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Semi-Trailer RV vs. 5th Wheel


TheLongWayHome
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What are the pro/con trade-offs between a semi-trailer RV and a std. 5th wheel? Both from the RV perspective and a HDT tow vehicle?

There seems to be more belly/basement storage in the semi-trailer model and somewhere it stated that the frame on the semi model had a more rigid frame. Also dual 22K axes, 22.5" tires and air-ride. Seen both at the HDT Rally, but forgot to ask!!

Semi-Trailer RV:-

DSC00373.jpg

 

More common 5th Wheel RV:-

DSC05178-edited.jpg

 

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I think both of the pictures above are of Spacecraft.  I know the red one is, and if memory serves, it's 57'.  Legal in about 6 states.

If money were no object, I'd have a custom semi trailer(45') built by Spacecraft.  They build their own frames to accommodate placement of various components.

But, in real life, there are a lot of gently used 5ers out there that would serve you well.  You might have to be patient to find the one you want.  I looked for nearly a year.

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Just to clarify.

I'm assuming a HDT. Therefore the second part of the question. What is the hitch or bed impact of a semi-trailer RV. Read a post from November on someone trying to future-proof their HDT bed by trying to cover both a regular 5th wheel hitch now and a potential future semi-trailer hitch. It was confusing to me. So looking for some clarity on the different options of a semi-trailer hitch and the impact to the HDT bed design.

The pictures were just to represent samples of the different types of RV. Yes, that is a 57' Space Craft semi-trailer RV. Absolutely no intention of going there!! Actually you can obtain a DOT permit to move it through any state. Just cost you money and time. Space Craft will build a semi-trailer in lengths from 28' to 57'. So lengths other than 53' or 57' are possible.

Have been looking for the right RV for almost a year and the search continues.

So to clarify the original question:-

Assume an HDT for either option (and it will be a short WB, with no Smart or deck vehicle). Assume either option would be about 40-42'. What are the trade-offs between a semi-trailer RV and a 5th wheel RV.

What I hear so far:-

  • Greater ground clearance on most 5th wheels versus more underbelly storage for a semi-trailer.
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16 minutes ago, GlennWest said:

There is actually a semi trailer conversion 2 campers over from us. It is same height as ours. They put a 5ther wheel ball hitch on it. Tow with a 5500. Looks like a horse trailer but is an rv.

Thanks Glenn. How does the ground clearance compare to your 5th wheel? Any estimate on the length or GVWR? Interesting that it has a 5th wheel hitch - was not sure if you could do that. I believe there is a height difference between the ball location on a semi-trailer versus a 5th wheel. Therefore different hitch and bed heights and locations.  Just trying to learn, as I had not considered or looked enough at Hutch.

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Semi trailer based 5th wheels typically have a flat or very close to flat floor the entire length of the RV.  This does mean the entry steps will have to be taller for initial entry.  RV based 5th wheels typically have steps going up to the front of the trailer on the inside, which allows for a lower main entry from the outside.  Other than this, the main differences will be running gear and framing.  A semi trailer base will give more options for running gear and typically have a stouter frame than an RV.  This means (typically) more potential carrying capacity for a semi based trailer than for an RV based trailer.  The storage configurations will also be different (as already mentioned).  Of course the biggest difference is a semi based trailer will have to be custom built while an RV based trailer can come in many forms from many manufacturers.

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The semi will have a greater load capacity and more basement storage but you will sacrifice ceiling height and inside storage to do that. Some of that height can be recovered with a split unit AC in the basement and raising the sidewalls but it will never match the ceiling height of a std fiver or have the interior storage of a fiver

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And to muddy the waters a bit further......ground clearance is affected by axle placement.  It takes more clearance if the span from hitch to axles is further.

That said, you can find semi trailers with extendable suspensions, so you can raise the unit to clear an obstacle, or even put all the weight on one axle for a short time to decrease turning radius.

Look on racingjunk.com,  under trailers for ideas.

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The average van trailer has a 108-110" inside height, even with subflooring it would have 8' ceilings.    The trailer pictured is a straight frame van with belly boxes, a drop frame van offers more options IMHO.     The down side to semi van trailers is the basic weight, they are 10-15K pounds depending on type and length.     That is near the unloaded weight of many 5th wheel RV's.     Add the slides, mechanical, interior and rest your about 24-28K.     That is not a big deal for a HDT truck but a non starter for the pick up drivers.       Even a deep drop van with 17.5 tires is going to have 24"+ clearance under the trailer frame.

 

The above is based on commercial trailers, the RV built semi trailers may be far different.    

 

Steve

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5 hours ago, TheLongWayHome said:

Actually you can obtain a DOT permit to move it through any state. Just cost you money and time. Space Craft will build a semi-trailer in lengths from 28' to 57'. So lengths other than 53' or 57' are possible.

And since you are not commercial, in Texas alone, you would need to post a $10,000 cash bond for a permit. If other states are roughly the same a move from Texas to Kansas for the HDT rally would required a $30,000 investment. Tickets all along the way would probably be cheaper.

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3 hours ago, Chad Heiser said:

Semi trailer based 5th wheels typically have a flat or very close to flat floor the entire length of the RV.  This does mean the entry steps will have to be taller for initial entry.  RV based 5th wheels typically have steps going up to the front of the trailer on the inside, which allows for a lower main entry from the outside.  Other than this, the main differences will be running gear and framing.  A semi trailer base will give more options for running gear and typically have a stouter frame than an RV.  This means (typically) more potential carrying capacity for a semi based trailer than for an RV based trailer.  The storage configurations will also be different (as already mentioned).  Of course the biggest difference is a semi based trailer will have to be custom built while an RV based trailer can come in many forms from many manufacturers.

 

3 hours ago, GeorgiaHybrid said:

The semi will have a greater load capacity and more basement storage but you will sacrifice ceiling height and inside storage to do that. Some of that height can be recovered with a split unit AC in the basement and raising the sidewalls but it will never match the ceiling height of a std fiver or have the interior storage of a fiver

Thanks everyone for the great insight. In particular the Kenworth guys!!! Very educational. Looks like a traditional 5th wheel provides more options, better availability and better livability. Probably a better full-time travel option? Not sure how well a semi-trailer might do in Alaska. It would seem that the semi-trailer RV is a great park option. Thanks for the continued education.

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7 minutes ago, Alie&Jim's Carrilite said:

The above is based on commercial trailers, the RV built semi trailers may be far different. 

 

Actually, Spacecraft builds all their frames in-house.  That is not a "Converted" cargo trailer.  Every RV they build has a purpose-built frame.

Jim,

I believe  you still have a design with Marsha and know a lot about Space Craft. So, what is fundamentally different between a SC semi-trailer build and their 5th wheel build.  I'm looking to visit them after the holidays.

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The flat floor plan of the semi style can be a plus because it opens up room for designing the layout you want.  to me, the downside of the semi is the steps to gain entry aren't as convenient if you want to overnight at Wally world or a rest stop.  The interior storage is as much if not more than a regular frame 5th wheel.  And as someone else stated with the advent of the LG mini-split systems, a true clean roof can be achieved with no openings if you want it.  This allows for a taller interior.  I believe Marsha has a package option that raises the sidewalls 4".  There is more basement storage in a semi.  essentially you have storage from end to end, side to side, 36" tall or so.  (I don't know the exact height)  Subtract room for tanks and systems and it's still a huge area. The downside is the "Look".  Being a big rectangular box can be intimidating when arriving at a campground.  I already get enough comments about the truck.  Having a semi style 45' trailer might become an issue at some parks.  Granted they are heavy, but people associate big semi truck/trailer to weigh 80k or more.  With the semi-trailer, you can use the regular commercial hitch on your HDT.  The frame is beefy enough to withstand the twisting and turning.  I don't think there is an air ride hitch that can handle the pin load.  (Getting close though)

A 5th wheel style is more conventional.  You can have the same interior height in the main area, but you do loose bedroom height.  And your floor plan is more limited due to the interior steps.  It can be towed by other than HDT or MDT and lesser trucks.  This will help when reselling occurs, or a roadside breakdown.  You can have a hybrid air ride system.  Dexter Ridewell uses a combo torsion axle and airbag assembly.  It works well.  True air brakes I don't know about.  With a 19.5" wheel, I know you can source air brakes for trucks, but I haven't sourced them for a trailer axle.  You will sacrifice room in the basement though due to a larger wheel well.  

What I do know, we ended up with a DRV 44 Memphis..... It's 47'+ overall, big, boxy, tall....  I know there are places we will not be able to go back to with this rig.  Too long.  At the last campground, we were at in Biloxi Ms, when we walked in the office, the lady commented: "I didn't realize your camper was so big".  She was holding our reservation slip that stated 45' 5th wheel, pulled by a WalMart style truck...

Marsha builds both frames from the ground up in-house based on your needs for slides, layout, tank capacities, etc.  You can't go wrong with either style.

 

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15 minutes ago, Alie&Jim's Carrilite said:

The flat floor plan of the semi style can be a plus because it opens up room for designing the layout you want.  to me, the downside of the semi is the steps to gain entry aren't as convenient if you want to overnight at Wally world or a rest stop.  The interior storage is as much if not more than a regular frame 5th wheel.  And as someone else stated with the advent of the LG mini-split systems, a true clean roof can be achieved with no openings if you want it.  This allows for a taller interior.  I believe Marsha has a package option that raises the sidewalls 4". 

....

Marsha builds both frames from the ground up in-house based on your needs for slides, layout, tank capacities, etc.  You can't go wrong with either style.

 

Thanks Jim for your insight.

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Jack is correct. A semi trailer can be built in any configuration. In the last 15 years I have hauled specialty vans from 22' to 57' long purpose built with drop decks, double drops, flat floors, suspension systems that take up almost no floor space, almost anything you can imagine. Nascar hospitality suites, medical labs, military aircraft simulators the list is absolutely endless. All with a pin designed to be hauled by a typical truck tractor and with multi million dollar equipment inside with special gauges indicating what g forces in any direction the trailer was exposed to.

It all comes down to price. And certainly Spacecraft is as good as anyone addressing this market.  

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9 hours ago, beyerjf said:

It all comes down to price. And certainly Spacecraft is as good as anyone addressing this market.  

Yup, that is the bottom line.

You can build a semi-style trailer that has 8' headroom, a large under-floor storage area and great inside storage. You will lack the 9' ceiling that is in parts of some 5ers, but you will have the 8' the entire length (well, almost, you do have some slight rises, but you will always have 7' 6" at least). You can have RV-style end caps, RV axle positions....it will look just like a conventional 5er, but on steroids. You can have bleeding edge technology like mini-splits. You can have an all diesel unit. You can do pretty much whatever your innovation senses and pocketbook allow. You can build it yourself - or you can engage a builder. You can have any type of staircase for entry that you like....Spacecraft has several entrance systems. And some others coming. 

Bottom line - the main advantages of the semi are:

  • less stairs inside- almost flat floor; Allowing for some significant improvements in the bed/bath areas.
  • commercial running gear that can be fixed anywhere and is unlikely to break; Allowing great confidence at highway speeds and easing ongoing maintenance
  • significant under-floor storage.

After that, it is up to you to specify the rest of the infrastructure and put in what you want...most of which could also be put into a conventional 5er.

Look for some new stuff in the Spring. A combination of existing technology with a new look and feel. 

Edited by Jack Mayer
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