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Building a truck bed shell
- Thread starter Doug Briggs
- Start date
I’m going to leave out a few details but, years ago I met the owner of a company that told me how they tested for wind loading. Product (about 30’ x 40’) strapped to the top of a F250 and drive at close to a 100mph on the Bonneville Salt Flats. Imay be crazy but 
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Is that rocket surgeon actually serious? I couldn't bring myself to watch the whole thing. Does he believe he created a working perpetual motion machine or does he explain in the end that the idea is just dumb?
As serious as a high school science experiment; he makes several observations that he will use later in the 7000W turbine video, including lift proportionality to angle of attack, minimum drag angles, relative wind, how much to change pitch with radius, and, most importantly, he begins looking at Betz' limit (16/27) to how much energy he can extract. Given all that, and youtube monetization, yeh, dead serious.
He says that the wind turbine he is using is cannot handle anything but driving at low speeds.
I sub to a RVer Youtuber who has experimented with setting up a wind turbine when camped. His conclusion: The size of turbine needed to produce a decent amount of electricity would be so large as to not be practical.
Is this guy available?
Florida man seen on video riding on hood of truck down busy highway
A Florida man went for a nine-mile ride down a busy highway but in a highly unusual fashion: on the hood of a tractor-trailer. The South Florida Sun Sentinel reported that the unidentified man climbed onto the hood Saturday after stopping his vehicle along Florida’s Turnpike and walking out onto...www.winknews.com
Another story that begins "A Florida man... " lol
Same conclusion - and the reason for the truck is that he almost burned out his lathe motor before he got half the rated power out of that itsy bitsy turbine. The cheap little turbines don't even begin to live up to manufacturer claims.
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Thread Starter
TS
As the season for fiberglass work approaches I'm searching for ways of building the fairing for my shell. I'm going to build a mold then lay fiberglass over it. The side that is in contact with the mold will be the inside of the fairing and I'll have to fair the outside of the fairing to make it look nice.
The mold will be built on a wooden frame that is then covered in steel lath which in turn is covered with something approximating tooling dough. Epoxy tooling dough is very expensive for the surface area (10 - 15 square feet) I require so I was contemplating using plaster of paris as it is much more affordable. It can be sanded to make a pretty smooth surface to lay the fiberglass up on and a release wax applied to it prior to glassing. After the epoxy has cured from fiberglassing and I have faired the fiberglass, I'll remove the mold by pulling out the lath and plaster, destroying the mold in the process.
My reasoning for doing this is that I only need one part, I want to keep costs down and a 'perfect' finish isn't essential; I'll be content with a well faired appearance which I think I can achieve by the method I have presented.
None of this process is locked down so I encourage comments or suggestions on how to achieve the creation of the fairing with low costs and reasonable results.
The mold will be built on a wooden frame that is then covered in steel lath which in turn is covered with something approximating tooling dough. Epoxy tooling dough is very expensive for the surface area (10 - 15 square feet) I require so I was contemplating using plaster of paris as it is much more affordable. It can be sanded to make a pretty smooth surface to lay the fiberglass up on and a release wax applied to it prior to glassing. After the epoxy has cured from fiberglassing and I have faired the fiberglass, I'll remove the mold by pulling out the lath and plaster, destroying the mold in the process.
My reasoning for doing this is that I only need one part, I want to keep costs down and a 'perfect' finish isn't essential; I'll be content with a well faired appearance which I think I can achieve by the method I have presented.
None of this process is locked down so I encourage comments or suggestions on how to achieve the creation of the fairing with low costs and reasonable results.
Might I suggest foam, carve it with a hot knife, plaster is a good idea, shellac it, wax it, lay the glass (carbon fibre) and vacuum it for best and lightest strength.
Faster, cheater, stronger.
Kevlar is so much better than fibreglass when it comes to canoes. How hard would it be to use that?
Both hard and expensive - and without a need for abrasion resistance or fire resistance it simply isn't justified.
S-glass is cheap, drapes well and wets out well by hand. Kevlar and most other aramids are more expensive, don't drape as nicely because most weaves don't have enough multi-directional stretch, and have lousy wet-out so the epoxy either flows off the fabric or through it, lifting the fabric off the mold. The fix for the epoxy problem is a) vacuum bag or b) face the Kevlar or Nomex with fiberglass
.So, since OP isn't going to vacuum bag, it would be a significant PITA for no substantive end benefit. Canoes and kayaks, ofc, need all the abrasion resistance they can possibly achieve and bagging is part of the process cost .
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Thread Starter
TS
As ski season (sort of) winds down, I've been returning to working on the shell.
My first task was to install a pair of bike mounts in the bed.
The stick on the right that is attached with a hinge will keep the back of the mount down. A steel angle at the forward end keeps the mount from flexing to prevent two bikes from wobbling (through flexing the wood) in opposite cycles and hitting each other. The angles of the mounts permit the bars to pass each other as well as to have the bikes nested and shifted to the right, making more room in the bed.
The rear wheel tie downs.
The old school quick release mounts with through axle adapters. I did this because I still have bikes with quick release and already had the through axle adapters from my old Yakima mounts.
The front of the mount system is attached with a plate from underneath. The wood that crosses over the top is tied down on the left as well as the right with the same type of plate underneath.
My next effort was to determine the airflow over the hood and cab. I plastered the hood and cab with telltales and drove around with a camera running video.
I added more telltales as I determined their need.
The flow over the windshield was as expected and it 'stuck' to the cab for a few inches. Then the turbulence from the front of the shell seemed to kick in and create a turbulent/dead area over the middle of the cab in front of the shell. Some flow did manage to continue under the leading part of the shell while it was quite turbulent along the top, leading edge of the shell.
I'm leaning towards building a wedge shaped fairing which continues the angle of the windshield to direct the flow over the front of the shell and taper it to match the roof line. It will cover the entire front of the shell. The leading edge of the fairing will have a gasket to allow it to contact the cab while also permitting slight shifting of the cab/shell interface. Similar, but certainly not identical to below.
An alternative is to build an elongated 'dome' that would be symmetrical. If I did this style, it would go edge to edge, unlike below.
The third possibility is to build the wedge without bringing it down to the cab.
I'm open to any thoughts you may have on this. I'm still waiting for warmer weather for glass work.
My first task was to install a pair of bike mounts in the bed.
The stick on the right that is attached with a hinge will keep the back of the mount down. A steel angle at the forward end keeps the mount from flexing to prevent two bikes from wobbling (through flexing the wood) in opposite cycles and hitting each other. The angles of the mounts permit the bars to pass each other as well as to have the bikes nested and shifted to the right, making more room in the bed.
The rear wheel tie downs.
The old school quick release mounts with through axle adapters. I did this because I still have bikes with quick release and already had the through axle adapters from my old Yakima mounts.
The front of the mount system is attached with a plate from underneath. The wood that crosses over the top is tied down on the left as well as the right with the same type of plate underneath.
My next effort was to determine the airflow over the hood and cab. I plastered the hood and cab with telltales and drove around with a camera running video.
I added more telltales as I determined their need.
The flow over the windshield was as expected and it 'stuck' to the cab for a few inches. Then the turbulence from the front of the shell seemed to kick in and create a turbulent/dead area over the middle of the cab in front of the shell. Some flow did manage to continue under the leading part of the shell while it was quite turbulent along the top, leading edge of the shell.
I'm leaning towards building a wedge shaped fairing which continues the angle of the windshield to direct the flow over the front of the shell and taper it to match the roof line. It will cover the entire front of the shell. The leading edge of the fairing will have a gasket to allow it to contact the cab while also permitting slight shifting of the cab/shell interface. Similar, but certainly not identical to below.
An alternative is to build an elongated 'dome' that would be symmetrical. If I did this style, it would go edge to edge, unlike below.
The third possibility is to build the wedge without bringing it down to the cab.
I'm open to any thoughts you may have on this. I'm still waiting for warmer weather for glass work.
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Thread Starter
TS
This is a prototype for the fairing. I'm going to forego a more sophisticated fiberglass construction and simply glass and paint the thin piece of plywood and attach it to a simple commercial fairing system to a rail (INNO roof rack system) on my truck's cab. The INNO fairing has feet to protect the cab and the plywood is bolted to it using the provided mounting hardware from INNO. The 'live' fairing will be as wide as the shell but overall will look the same.
On my trip to Gypsum and back today, I got 20 mpg, which is as good mileage as I've ever gotten. So the fairing is doing its job of aerodynamics. I had been getting 16 and 17 mpg without it. The fairing will also protect the front of the shell from debris, bugs and weather.
The black rectangles on the fairing are duct tape which holds the yarn I used for evaluating airflow.
The position in the video is different than in the images. I'm going to keep it like in the images.
On my trip to Gypsum and back today, I got 20 mpg, which is as good mileage as I've ever gotten. So the fairing is doing its job of aerodynamics. I had been getting 16 and 17 mpg without it. The fairing will also protect the front of the shell from debris, bugs and weather.
The black rectangles on the fairing are duct tape which holds the yarn I used for evaluating airflow.
The position in the video is different than in the images. I'm going to keep it like in the images.
Thread Starter
TS
@Doug Briggs do you realize your cap is now worth about 50k given lumber prices 
You might want to increase the theft insurance as they might steal your truck just to get the plywood.
You might want to increase the theft insurance as they might steal your truck just to get the plywood.
Well done.
In the forward position, the videos clearly show a giant vortex behind the fairing, not what you wanted at all. Counterproductive, really.
Thread Starter
TS
Thanks. I knew the first prototype was not ideal.
The forward position was 'decided' by the instructions for the mounting point provided by the rack manufacturer and the size of the piece of wood I had to prototype with. I'll also fabricate some metal triangles to support the upper part of the fairing.
I'll be adding the second bar, moving the forward bar forward a bit to accommodate the second bar and using a slightly larger sheet of plywood. I'll also add a bit to the trailing edge of the fairing that will allow a rounder transition from fairing to shell.
Fortunately, the plywood I'm using now for the fairing is 'scrap' and the wood I need for squaring/boxing in the back as mentioned elsewhere is all on hand. No trips to the yard for lumber for me.
I must say that the use of yarn and video was quite helpful as it illustrated clearly where the drag was.
Thread Starter
TS
I've considered natural as I'm using Luann as a first attempt at a production version. My choice of material is because I have it on hand. It is slightly warped but when it is bent I'm hoping that it will not be evident. Probably, though, it'll be gray to match the shell body. I don't have any more white and don't care to dish out for it when I don't need much. Also the natural Luann wouldn't match the natural accent around the roof edge.