Skip to main content ↑ ↓
Topic: Bulkhead ventilation (Read 1053 times) previous topic - next topic

Bulkhead ventilation

 I cut and installed a 12 volt Fan to blow air from the cargo compartment into the bulkhead space between the floor and underbelly and vent underneath to help keep it dry and help dry if water gets in to the bulkhead space.  Everything looks good looking through  the hole I cut everything looks dry and good  I keep a close eye on the wet bay and compartment and keep the underneath well seal I also put a vent underneath. has anybody try to put a ventilation system in like an air exchange to keep this area  vented if water gets in .it seems to have a hard time drying last year the rubber gaskets on the garden hose leak before I noticed so now I keep a plastic container under the hose and inlet  I'm sure water got under the floor I rebuilt the bulkhead  18 month ago and I seal the underbelly so I was thinking if water gets in there it got no place to go and the air can't get in there to dry
Rick & Hilda looking forward to full- timing one day for now couple of months at a time
1999 U270 3602
Built number  5530.  Feb 1999            Motorcade  number 18438
8.3 Cummins Allison six speed with brake  retarder
Purchased Nov 28 2019

Re: Bulkhead ventilation

Reply #1 –
Rick,

I have trouble picturing how that can work.  The basement structure is fiberglass top and bottom tightly adhered to the box beams with block form insulation between the box beams.

How can air circulate between areas "divided by" the box beams??
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Bulkhead ventilation

Reply #2 –
I'm  not sure it will help but  I did rebuild the bulkhead in the winter of 2020 and put in a new compartment floor in, cushion flooring  I did glue it in. And use the old plastic underbelly which I glued when I dropped the old bulkhead it was rotted from front to back so water was traveling all over and staying in bottom part of bulkhead to rot it out about 60 % or more  Last summer 2020 I had afternoon water leak about 4 hours before I noticed it just dripping I tried to air it out two months after I cut a hole in the underbelly at the back and water came out I guess we didn't seal it tight in the wet bay I tried.that when I put the vent under the coach two in the back one on each side and put a fan blowing into the vent all winter in a heat garage I hope it dried out once water gets in to the bulkhead area it sit there and this has been playing on my mind how to dry it out if its still damp  so this week I cut the cushion floor in the storage compartment and installed a 12 volt Fan hoping it may circulate the air . If the water can travel so can the air after rebuilding the bulkhead it is no longer vacuum sealed if it was I do not believe I glued it 100% airtight  that's why I'm asking how can someone dry it out and how can you tell if it is dry that bulkhead is all ways on my mind even if I'm driving in the rain
Rick & Hilda looking forward to full- timing one day for now couple of months at a time
1999 U270 3602
Built number  5530.  Feb 1999            Motorcade  number 18438
8.3 Cummins Allison six speed with brake  retarder
Purchased Nov 28 2019

Re: Bulkhead ventilation

Reply #3 –
So, I'm looking at pictures of the structure Cape Bretoner kindly posted, and playing a game called "find the loadpath."  Seems like a perimeter frame, a couple of longitudinals with structural foam infill and vacuum bagged skins would be a simple and far more durable assembly than this hodgepodge of square tubing. 

Unfortunately I suspect the best you could do would be to provide weepholes for drainage in the original structure.
"Not so  long ago we were a nation of risk takers, riding five million pounds of  thrust straight into space."  Joe Gresh
Chuck Pearson
1996 U295
2018 Can Am X3 TurboRS

Re: Bulkhead ventilation

Reply #4 –
Weep holes kinda makes sense but they themselves provide a entry point. Having it sealed tight works well till you have the first entry point leak and the entire game changes from prevention to corrosion control. Often wonder if a small vacuum would dry out after trip? But you could also just be drawing in more moisture from the air. No easy answer
Scott

Re: Bulkhead ventilation

Reply #5 –
I have thought about perforating the underbelly and then covering it with something like this in black. 

Woven Visqueen Plastic Sheeting | Discount Visqueen

The idea being to keep spray out, and if leaking from above then the water could drain out. And maybe the woven fabric could also provide some ventilation.

Re: Bulkhead ventilation

Reply #6 –
The block insulation between the box beams absorbs water.  Very difficult to get it out.

And, the box beams are raw metal-- no treatment.

Bottom line-- keep the water OUT.  Much more effective than trying (mostly unsuccessful) to remove it.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Bulkhead ventilation

Reply #7 –
Anyone redoing their box beams should use Polysio foam board that doesn't absorb water.
Too bad Foretravel didn't.

Re: Bulkhead ventilation

Reply #8 –
I did install two vents at back of the bulkhead underneath on the underbelly  there the same vent used on the side of inclosed cargo trailers  trailers used for ski-do and motor bike trailers  the way there design I think it won't allow the water to come in. They slope downwards and have a round insert that should deflect the water from entering. Since I installed then I've never seen any water coming out of them.  I take all precaution to keep wet bay dry . I even put sponges in the compartment so I can Feel them for dampness for moisture or small leak from the plumbing  I believe in keeping it dry but plumbing leaks happens accidental leaks like the freshwater hose gasket leaks Old caulking letting water in over years
Rick & Hilda looking forward to full- timing one day for now couple of months at a time
1999 U270 3602
Built number  5530.  Feb 1999            Motorcade  number 18438
8.3 Cummins Allison six speed with brake  retarder
Purchased Nov 28 2019

Re: Bulkhead ventilation

Reply #9 –
Quote from: Travelin' Man –
Anyone redoing their box beams should use Polysio foam board that doesn't absorb water.
Too bad Foretravel didn't.
Many different foams available in both open and closed cell. I cut thousands of pounds of polystyrene foam with a hot wire and water is used in its creation. Young raw foam will expel water when being cut and when fully cured it dries out. Like wood it become nicer to work and more stable. It will actually grow and bow while it is not fully cured/aged. I actually like the two component liquid urethane foam to inject into cavities bonding everything together and becoming very strong and sealed. Used in several boats. Major pain if too little or too much is used. Cavities or excess mess. If you can disassemble after construction without destroying it, IMO it's wasn't done properly.
Scott

Re: Bulkhead ventilation

Reply #11 –
Quote from: Travelin' Man –
And your view on Polysio foam is...........?
Unknown. Never used that I know of. Hard to delete air pockets with block foam, always some gaps which collect condensation. It's difficult to control. Marine two component foams are closed cell and a lot are fuel compatible. 👍👍 but you have to delete any air pockets. My home built foam filled boat has been used probably harder than most boats. Getting airborne is common at higher speeds. Hull takes a beating to say the least. Any water that gets into closed cavities stays forever or until it is allowed to freeze and is liberated into a new area of new damage. Some things are difficult to control.
Scott

Re: Bulkhead ventilation

Reply #12 –
Quote from: Travelin' Man –
And your view on Polysio foam is...........?
Well I did a little reading and recognized it.
The difference between Polyiso, EPS & XPS Foam Insulation & Styrofoam - Ecohome
It's a higher temperature petroleum based foam. I used around my below ground hot water storage tank for my solar heat collectors. And actually used a scrape I've had for years in my recent cooling unit install for its higher temperature capacity.  I did note I was unable to cut using my hot wire foam cutting table. Hot wire would just set on it and just kinda turn it into charcoal. Cut with a sharp knife. Double layered in foil to keep out gassing inside it. So I guess I have used but it's not a common tool in the box for me. Never would of put a name with it if that makes sense.
Scott

Re: Bulkhead ventilation

Reply #13 –
The water in, water out is a real Catch 22 with regard to our box beams rusting out.  I like the idea of being able to let the water escape if ingested, and I like the sound of this foam being used instead of some that is absorbant.

March, 2020
Is Styrofoam insulation waterproof?

"Polyiso is a rigid foam board insulation used for roofing and for insulating walls and ceilings. It is a composite insulation made from various chemicals and synthetic materials, which are heated and then cooled to form rigid panels. This creates its closed-cell structure and makes polyiso exceptionally waterproof."

Maybe hot-mop the box- beams?  Lol

Re: Bulkhead ventilation

Reply #14 –
I have my own issues with the bulk head.
But what I have done since I owned it is to turn the valves for the hot and cold water wet bay spigot on the water manifold off .
When I need to use that spigot I simply go the the manifold and turn it on and when I'm done I turn it off.
Having said that my under belly looks the same from front to back.  But I have a little opening, 1/4 inch for almost a foot, (near the wet bay area opposite the drivers rear tire where there is some rust flaking off.
I'm not sure what to do.  I haven't tried to torque any of the bolts;  what would I do if they broke off.  And one bolt is missing.
In the meantime should I get as much rust out and then seal it up.
Rick & MJ Berry
1998 U320 40'
Ohio

Re: Bulkhead ventilation

Reply #15 –
Yes, you need to open that area up and determine the extend of the damage-- may just be superficial or may be structural.

If just a couple of broken Rolock bolts, the fix is pretty simple and is covered in the Bulkhead discussion pinned at the top of the Tech section.  Nothing has really changed since that was written 12 years ago.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Bulkhead ventilation

Reply #16 –
Quote from: 18360 –
I have my own issues with the bulk head.
what would I do if they broke off.  And one bolt is missing.
Fix it.
Better than ignoring hoping it will get better. Or wont get any worse?
So is the missing bolt missing or already broken?    My money is on broken.
Scott

Re: Bulkhead ventilation

Reply #17 –
How do I open that area up.
Rick & MJ Berry
1998 U320 40'
Ohio

Re: Bulkhead ventilation

Reply #18 –
A picture of the  area would help, as what you need to do depends on the extent of the opening/damage.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020