Gap filler short cap for pickup + 5th wheel RV

[KamperBob]

In respect for http://ecomodder.com/forum/showthrea...-cab-3996.html I felt a separate thread was appropriate for this topic.

Originally Posted by kach22i

I saw in another forum where the leading edge was not flush/sealed and the owner was not happy with the results. Everyone in that forum pointed out the flaw.

Could you just leave the glass lid open and have that act as a RV deflector?

Slide Hitch/Short Cap

Indeed! Originally the hatch doubled as a deflector.


Albeit limited functionality. The gas struts held it up fully sitting still. On the open highway the wind had it pushed down to a pretty low angle. While putzing along back roads at lower speeds it stayed angled up enough to deflect bugs noticeably. Rigid supports could have been interesting. (shrug)

I should mention that while aerodynamics is important it is not always top priority. For me safety and usability of the vehicle come first. Then I aim to get high bang for the buck. If starting from scratch building a truck bed and/or trailer I would no doubt end up with something very different.

That background may help explain the method to my madness. Here's a bit of relevant geometry that seems worth mentioning. My truck bed is 6.5' long with the trailer hitch pivot point in the middle. The bed area breaks down roughly into thirds. The short cap closes the front 2' of the box. The leading edge of the trailer overhangs the rear third of the bed.

Normally with this rig the gap between truck cab and trailer nose would be about 4' so the short cap cuts that in half. The middle third is mechanically open for articulation but that gap is partially filled with a generator cantilevered off the nose of the trailer over the hitch point so it more or less pivots on itself as the trailer turns. As such the gap between truck and trailer is now down to inches.

My motivation for a cab deflector on top of the short cap is manifold. I'd like to blow more bugs around the trailer. When driving in rain I'd like less spray to hit the generator directly. It may not do a lot of good aero wise but it could do a little and should not do any harm.

In keeping with RVer's Rule #1 -- that every item serves at least two purposes -- my cab deflector project has at least two phases. Initially, I plan to just install a fiberglass deflector like this. Eventually, replace the fiberglass sheet with a solar panel.

[jime57]

Hucho, 4th edition, figure 4.104, showed that the deflector lowered the combination from .53 to .45, a major improvement IMO.

[kach22i]

Originally Posted by KamperBob

Albeit limited functionality. The gas struts held it up fully sitting still. On the open highway the wind had it pushed down to a pretty low angle. While putzing along back roads at lower speeds it stayed angled up enough to deflect bugs noticeably. Rigid supports could have been interesting. (shrug)

I experienced something similar when experimenting with a piano hinged rear spoiler. I thought at the time that there must be some way to calculate the down force generated at a certain speed based on how far down the spoiler angle changed. I never really figured it out, and ended up with a seat of the pants guess at what it was doing.

I agree with you about safety first, half the things I've done to my pick-up truck helped the aerodynamics and lowered drag. The other half increased down-force and drag. In the end it's a wash mpg wise, but it is also a safer ride in bad weather.

[Snowman9000]

KamperBob,

With such a light fiver, could the Tundra handle it with the hitch ball set in the rear position all the time? If so, maybe a bed cover of sorts could be fitted which still allows for pivoting of the gooseneck?

[KamperBob]

Originally Posted by Snowman9000

KamperBob,

With such a light fiver, could the Tundra handle it with the hitch ball set in the rear position all the time? If so, maybe a bed cover of sorts could be fitted which still allows for pivoting of the gooseneck?

I think so, snowman. But it would add not reduce gap. Not just between the cab and upper shell, but also between the tailgate and lower shell. Some stability from the elegant tow geometry might be sacrificed as well.

[skyking]

Bob, if your travels bring you to the Seattle area you are welcome to stop by and use the shop.

[KamperBob]

Originally Posted by skyking

Bob, if your travels bring you to the Seattle area you are welcome to stop by and use the shop.

Wow - I really appreciate that offer. Pacific northwest is on my list eventually. I love meeting other members from the this group. A place to get some mods done on the road would be icing on the cake.

[KamperBob]

I've been away from this forum for a bit (life - shrug). Meanwhile, I used to have a website with pix hosted there and linked to forum posts like this. That website since went bye bye so those pix disappeared. (Note to self: unlink signature too.) Sorry 'bout that.

My rig has changed. My 19' Scamp fifth wheel has been parked while traveling instead in a 25' class A (brick) motorhome with my new companion. I picked up a 13' Scamp for short excursions. She hauls that behind her MH while I trailer her AWD car behind my truck. Very recently I built my own car hauler to improve upon the UHaul situation we had been using. Here's a recent pic of our entourage. I thought some members may appreciate a few things I've done to optimize what I had to work with.

[skyking]

Good to hear from you Bob. Offer still stands. Life keeps me busy elsewhere as well. Currently remodeling my new-to-me 5th wheel.

[KamperBob]

Skyking, Pac-NW still on my radar just no eminent plans. Shop offer still very much appreciated! The planets will align - eventually. Meanwhile, are you documenting your 5er build? If so, please share a link.

All the best,
Bob