5th wheel design

[skyking]

I am posting for some input on boat design forums. Here is a sketch of the moving part, the roof section. Some have suggested closed cell foam laminated with ply on both sides. I don't know how I'd build the 12" radius with that.


I was thinking plywood stations, and bend the roof ply over the large radius.
I'd pre-build the 12" radius section with 2 bending plys over a form with a vacuum bag. Trim it and install over the stations or ribs.

[aerohead]

On my first trailer I ripped Schedule-40 PVC pipe in half with a circular saw and used the inside surface as a mold to make wet layups of radius sections.
Triple waxed,and Polyvinyl Alcohol,and the parts came out with little prep work required before prime and topcoat.
A children's green ABS outdoor play slide might be about the right size for you.Sometimes you see them at yard sales and flea markets.

[skyking]

Originally Posted by aerohead

On my first trailer I ripped Schedule-40 PVC pipe in half with a circular saw and used the inside surface as a mold to make wet layups of radius sections.
Triple waxed,and Polyvinyl Alcohol,and the parts came out with little prep work required before prime and topcoat.
A children's green ABS outdoor play slide might be about the right size for you.Sometimes you see them at yard sales and flea markets.

Thanks Phil. I will use pipe for mine, only it will be an outside mold if I go that direction. This will be finished 'bright' like my truck if all goes well.

[skyking]

One of my local friends and the welder that helped me with all the truck frame and suspension mods is telling me i have to follow the template now. This guy is not an ecomodder, but he sees the beauty.
I will feel the pain
We can build the radius sections with either:
Strips of 2" foam faired with epoxy putty like this.
Bateau2.com - Technical support for builders

Or we can try layering a couple of 1" thick panels. I doubt we can bend the 2" that tight.

I did research the foam available. The standard is square edge, at 25 PSI and 1.5 lb/sq.ft. I can get it in many thicknesses.
There is high strength 40,60, and 100 PSI. It also has double the flexural strength.
It is typically used under concrete runways and road sections.
The 40 and 60 weigh in at 2.2 lb/sq.ft. and the 100 is 3.0 lb/.sq.ft.
I think I'll build a floor sandwich with light ply and the 60 or 100. it is incredibly strong, and all of it is rated at R5 per inch. The high strength is only available in 2" and 3" thickness.
The design has morphed again to utilize the space that is wasted behind the cab of the truck, and shortened by 4' at the back.

I'll build an aeroshell as proof of concept, to perfect the lamination, foam bending, and final layup techniques.
This plastic top sheet layup is very promising. I'll be trying that out shortly.
A new Technique for Epoxy-Glass

[skyking]

OK, calling fellow truck owners. I need the bed rail height numbers for your trucks.
I can get some online but if you could just take a tape to the highest point on your bed top I'd appreciate it, along with model and year. If you have a short box, give me the centerline of axle to back of cab as well.
I could make this trailer for my custom bed height, but if I wanted to make many of these I'd be better off if my prototype fit current pick truck beds.
Now I'm thinking I should make it to fit the 6'4" short bed trucks without a slider hitch!

I can do that by reducing the width up front a little more. Even if I taper it to 72" outside, it would still be bigger than a queen sized bed up there. With the proposed ~1200LB hitch weight it would be an easy half ton truck trailer.

My prices for Corning closed cell foam, from Allied Building supply:
all prices are 4' x8' sheets
25 PSI square edge(1.5lb/cu.ft):
1" 18.85
1.5" 28.15
2" 37.60
60 PSI Hi Load(2.2lb/cu.ft)
2" 76.00

100 PSI Hi Load(3.0lb/cu.ft.)
2" 82.25

Specs are here.
http://building.dow.com/na/en/produc.../rigidfoam.htm
I plan on getting a hi load 100 PSI sheet and making a floor sandwich with 3/8" marine ply on both sides.
I'd test it for flexural strength to see how far I can span with it.

[slowmover]

Truck in sig. (OEM tires at OEM spec pressure; empty fuel tank weight cancelled by bed topper)

8' Long Bed Height:

FF: 50"
RR: 52"

[KamperBob]

My 2002 Tundra 4WD tailgate is 52" high. I'm not positive but I believe late models have 54-56" tailgate. Sunday AM: great time to walk around dealer lots with a tape measure.

[orbywan]

Originally Posted by skyking

Here is the first sketch of the trailer.
It has a roof that pops up 18"~24". I have not finalized anything, so the heights are still 'soft'.
Interior height is 70" collapsed, 88"~94" raised.
It has adaptive suspension that can raise it up 6" for driveways, railroad crossings, etc. This allows for a low 6~8" ground clearance at highway speeds.
I have pages of floor plan in my head, but that does not affect aerodynamics.
It will be faired very closely to the tow vehicle with movable fairings. Tow vehicle height is 72", trailer is 90" as shown.
Trailer starts at 80" wide to match tow vehicle wake. That may be changed with advice from aerohead and others. It tapers to 96" but I would happily start out wider if I can be convinced the drag penalty could be minimized.
Radii will not be true radii, but constructed with ~1" slices of plywood to approximate one.
I've been conflicted about building it 102" wide. Wider = more drag, and several states have areas with 96" maximium widths. 102" would give me a little more room to plan with.

Skyking I just found your thread on your 5th wheel. Really interesting project. I've wondered several times watching people tow those things down the road what would happen if you 'Aero'd' one of those. As people have said about my RV project, it's a very 'target rich' subject for aero improvements.
Looks like you're off to a good start. Good luck!

[skyking]

Thanks for that. I have made some more design changes, will need to get sketching.
The forward area over the truck bed is the guest bedroom.
I plan on a king size bed aft of the axles with an 18"~24" slideout.

[slowmover]

Hey, skyking,

Thought of you when I was perusing the national for sale ads the other day. There is a 1989 AVION 5'er for sale in Fairview, AL:

$8,900

Have you ever done a comparison from the earlier, higher-quality build trailers to the "nameplate" version AVIONs of later years? Was wondering if the (potentially) lower ground clearance would make for fewer changes for an equal mpg increase; or if roof height was lower (obviously, I haven't checked published spec). Maybe you are aware of deficiencies -- or other -- that I am not. Thought maybe someone looking for an "aero" 5'er might benefit if you already knew (according to gogitating you've already done). This is a good "big trailer" by design (mated to the proper TV, a CTD!)



http://rjmarq.org/airstream190/image..._5th_wheel.jpg

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