Friday, December 9, 2022


What do you think? Travel trailer design questions


Reader Brian Templeton posted the following comment on a recent article.

“I have ask two questions related to all trailers. Why can’t they have underfloor storage compartments like motorhomes, and why not put the air conditioning units underneath the floor like the ‘ALFA’ motorhome series in the past so the interior ceiling height could be increased to reduce the air drag of the trailer when moving on the road?”

We thought we’d toss that question out to you. What do you think? Please leave a comment below.

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Jesse Carleton
3 years ago

Don’t make them any closer to the ground.

3 years ago

Im trying NOT to be the unpaid expert on every post, but i’m surprised no one pointed out the biggest geometry reason trailers aren’t like buses.

My 32′ TT has 4 steps to enter. My 23′ had two. With a little thought, you realize the 32′ needs that serious ground clearance because every modest grade change *almost* hits the tongue jack or rear bumper. The angle over the axles is magnified by 16′ each direction, right? The tongue following the truck only makes it worse for the rear bumper.

Now, look at a bus – a change of grade is followed by axles close to each end. Your bumpers should never get close to the ground. The usable space stays lower.

Now, yes, you COULD add a layer of storage over my frame and then build the rest of my trailer on top of that… but the trailer would be 13′ tall in a blink, limiting where I could go, and my stairs might be 6 or 7 treads then? If builders did it, few buyers would actually like it.

Why they can’t put a window AC in the wall like my furnace, I can’t say. I’d buy that to gain the headroom.

3 years ago
Reply to  Wolfe

I have seen some A/C units through the wall and thought it looked good. I think it’s a good way to go to have less cut outs in the roof.

Arnold Larsen
3 years ago

I have a 35ft Cedar Creek TT that I added storage below the floor on both sides. I bought 3 compartment doors on line. had to cut down the height by 1 inch. Then cut holes in metal below the floor to fit the doors. the built ply wood boxes. they are all different lengths and about 12 high a depth of metal skirt to frame. excellent for small items.

Donald Wright
3 years ago

I have an Aliner Ranger 15, it has the Dometic Cool Cat A/C Heat Pump. Being an industrial unit, it is quite loud, and does not have a heat strip. However, it is built into the trailer in a cabinet, not hanging off the side or on the roof. Drainage is a problem…

Ron Cook
3 years ago

There was a new TT I saw in an article last year that was built with under floor storage, but with a memory like mine I can’t remember where I read about it.
My question is how come TTs have so little wardrobe hanging space compared to 5ers and MHs? That’s the one thing I dislike in my 26RR.
Ron Cook.

Herbert Lillibridge
3 years ago

We had basement air conditioner / heatpump in our 2001 Winnebago Adventurer 32V MotorHome and loved it. With it in the basement the weight wall low and on the opposite side from out generator improving the coach balance and with the weight low it reduced body roll on turns. Also reduced our overall height by about a foot. Another advantage was the fact that there were 2 less holes in the roof for leak potential.
Our newer 2011 Winnebago has two rooftop units with heat tape. They work well but are much noisier than our basement unit and we are now a foot taller and the condensation water now runs across the roof and down the sides in two locations.
Please bring the basement units back. We much prefer it.

John Koenig
3 years ago

Travel Trailers CAN (and SOME do have “Basement Storage”). To get basement storage, you’re likely to be looking at high-end to VERY high-end trailers (think six figures and up). Friends of mine have an AMAZING custom made bumper pull trailer with LOTS of basement storage built for them by Space Craft Industries. Space Craft does ONLY custom work, NO “cookie cutter” products. Bring a deep wallet.

3 years ago

I like everything about my TT, but why the unbearably loud AC. It has been the same
in every RV I have been in. Hard to understand why this is common, when a window AC
Is probably 25% as loud.

Tommy Molnar
3 years ago

I know this will go against the ‘thought grain’ here, but I’m quite happy with the storage we have in our TT. Just like a sticks and bricks house, the more room you have, the more your “stuff” expands to fill it. With a trailer, you just get heavier and heavier when you stuff your storage space full of all the “necessities” you think you have to have. Over the years we’ve learned to pare back on what we think we need. The last thing I want is MORE SPACE for stuff. Trailers and motorhomes are two different animals, as are travel trailers and 5’ers. Motorhomes are tricked out buses, made to haul much more stuff than ANY trailer. Big motorhomes anyway. With travel trailers you generally have your pickup bed to haul stuff (that 5’er folks can stuff in that usually large under nose storage area). Next thing you know, all us trailer people will need Peterbilts to pull our ‘campers’.

3 years ago

I like the low ceiling height in my Travel Trailer, My wife is vertically challenged and I have to open the vents in the Motor Home for her, in the TT she does it when ever she feels like it.

3 years ago

Biggest reason for lack of underfloor, or basement storage in units other than MH’s is the height of the unit. MH’s are usually running on truck size tires … 22.5″ rims. Average tire height mounted is about 40″, ground to center of the axle is +/- 20″. There just is not enough room under a TT frame to add underframe storage. Of course, you could put underframe storage on your TT, but your ground clearance would be about 3″ ….

Underfloor or integrated A/C units? COST, plain and simple. Rooftop units are direct wire, direct duct, direct air flow. Floor units would require a lot more space and access design. Want an A/C unit buried in the floor that you cannot get to ??

3 years ago

I’d prefer a heat and ac pump like used in tiny houses plus the new lightweight trailers only have a toilet and tub, why not a small sink so my husband could shave?

3 years ago

I think it would be a great option for those that don’t want to put the 5th wheel in the bed of their truck. Storage space is so limited in most TT. 5ers are better but still limited. For real storage area now you have to go with a MH. I don’t think anyone builds either with much storage.

3 years ago

I Don’t think I would be interested in a trailer unless it had auto levelers and some basement storage.

3 years ago

I think putting basement storage in is a good idea. It creates another choice for those that want it. No downside that I can see.

John Whitney
3 years ago

One advantage of travel trailers is their much smaller front surface area, as well as their lighter weight, allowing them to be towed by smaller vehicles. Making the suggested changes would make them more like fifth wheels requiring much more power to go down the road.
As far as basement air, it takes up a large area volume that can be better utilized for other things. My Winnebago, and others as well have basement air to the side of the rear engine. That space is now taken up by engine exhaust system. In addition they really too small for the sizes of coaches installed in. So we now worry about finding service for them.
If you are doing a lot of traveling, then I recommend a Motorhomes. If you are spending more than a couple weeks in one spot, I recommend a fifth wheel and appropriate size tow vehicle.
If you are mostly weekending and a week vacation here and there, I recommend a travel trailer and appropriate tow vehicle. If you have funds to throw away, then whatever you do works.
As Chuck says, however, DO NOT finance for 10 to 20 years. You will regret that the rest of your life.
Hope this helps.

3 years ago

Cold air sinks so it is much less efficient to try to push it up. Heat has to be dissipated and having the unit on the roof helps with that.

Storage is always a big problem. But so is weight… solve that issue and you can name your price as an RV designer.

James O'Briant
3 years ago

Under-floor storage would raise the center of gravity without having the extra weight of an engine and drive train to stabilize the trailer. If the center of gravity goes up, so will the number of trailers that flip over due to excessive speed, fast cornering or crosswinds.

I defer on the air conditioning question.

Norman Eichelberger
3 years ago
Reply to  James O'Briant

Putting weight below floor level will lower the CG not raise it. Physics 101

Tommy Molnar
3 years ago

You’re right, Norman. I was just thinking that.

Grampy's Buss
3 years ago

In order to accommodate under floor storage designers have to lift floor level. This raises the CG of the TT. Depending how the storage is loaded will adjust the CG back downwards, but may not be enough to bring it back down to original point. Leaving the factory and/or with unfilled storage bins the vehicle would most likely be unstable.

fred ford
3 years ago


Garry Hammond
3 years ago

These are some interesting questions! Thanks Brian!

I was just asking myself the same question about the under floor storage last week, and I’m trying to come up with a simple (removable) solution that might bolt onto the underside of the frame, and allow at least some lawn chairs, or a ladder to be stored there.

The A/C units could certainly be more aerodynamic than they are, (or mount onto the rear of the unit?).

Anyone else have any ideas?

3 years ago
Reply to  Garry Hammond

Make a easy way to mount storage like a truck tool box on the rear of the trailer.

3 years ago
Reply to  Garry Hammond

I’ve seen a few split units $$$ mounted on the back of TT’s. I would think maybe putting the compressor on a rack over the gas bottles would balance the unit better but I guess the weight on the tongue would be too much.

Garry Hammond
3 years ago
Reply to  Don

There are a ton of options here – I hope some trailer engineering types are paying attention.
I plan on adding a “back rack” to carry a gen and some misc. stuff.
I also want to add 30 lb tanks to the front of my TT as well as more batteries.

3 years ago
Reply to  Garry Hammond

Be careful adding that backrack – if attached only to the bumper, there can be serious metal fatigue resulting in detaching at random on the highway. As far as adding batteries I wondered about what the effect on tongue weight really is… I have run up to four batteries at a time, which technically adds another 300 pounds to the tongue weight. Empty or full propane tanks also add up to 60 lbs variably, so nominal 500 lb tongue weight can go up to almost 900…. hmmm!?