design. Getting the right offset in the hinging system is critical to good design.