Problems with outer skin on 21ft Bullett

[Cornfield118]

Has anyone had a problem with bubbling on the outer skin. We have had our camper 2yrs. Only used it three times (weekend trips). We just noticed some bubbling on the outer skin underneath the window on the slide out. There does not seem to be any way that it could be water getting in as the window is dry and secure.

Also after the first trip the rubber around the slide out tore on both sides. Has anyone else had this problem.

[JRTJH]

Cornfield 118,

Welcome to the forum. I moved your post and created a new thread for you. Hopefully you'll get the answers to your questions and be "on your way to more camping" soon.

[therink]

You would be amazed at how water can enter the smallest pin hole, which is likely on the window frame seal. I would sstart by removing the window frame and you may likely see where the water has entered, and you should be able to assess any damage.

[Ken / Claudia]

The bubble would likey be caused by water and water WILL get into a RV at any point where there is a window, door, vent, seam if there is any opening for it. It could be delamb'ed sliding due to bad/poor glue etc. You will never know what happened until the window is removed and the area checked out. If it is leaking water into the side it will not stop and get worse. The other question I have read about but, never seen or been involved with, others way be able to help.

[Wes Tausend]

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One other cause should always be a consideration when finding water damage, and that is condensation.

Many folks note that a considerable amount of water can collect on cool windows in cool weather. One thing that goes unnoticed is that nearly that same amount of moisture is also attracted to cool outside walls. It doesn't show up as beads of water because it is often absorbed by the wall and then migrates through the wall cavity towards the cooler-yet outer skin. Somewhere along the wall thickness the previously dry vapor reaches a cool enough gradiant to become wet by condensing (dew point).

Often condensation collects in the outer wood fiber used in the Filon siding and is trapped from full breathing and escape by remaining just under the vapor-resistant Gel-coat skin. During the next day, when the sun comes out, it raises the vapor pressure by rapidly warming the water... which cannot escape quickly enough back through the wood towards the cabin to save the skin. Therefore the gel-coat skin bubbles. It's a powerful process: steam engines use a form of vapor pressure.

One must realise that there is no other mechanism for water to physically lift (bubble) paint or Gel-coat. So all coating film bubbling is for this very reason; trapped liquid, warmth and revaporization.

It is possible for rain water to leak and do the same thing, but one should consider how much water may be produced by humidity. Scientific studies have shown that one person can create up to about one gallon a day (breathing, perspiration, cooking, showers etc). All this water has to go somewhere and the best defense is to always use the roof vents. Just a small opening on cool days helps a lot since water vapor collects near the ceiling.

One gallon per person adds up to way more than all but the worst rain leaks. Two people, two gallons, a family of four people, four gallons etc. Our little RVs have a hard time dissipating this compared to the greater outer surface area of full size homes, and condensation is occasionally a problem in full-size homes anyway. Food for thought while you are looking for the problem. Good luck.

Wes
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[Festus2]

Wes -
What effect, if any, does having a small fan running have on the amount of moisture inside the RV - especially during times of cold temperatures? In addition to cracking open the ceiling vents and windows, would the moving air help to reduce the actual quantity of water vapor/condensation or does it simply help to dissipate it faster?

[Seth]

Early this spring I decided to buy a full size dehumidifier for our travel trailer. With 5 of us in there, the moisture builds up pretty fast, especially since we bathe and cook inside most of the time. I turn it on full-blast and the tank is always full after 24 hours. The tank holds 4.5 gallons. That's a lot of moisture that would otherwise be absorbed into the interior surfaces of the camper. It's probably one of the best camping purchases I've made.

[Wes Tausend]

Originally Posted by Festus2

Wes -
What effect, if any, does having a small fan running have on the amount of moisture inside the RV - especially during times of cold temperatures? In addition to cracking open the ceiling vents and windows, would the moving air help to reduce the actual quantity of water vapor/condensation or does it simply help to dissipate it faster?

Festus,

A moving fan causes a few things to be different. But "stirring" with a fan does not reduce the overall humidity contained within the cabin.

I might be telling you more than you want to know following, and if so, I apologise.

To imagine part of what is happening, a comparison to a glass of water may be made. Imagine the glass of water has a small amount of cooking oil in it. Since the cooking oil is lighter, it will float to the top of the glass when left alone. But when stirred the oil/water will form an emulsion with the oil seemingly evenly distributed throughout. When left alone the oil will again eventually collect at the top.

This floating aspect is similar to humidity in air. Since a dry water molecule is made up of two tiny, lightweight atoms of hydrogen, and a single atom of oxygen, the "water" molecule doesn't weigh much more than just the single oxygen atom alone. A peculiar property of oxygen, and nitrogen, is that these atoms generally exist freely as attached pairs, that of O₂and N₂. As an example, an unbalanced triple oxygen variation is known as ozone (O₃), and the third oddball quickly combines with another atom if it can (our tires for instance). Nitrogen becomes active smog when unbalanced. At any rate, one can see above that Oxygen (21%) and Nitrogen (78%) together constitute 99% of our atmosphere and they do it in relatively heavy pairs of atoms. These pairs are nearly twice as heavy as water vapor, H₂O, so invisible water vapor floats to the top all over earth. When the invisible water begans to condense in the air, we finally have visible breath, clouds, or fog, all the same thing. The dry water rises and only falls to earth as rain when cool air causes condensation formation (a sort of atomic coagulation) and the tiny cloud/fog droplets both become visible and get too heavy to float. So that is the story of why this "floating" occurs.

Why does moisture collect on cool surfaces? Moisture collects on cool surfaces because they are "quieter". Heat is actually a vibration of molecules and hot surfaces and warm air vibrate more, driving water molecules away. Cool surfaces are calm, great for resting (condensing). This is most lkely to occur when the air is getting to the point of holding all the water in suspension that it can (saturation).

Then why does the fan seem to clear the RV windows? The reasoning is that the water molecules are literally torn loose from their tendency to moor on a cool surface and the moving air does hold more vapor in suspension because of this. The air becomes supersaturated to some small degree. It may be likened to snow blowing around. Snow will only collect where there is calm, behind a snow fence for instance. This is an ominent thing when it comes to humidity in our RVs or homes. Water will collect in quiet places and fans will actually increase this "hiding" tendency because the air is supersaturated. Think of all the cool areas where the fan does not reach to imagine this horror.

This may go against intuition, but the end result is that the windows are the best place for condensation because the water does not easily soak into them. They actually act like dehumidifiers by safely removing water from the air, especially if the water can be collected and disposed down a drain. There is the danger of water damage on the sills of course, but one might be able to actually take advantage of this by applying a trough of plastic tape against the glass near the bottom to redirect the water into a container which can be dumped.

Cool outer walls don't resist the water soaking so well. For this reason they may appear dry. Since water molecules are so small, water easily fits in between the molecular matrix of many substances. Walls are relatively quite porous. Water even slowly migrates through glass. The best we can do is slow it down at some level with materials that have a low permeability. In cold climates, it is best to do this on the warm inside of a wall as these homes are done with the vapor barrier just under the wallboard. The warm side does not allow condensation and water is rather harmless until it condenses to become wet, which it will do in the cavity nearer the cold outside wall portion. Unfortunately, in cool clmates, our RVs often have a vapor barrier only at the thin Gel-coat skin on the coldest, very outermost thickness of wall. Thus the warping and blistering. They are however ideal for preventing outside humidity from migrating inward in warm moist climates like Louisiana. There the warm side of the wall is the outside and the inside cooled by A/C.

I know this is a lot of info, but it may help in a clearer understanding how moisture can harm our homes and RVs. It could be worse. Think of living aboard the International Space Station with all the wild temperature extremes outside. The HVAC is carefully planned no doubt.

EDIT:
Good point Seth. I also have a dehumidifier for our TT.

Wes
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[Festus2]

Originally Posted by Wes Tausend

Festus,

A moving fan causes a few things to be different. But "stirring" with a fan does not reduce the overall humidity contained within the cabin.

I might be telling you more than you want to know following, and if so, I apologise.
EDIT:
Good point Seth. I also have a dehumidifier for our TT.

Wes
...

Wes -
No, not more than I wanted to know but very close .

Now, do I dare ask another question........Here goes..
What about the use of moisture-absorbing crystals? I take it that a dehumidifier would be a worthwhile investment?

I think my brain might have room for a little more information....

[Wes Tausend]

Originally Posted by Festus2

Wes -
No, not more than I wanted to know but very close .

Now, do I dare ask another question........Here goes..
What about the use of moisture-absorbing crystals? I take it that a dehumidifier would be a worthwhile investment?

I think my brain might have room for a little more information....

Festus,

You surely do have room if you are willing. I see your curiosity matches mine.

The moisture absorbing crystals do absorb moisture but they work best at low humidity levels. Thanks to Seth, we have confirmation offered that human produced water vapor can amount to gallons. I believe the crystals would be overwhelmed by that type acumulating humidity level.

I haven't actually used my dehumidifier in the TT, but under the conditions Seth lists I would. My plan was to camp for extended periods in all weather, hunting and fishing with grandsons, but we haven't actually done that yet. It will take some thought to decide if a dehumidifier is a worthwhile investment. They do work great in case of flooded basements too.

One way to look at the most severe damaging humidity levels is to realise that with confined human habitation the humidity reaches 100% which is the max that the air can hold. Then still more water is added forcing saturation of all building substances and condensation on the slightest cool spot. Ideally interior home humidity should be held to 50% or lower. Cold climate homes often have an air-to-air exchanger which draws in cold, dry outside winter air and preheats it with the stale exhaust exchange air. I do even know of some RV use of such devices that I read about on another forum.

Where crystals do work well is at lower humidity levels, certainly less than 100%. Suppose the manufacturer wanted to ship the RV with an open box of iron nails on the table and it was important that the nails not rust. Dry vapor will not rust the nails, not unless it condenses. There would be no human habitation, or other water contribution, but just normal starting humidity levels of maybe 60% in Indiana where the rig is made. Crystals could be placed in the rig to absorb this initial amount and due to the outer Gel-coat and the "perfect air infiltration sealing ", the inside cabin air would become quite dry and stay that way. The only reason for concern is that temperature changes inside the cabin might cause the nails to lag behind during warm-ups and even minute condensation on cool nails could cause rust spots. Ideally one would close the nail box and place the crystals inside so that they would only have to absorb that moisture which migrates inside. Even a paper box slows the migration and by then the nails may warm up and quit attracting water besides being more insulated to temp changes.

So the moral of the story is that crystals may be more useful in keeping a closet or cabinet from getting moldy under mild conditions. Still some folks claim they work well in controlling interior moisture during storage, similar to the imaginary nail-ship scenario above. We do use such a reuseable device (made for gun cabinets) to continue drying compartments that have been wetted. We use fans well past normal dry then let the crystaline device absorb whatever may be left in the substrate. The device turns color when it needs to be recharged and discharges the moisture by any well ventilated 110v outlet, ready to work again.

Wes
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