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There appears to be some misinformation in the hymnal. The reason for mounting the bases from the inside is primarily due to the fact that the front of the teardrop is curved and will prevent a flush exterior mount of the flange as intended by the manufacturer. It is true that the mushroom will be about 5mm lower in profile if mounted from the inside of the camper and the lack of full flange contact with the shell will be hidden by the liner and gobs of caulk will fill the gaps.
In the prototype, CLC has elected to remove/omit the rain baffle, not the “screen” as stated in the hymnal. They replace its function with a circle of hatch weather stripping. I think this is a BAD idea. The manufacturers baffle if the side labeled “front” is installed facing up in the camper, will act ,with the help of gravity,as a baffle does in a dorade vent to keep the water out. The available screw thread length to screw the cover out for ventilation in the weatherstrip method is VERY limited, won’t allow much air in, and will result in a cap on the road when you forget to screw it in tight each time before driving away. And the ABS thread in the cap won’t stand up to repeated screwing in and out. The hymnal gives the misimpression that omitting “the screen”, which is actually the baffle, will produce a lower profile mount. I believe these are important technical points builders should know. Even if the baffle should prove to be less than 100% effective at driving speeds, I believe there are far better ways to deal with water intrusion,diameter.home sewn canvas covers with elastic hems (like the plastic haircovers your grandmother wore in the rain).
By the way, the hole size for interior mounting is 4 1/2″ diameter.
I plan to modify the mushroom vents by gluing a nut into the base and using a piece of all tread glued to the cap, extending through the nut at the base, to a knob in the interior. This should allow me to fine tune the vents from the inside and keep them from unscrewing entirely on the road.
Fritz,
What is “all tread”? Do you mean a piece of threaded rod threaded into the cap on one end and a knob on the other end? If so you will need to jettison your baffle, which is held in place by the nut. The only problem I see with that is if you are in your camper andmitmis raining cats andndogs andmyou wish to open your vent, there will be no baffle to keep rain water fro coming through your vent. The baffle is essential mission critical to prevent leaks. The second problem is finding angle that will stick to ABS plastic. If there is an answer to these problems, your idea is attractive.
Finding a glue is the second problem. I hate this spell check or whatevernit is that keeps changing what I type before I post my messages.
Eric, I appreciate your post, only wish I had read it before installing the vents. I missed the phrase on page 373, “remove the middle screen,” so when I drove through a hard rain, I got about three or four ounces of water in through the front vents–so even though I installed the baffles properly they didn’t do much good. Today I removed the rain baffles and replaced the 1 1/2″ bolts with 1″ bolts. The covers can be screwed down tight against the weather stripping, so I hope that works. My thinking is that I got what little water I did inside because I was driving 50 – 60 mph in heavy rain. I’m hoping that since the covers are nearly vertical I will get little or no leakage unless facing into a very high wind. Time will tell.
If (when) the threads start to give out, I’ll just have to order new covers (if they sell them). Otherwise I will have to find a way to mount a nut in there. There are glues that melt the plastic for a “weld,” but I don’t know how well the melted plastic adheres to metal. Will have to do some experimenting.
Also, when the baffles were in place I could not get a good air seal with the covers–seemed to make no difference at all. Now I can seal them pretty well, which will help in cold weather (and I will have to hope my dog doesn’t have one of his gas attacks).
Eric,
I’ve been giving your post some more thought and examining the rain baffles and now I think I get it. As you said, the weather stripping is a bad idea. What was happening is that it was holding the water in so that instead of flowing out the bottom of the baffle it was forced up and into the cabin. The only problem is that if I re-install the baffles there still will be no way to get an air seal when the covers are closed–I think because of the way the flanges are mounted on the inside.
So I’m going to try it the way I have it for now. If I’m still getting water in I’ll remove the weather stripping and replace the baffles. I think I can find all the “plugs” I drilled out of the liner. I can use them to devise covers for the vent holes in cold weather.
This may be only mildly applicable to this situation. Instead of mushroom vents, I installed clam shell vents. Ordinarily these are used on boats. I purchased mine from here: http://www.iboats.com/Seadog-Clam-Shell-Vent/dm/view_id.886137
They’re stainless steel, so no UV deterioration of plastic. And no moving parts to wear out. I did add window screening underneath to keep out insects. And I fashioned plugs from packing foam to seal out drafts. An application of RTV silicone around the inside edges made an excellent gasket.
Best of all, they have not leaked at highway speed and rain.
This is my plan of action. I plan to use the vents as designed because I want to be able to get air when it is raining. I have to front indicator on the baffles facing up. I plan to cut foam disks about 1 in thick to place under the cap for transport. My hope is that it will seal the opening and press the baffle into the base to seal that as well. Wish me luck.
I have been thinking about this for quite some time. I wanted to be certain before I cut more holes in the shell. What are peoples thoughts on this- adding a gasket to the inside of the mushroom vent dome so it seals tightly against the shell mounting bracket for travel and for draft protection in colder weather? I also like the idea of a nut/handle/threaded rod so that the vent can be opened and closed while inside the TD. I haven’t figured out how to bodge that together yet though…
I weathered a thunderstorm in my camper over the weekend. I left the travel seals in the front facing vents and had the rear facing open. I had no water inside. The reason i left the seals in the front facing vents is because the curved surface warps the base and leaves a gap between the baffle and the base without the pressure of the travel seal.
I used the largest size they have.
Also, haven’t mounted these yet, and may only use one of the pair purchased: https://www.amazon.com/Mr-Auction-Brass-Clamshell-Cover/dp/B00OTZOM1A/ref=sr_1_sc_1?ie=UTF8&qid=1497234949&sr=8-1-spell&keywords=clamsehll+vent+brass
They’re not brass, but instead are cast iron. Probably salvaged from a ship. I’ll paint a complimenting (or contrasting) color and most likely mount on transom.
Even with the largest clamshell iboats.com has, the openings can’t keep up with the exhaust fan. I suspect the mushrooms vents don’t either, unless two pairs are installed.
Perhaps I should stress is that these clamshell vents must be mounted on flat surfaces. They will not adapt to curvatures.
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