Comparing Thor to Impulse

Note the flat roof on that older model Impulse photo immediately above.

It's hard to tell whether or not the roof is flat or slightly crowned in Ron's photo of a later model impluse.

Ron, the photo you found is an Impulse Silver, which is what the OP is looking at.
For the heck of it, here is a regular Impulse, from their website. Old style construction.

pnichols wrote:
I believe that cabover running lights may be a very big and subtle gotcha causing leaks in Class C cabovers...

I agree with you pnichols.

Our first motor home SEEN HERE had a seamless body. It's running light gaskets never did their job right. To completely resolve the leaks, I ended up sealing shut the holes where the wires passed through with silicone caulk. The lights looked great and water never got inside the rig again.

My 2005 Itasca Class C (by Winnebago) has corner seems in it's cabover, which are easy to inspect and these seams in mine still look tight, with no breaks in the caulking due to good Winnie workmanship.

However - what mine also has that is far more jeopardy than easy-to-inspect-and-take-care-of cabover edge seems - is the big Class C no-no. It has a cabover window. NEVER get this in a Class C if you have a choice. Mine has never leaked from general aging, even though my window in the cabover is now the 3rd one. My cabover window was shattered (it's not sandwich safety glass) a long, long way from home from a flying rock from an approaching construction truck! It took two replacement installs of the cabover window frame and glass assembly (one back East, and one here in CA) to finally get a window assembly in there that (now) doesn't leak.

Also, what my cabover now has to help insure no leaks up there is running lights that are blocked off with Eternabond so no water can ever be forced in around those lights when driving in the rain. I believe that cabover running lights may be a very big and subtle gotcha causing leaks in Class C cabovers - unbeknowns to most owners. The natural thing to suspect is the window (if you have one) and any cabover seams. I wouldn't trust the cabover lights, either. Notice that those newer Class C motorhomes with seamless cabover shell assemblies of course still have cabover running lights!

Note: Another thing to look for, in addition to a seamless fiberglass roof, is a fiberglass roof that is crowned. Some Winnebago motorhome models have (or may still have, if new) seamless fiberglass roofs that are flat. Flat is not good - even if seamless.

mlts22 wrote:
Ron Dittmar has a very good article on this.

When shopping for any conventional class-C, the most important consideration is how it is constructed. What methods are built to last, and what methods are built to be most affordable.

Some motor home manufactures offer different levels of quality through their various model lines. Instead of providing a list of brands to consider, it is best to identify what "Better" is.

When shopping for a motor home, don't get distracted with what I call "Eye Candy" and/or "Square Footage". You want to pay close attention to how the house is constructed. Water penetration is the number one killer of motor homes, rotting them away long before anything is worn out. Once water gets in, it is like termites. By the time you realize there is a problem, a lot of damage has already occurred. Mold can also form and then you have a health hazard. My advise focuses on identifying a Reliably Well Sealed motor home.

#1 BEST (Very Expensive, Can Be 1.75 to 2 times the cost of Second Best)
NO structural seam work. The brand Coach House is a fine example. It is seamless, made from a mold. The only places where water can leak is cutouts for windows, door, roof-top vents and a/c unit, all of which are in areas of very low stress. Because they have a seamless shell, these motor homes are limited in size.

#2 SECOND BEST
Common, Affordable, & comes in Many Sizes so this is my main focus
I own an example of this type. My Rig Here manufactured by Phoenix USA.
Made in sections, but assembled in a way that greatly reduces the threat of water. Here are the good things you want to look for.

a) Structural Seams Away From Corners
When a motor home is driven, the house bounces, resonates, shakes, and leans, many thousands of times. Corner seams see greater stresses than seams located elsewhere. Corner seams are more easily split, especially when the caulk gets brittle with age & exposure to the sun. One extremely bad bump in the road can instantly breach a corner seam. Seams hold up much better when they are brought in from the corners in lower stressed areas.

b) A Seamless Over-The-Van Front Cap
A huge bed above the van’s roof is the most vulnerable area of a motor home. No matter how well they are made, that long frontal over-hang resonates when the RV is driven. It is common for seams to split there, most troublesome with age & exposure to the elements. The small front aerodynamic cap of a B+ design eliminates the overhang which eliminates most of the resonation, along with most seam work.

There are a few conventional “C” Designs (big over-van bed) where that area is seamless. If you absolutely must have that huge bed, then look for a seamless bucket-like design. Born Free offers a seamless bucket design as seen in This Model. Winnebago's View Here is another fine example. Some manufactures as of late offer a partial bucket design with fewer seams located in less-stressed areas. The Nexus Phantom applies a partial bucket concept. If you plan to accommodate more than 2 people, that extra bed would be extremely important.

c) A Crowned Roof
Rain and snow melt runs off a crowned roof. A flat roof will sag over time, then water puddles around heavy roof-top items like the a/c unit. Water eventually finds it's way inside after the caulk has dried out from age & sun, as well as fatigue from the change in seasons.

d) Rolled-Over-The-Edge seamless Fiberglass Roof Sheathing
A single sheet of fiberglass that rolls over the right & left sides of the roof, down the wall a few inches. The fiberglass sheathing holds up better than roofs made of sheet rubber or thin plastic called TPO, which require more attention to keep your RV well protected.

e) A 5 Sided Rear Wall Cap
This 5 sided back wall moves the seams around to the sides to areas of much less stress.

Potentially Troublesome Construction
Entry level motor homes are made with seams in corners and finished off with trim, including the massive cab-over bed. Their roof is flat and finished with rubber or TPO. They are most affordable, and come in all sizes. HERE is one such example. If considering this construction type, keep in-mind they require more regular care with bi-annual inspections. Plan to use a caulking gun now and then. When buying a used one, consider that you really don't know how well the previous owner maintained it. Buying new or used, that construction method will be counting on you to be a good non-neglectful owner.

There are also rare exception like the Lazy Daze which has seam work in the corners, but the substructure and sealing method is of the highest quality that it holds up like a seamless body. It's excellent sectional construction methods are not commonly found in other brands. I am no expert on this, but I'd give it a #1.5 Almost Like Best

About The Chassis
The most popular is the Ford E-Series with the V10 engine. The Sprinter diesel is a popular alternative to the E350 in the smaller sizes. The GM chassis is not popular, but is a very good choice for the right application. Any of those three brands since 1998 are real good, new or used. If you plan to tow a car or heavy trailer, be aware that the Sprinter is the least powered chassis. People who tow with a Sprinter, take it slower.

If considering a recent “small” class B+/C motor home, here is a comparison between the two main contenders, the Sprinter with the V6 diesel engine and the Ford E350 with the V10 gasoline engine.

Advantages Of The Sprinter With Diesel Engine
- Offers a 35% improvement in fuel economy over the Ford-V10, when both are loaded and driven identically.
- More ergonomic driver compartment with more leg room.
- Comfort continues with a car-like feel & quiet ride.
- A grander view out the windshield
- Made by Mercedes which people are attracted to.

Advantages Of The Ford E350 with V10 Engine
- Given identical motor homes both brand and model, the Ford is around $13,000 MSRP cheaper
- The Ford V10 engine has 50% more horse power and torque
- The Ford E350 chassis handles 1430 pounds more weight.
- The E350 is able to tow a heavier load.
- The E350 rear axle is significantly wider which translates to better stability.
- In most places traveled, gasoline costs less than diesel fuel
- The Sprinter diesel has limited mechanical service shops around North America
- The Sprinter diesel is typically outfitted with a propane generator. Propane is a critical fuel for RV operations, and generally needs to be rationed when dry camping.
- This Next Point Is Debatable But Still Worth Noting....The V6 Sprinter diesel engine is not allowed to idle for extended periods. This limitation is detrimental when you need a/c but there are generator restrictions or you are dangerously low on propane, or you have a mechanical failure with the generator or roof a/c. The Ford V10 can safely idle for hours on end, heating, cooling, and battery charging, all valuable if you have a baby, pets, or health/respiratory issues.

You decide what your priorities are, and pick the appropriate chassis. There are some really sweet motor homes being built exclusively on the Sprinter chassis, such as the Winnebago Via, View and View Profile. Others like Phoenix USA build their model 2350 and 2400 on both the Sprinter and Ford E350. They will even build it on the heaviest duty E450 upon request for a nominal fee. People who request an E450 for a small motor home, tow heavier things like for example, a multi-horse trailer. You can even special order a E350 & E450 4x4.

There is so much cool stuff offered in recent years, and even more anticipated with the upcoming Ford T-Series chassis. The general public hopes it will become available for the RV industry. It is kind-of like a Sprinter in size and fuel economy, but hopeful to be much more affordable.

The Chevy GMC 3500/4500 Chassis
I do not understand why this chassis is not more popular. It offers more interior comfort than the Ford, but not as much as the Sprinter. It's power & weight ratings are a little less than their Ford counter-parts making them a great chassis for all but the heaviest of class Cs. They are also a little better on fuel consumption. One thing to keep in-mind, if you are counting inches to store your rig, the Chevy/GMC adds an additional 9" to the front bumper compared to the Ford. I learned that researching rigs that could fit in my 25'-0" deep garage. By default, the Ford gave me 9 more inches to work with. If you examine my motor home in my garage HERE, you will see an extra 9 inches in length might have been detrimental.

Engine Power Ratings of Ford, Sprinter, & GMC/Chevy
Ford - 6.8L-V10, 305hp, 420ft
Srinter Diesel - 3.0L-V6, 188hp, 325ft
GMC/Chevy - 6.0L-V8, 323hp, 373ft

If the internet pictures I found are correct, run away from the Thor and run toward the Silver Impulse. The Impulse has a seamless cab-over bed structure, the best to avoid water damage in the most vulnerable part of any class C. Surely worth spending more money to get it for that reason alone.

I cannot understand why any motor home made today would still be made so cheaply with seam work in the cab-over bed area. Whatever the savings, it is never worth it to the educated consumer.

Winnebago Silver Impulse :)


Four Winds Thor :(

I'd lean towards the Winnebago. Both are decent, but Winnebago has a one piece fiberglass roof and nose cap. The Four Winds has a rubber roof and corner seams which historically tend to leak after a while. Ron Dittmar has a very good article on this. Driving through rains at 70mph will drive water in even small cracks if the seams are directly at the corners.

There are a lot of happy owners of Four Winds vehicles, so I don't intend this to be a bashing of a make, but it is a good feature comparison.

In fact, being able to pick up a 22 footer at a $50k MSRP is pretty good, and makes the little Four Winds C something that I'd consider if I can store it somewhere.

Were I to buy a FW 22E (most likely I can't, so it likely will be a "B" or nothing), I would seriously consider using Eternabond RoofSeal plus (65mil thickness of sealant) on the cabover corners facing the wind and other places, then the "regular" RoofSeal on all other seams. I'd replace the batwing antenna for a Jack model, replace the water pump with a variable speed, and if the converter is a single stage, chuck it for a three stage model. It will take some work, but a FW can be improved.

Winnebago has a good name but I have been very happy with my Four Winds. My neighbor and friend had a Winnebago and had problems with the slide which were never resolved.

Comes down to which floor plan do you like best, and the price.