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Travel trailer opinions wanted
Hello all. I will be purchasing a travel trailer and have it narrowed down to a couple options and would like some thoughts as to the aerodynamic consequences of the two. Tow vehicle will be a 2011 Toyota Sienna SE. I chose these two because of the lower weight, single axle, and narrowness of them.
First option is a K-Z Sportsman Classic 19BH. What appeals to me about this one is that it is only 7' wide and 8'2" high. Unfortunately it is very squared off. It is also much less expensive than option two. http://lh5.ggpht.com/_KBUbO5zit_E/TK...-Sportsmen.jpg Second option is a Gulf Stream Visa 19RSD. This one has what seems to be an aerodynamic shape to the roof line. Unfortunately it is 6" wider at 7'6" and 1'6" taller at 9'6" (including the AC). http://lh3.ggpht.com/_KBUbO5zit_E/TK...ienna-Visa.jpg My question is; Do you think the taller & wider Visa cause more aerodynamic drag because of it's height & width? Or would the better shape negate it's size? I would consider removing the rooftop AC on the Visa to help out the aero. http://lh5.ggpht.com/_KBUbO5zit_E/TK...-Sportsmen.jpg (If your wondering, I used Inkscape to create the images.) |
For the issue of the AC you could just add an angle to help direct air over, around and back down it remove some of its extra drag. I would assume that adding a ramp on the roof of the van to direct the air over the trailer would help reduce the drag.
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The main aerodynamic gains are to be made at the rear, not at the front.
Neither design is anything like aerodynamic at the rear, but the visa has a curved top with a slight downslope that might offset its bigger bulk. |
Based on your pics, I'd go with the second one: Better overall shape, less draggy stuff hanging off the side, appears to have had at least some attention to aero drag in the design. You could make a simple and light aero fairing for the AC on top. After going past the relatively sharp leading edges of the first trailer, aftward flow would probably be so buggered as to exceed the drag of the second design.
Which would be easier to add Coroplast belly and wheel fairings to? Which has better surface texture from the getgo? Which weighs less? |
the second one is about 25% more frontal area, and about 12% heavier
19bh frontal area 8232 sq in, about 2500 lbs visa frontal area 10260 sq in, about 2800 lbs given the general boxiness of both of them and a van to break the wind up front, I think the 19bh is gonna start out ahead and pull away from there efficiency wise. |
I second the "add a wing to the van" comment, they make a big diference.
Unfortunately my toyhauler's ramp doesnt lend well to a kamm, but the 19bh does. Oh, and i love my KZ, great trailer, see below. |
All great comments so far. Thanks.
The wing idea would be doable... perhaps attached to the roof rack. As far as the weight difference, I'm not too concerned as the van's max is 3600 lb so I would be staying close to that with either trailer. They are both single axled so that also limits total weight. I am having a hard time believing what's listed in the brochures for weights as I have seen it vary 200ish lbs on the same trailer from different sources. However, the Visa makes sense that it weighs more. A little research last night on my part showed that weight makes little difference at speed. The exterior on the Visa is very smooth besides the windows and awnings. The 19BH is the traditional corrugated aluminum sheet. That's a huge difference in frontal area! The Cd would have to be much better on the Van-Visa to make up the difference... correct? I will be looking at a Visa this weekend. I am afraid I will like it more as it appears to be of better quality. The price reflects that also at almost $5K more. |
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The Visa has it external tent on the other side, but overall it looks better streamlined on the bigger pictures :
http://www.gulfstreamrvtrailers.com/...ERDHighExt.png Actually, it looks a lot like the streamlining template - it's just cut-off very early. |
I think in this case the rearal area is key, as the tow vehicle is blocking frontal area in ways which may not be clear cut i.e. if #2 has 25% more frontal area does that mean it is presenting 25% more area to the wind? Not this time.
So I think aero load differences tween the two will be very minor compared to the functionality of them (which one suits your needs better?) and of course the price. |
Hucho's book/ caravan trailers
Hucho has a section on travel trailers and some wind tunnel results for generic forms.
I don't have my book with me.Anyone? |
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For one, it's leading surface is further away from the tow vehicle's upper trailing edge and surface. Larger gap = bad. Second, more radius on leading edges than necessary to promote "attached" flow does not reduce drag further. Yes the side edges are sharp but they are on both of them. The "old school" trailer appears to have a generous enough radius on top so no advantage there for the "aero" design. Third, there is the additional frontal area. That simply ain't gonna help. (BTW-there's that semi thread re: that humpback trailer that's supposed to reduce drag. I don't see how. :confused: ) Fourth, the "aero" trailer appears to actually have more rear area, thus it will have a larger trailing wake. That is where most of the aero action is anyway. Fifth, as a larger unit, it will have more "wetted" area, possibly leading to more surface drag. I wonder how much of an aero hit those corrugated sides cause on the old school unit? The concept of the aero trailer is sorta nice but the execution of this one makes me think it is not much more than a marketing ploy OR they decided to bias the design in favor of increased interior volume without necessarily adding drag commensurately. |
I know this discussion started as trailer A vs B but what about C-Z? If aero is NOT a primary decision factor then other requirements trump. If aero IS important then it's hard to beat well rounded trailers from Airstream (aluminum) and Scamp et al (fiberglass). You can learn more about the latter breeds here.
Egg Central Cheers KB |
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Hucho's book/ caravan trailers
I looked at Hucho's book last night.His trailers are generally the same as the two under investigation.And according to Hucho,the 1st trailer would actually have the car/trailer lower drag,around Cd 0.45,based on the frontal area of the trailer.
The 'aero' trailer car/trailer combo would be around Cd 0.53. The caveat is that the 1st trailer would reduce tongue weight with speed,the 'aero' trailer would be dead neutral and pull well under all conditions. |
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Uni-Arch fiberglass roof eliminates seams at critical water runoff areas and... Visa’s unique arched roof provides 82” of headroom at the highest point Both of which are very true. Quote:
I looked at one last weekend and it seems much larger than the K-Z inside. That taller roof gives it a cathedral feel to it. We will probably go with the Visa. It simply feels much larger inside and has many other features I like. I will have to try to squeeze as much MPG out of it as I can of course. I towed a 4x6 enclosed trailer last weekend and MPG dropped from 21.5 to 15.5 with just that combo. Acceleration was fine but over 55mph and MPG tanked. It also tows quite far behind the van. I would guess just <10 with the camper??? |
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contest?
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Cheers KB |
How about your thoughts on this one. I was toying with the idea of building one from scratch but the reality of it (the lack of time) proved otherwise. It is 8.5 ft at it's highest. Never quite finished the design.
http://lh3.ggpht.com/_KBUbO5zit_E/TL...camper%201.jpg |
Just going on what I've learned from reading + hobby experimentation, I'm going to guess the oldschool trailer is going to be the more efficient one. It's significantly lighter, draws a significantly smaller wake than the "aero" one, and isn't significantly less aero in the rear at all.
Up front the biggest improvement would come from closing the gap between the van & the trailer, as has been mentioned. Might be feasible to attach a "bulb" to the front of the trailer with its midpoint around the roof height of the tow vehicle, extra storage for tarps or muddy boots and at the same time closing the gap a little & providing a bit of radius for air passing to the sides of the trailer. |
While I'm pretty sure it's not what you're looking for, somebody does get it. There's still a small company in Cali making teardrop trailers. Socal teardrops
http://www.socalteardrops.com/images/5x10_small.jpg Not exactly something I'd want to spend the weekend in with the wife, a couple kids and the dog, but definitely perfect for someone wanting something more than a tent, but only has a compact car to tow it with. |
I've looked at/admired teardrops whenever I see 'em... but sadly I had to conclude that they are more about style than aero. At least, many of them I've seen seem to have too steep a drop-off at the rear for good flow... so if they have giant trailing wakes across their backsides, one might as well have a cube trailer and enjoy the room.
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Don't ever go off road! :eek:
The rear can be a vertical cut... just sayin'. The upper front can be "sharper", gaining interior standing room with I think no perceptible loss of aero. Similarly, the boat-tailing of the roof and sides appears shallower than necessary, which unnecessarily cuts into headroom and floorplan room. I think the boat-tailing can start a bit later. Put it up against the aero template. Something I'd like to see on trailers, which seems to be universally lacking (except on Airstreams) is good radii on the side-to-front and top junctions. |
thoughts
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He and Kamm and Fachsenfeld would have liked the rear as it embodies the 50 % frontal area cross-section and reduced wake. I would think about some radius on all your forward and upper edges. A foil on the tow vehicle and movable gap-fillers between 'vehicles' might allow you extra interior space in the trailer,using the tow vehicle for all the 'penetration' with the trailer in full draft behind.Hucho says there is as much as 10 % extra fuel economy right there. If you were near a university with a modest wind tunnel you could throw some money at the grad students and let them do a scale-model study. I have a 22-foot sailboat which will be reversed and inverted to create the body for a 5th-wheel RV trailer with full boat tail.I believe it would pull like magic. I think yours might too! |
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Cheers KB |
To the OP: I don't think you're going to see a significant difference between the two. A box is a box. Non-radiused edges are a killer for mpg AND for crosswind handling (much more important than the last two mpg).
And neither of these trailers is as well built as an all aluminum trailer from earlier years. A used SILVER STREAK, AVION, STREAMLINE or even downmarket AIRSTREAM would be better. Cheaper to buy and longer lasting as well. The joke about todays square white boxes is that they are ten year trailers on a twenty year note. They don't last. An older, truly aero trailer -- especially one with independent suspension -- is the best bet for fuel mileage and overall costs. What may need to be replaced is straightforward (appliances are generic, as is flooring, etc), and there are large -- very large -- groups of enthusiasts. No need to break trail as it's already been done. The separation between TV and TT is too great for wings, etc. Treat each vehicle separately. Get a PRO PRIDE hitch. There is no substitute for a sway-eliminating hitch. The best the rest can do is resist sway. Same for disc brakes on the trailer. Mile for mile, towing doubles the risk of a serious or fatal accident. And, with that contemplated TV go read everything you can find from Andrew (Andy) Thomson of CAN AM RV in London Ontario. RV Lifestyle - Hitch Hints & Wagon Masters Pay special attention to tire/wheel combinations for the TV. Get good tires well matched. NOTHING will make a bigger difference except certified scale hitch rigging (assuming a PP hitch and disc brakes). Fuel economy doesn't mean much for a traveler only moving 5k annually. It's the guys traveling 10k or more annually who benefit. Keep your speed to 58-62 mph at most. The trailers shown are about good enough to run up to the lake. In clear daylight, with no winds or semi's on the roads. Depreciation and outrageous increasing maintenance costs make the trailer type shown a true money pit. Mpg decrease is only the icing on the cake. Economy is the lowest cost over the most years. My folks had their aluminum trailer 27 years, and full-timed for nearly ten of those. They replaced the AC in that time. Nothing else. I'm in the market for another aero aluminum trailer, and I keep my search confined to 1972-1990. As to the other subjects on here, keep in mind that the tradeoff between aero and live-ability was worked out more than 50 years ago. The available power in cars, and the state of pre-Interstate highways made aero a highly viable subject. But most of the time spent with a trailer is not in driving. Today's excellent drivetrains, and the Interstate, make 15 mpg easy on a well-spec'd rig. I've seen 18 for European TD SUV's and new 25-28' Airstreams (heavy trailers). The OP's van can tow a bigger, better trailer than the ones depicted for a lower initial cost, and, once repaired/upgraded, for a lower road cost. With FAR better handling and wind resistance (crosswinds). And an indefinite life. Good luck . |
I have to agree with Phil, Frank and slowmover. Airstream set the standard. Their radii are second to none
http://www.roamingtimes.com/rvreport...d-exterior.jpg and they can last forever with proper care and feeding. So do molded fiberglass trailers from Scamp http://www.co.cass.mn.us/ccedc/images/scamp.jpg and Casita, http://www.viewrvs.com/tt/casita/200...om_dlx_a01.jpg plus several others still in production in the US and CAN, and dozens of cousin brands over the years that came and went as a business but the fruits of their products live long and prosper. Boler is the archetypical example (Google image search) being the forefather of Scamp (MN) and Casita (TX) FWIW. Airstream makes 19'+ campers for 2+ people which hold their value well but you may need lots of these http://elementaryteacher.files.wordp...on-p-chase.jpg to join the ranks. Molded fiberglass "eggs" (as we affectionately refer to them) in 13'-19' sizes sleep 2-6 within a Class II (3500# GVW) rating that is truly fuel friendly. They also last decades (I just sold a nice 88) and you can get in the game for much less cash investment making the value excellent. BTW my 19' fifth wheel Scamp (pic, pic) is sway proof being pinned over the truck's rear axle. I'll press my luck by repeating a link to Egg Central (bookmarks) for anyone who wants to learn more about these wonderful campers then back off so as not to hijack this thread. :) Cheers KB |
I was admiring the teardrop shaped travel trailer idea shown above, and wish to add these 1940's designed travel trailer pics and a video for consideration. Wally Byam, the founder of Airstream is given credit for the all aluminum travel trailer. The man was a marketing genius of sorts, and for those of us who love car camping, his death in the mid-1960's marked a turning point. But during the war there were plenty of others who'd seen, thought and experienced travel trailers from the 1920's forward, and the sheer number of skilled sheet metal workers and aluminum fabrication facilities in Southern California from airplane production led to other companies as well, and they charted their own paths. One of these companies to form was the SILVER STREAK Corporation. Over it's years of production (ending in the 1990's) they turned out but a handful of trailers per week and never suffered, as did Airstream, the vagaries and cost cutting of changed ownership. And they always built to a higher standard than did AIRSTREAM.
During the 1950's these two competing companies built a highly similar trailer from their joint venture under CURTIS WRIGHT Corporation during the early postwar years. By 1960 things had changed in design direction. Below are links to pictures and a video of early '50's SILVER STREAK trailers. #"VINTAGE!" 1954 Silver Streak Clipper.. 1953 silver streak clipper | Flickr - Photo Sharing! http://www.youtube.com/watch?v=RbDtE2xkssA better shelter blog: 1952 Silver Streak Trailer 1953Clipper The restored trailers you see here are expensive. Think sailboat/airplane/1930's Packard. The appeal is timeless, as the shape and interior design is an outstanding version of form following function. Trailers aren't on the road -- for most Americans -- much more than 5k miles per year. Even those who fulltime may not run 20k annually. After all, the point is to have comfortable accommodations at a variety of locations across the continent. No unpacking in a strange hotel. No reliance on generic fast food. Mediated privacy as I see it, for RV campgrounds run the gamut from cheap (free overnight at WalMart parking lot) to exclusive members-only resort quality. Plus state, national, Corps of Engineers, etc. So a trailer is mostly about 3-day to 2-month flexibility in only a few locations. And the era of these trailers ended in the 1970's. Until this point it was doctors, lawyers, business owners . . these trailers cost as much as a starter home. In todays money, over $100k (for early 1970's comparisons of larger units). Some even more. But all of them well more than a new Cadillac or BMW. The ruination of the airlines -- called de-regulation -- and the ascendance of finance since 1980 (longer work hours, fewer benefits, women having to work) PLUS the increase in fuel costs (Peak Oil having arrived in the US after 1970) caused those who could afford these trailers to fly and rent on their shortened vacations. AIRSTREAM survives due to deeper corporate pockets, but cheapened construction (and glitzy interiors) as a sort of prestige brand for it's owner (THOR). Enough of context. Note the length and the accommodations. Search elsewhere for capacities (fuel, fresh water, holding tank) as well as weights. The entry and exit angles reduce interior space without a commensurate interior benefit (and expensive, fitted interior not amenable to assembly lines). More powerful cars and better roads plus a desire for a bigger set of trailers ended the era of the Clippers. I would offer that this is still -- likely -- the best overall shape for a travel trailer as headroom and shoulder room do not change. I've had the time to view one (a survivor) and the ingenuity of fittings (interior accommodations) is excellent whether standing or sitting. While I prefer a later shape and larger size (for extended travel), these trailers shown offer an outstanding blend of road-ability and live-ability. It is the latter which most matters. Fuel economy is down mainly to the tow vehicle. Aero means more than weight. But live-ability trumps road-ability at an early point. I believe the trailers shown in links above are still the best point of departure for modern iterations where aerodynamic considerations are fundamental. . |
I purchased the Visa and picked it up last weekend. I compared an actual picture to what I posted earlier... the gap between them is a little bigger than the "concept" photo. Obvouslly not good for aero.
http://lh5.ggpht.com/_KBUbO5zit_E/TL...re20101016.jpg I kept a close look on the MPG on the way home. There was a 30mph'ish crosswind most of the way. Highway averaging 63mph: 10.5 mpg Reset the onboard computer and drove another 30 miles off the highway averaging 53mph; 11.5mpg The entire trip there w/o trailer; 69mph avg, 24.5mpg. |
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The only reason the rear is not vertical was an attempt to shorten it visually and help with looks. Yeah, your right, the front could be steeper. The more research I do is telling me the same thing. Also true of what you said about radiusing the side-to-front and top junctions. I'll have to play with those ideas some more and see how things work out. I used the aero template profile to create the shape. It actually matches quite well I thought. Now, I guess the question would be... Where would you put the peak? I chose the doorway simply for practical purposes. http://lh3.ggpht.com/_KBUbO5zit_E/TL...20template.jpg |
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Do you have a link to a photo of his trailer? I did some searching but couldn't find anything. Some radiusing is in the future. Seems like the right thing to do. I think I'm going to play with a deflector/foil on the Visa. Hopefully some gains for a simple mod. |
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We review your priorities and look for the simplest solutions.
Hybrid collapsible hardwall campers solves the frontal reduction & still have usable (standing) volumes. Smaller SUV's and lower displacement vehicles could now pull larger campers. Unfortunately, Hi-Lo Trailers are going out of business and may have great deals. http://www.campingearth.com/images/t...d-and-open.jpg http://www.travelizmo.com/archives/t...r-interior.jpg |
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That Pro Ride hitch... WOW! $$$ As for as fuel economy... if I can save $ on a couple fill-ups on a long trip, I think it would be worth it. Makes going on trips a little easier on the wallet. Are Airstreams under 3500lbs? I don't believe so. That's my tow limit. I realize that's debatable but that's what it is. Another different TV isn't an option right now so I am definately compromising there. You are definately correct, todays trailers are not as well built, even the Visa I just got. It definately has issues with quality. |
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TrailManor|Easy Towing|Lighweight Travel Trailer |
Time is my main consideration for buying new. Used is ok but everything I have seen needs TLC and interrior updating. That said, I am still on the watch for something used but nothing seems to fit what I have in mind design wise. A friend is selling his Avion because he thinks the large radiused upper corners are too confining.
I come from a family with three generations of full-timing in aero aluminum trailers over more than fifty years. None of us ever felt confined (and I am over 6'). The perspective may be different visually, but remember you spend most of your time seated while "indoors". Plus, these trailers tend to have FAR better outward visibility when seated than a square box (their structure is too weak, in general, for the same sq/ft to glass ratio). That Pro Ride hitch... WOW! $$$ Your family is worth how much? You have how much into van and trailer? A sway eliminating hitch is much less than 10% the value of the rig, isn't it? Maybe 5%? As for as fuel economy... if I can save $ on a couple fill-ups on a long trip, I think it would be worth it. Makes going on trips a little easier on the wallet. Not at the expense of repairs, even DIY, if RV quality is low. Are Airstreams under 3500lbs? I don't believe so. That's my tow limit. I realize that's debatable but that's what it is. Another different TV isn't an option right now so I am definately compromising there. Some AS trailers are light. You are not weight-limited in the same way with an aero trailer if you'll educate yourself on the advantages. CAN AM RV in London, Ontario sets them up like was done in the 1960's. Understand that your van has not been subjected to proper testing, nor that the new J2807 standard is in any way realistic. Search for articles and posts by Andy Thomson of that firm. They've been doing this for forty years and have set of hundreds of your brand of van, and thousands of minivans to tow. Weight rating is relative to many factors. Reading will inform you of considerations. And, yes, you can tow a heavier aero trailer than the ones shown here. You'll enjoy reading around on the subject. You are definately correct, todays trailers are not as well built, even the Visa I just got. It definately has issues with quality. All RV's are not as good as they ought to be. Important that you set up the hitch rigging with a certified scale. And keep records and photographs; document everything as you may someday want a better trailer, so records of service/warranty work are better than memory and a credit card receipt. My mother -- on our 3-4 week trips in the 1960's & '70's -- used to write away to states, societies, etc to gather information for an upcoming vacation. Books, magazines, correspondence piled up comfortably. I see vehicle maintenance the same way, it's a touchstone for comfort and confidence while on the road. A pleasant diversion most evenings. WOODALLS.NET has a decent forum. Start there with searches about your two vehicles. You can also PM me for a continuing draft I add to about towing and FE, it's essentially just notes past about page 40 but has now reached 101 pages and well above 100 links. Much of your FE is now set in stone. Driver attention to details (details of TV and TT), plus trip planning will give you the final percentage increase for FE. Safety & FE work hand-in-hand, so it's a reassuring list. ON the trailer, start by having a big truck shop perfect TT axle alignment. If TT does not have shock absorbers, add MONROE Retrofit kit. CENTRAMATIC Tire Balancers are also good. If the TT has cheap no-name tires I'd consider GOODYEAR MARATHON the default choice for ST tires. Good luck . |
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Its neat how the expensive hitches give you the sway stability of a fifth wheel trailer. The propride and hennsley connect to the trailer with a a 4 bar trapazoid link. The converging links make the trailer move around a virtual pivot point near the rear axle. The Pullrite connects underneath the vehicle and has an actual pivot at the rear axle.
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