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Thor Chateau Citation, Four Winds Siesta

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Old 08-16-2018, 03:49 PM   #1
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Default THOR "SYNERGY" Floor Issues...

My MY 2017 THOR SYNERGY 24SD was built and delivered in summer of 2016. Now more than 2 years aged (22,000 miles) and having just returned from a "full time 2 month trip of some 5000 miles, I need to discuss with those to know and care, what I call a "soft and noisy floor". As most know, the SYNERGY model is made by THOR under other names however, it is my impression that the basic RV assembly as mounted on the MB 3500 cab/chassis is essentially the same regardless of it's retail and advertised name.

My unit suffered from some of the usual growing pains but virtually all have been remedied by my dealer, who is also helpful and informative respecting how this unit is constructed. I asked him recently what materials are used in the construction of the floor.

He tells me..."There is a layer of a synthetic product first on which a layer of a blue insulating material next, then the top layer of a synthetic product. Then the vinyl wall to wall surface. The blue material is so dense and strong you could put someone on each end over a table and it would not break. There is no wood in the floor."

I expect to discuss this further, but first, I would like to have your knowledge and findings with respect to what you know to be the materials used by THOR in the construction of the floor for their 24' model(s) in particular those built during the period 2016/17.

Your help and shared knowledge could benefit many!
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Old 08-22-2018, 02:25 AM   #2
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Default Re: THOR "SYNERGY" Floor Issues...

Mr Enuf,
Welcome to the club!! The spongy floor club, that is...
I recently purchased a 2010 Four Winds for considerably below market value because it had the same issue.
Upon my research and inspection, I have found that the floor in my unit (yours may differ but there are similarities) is as follows:

Some sort of thin (1/8"?) wood, Luan or similar
2" thick stryofoam, yes, stryofoam
Another layer of 1/8" Luan-like wood
Vinyl sheet flooring

Obviously, I described the lay up from exterior to interior.

I happen to be an extremely experienced canoe and sailboat builder, particularly strip built and/or stressed skin construction.
Not unlike the attempt at a composite floor in the Thor/Four Wind.

I also am a retired aerospace design engineer. I would further describe the floor design as inadequate.
The attempt by Thor to build a stressed skin composite floor has several fatal design and material flaws.

If you know your engineering principles, you know that the floor experiences compression loads from various live and dead loads. These loads deflect the composite floor and force the exterior skin into tension. The core material must not plastically deform under these loads. Additionally, the bond between the skin and the core must not fail in shear, the core must not fail in shear, and the skin must have adequate tensile strength.
None of these conditions are satisfied with the implemented design and materials used.
Oh, I should also mention that the support structure below the floor has 72" between lateral supports.
Apparently, newer models have replaced the Luan wood skin with a "synthetic" skin. Seemingly, not solving the problem.

With all that said, what are your options?
Add some stiffness to the floor. Some have simply added some cross braces welded to the existing supports.
Others have added some 3/4" thick plywood beneath the floor, as well as adding welded in cross braces.
There are premade panels available with fiberglass and epoxy resin skins bonded to PVC foam core substrates, extremely strong and lightweight (developed for ocean going racing sailboats and used now for all sorts of highly stressed vessels). These panels could be retrofitted to the coach, but would require a major restorative effort. But that would be an ideal repair.

Why these coaches were not built using those panels is for you to ponder, I know the justifications behind such decisions.
As for your specific lamination schedule for your floor, you should be able to determine that for yourself with a quick inspection through any of the floor penetrations (water lines, drain lines, electrical wiring, etc). It could take 10 minutes of your time...
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Old 08-24-2018, 03:11 PM   #3
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Default Re: THOR "SYNERGY" Floor Issues...

and my thanks to "Mr. Stripperguy"!

I was beginning to wonder if I am the only 24' motorhome owner with the "soft and noisy floor". Thank you for sharing your expertise, knowledge and personal experience.

I do know another THOR "Synergy" owner who has exactly the same floor issue as mine. He too is looking for insight and personal experience from others. I will share your comments directly with him.

Your post keeps my question alive and here's hoping more owners of small motor homes like mine and yours, no matter who builds them, will comment.

Thanks again!!
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Old 10-12-2018, 11:03 PM   #4
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Default Re: THOR "SYNERGY" Floor Issues...

Yes, sorry to say but same issue with my 2010 Freedom Elite 23s.

I noticed a round 12 to 15 inch soft spot when we purchased in 2015 near the doorway entrance as you walk onboard inside
where the ladder to the bunk would be placed on the floor right after you step up inside the house past the stairs and steps.

Felt a larger area of cushion or compression on the floor about one year ago, or two years into us using and being on the RV a few months consistently each year.

Area has gradually gotten spongier and the area is in the walkway thru the kitchen area and in front of the slide out only. About a 4' x 5' Area.

In 2017, I Emailed and Spoke to "Jaime M. Rienks" <jmrienks@tmcrv.com> at Thor multiple times.

I was told it was a problem from the lack of structural floor support under that area and that it had been identified by Thor years ago as a problem in their design and materials used.

It was not a required recall notice to owners because it was not a safety issue.

Also, it was not their issue now because the warranty was over in 2011 or one year after original purchase date. It is now normal wear and tear due to the years of being in use and service.

After a few emails and calls, a repair kit that was supposed to fix issues arrived but it was not the right fit for my model nor were the 3/16" laminate pieces enough to stiffen the floor from the bottom up using them and bracket plates with screws to drill into the frame beams to add the support on the underside.

Propane tank will also need to be dropped as well as other large components on the underside.

Not an easy task to complete for anyone or professional business without prior weeping thor floor / freightliner frame assembly experience.

I called Thor back and spoke to another Thor warranty rep by the name of Larry.
He said that an RV company in Lakeside, FL had some experience repairing this particular models problem but when I called them they were months into existing projects and it would need to be something for me to call back at a slower time.

They did say they would be welding pipes or metal stiffeners to the existing framework under the existing floor to stiffen the area from the bottom up...might takes a few days in the shop.

On my project list for 2019.

Hope this helps and maybe a simple or single solution will come from a few of us writing what is known or has been attempted.
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