motorhome aerodyamics
 

Hi
own an american imported motorhome built on a hilux chassis. this was built 24 years ago and when aerodyamics where just starting on main stream cars. i understand my motorhome is an aerodyamic brick. so looking for reasonably easy and cost effective improvments. will take a photo tomorrow and using supplied tool in this forum. looking tofit an airdam at front and down the sides. motorhome body sticks out bothsides from cab approx 1 foot. airdam would run from front down sides to front of rear wheel arch. also smooth wheel trims on rear wheels only. front wheel design makes it impossiable to fit wheel trims. will try to post photos to show what i am trying to explain. or google dolphin motorhome 1989 model.

Dolphin
 

I grabbed a image:
a second image
The big offenders are all the leading edges of the motorhome.
*The nose above the cab should be more like an AIRSTREAM trailer or motorhome.Very bulbous,which really helps in crosswinds and guarantees full flow attachment onto bottom,sides and top.Consider having an awning company construct a rolled aluminum superstructure and fabric cover which would mimic (without compound curves) what AIRSTREAM does.
*You would need full-height,12-inch radius fairings attached to the doors themselves which,when closed, smoothed the airflow onto the sides,killing the separation which is there right now.
*Everything on the roof should be streamlined as Orbywan has done with his Ford-based motorhome.
*I streamlined the front of my next door neighbor's Toyota,just like yours,with sheet aluminum grille-block,airdam,with rolled-radiused outers.Since you will at times need all of your radiator,consider blocking only the grille opening which is not directly ahead of the radiators tube and fins.Extend the dam down even with the lowest suspension members.
*Run your side skirts at the same elevation as the bottom of the new airdam.
*The rear wheels could also be enclosed within skirts.
*Consider some length of boat tail after the front is cleaned up,to reduce the enormous turbulent wake which is eating your lunch at the filling station.This wake represents 72% of your aerodynamic drag.

And posted:
http://hd.sr5.com/wp-content/uploads/2009/08/89mh1.jpg

Check out a few relevant links here:

• http://ecomodder.com/forum/showthrea...-rv-25660.html
• http://ecomodder.com/forum/showthrea...nge-26792.html
• http://ecomodder.com/forum/showthrea...d-e-18151.html
• http://ecomodder.com/forum/showthrea...ods-24435.html

thanks on pointers
 

Hi
could you draw a rough sketch of door fairings you where talking about. roof next spring will have air con unit and front sky light removed. mirrors have been thought about. thinking of mount ing on bottom of overcab unit and some sort of drag reduction fitted. this hopefully will remove the scaffolding holding mirrors at present. Mirrors will go to 10x6 instead of 4 units of 6x6.
Thanks
dave

It has been my observation that the underside of pickup trucks are as un-aerodynamic as you can get. Simple flat panels covering much of the underside has quit an affect on fuel economy. On my 2012 Sprinter van my fuel economy went from 11L/100km to 8.6L/100km with a not yet finished belly pan.

My oldest brother had one of thos (1983) but parked it under a Magnolia tree which rotted the camper portion out and we ripped it off. Welded the back of a regular pickup cab on what was left of the cab and put a trailer like this on the back (minus the frame and axles). We swapped the tailgate and the corresponding panel in the front of the trailer to get the fenders to sit over the rear wheels on the Toyota truck chassis.

Later he put a real one ton Toyota rear axle on it and got rid of the dual wheels. It really is a neat looking truck, now 30 years old. Got the engine out of my youngest brothers truck and a 5 speed tranny when the donor truck got flooded in Isabel, 9 years ago.

TNJ Murray: Military vehicles and parts surplus - Trailers - 1987 AMA CO MDL M101A3 2 WHEEL 3/4 TON CARGO TRAILER SER# 5000270249

regards
Mech

hi red yaris
 

Hi red yaris
what did you use for the underbelly to streamline it. also how did you fix it to the chassis

John O' Groats eh?

I may need to take a drive:-P

I used 1.5mm [0.06"] thick aluminium for the belly pan, which I afixed to the main frame rails with self drilling screw covered with silicon sealent to prevent rust. What you need to do is take a look around under the vehicle and see where it would be conveniant to attach. I would take some pictures of what I have done, but there is over 20cm of snow on the ground.
On one section at the front I instaled a peace of pressure treated wood onto which I could scew the aluminium panels.
I had a sheet metal shop make some angle peaces for the section behind the rear wheels.
What it all comes down to is each vehicle is different and needs its own solution...

the front vent cover only serves to allow the vent to be open in all conditions. If you simply remove that cover and build a very simple fairing behind it, no need to delete.
Same with the roof air. if it is not needed/not functional, it is easy to replace with another low fan cover. A small fairing behind each of those will re-attach flow nicely.
The roof air is typically installed through a standardized 14" by 14" hole.
I picked up a replacement fantastic fan for my bathroom for $126 at PPL motorhomes.
The better unit is about 160, with a thermostatically controlled fan.
I have one of those at the back of our trailer and it is very nice to turn on the fan, set the thermostat and go out for the day.
As the temperatures go up, it only runs as needed to keep things reasonable.

It is also easy and very nice to replace the roof air with a faired skylight. I really appreciated all the skylights I have had in my trailers. The small bump in frontal area is a small price when you fair it properly.

sketch
 

Here is an image of what NASA did to a Ford Econoline van.The large radius nose sections of the van would be placed in front of the squared-off leading edges of the RV.
They could be 1/4-section members,hinged at the outer edge,and swung into place and latched after the doors were closed,or attached to,and move with the doors (which would be safer if you had to egress in an emergency),with the upper section of Plex or Lexan so you could see through it,just as NASA has done.
Here's the photo

hi
had put aerodynamic tool on photo of my motorhome. ummmmm not fesiable to do boat tail but can alter back to make it aero dynamic make upright courners curved add a small roof extension to carry air flow away from rear wall. hope to design some sort of diffuser on bottom rear to aid air flow and cover grey water tank found some lawn edging on ebay made out of recycled plastic an is 1mm thick by 165mm. got some bracing sorted out. going to add skirts and front airdam of this lawn edging. suggestions on how to cover rear wheel arches to allow for change of tyre and if nessasscery rear brakes. underbelly on engine looking to fit sump guard and follow on from there.

Nice project !

So which is the most streamlined approach for the does to cabin section ?
A nice fat radius or a tapered angle ?

If it happens to be the angle, you can even use standard doors on a dummy frame for a little more room and a nicer look and fully functionning doors.

which
 

The air prefers the acceleration/pressure profile of the radii compared to a simple angle.If you're forced into using an angle due to some project constraint,it will be better than a hard 90-degree corner.
If you purchase a couple ice cream cones and take them up to the laboratory elevation of the Eiffel Tower and drop them onto the American tourists below,ice cream first,then cone first,you'll find that the ice cream first type will fall at twice the velocity as the pointed ended one.
The blunt,convex-hemispherical nose is the benchmark for lowest drag in sub-transonic flow.

Sure, that was my first thought but then I wondered because it is a transition area so the flow is along the (half)door then turns around then back to the initial direction.

The door at an angle with appropriate radius everywhere possible sounded like a smoother transition in the full system that is the motorhome.
But I assume I was wrong ...

transition
 

There's no 'wrong' about it.
The original cab-top air deflectors for tractor-semi-trailers did the angled panel and to good effect.
You could probably put the RV in a wind tunnel and actually 'open' the doors with the windows rolled up,at varying angles until you found the degree of 'opening' which produced the lowest drag.Then fashion 'spoilers' which mimic'd the open door.

Hi
have fitted some rear wheel covers and altered the front of my dolphin. i had a full width bull bar on front. made a cover out of 3mm ply that covers radiator grill. this was fasten to front of bull bar. so nowair that would normally go through grill is now forced over the bonnet. as the bull bar keeps the plywood away at top by 1" and 5" at bottom. also air can get in around the sides for cooling. hope this makes sense. if not i will take photos and post.

Let's hope you don't run in cooling issues.

Do you plan on using the dolphin anytime soon ?
I am curious of of the evaluation of aero mods on such a big vehicle

Hi
use my dolphin as a daily runner. cooling at moment is not an issue but will moniter it. as air temp is just above freezing don't expect any probs until spring. initial feeling is good. can feel overdrive coming in at 45mph. when gliding up to a junction i can lift off accelerator a lot earlier. have log fuel condumption on every tank since i bought it. gone from 13mpg to best 16mpg. am trying to reach 20mpg. any higher is going to be very difficult. toyota camery with same engine finds it hard to reach 30mpg.

Hi
took photos today but resalution is too high for upload. at the moment according to fuel gauge i have increased mpg by 1-1.5 mpg. when i fill tank again the figure will be more accurate. next job is to order parts for front airdam. also remembering some in past whst saab fitted underneath 900? To aid road holding and drag reduction. think it was along the lines of an airdam in front of rear wheels. basically a v shaped dam with the point of v along centre line of car. wide part of v finished just in front of rear wheels. will need to do more googling on this.

If you happen to have a google account, upload the pics there and then link here.

And show the percentage fuel economy improvement . . at the high consumption rate of this vehicle type that is where the gains really stand out.

Better yet, use a photo editor such as Photobucket to resize them down to, oh, 700x700 or less, so they don't take an hour to load and for those of us without 6' wide screens, they don't need to "resize".

Hi
if my maths are correct its about 8% improvment. still more mods to come front airdam and sort out air flow underneath. chassis and underbody are and aerodyamic mess even worse than body shell. if i can get a smooth air flow underneath should see a reasonable improvment in mpg. this will wait until it warms up and wind drops probably next spring. so will have lots of time to plan and gather material etc etc ready for installtion

Hi
have sorted out a mk 1 version of airdam. dosent look to bad. altered slope of grill cover. when passenger wiper fell off at 50mph it just sat on bonnet and never moved. leads me to think there is now an area of static air in front of windscreen. done some temperory wheel arch covers and fitted wheel trims to rear wheels. also altered maf spring to lean out a factory set very rich fuel mix. cannot give an accurate mpg due to coil wire playing up and servre weather conditions. last week 143mph winds now chill factor is diwn to -10c. so cannot replicate journeys with any consistency. what i can tell is my dolphin is a lot less twitcy in a cross wind. even if mpg does not improve the whole driving experirnce is more pleasent.

So what did you find out? It sounds like a bad idea to me. Two V's in front of and/or behind only the tires would be a wheel spat, which would be helpful. Including the area between the tires would trip up the airflow exiting the underbody. Of course unless you have a bellypan it's probably a mess anyway.

:eek:

Hi
still cannot find anything on google but sure it was a saab 99. Will delve into old car mags an article writtern by performance car magazine in mid 80's
Yes 143mph winds. check scottish weather for far north of scotland (orkney islands) been told we have 2 weeks of 90mph winds. dolphin is less wandering but lean with wind is a strange feeling. need to get rid of air con unit (all 40kg) to help with lean.

I would love some pics.

99
 

It might be the 900.I spent some time on my back at a Dallas SAAB showroom in the early 1980s looking at all the plastic bits of the 900's underside.It did have some V-shaped components.
I felt as if these were all for splash and spray control rather than drag reduction.Don't know,and as far as I can tell,nothing was ever published about it.:o

Well, I've driven Hwy 99 on the Oregon coast in 80mph crosswinds (in the horizontal rain), but at 140mph I'd want somnething like this:http://blogs.cars.com/.a/6a00d83451b...4fff970c-800wi

Any improvement in driving experience is a huge success, IMO. Keep it up :)

Hi
will take phots when weather breaks. have you heard about the storms bsttering uk. where i live is 90+mph winds. all mods so far are a bit rough but hope to improve them in spring time.

Hi freebeard
what were you driving in 80mph winds. my dolphin is like a huge brick not the best vehicle for strong winds but more stable than my old 4wd.

hi have manged to take some photos of mods before wind goes back to silly speed. had to brace myself against a wall to stop camera shake. you cannot see front air dam very well but goes from bull bar mounting points to just below number plate. hopefully in new year my mate who works with stainless steel and aluminum will do a far better job than me. feel free to comment good bad or indifferent.Aero Mods Dolphin Motorhome Photos by chefdave42 | Photobucket

Aero Mods Dolphin Motorhome Slideshow by chefdave42 | Photobucket. estimated 6% improvment

Put a sail on it and get infinity mpg.

:):):):):):):):):):):):):):):):):):):)

LOL why did i not think off that

:):):):):):):):):):):):):):):):):):):)

Rear Spoiler Idea Photo by chefdave42 | Photobucket
hi would this rear spoiler idea work on my dolphin motorhome. am planning to use plastic drain pipe or guttering to form base of spoiler then use gaffer/duct tape to cover up gaps for road testing. would it be better to angle down 12-15 degrees or keep parallel with roof line.
thanks
dave

http://i783.photobucket.com/albums/y...swmpyensn.jpeg

Which part are you talking about? The light gray cornice is a decorative appliqué. The stair-stepping abaft the side door will induce separation which may not reattach, transmitting base pressure up to full cross-section.

If they had mimiced the plan taper and rear edge shaping of the Prius, just scaled 100% in Y and 15% in X, that would be awesome. Flat sheet materials with curved, obtuse edges.

As for that drive on the coast—I've been trying to remember. I recall it was around Neskowin in the 80's, and the car had really good windshield wipers. So it wasn't a VW. I also drove that road in a rental Mercury Sable station wagon with 7 miles on it, on ice. I really liked the tires. OTOH, what I was telling people earlier this month: "Ice—the Great Equalizer."