FRP vs. Aluminum

DrFun · 08-25-2003, 04:56 PM

Greetings!
I'm new to this forum but have been researching a truck conversion RV for about 18 months. What a wealth of information is in this forum and "in" the Internet.

The topic I'd like to get more feedback on is the pros/cons of fiberglass reinforced plywood (FRP) versus aluminum skin. Some items to start the discussion include:
<UL TYPE=SQUARE>
<LI>Durability
<LI>Repairability
<LI>Strength
<LI>Puncture resistance[/list]
Most of the discussion in this forum seems to be about Show Haulers (aluminum skin) but I'm sure there are plenty of opinions about FRP as found on Kibbi/Renegade models.

Regards,
Alan

Patrick · 08-25-2003, 05:49 PM

I rank the different choices in this order:

1. .063 aluminum, bonded.

2. FRP

3. .030 rivited aluminum

Aluminum bonded looks the best, is dent resistant and lasts forever.

FRP looks way better than rivits and wavy .030. It has the potential for water damage or delamination but is easy to repair small areas.

Thin aluminum looks terrible, the holes with rivets are asking for corrosion and a bird strike, golf ball or kids toys will dent the hell out of it. Each hole and rivit causes drafts, leaks and is hell to wash/wax.

WERA · 08-25-2003, 06:38 PM

I've got a Showhauler truck and a Renegade trailer. They both have some positives and negatives, aluminum is easier to dent/scrape etc.. but it's also much easier to replace. In my case if I want to sell my trailer I can't just resking the side where I put in windows. But the FRP does look good and is much more resistant to the normal dings that the aluminum gets (altough the thicker alum used on the RV doesn't ding easily at all, ours is blemish free so far). The FRP also requires that you seal the plywood anytime you put a hole in the fiberglass or is will soak up water and that would be very, very bad. It's not hard to seal up though so no biggie, I am a bit more paranoid about putting holes in it than I ever was with aluminum. I like the extra room in the trailer it gives and as I said I really like the finish on it.

Basically flip a coin, you'll be ahppy with either.

Sean P. Clarke
WERA Motorcycle Roadracing

geof · 08-25-2003, 10:18 PM

I understand that if one backs up the aluminun with spray polyurethane insulation or even plywood that the ripples and dents are grately reduced.....I'm trying to locate the SPF guy here locally it find out what he knows about this process....the ripples have to do with heating/cooling of the skin while still and flexing of the frame and wind load while moving....I will find out more and report this to you all asap.....geof-Near Cincinnati

DrFun · 08-26-2003, 09:26 AM

Thanks for the insight and information!

The one item I'd like to follow up on is the discussion about insulation... I expect to do some extended cold-weather use of the RV. I don't know that either the SH or Renegade wall/ceiling construction offers sufficient insulation. The "bubble" insulation shown in the SH web pages and photos doesn't look adequate. I don't know what the wall construction of the Renegade is (steel framing similar to SH but skinned with FRP??).

The spray-in polyfoam insulation looks promising so I'm anxious to hear what Geof has to share.

Regards,
Alan

Patrick · 08-26-2003, 11:19 AM

I paid an extra $900 or so for high density foam to be added in my SH in addition to the bubble stuff. I got double pane glass as well.

Junk Man · 08-26-2003, 12:27 PM

>I don't know what the wall construction of the Renegade is (steel framing similar to SH but skinned with FRP??). Regards,
Alan<

Alan,

With most FRP truck boxes, trailers and such, there is no frame, just top, bottom, and corner aluminum extrusions. The FRP is bolted or rivited to these. One site that I looked at (can't remember which one at the moment) said thet they glued furring strips to the inside of the box, to allow for insulation, wiring, plumbing, ect. then finished the inside off like you would any other RV, with paneling, or whatever.

They also make a special FRP panel for the roof, that has a slight bow in it, so that water doesn't lay on it.

Another advantage to FRP is that it can be made in just about any size or color you want.

Jeff in South Dakota
1995 Ford F-250 4X4 PSD
1992 Skamper Slide in camper
1984 Holiday Rambler 5er
1979 Mercedes Benz Unimog

Warpath · 08-26-2003, 01:55 PM

The downside issues I have heard and spoken to people about that are not listed:
Weight - 5/8" panels are heavy.
Wall & Ceiling joints loosening up over time & miles.
Cabinets not having enough support on walls.

You are going to find +/- with either type of construction, it all comes down to how well the materials are used to get more +'s.

As for insulation, you can insulate the box area like a refrigerator, but if you do not do the same to the cab then you are going to loose all of your effiecency. You cannot imagine how much heat or cold is lost through the cab, it's huge. If I shut the leight weight curtain I have now it makes a world of difference, but it is not like the R rating your going to get from heavily insulated walls. Some of you guys that are talking major insulation, may want to look at ways to block off the cab with either a insulated curtain or some sort sliding wall.

BTW I have the standard insulation and have yet to encounter a problem with heating or cooling.

2003 28' Show Hauler Motorhome on a 1995 FL 120 www.showhauler.com

[This message was edited by warpath on August 26, 2003 at 04:15 PM.]

geof · 08-26-2003, 10:21 PM

....I looked at Inovator Trailers in ELkhart that makes a type of FRP trailer...it had a noticable belly in the roof-thanks to my tape measure-I convinced the salesman also....had it rained while I was there-it would't have taken anything besides a ladder to prove my point. I truly believe that unless there are roof trusses/bows or tubing frame of aluminum or steel-a box will have a belly sooner or later-snow and ice will be a concern as the added weight will increase the belly with time....The insulation issue is still nagging on me-an installer in Hamilton is supposed to call Wednesday...Our local OTR Trailer repair shop uses spray can foam for small repairs and has access to larger quanities at about $2.00 a board foot retail. Material cost of the foam is about $0.30 a board foot approx. as per the manufacture. I'm waiting for local installers to contact me-so far there is only one in the tri-state area.....geof-Near Cincinnati

08-26-2003, 10:36 PM

A sample wall section that I saw for a Renegade motorhome/toterhome had an aluminum frome inside the FRP. I believe the tubing was 2 inch. Polystyrene beadboard insulation is between the studs and I believe the inside is luan plywood. I don't think they use the studs in the race trailers.

Does anyone know of another manufacturer besides Renegade who uses FRP? An aluminum skin with metal studs would not be the most desirable in a cold climate.

The one thing for cold weather use that the truck conversion manufacturers are weak in designing is enclosed holding tanks with insulation and heating. I even had one rep who was displaying a motorhome with open holding tanks ask why would you need to enclose them. I explained that the build up of ice under the chassis would coat the tanks and the dump valves. He said we can put pad heaters on the bottom of the tanks. When I asked about insulation and how would you dump the tanks in the winter if there was ice buildup and he just gave me a blank stare. He did not understand what I was talking about.

That is one drawback I have seen with the truck conversion mfr's. They come from building rigs for the racing market and auto racing is a warm or moderate weather sport.

Patrick · 08-27-2003, 03:56 AM

Haulmark uses FRP as well.

WERA · 08-27-2003, 08:20 AM

Renegade does use steel trusses in their trailers for roof support. Nothing on the walls though except by the door.

Sean P. Clarke
WERA Motorcycle Roadracing

geof · 08-27-2003, 09:52 AM

In looking at a refer trailer the walls were "Z" shaped studs-not Box or Hat channel...Insulation was sprayed between the "Z's... The trailer was a freezer unite...though there was some condensation on the outside of the trailer in places....I am not sure where /why that was coming from....I'll keep all posted on construction of a reefer/chiller/freezer trailers....especially the insulation issue...geof-Near Cincinnati

08-27-2003, 06:21 PM

goef the Z studs that you saw on the reefers still have a metal to stud contact so the metal skin will transfer heat or cold. The advantage of the Z studs vs tubing is that the foam has less gaps, the Z stud material probably being 1/8" or so thick. With 2" tubing you have a 2" gap between the sections of foam.

The Bigfoot class c motorhomes actually use tubing but they put foam inside the tubing. They are probably the best insulated motorhomes I have seen.

Patrick, Haulmark does not use FRP. I have looked at them twice. The FRP that Renegade uses is 5/8" thick with a plywood core. The FRP stands for Fiberglass Reinforced Plywood if I remember correctly. It was the Haulmark person who wondered why you would want to enclose the holding tanks and dump valves.

Haulmark uses a aluminum tubing frame with what their brochure calls "Gel-Coated Outer Shell w/ Luan Reinforcement". It is probably only 1/4" or so thick.

I hope to go to the Renegade factory this fall to see how they are built. One concern is the stainless steel corners (I think they are stainless?) that they use to join the side and end walls together. I wonder if there is any insulation in these corners?

Also, the term FRP is used for more than one type of product. The truck/semi trailer FRP has the plywood core and is 5/8" thick. Go to your local building supply and you will see FRP which is a 4' X 8' panel that is all plastic about 1/8" thick and has a pebble like finish on one side. I have seen it used on the inside of reefer trucks and was called Glassteck or something close to that. The truck body builder bought it in rolls that were at least 100 feet or more long and 8 feet tall. That way they could line the full length side or roof of a reefer semi in one piece. The size you find at the building supply is often used to line the walls of commercial bathrooms. I have seen in the bathroom of the grocery store and I believe that it was also in the bathrom at a Home Depot.

08-27-2003, 06:28 PM

drfan I just looked at the post again and realized that we are not very far from each other. I live on the west side of the Eizenhower Tunnel near the south east corner of Lake Dillon. Just heard the weather forcast on the news and with the cold front coming in we might get some snow tomorrow night or Friday night up here above 10,000 feet.

I would enjoy talking to you if we can figure out how to get together.

DrFun · 08-28-2003, 01:07 PM

cm: I sent you an invitation for a Private Topic so we can continue our discussion without disrupting the main forum.

Click on 'My Space' at the top of a forum topic and select 'Private Topics'.

"Talk" to you there...

Regards,
Alan

Junk Man · 08-28-2003, 01:48 PM

CM,

The FRP that is sold at Home Depot type stores is fiberglass reinforced plastic, and is also used in many restraunt applications (I know, I just hung about 60 sheets of it in the last couple of weeks).

It will also make a nice shower stall. I made one in the last bus I converted, just bought a shower base, and finished the rest in FRP.

The fiberglass reinforced plywood comes in different thicknesses, 5/8" being the standard for freight trailers I think, but for smaller boxes, I think they told me that you could use 1/2".

I have a number for a FRP manufacturer somewhere around here, if you want, I will try to find it. I takled to them a while back when I was thinking about making my own box out of FRP. I think they were in Ohio or Illinois. The one thing I couldn't find was a source for the aluminum extrusions to put the box together with, although I am sure there are many places out there that carry them, I wasn't able to find one.

Jeff in South Dakota
1995 Ford F-250 4X4 PSD
1992 Skamper Slide in camper
1984 Holiday Rambler 5er
1979 Mercedes Benz Unimog

stickdog · 09-06-2003, 03:09 PM

Jeff, here's a link to Aluminum Extrudes Council they have a members directory. I'm sure you can find your way from there.

stickdog

cjc · 01-18-2004, 10:54 PM

After visiting all the factories that are mentioned in this topic, this is the scoop on their exterior wall structure. Showhauler uses a steel cage and skins it with .063 sheet aluminum that's bonded to the steel with a super sticky double back tape. Renegade uses FRP (a 3/4 inch plywood sandwich with fiberglass cloth that's saturated in resin and a thin layer of gelcoat and covers both sides of the plywood sheet). There is no metal structure except the corner reinforcement. Essentially, it's a plywood box. Scary thought in a rollover situation isn't it? Haulmark uses an aluminum frame that's skinned with 1/4 inch luan plywood that has fiberglass mat saturated with resin and covered in a thin layer of gelcoat bonded to the plywood on one side of the wood. The skin is attached to the aluminum frame with an adhesive. This process is the one that's used on the majority of conventionally built motorhomes because it's pretty and doesn't have any seams as long as it's done correctly. Otherwise, you get a visible oilcanning effect and see all the aluminum framing. Aluminum framing is more expensive and lighter than steel, but obviously weaker and has to be engineered correctly and work in conjuction with the thin luan skin for strength. When choosing a truck converter there are other considerations that must be made in addition to which exterior wall system is the best. Good luck.

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