Boardhead build thread

Airtime

Active member
Hi everyone—new member and new Sprinter owner. I’m starting a build thread for my new project. My new rig is a 2019 Sprinter 3500XD 170 4x4 high top DRW (pictures to follow). I’ve been soaking up a lot of info from this great forum, and I hope to contribute back as I go.

I’m a longtime windsurfer/skier/snowboarder, and I have had cargo vans (gear inside but roughing it) and class Bs (comfy inside but gear on the roof is a pain). My goal now is to have all my gear inside AND have class B comfort, for me and for my wife.

I also want to use it this summer, so it is clear this will be done in stages. I plan to get a temporary set up in place and usable this spring, and finalize full conversion plans to do next winter, while I use it. But it's a catch-22, I do want to mount solar and cut holes for vents and windows, so I'm trying to map out both short and long term plan before I do too much irreversible stuff.

So here’s my starting point, any and all feedback is welcome. You CAD experts please try not to laugh too hard at my simplistic drawings--they aren't perfect but should help get some ideas across :D:

Usage:
1) Columbia Gorge/Oregon Coast trips chasing the wind, carrying a lot of gear
2) traditional RV-ing, seeing the country
3) possible future winter trips skiing and snowboarding

Floorplan:
- Front swivel seats as main seating
- 2 person folding bench seat under window behind driver’s seat
- Platform bed in rear, 6’ long gear garage under the bed with one 8’ extended section
- Galley on passenger side, extending forward to 1/2 of slider door
- Toilet/shower in front of driver side wheel well, behind bench seat

Main floor -- a pretty conventional gear garage layout
Main floor plan.jpg

Gear garage -- I think this is pretty well baked, the 8' long sailboards sort of drive the layout.
Gear garage.jpg

Roof layout -- yes there are a lot of holes in the roof, still thinking about what I really want for light and ventilation. I am 6'2 and like the idea of a skylight in the shower--but also want good ventilation. Also like the idea of a skylight/hatch in the bed area vs. a dark cave.
Roof layout.jpg

Basement (undermount stuff) -- still thinking about gray & black size and locations.
Basement layout.jpg

I plan to implement in stages:

Stage 1: Temporary setup for summer 2020

Minimum:
- Interior: Cargo mat floor, no insulation or interior
- Gear: tie down on floor in rear
- Bed: 36” high temporary bed platform in rear using Harbor Freight ATV ramps and plywood
- Galley: Isotherm 115 fridge (or a cooler), portable propane stove, plastic tub for a sink
- Toilet: Thetford Curve Porta-Potti (4g water, 5.5g black tank, battery powered flush)
- Shower: Eccotemp L5 outdoor shower
- Fresh water: Temporary 42 gallon stock water tank, 12V pump for shower and galley.
- Electrical: 200 Ah Li batteries charged from alternator via Kisae DMT1250

Bonus:
- 320W solar (2X Renogy 160W panels 25.9" x 51.2" direct mounted to roof rails)
- Maxxair roof vent and windows installed

Stage 2: 3 season full conversion, complete next winter (may stop here)
- Insulation, interior, cabinets, windows
- Galley
- Indoor shower/wetsuit closet
- Rixen Espar D5 hydronic system for air and water heat
- Permanent plumbing including tanks
- Permanent electrical including solar/alternator/shore charging and control panel

Stage 3: Full 4 season off-grid (may never do this, but want to keep options open)
- Hydronic heating loop for undermount tanks and plumbing
- Insulation and heaters for undermount battery banks
- Higher capacity solar--add 3rd panel for 480W total
- Possibly second alternator--since solar in Canada in January could be pretty marginal
- Possibly hydronic in-floor heat added to Espar D5 system

That's it for now...
 

Airtime

Active member
Thanks for the reply! I'll add a weight budget to my planning. What is a reasonable level of weight imbalance? I do have a 3500XD which has dual rear wheels and 11k GVW.

I'd be surprised if the imbalance is over about 500 lbs--would that be an issue in a vehicle this size? Large water tank on left is the biggest imbalance, up to 500 extra lbs on left if I do go with 60 gallons. Maybe I could distribute that differently.

Black tank is in middle, gray tanks roughly balance, batteries balance. Hydronic tank and heat exchangers are on the right. I'll have to add it up.

You may want to look at your weight distribution. Lots of weight on the left side can cause a lean.
 

Midwestdrifter

Engineer In Residence
You can do the CG shift calculations (moment arm/distance times weight). I would strive to have the total weight imblance on the rear axle less than 10%. So 45/55. The farther the weight is from the centerline the more it affects the weight distribution.

I don't think you will have a major problem, but you need to pay attention.

Same goes for weight really far back. Not likely to be an issue, but worth consideration.
 

Airtime

Active member
Thanks, I've been looking through the BEG (312 pages!) and all I have found so far that is relevant is section 9.1 Center of Gravity. And that only speaks to the x axis (front to back) and z axis (vertical). No mention of the y axis, which I assume must be the left to right axis we are speaking of here. If you could point me at the relevant section for left to right loading, I'd greatly appreciate it :thinking:
 

Airtime

Active member
I found something relevant to the y axis (side to side) weight distribution in 4.1.2 of the BEG: "The maximum wheel load (1/2 the axle load) of the laden vehicle may only be exceeded by 4%."

Note that this doesn't provide weight distribution guidelines at lighter loadings--it is just a maximum weight limit per wheel.
 

vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
I’m fighting some weight imbalance issues in my rig... currently causing leaning on right hand turns AND I have too much weight behind the rear axle causing outer front tire wear and shaking while driving. My build is somewhat set unfortunately so I’m considering stiffer leaf springs in the rear, but I wish I would have given all this more consideration back when I was in the design phase of my build..
 

MTGJR1

Active member
As a retired mechanical engineer the f/r and l/r balance is important to me in my design. I'm on the road right now and don't have my Sprinter folder with me so can't offer much help. Will hopefully be able to add to the conversation next week. I have been interviewing upfitters the last few months and it amazes me how unimportant overall weight and distribution of loads is to most of them.
 
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Airtime

Active member
Thanks for the replies!

vanski: is your box van build on a 2500 or 3500 chassis? Single or dual rear wheels? Have you weighed it? What would you change on weight distribution if you were starting fresh?

MTGJR1: I see you have a new 170 4x4, same chassis questions? Would be good to compare notes as you proceed.

I ask because I intentionally bought the 3500XD dual rear wheel so that I wouldn't have to worry so much about weight and stability. It is about 6k empty, 11k gross, I have 5k lbs available for conversion and payload. And I bought a 170 so I can fit all my gear inside down low, instead of up on top of the roof, and still have some room to live.

My last rig (10-20 years ago) was a 1995 Airstream B190, a class B built on a Ford E-series van with a fiberglass top. It had nice thick solid oak cabinets etc. and other heavy stuff. It probably would still have driven OK except that I piled four sailboards and associated gear on top of the roof and drove at unreasonable speeds. It served me well, as long as I never ever ever EVER went into a turn near the posted caution speeds.

You can imagine that it did not corner very well. I did find that if I ran with a 10-15 lb difference in tire pressure (i.e. 60 lbs in front and 70 lbs in back) it would at least track better. I ran across a deserted weigh station somewhere in SE Washington one time and weighed it at 9800 lbs. Rated GVWR was 9300 lbs so I was 500 lbs over, and much of that on the roof so no surprise it was a handful.

Back to the Sprinter--still looking for some more quantitative information on weight distribution for planning purposes. Specifically for the 3500XD. I'm guessing my conversion will end up well more than 1000 lbs under the 11,030 lb GVWR. I plan to go lighter on materials etc., although I do plan to allow for larger tanks for more off-grid capability.

I do plan to have a monster spreadsheet including a tab for weight/CG, I am after all an engineer at heart. I'll post on that as I go. Any pointers on references or useful threads in this area would be great, I've been searching but not found too much yet. What I have so far is the BEG limits in section 4.1, which are really upper bound limits.

For front to back:
4.1.1 Steerability
In all load states, the front axle load must represent at least the following proportion of the gross permissible vehicle mass:
General Up to 4.2 t > 35% of gross vehicle mass
Up to 5 t > 30% of gross vehicle mass

For side to side:
4.1.2 Maximum permissible position of the center of gravity
Y-axis: The maximum wheel load (1/2 the axle load) of the laden vehicle may only be exceeded by 4%.

For CG height:
The overall center of gravity height must not exceed 1300 mm/51.2 in.

Irrespective of this, the tendency of vehicles to tip over
becomes more likely as the center of gravity height increases.
The ESP® in the new Sprinter is optimized to
reduce the vehicle’s tendency to tip over at overall center
of gravity heights up to approx. 1000 mm/39.4 in.
In this context, it must always be ensured that the vehicles
are fitted with the recommended suspension and
ESP® variants according to MY20 Dealer Ordering
Guide (DOG). This applies in particular to vehicles with an
overall center of gravity higher than 1000 mm/39.4 in.
 
Last edited:

vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
Thanks for the replies!

vanski: is your box van build on a 2500 or 3500 chassis? Single or dual rear wheels? Have you weighed it? What would you change on weight distribution if you were starting fresh?
3500, dually.

In the far rear drivers (left) side corner I have a large Adrain Steel industrial style work cabinet which just by itself probably weighs 200 lbs and then I have it loaded with many heavier tools, dishes, chains saw, etc, etc. directly across from it there is a door well which in the winter gets loaded up with all our ski equipment, 5 gallon diesel jug, a pretty heavy tool bag, some other stuff. In the summer I usually have bikes there. When initially trying to diagnose the issue I thought I had worn out front leaf springs but after consulting with someone who sees a lot of sprinter work trucks he quickly led me down the path of having too much weight behind the rear axle causing the front end to float a bit. It also doesn’t help that my box is mounted much higher than most regular van bodies so there’s more of a levering affect.

I may remove the cabinet and put some different out side type of weather guard type cabinets lower under the box. But, I still need to put proportionate weight on the other side but this is difficult due having to large stairwells on the right side which make mounting storage difficult inside and out. It doesn’t help that on the driver side a bit further up I also have my battery bank, interior wood cabinet build, water, and of course fuel tank...

As stated above I’m hoping there may be a way to stiffen leaf springs in the rear to even things out but of course this will cause some varying spring load issues while driving.. actually interested in folk’s opinion of what I might be able to do along those lines as I’m not all that adept in these areas...
 

Midwestdrifter

Engineer In Residence
The best option is to rework the interior to move some weight around. Water tanks, closing off part of a door, etc. You can add airbags, or sometimes extra spring leafs. That can cause odd handing if you have too much of a difference though. 3500s are ever more prone to the lean, because the springs are farther inboard. Cab/Chassis are about the same as the 2500s, as they typically have the same spring width due to the wider rear axle.
 
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Airtime

Active member
Vanski - yes, it sounds like front end float could be an issue. What wheelbase? And how much overhang aft of the rear axle? Shorter wheelbase, and higher rear overhang, will be even more sensitive to load behind rear axle since the heavy engine/tranny up front has less of a lever arm to balance weight in the rear.

I don't have the 2005 data, but I'm doing some weight & balance calculations on the 2019. What I've found on my 3500 XD 170 4x4 is that in order to have 30% of the weight on the front axle when fully loaded, the payload--excluding driver/passenger and fuel--must have a CG that is no more than 6" behind the rear axle. I ran the same calcs on a 144 WB and it would need payload CG at or forward of the rear axle. I'll post it when I clean it up a bit.

But I'm guessing yours will have similar results. If you add up the weight * moment arm (referenced to rear axle) of your box + all contents, it should have a CG forward of the rear axle. Exactly how much forward depends on specs for your 2005. Otherwise, too little weight on the front axle. All that weight at the back, on the overhang lever arm, needs to be balanced out somehow.

In the short term, have you tried running lower tire pressure in front than in rear? My old Airstream B190 was overloaded to the rear, don't know exact numbers. But I found that if I kept 70 lbs in both front and rear, steering would wander. Putting 70 in rear and 55-60 in front improved steering greatly--I assume due to balancing out the loaded tire flex since rear tires probably had at least 2X the load of front tires. Although with your dually, it may not help so much since you have 2X the tires on the rear axle.

3500, dually.

In the far rear drivers (left) side corner I have a large Adrain Steel industrial style work cabinet which just by itself probably weighs 200 lbs and then I have it loaded with many heavier tools, dishes, chains saw, etc, etc. directly across from it there is a door well which in the winter gets loaded up with all our ski equipment, 5 gallon diesel jug, a pretty heavy tool bag, some other stuff. In the summer I usually have bikes there. When initially trying to diagnose the issue I thought I had worn out front leaf springs but after consulting with someone who sees a lot of sprinter work trucks he quickly led me down the path of having too much weight behind the rear axle causing the front end to float a bit. It also doesn’t help that my box is mounted much higher than most regular van bodies so there’s more of a levering affect.

I may remove the cabinet and put some different out side type of weather guard type cabinets lower under the box. But, I still need to put proportionate weight on the other side but this is difficult due having to large stairwells on the right side which make mounting storage difficult inside and out. It doesn’t help that on the driver side a bit further up I also have my battery bank, interior wood cabinet build, water, and of course fuel tank...

As stated above I’m hoping there may be a way to stiffen leaf springs in the rear to even things out but of course this will cause some varying spring load issues while driving.. actually interested in folk’s opinion of what I might be able to do along those lines as I’m not all that adept in these areas...
 

Airtime

Active member
That is a very good point, I had not thought about the narrower rear leaf spring mounting. My thinking was that the dual wheels on the 3500 would help, since there will be less rear tire flex.

Wonder what is best overall? It would be interesting to drive fully loaded single and dual rear wheel versions of the 3500 to see. Although a moot point for me now.

3500s are ever more prone to the lean, because the springs are farther inboard.
 

Coolmaxt

Member
I am looking forward to seeing this build! I have a 170 3500xd 4x4 project as well. I have a couple questions- why not use AGM instead of lithium since they are under body? AGM would be better out in the elements wouldnt they? It looks like cost is no issue hence the lithium- but maybe a row of 4 AGM batteries on the passenger side would offset the big water tank on the drivers side. 4 full river batteries would give you 280lbs that plus a fridge (100 pounds when full) put you at 380lbs on the passenger side vs your 500lbs on the drivers side.
 

Midwestdrifter

Engineer In Residence
That is a very good point, I had not thought about the narrower rear leaf spring mounting. My thinking was that the dual wheels on the 3500 would help, since there will be less rear tire flex.

Wonder what is best overall? It would be interesting to drive fully loaded single and dual rear wheel versions of the 3500 to see. Although a moot point for me now.
Its hard to say, the 3500s have a much heavier rear sway bar, so it may be a wash driving an empty van.
 

vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
Vanski - yes, it sounds like front end float could be an issue. What wheelbase? And how much overhang aft of the rear axle? Shorter wheelbase, and higher rear overhang, will be even more sensitive to load behind rear axle since the heavy engine/tranny up front has less of a lever arm to balance weight in the rear.

I don't have the 2005 data, but I'm doing some weight & balance calculations on the 2019. What I've found on my 3500 XD 170 4x4 is that in order to have 30% of the weight on the front axle when fully loaded, the payload--excluding driver/passenger and fuel--must have a CG that is no more than 6" behind the rear axle. I ran the same calcs on a 144 WB and it would need payload CG at or forward of the rear axle. I'll post it when I clean it up a bit.

But I'm guessing yours will have similar results. If you add up the weight * moment arm (referenced to rear axle) of your box + all contents, it should have a CG forward of the rear axle. Exactly how much forward depends on specs for your 2005. Otherwise, too little weight on the front axle. All that weight at the back, on the overhang lever arm, needs to be balanced out somehow.

In the short term, have you tried running lower tire pressure in front than in rear? My old Airstream B190 was overloaded to the rear, don't know exact numbers. But I found that if I kept 70 lbs in both front and rear, steering would wander. Putting 70 in rear and 55-60 in front improved steering greatly--I assume due to balancing out the loaded tire flex since rear tires probably had at least 2X the load of front tires. Although with your dually, it may not help so much since you have 2X the tires on the rear axle.
158 3500 cab chassis geared @ 4.11. I only mention the 4.11 because it’s fairly rare.

Load in left rear corner starts about 2’ aft of axle, is about 5’ long, 2’ wide, 5’ tall, I’d guess holding 500lbs of stuff.

I do have the fronts at a lower than rear psi but need to check what I’m running. Good idea to revisit all that..
 

Airtime

Active member
Thanks, and looks like we have a lot in common on our projects :cheers:

I've gone back and forth on AGM vs. lithium. Started out AGM due to both cost and handling cold. But after talking some with Hein I was less worried about cold if I insulate the batteries and have some kind of heating. I am planning on Espar D5 and a coolant loop to warm the batteries and tanks. I'm not a full-timer, and I also have heated inside storage when not traveling, so no worries there.

I'm starting with 200Ah Lithium. With AGM I think I would need to start out with 400Ah. Both for usable capacity, and to handle peaks up to 200A from a 2000W inverter. The Battle Born 12V GC2 100Ah batteries can each handle 100A continuous. As a backup I'm planning my layout to be able to easily add 200Ah more Lithium in the future.

Still working out my daily Ah budget. For 3 seasons I think I'll be fine--I like to cook outside on the coleman stove when I can, and there is always the french press in place of an espresso if the batteries are low. The winter use case with Espar D5 running 24/7, all indoor cooking, and poor solar is something I'll need to work out but I'll most likely go to 400Ah if/when I do that.

I am looking forward to seeing this build! I have a 170 3500xd 4x4 project as well. I have a couple questions- why not use AGM instead of lithium since they are under body? AGM would be better out in the elements wouldnt they? It looks like cost is no issue hence the lithium- but maybe a row of 4 AGM batteries on the passenger side would offset the big water tank on the drivers side. 4 full river batteries would give you 280lbs that plus a fridge (100 pounds when full) put you at 380lbs on the passenger side vs your 500lbs on the drivers side.
 

Airtime

Active member
I'd like to return to my layout (which has evolved a bit) and focus in this post on my first pass frame using 80/20 series 10. After a few month hiatus I'm reviving my build thread. I had a couple life events slow down the project, but I am now getting more serious on it. I have done several things, I will post on each.
- Designed and built a DIY LiFePO4 system with 280Ah @ 24V after spending some time on the DIY Solar Power forum
- Abandoned roof-top board racks in favor of more solar--my gear garage is big enough
- Learned to use an Arduino and using it to remote monitor my electrical system
- Decided on Espar D2 for air heat and Isotemp Slim Square for water heat, for simplicity and lower cost than the D5 I was planning
- Looked into using 3D CAD, and then learned Solidworks and its weldments feature well enough to use it for my design
- Learned a bit about sizing 80/20 and then decided to go with series 10 rather than 15
- Designed an 80/20 framework for my van--the focus of this first post

Here's the layout and some views, mostly unchanged on the general layout:
Floorplan 8 Aug 2020.jpgLeft front view 8 Aug 2020.jpgRIght rear view 8 Aug 2020.jpg

My design approach for the 80/20 frame is as follows:
- several independent modules, individually removable (images in next post due to 5 file limit)
- all modules will bolt together and to the van for maximum installed strength
- series 10 with 1010-S as default frame member. 1020-S (1"x2") where needed for higher loads
- planning on mainly end connectors, which only need a simple tapping operation and non-precision access hole drill

The modules:
- Utility Module: holds electrical system over wheel well, water tank behind wheel well, and water pump
- Sailboard Module: Holds sailboards up to 8' (can push to 8'6) with tips extending into Fridge/Microwave module under microwave
- Fridge/Microwave module: full height cabinet with Isotherm Freeline 115 fridge up high and microwave/convection oven below
- Galley module: 48" module with sink, Isotherm Slim Square water heater, and a bank of drawers
- Shower module: Full height module 24" x 36"
- Bench seat: 42" bench/storage behind driver seat, forward of shower
- Platform bed: Can use at two heights: 1) at 33" on top of the Utility and Gear Garage cabinets or 2) at 42" on side rails, opening a 9" area for stowing sails, booms etc.

I''ll include images of the modules in next post. Feedback on anything is welcome, but especially on my use of 80/20 on the frame.
 

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