Platform on the roof

olley · 01-02-2006, 07:49 AM

Hi I intend to make a flat plarform on the roof of my 30w brave, it would be made out of aluminmum section and marine ply, and will cover about 2/3 of the roof from the back forwards.
The question is how do i fix it down?

1)screw through roof into cabinets where possible and accept some fixings will be seen (i have twin slides)

2) screw into roof, would this be strong enough?

3) bond to roof in someway

4) bit of all

5) stupid idea don't do it at all

Olley

olley · 01-02-2006, 07:49 AM

Hi I intend to make a flat plarform on the roof of my 30w brave, it would be made out of aluminmum section and marine ply, and will cover about 2/3 of the roof from the back forwards.
The question is how do i fix it down?

1)screw through roof into cabinets where possible and accept some fixings will be seen (i have twin slides)

2) screw into roof, would this be strong enough?

3) bond to roof in someway

4) bit of all

5) stupid idea don't do it at all

Olley

John_Canfield · 01-02-2006, 08:52 AM

Olley - for something as important as the roof, I recommend you contact Winnebago and try to get to one of their engineers in a discussion. Perhaps you can do this via email.

We have a Datastorm Internet dish on top of the roof - it is about 53" long, 39" wide and weighs about 100 lbs. The installer used screws (lots of them - maybe 15 or 20 in total) and Dicor (self-levelling sealant).

Perhaps some of the screws found their way into some roof ribs - I don't really know since I wasn't the one running the drill.

I beleive that the roof would rip off before the dish mounting would.

Cruzer · 01-02-2006, 09:27 AM

I'm not quite sure "why" you want to do this, so it's tough to offer any advice. Having mounted lots of stuff on my previous coach, a 2003 33' Suncruiser, I am familiar with the Winnebago roofs and have several areas of concern regarding your plans:

First, the existing fiberglass is very thin on Winnebago roofs. I'd be very careful regarding fastening anything of substance to it. When I mounted my KVH L3 satellite dome I used 3/16" pop rivets rather than screws because they "knot up" behind the fiberglass rather than expecting screw threads to hold in the thin fiberglass.

Secondly, I'd be sure to find the crossmembers to help support the load. After my first winter I could see where the snow load allowed the fiberglass to sag somewhat between the crossmembers so you'll want to find them to support any additional load.

Thirdly, a huge flat roof will undoubtedly have air circulating underneath at highway speeds and that could put a fair amount of lift over that large of an area which would tend to pull upwards on the roof.

Fourthly, you won't want to bury any plumbing vents, skylights, roof vents, or any other items on the roof.

Fifth, if you are adding this as a cargo carrier, it'll impact your cargo carrying capacity. Chances are, on a 30' RV you won't have a very high capacity and you may be getting close to the GVW allready. Plus, that weight (both the platform and the cargo) will be up top, where you'll really feel it wanting to help lean in the corners.

As I said, I don't know the specifics of what you want to do but I'd keep these points in mind.

olley · 01-02-2006, 12:58 PM

Hi cruzer thanks for reply, the main reason for doing this is beacause I want to mount additional LPG tanks on the roof, about 200litre in 2 separate 100litre tanks. Petrol here in GB is about 88p a litre LPG is about 38p. we had the conversion done last year but we are short on space for the tanks and could only fit in 2 100litre tanks.

The two slides, water tanks, genny ect. meant on a 30' we haven't got the room and it seem to me that the roof was one area for consideration.

The brave is on a W22 chassis which gives us a payload of nearly 2 tons, even with the LPG conversion and our bits I think we still have about a ton left.

I realise that it will effect driving, but I tend to rollalong at about 55mph the same as the hgv's, so being aware of the problem I should be ok. If its not I can always choose not to fill the tanks completly or ar all.

"007" · 01-02-2006, 01:13 PM

olley, do you have over passes over there how much clearence under, how bout mounting under on chassis

may have to give up compartment.

"007"

olley · 01-02-2006, 02:03 PM

Hi 007 the tanks will sit behind the first aircon. and shouldn't be higher than that.

Cruzer mentioned lift caused by airflow but as long as i have it secured properly i don't think this will be a problem.

To get the two existing tanks in they had to reduce the size of the petrol tank by about a third, so there is no space under, and I don't want to lose any locker space.

So thats when i came up with the idea of the roof.

Olley

Tom N · 01-02-2006, 02:40 PM

#5

rebelsbeach · 01-02-2006, 04:07 PM

Sorry but I'm with Tom N on this one,especially given the "weight" of propane as compared to air....Knowing it's up there and the potential volatility of it,I'm choosing reason #5...

Cruzer · 01-02-2006, 04:17 PM

Propane settles. If you have the slightest leak it'll filter down around and into the coach, looking for a point of ignition. It also gets hot up on the roof and I don't think that the LP tanks would be very comfortable up there, what with expansion and all that. Plus they're not very protected against tree branches, road debris, or anything else that goes ballistic up there. Personally, I wouldn't do it.

olley · 01-03-2006, 04:30 AM

Hi guys I get the idea that your not keen on this

When I said platform I meant that it would be about 2" above the existing roof, and mainly be in-between the two aircon's. With cut-outs around any vents etc. Sorry for not making this clear at the start

The concerns appear to be:

1) Extra weight
2) Increase in the centre of gravity effecting handling
3) Danger of leaks
4) Risk of damage to tanks from trees etc.

1) As already stated I believe I have about 1 ton of surplus capacity.
2) I accept that handling will be effected, if its to bad then I will have 2 hardly used tanks for sale.
3) As long as all the pipework is done correctly there should be no more danger than from existing pipework, feeding fridge, oven ect. However any small leaks would I think disperse into the atmosphere and a large one would be apparent by the smell.
4) I intend to fit a ventilated reinforced box around the tanks to protect them from sun and damage, they will also be lower and behind than the forward aircon.

The greatest danger I see is in the event that the RV catches fire, I will have two potential bombs sitting on the roof, but then I have two 100litre tanks behind the 35 gallons of petrol to the rear.

It should be possible to coat the inside of the box with a fire activated paint or foam as used to protect steel work to lessen the danger. And all LPG tanks have a built-in mechanical cut of valve, in the event of a pipe fracture the valve automatically stops the flow of gas.

Propane weighs about 1lb a litre so 180litres plus tanks and framework will come in under 300lbs additionally the weight will be on the centre line and in-between the axles, not hanging off the back.

I think from comments I need to bolt through the roof or screw into cross members, being a belt and braces kind of guy, I will do a mixture of both.

Olley

skigramp · 01-03-2006, 04:45 AM

What is the purpose of the plywood?

DonavonP · 01-03-2006, 06:05 AM

Click on the smiley.

Tom N · 01-03-2006, 07:10 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Click on the smiley </div></BLOCKQUOTE>

Not unless you tell me where it goes or what it does.

DonavonP · 01-03-2006, 07:41 AM

Hi Tom, I understand your concern, here's the link to a propane explosion that is called a bleve. http://www.thermdyne.com/

If you run into this situation in the future, you can "right" click and go to properties. That will tell you where your computer is about to go.

Thanks for pointing this out.

Tom N · 01-03-2006, 07:58 AM

I receive this forum via email and not the web. Thus a right click for properties does nothing. Emotions and their associated links are not sent via email but URLs are if preceded by http://

CHIPPYSGT · 01-03-2006, 11:28 AM

You might want to check with the local constabulary regarding such a setup.

That's basically a big bomb sitting up there to catch every tree limb, low bridge, etc.

I'd vote for choice #5.

olley · 01-03-2006, 03:10 PM

Hi chippysgt the danger from a low bridge is overstated, how many people do you know who have taken their forward aircon. off. These tanks wouldn't just be sitting up there, if i went under a low bridge and hit them they would take half the roof with them, they are also very strong, try hitting your existing tank with a hammer.

I still think that the main danger is a fire in the RV how so ever caused. But then I am from Suffolk "Strong in the arm thick in the head"

Olley

rebelsbeach · 01-03-2006, 03:27 PM

Glad we could offer you some opinions,maybe come back and post some pics when you get the bomb rack installed.....

tderonne · 01-04-2006, 03:38 AM

I think I fall of the other side of the majority of opinions here. A propane tank hanging under you is just as likely to explode as over you. Folks have no problems with them below. As for A/C covers, they blow off, RV's are shorter than trucks. There are very few places an RV could hit a bridge here in the states, certainly not on a major freeway.

Compressed Natural Gas (CNG) is stored in a simliar manner to propane, at least with respect to there being tanks (different type for 3000 psi). It takes large tanks to get decent range, similar to your experience. One place CNG is used a lot is city busses. Guess where the tanks are? Yup, on the roof. You might try some searching on that application.