Truck Cap Aerodynamics: Wedge vs Standard

calicamper

Expedition Leader
The Oregon back roads guy actually did a mod that totally changed his cap in a great way. 1/2 the rear full barn door he made fixed with a bump out to give him extra bunk length that also would help structurally for the twisting challenge
 

olshaggy

Member
You can make it cheap, custom, flexible, strong, light and insulated. Since you want insulation, it seems like the way to go... to make it part of the structure. And since you are asking I'm guessing you have a garage and a few tools? It's a pretty simple project. You could still do barn doors I think (or any full size door), but if you go all the way from top to floor with any door it increases the amount of relative motion when twisting happens
You're making a strong case for the DIY shell. I do have access to a garage with plenty of tools and some family members with far more experience using them than I've had. Is the Build - Fiberglass & Foam Truck Camper thread the best one on the topic here? Any other suggested resources?

The Oregon back roads guy actually did a mod that totally changed his cap in a great way. 1/2 the rear full barn door he made fixed with a bump out to give him extra bunk length that also would help structurally for the twisting challenge
Can you point me to a link for that build?
 

rruff

Explorer
Is the Build - Fiberglass & Foam Truck Camper thread the best one on the topic here? Any other suggested resources?

No... I wouldn't suggest that... as the method is too close to what I'm doing now, and I hate it! Although you could. The worst aspect is sanding the fricken FG and getting the dust everywhere. Yours will be light and small though, so you can probably do that outside...? That would help a lot. My garage is coated with it.

I was thinking of using 2.7mm luan plywood, and a core of 1/2" XPS and wood slats (for hard points and because I don't trust the XPS). That's the cheap way (and what I've done before)... except that I couldn't find the plywood anywhere. If you had to buy marine ply, that's going to cost over $1000 for 10 sheets shipped; maybe $750 if you can get it locally. And if you are spending that sort of money, springing for PVC foam (bought mine from Carbon Core) would make sense, and even doing hand layup of FG.

I should be able to give you pointers on either.

Are you planning to to have vertical sides, or follow the slant of the cab sides? How will you insulate the bed?
 

olshaggy

Member
Are you planning to to have vertical sides, or follow the slant of the cab sides? How will you insulate the bed?
Need to give those questions (and lots of others) some thought. Just bought my truck on Friday, and hadn't really considered building a cap myself until you brought up the concerns about DCUs holding up under all that flex. Guess my next step is going to be digging into more research on DIY builds.
 

rruff

Explorer
This is something I put together awhile back that might give you some ideas. I would definitely not go thicker than 1" on the core. Check towards the bottom, there are two examples with XPS+wood cores and different hand-laid FG skins. The 1" with a change to a little thicker outer layer would probably be a a solid choice.

The finish will end up sort of lumpy; you'll be able to see where the wood slats are for instance. I was surprised how obvious a 0.5mm discontinuity is! "Painting" it with some texture will help, but it's still going to look homemade... unless you spend a crazy amount of time filling and sanding.

I doubt you'll find builds online like this... I haven't. I made a couple large panels with XPS+wood core before I changed my mind and went with PVC core and no wood.

If you don't like the wood, you can use pultruded fiberglass square tubing. It's very pricey though: https://www.usplastic.com/catalog/item.aspx?itemid=23192

Panel_Detail.jpg
 
Need to give those questions (and lots of others) some thought. Just bought my truck on Friday, and hadn't really considered building a cap myself until you brought up the concerns about DCUs holding up under all that flex. Guess my next step is going to be digging into more research on DIY builds.
With my DCU I have had no issues with it holding up to flex so far I have had it since 2017 . So far I’ve spent around 125 nites in it and it’s been on my truck for about 100000 km. (2300 km of gravel roads one one trip )
If I was to do it again I would the wedge style and have it start about 6 inches above cab height so the slope would start at rack height as shown.


5ABF972B-97F0-4F54-A069-B65F57F41247.jpeg
9AC96B6C-4252-42DF-B9FC-66D759BD39B8.jpeg
 

olshaggy

Member
This is something I put together awhile back that might give you some ideas.
Wow, this gives me a lot to dig into. Thanks!

With my DCU I have had no issues with it holding up to flex so far I have had it since 2017 . So far I’ve spent around 125 nites in it and it’s been on my truck for about 100000 km. (2300 km of gravel roads one one trip )
Oh that's good to know Canadian Joe, especially given that you've got barn doors on yours. Occurs to me now that one quick way to test this is just to get one rear wheel up a foot or two higher than the other and take a look at how, if at all, the shell appears to be deforming. Got any photos from the back on uneven surfaces like that?
 

simple

Adventurer
It would be interesting to build an inexpensive plywood test unit, collect some data and then cut it down to form the wedge shape and see what the difference is.
 

olshaggy

Member
I started this thread off thinking I'd be choosing between a wedge and a rectangular box and ended up discovering there was another option: the radius front that @Canadian Joe is running (even though he said he'd rather have a wedge!) After a lot of discussions with dealers all over the country (and ruling out the idea of building a cap from scratch myself), I finally put down a deposit on a DCU a couple weeks ago through Suburban Caps just outside of NYC (where I'm still living for another month or two). I went with them not only because of the geographic convenience, but also because they came highly recommended by Chris at Suburban Toppers out in Colorado, which is the nation's largest ARE dealer. Even though I told him up front that I was on the east coast, Chris was a big help, recommending several options I wouldn't have known about otherwise. I told him I wanted this truck to be able to handle some light /moderate off-roading, and he assured me that he's successfully worked on a number of orders for search and rescue teams, surveyors, and other folks who expect their trucks to handle fairly rugged conditions.

There's also a family connection between the two shops, but Scott has been in the business in NY for four decades and he really knows his stuff too. While I'd often prefer to give my business to a smaller outfit, bigger dealers have a number of advantages, including more experience with custom orders, and much quicker turnaround times. I was quoted anywhere from 14 to 20 weeks by most dealers I spoke with, but the largest ones had estimates of 5-7 weeks. My cap should be ready by the end of this month. Here's what I ordered:

  • 36" high DCU with straight (vertical) side walls and radius (rounded) front
  • Double full back doors with windows
  • Vented Windoors on both sides
  • Radius three panel sliding front window
  • 4 extra side wall gussets
  • Roof tracks (to mount a Yakima rack)
  • Backup camera with wiring harness
TOTAL (before tax): $4375

The cap is going on a 4WD 2016 regular cab long bed that I expect to be living out of for most of the year. As a reminder, I'm a little over 6'2", so the 36" height was important for me to be able to comfortably sit upright after factoring in room for flooring and insulation. While I originally had my sights set on a wedge to make the cap more aerodynamic, when I learned about the option for a radius front, I decided it was better for my purposes because a) it'll have almost a full 8' of flat roof length available for the rack, solar, and vent fan, b) the vertical side walls will make building out the interior easier and give me a little more room (at the cost of a little more drag), and c) I was told the whole structure will be a little sturdier than a wedge would be. I'm also planning to install a set of Total Chaos Bed Stiffeners to protect the rear doors and the cap more broadly from the twist and flex of the bed on uneven terrain.

In addition to Suburban Toppers (Colorado) and Suburban Caps (New York), I also got knowledgeable, helpful guidance from Dallas at Louisville Toppers (Kentucky), who knows Chris too. Thanks to those of you here who shared your insights in recent months. I'll be sure to update ya'll once the cap gets installed. I'd like to get a thread going where those of us running aluminum commercial truck caps can share build ideas. May either start a new one or try to revive Anyone out there running an Aluminum Contractor Topper?
 
I started this thread off thinking I'd be choosing between a wedge and a rectangular box and ended up discovering there was another option: the radius front that @Canadian Joe is running (even though he said he'd rather have a wedge!) After a lot of discussions with dealers all over the country (and ruling out the idea of building a cap from scratch myself), I finally put down a deposit on a DCU a couple weeks ago through Suburban Caps just outside of NYC (where I'm still living for another month or two). I went with them not only because of the geographic convenience, but also because they came highly recommended by Chris at Suburban Toppers out in Colorado, which is the nation's largest ARE dealer. Even though I told him up front that I was on the east coast, Chris was a big help, recommending several options I wouldn't have known about otherwise. I told him I wanted this truck to be able to handle some light /moderate off-roading, and he assured me that he's successfully worked on a number of orders for search and rescue teams, surveyors, and other folks who expect their trucks to handle fairly rugged conditions.

There's also a family connection between the two shops, but Scott has been in the business in NY for four decades and he really knows his stuff too. While I'd often prefer to give my business to a smaller outfit, bigger dealers have a number of advantages, including more experience with custom orders, and much quicker turnaround times. I was quoted anywhere from 14 to 20 weeks by most dealers I spoke with, but the largest ones had estimates of 5-7 weeks. My cap should be ready by the end of this month. Here's what I ordered:

  • 36" high DCU with straight (vertical) side walls and radius (rounded) front
  • Double full back doors with windows
  • Vented Windoors on both sides
  • Radius three panel sliding front window
  • 4 extra side wall gussets
  • Roof tracks (to mount a Yakima rack)
  • Backup camera with wiring harness
TOTAL (before tax): $4375

The cap is going on a 4WD 2016 regular cab long bed that I expect to be living out of for most of the year. As a reminder, I'm a little over 6'2", so the 36" height was important for me to be able to comfortably sit upright after factoring in room for flooring and insulation. While I originally had my sights set on a wedge to make the cap more aerodynamic, when I learned about the option for a radius front, I decided it was better for my purposes because a) it'll have almost a full 8' of flat roof length available for the rack, solar, and vent fan, b) the vertical side walls will make building out the interior easier and give me a little more room (at the cost of a little more drag), and c) I was told the whole structure will be a little sturdier than a wedge would be. I'm also planning to install a set of Total Chaos Bed Stiffeners to protect the rear doors and the cap more broadly from the twist and flex of the bed on uneven terrain.

In addition to Suburban Toppers (Colorado) and Suburban Caps (New York), I also got knowledgeable, helpful guidance from Dallas at Louisville Toppers (Kentucky), who knows Chris too. Thanks to those of you here who shared your insights in recent months. I'll be sure to update ya'll once the cap gets installed. I'd like to get a thread going where those of us running aluminum commercial truck caps can share build ideas. May either start a new one or try to revive Anyone out there running an Aluminum Contractor Topper?
It will be interesting to see how you build out your interior !
You have a lot more space then I do to work with.
 

SpaceJamHikes

New member
With my DCU I have had no issues with it holding up to flex so far I have had it since 2017 . So far I’ve spent around 125 nites in it and it’s been on my truck for about 100000 km. (2300 km of gravel roads one one trip )
If I was to do it again I would the wedge style and have it start about 6 inches above cab height so the slope would start at rack height as shown.


View attachment 754121
View attachment 754126
What DCU is this? I can't find vertical walled ones anywhere. Thanks!
 
What DCU is this? I can't find vertical walled ones anywhere. Thanks!


Here the info from what I ordered ,they do Not make it easy :( but they appear to still available,

This is the link to the DCU pages

https://www.4are.com/product/brochures/ARE_Commercial_Products.pdf

If you go to page 4 you will see
Build Your Perfect Commercial Aluminum Cap
I will list what mine is
1 - DCU (035)
2 - 29 inch
3 - A- colour matched B - standard ( no interior skin )as I want to insulate with 1 inch styrofoam. Did not get a roof vent but am going to add a 12 volt fan vent at some point.
4 - I choose Double Full with Windows , this gives doors that are the same width as the wheel wells when open.
5 - I got the Clear Mitered Sliding window for optimum ventilation. I took the latch off the exterior and put on the interior so it can open from inside then put a screen on exterior.
6 - I don't think this was available when I got mine
7. - I got the radius sliders as they come with screens
8 - got no toolboxes or shelves
9- I got the ladder rack with the centre support and third leg
10- I did my own lighting
11- I did not get a camera but still my add one
12- did not get
To the right of # 11 on page 10 you will see a list called Commercial Aluminum Options List and 7 rows down you will see Radius Front/90 degree side walls on 29'' and 36 '' only ,that is what mine is and it give more head room so I can sit up straight
The web site much better now,hope this helps ,if you that this to any dealer it should be fairly easy
Another important detail, you will see mine sliding bins are not full width, there is a space in the middle ,this allows a space to climb into
and sit with space for my feet .
Hope this helps ,
Joe
 

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