Increasing frontal area and reducing drag

[skyking]

I have been kicking around my travel trailer design for years now, and like all things it has gone through several changes. it is a good thing I have not started construction yet!!

Here are the nuts and bolts of the latest changes.
before, I was committed to the lowest possible frontal area while keeping certain interior size goals.
This meant compromises in the shape, compromises that would not produce the lowest possible CD.
Now I see the folly in that approach.
If I increase the area from 60 to 64, for example, it means a change of around 7%.
If the new shape, (which still meets the interior size goals ), improves the CD from .30 to .27 I have made an overall improvement in CDa.
If it goes from .30 to .23 I have made some serious improvement.
Basically the more I can do to match up with the template the more I can gain, regardless of increase in frontal area.

[AndrzejM]

You should share some drawings... Good thinking anyway!

[freebeard]

I have been kicking around my travel trailer design for years now, and like all things it has gone through several changes. it is a good thing I have not started construction yet!!

Myself also, but I'm dangerously close to sliding into doing something.

60 to 64 what? Square feet? That's 7x9.14 feet. Here's my attempt at a trailer. Although it was intended as a teardrop, It would scale up to Airstream size. The rear entry is cribbed from the Bowlus, only backwards.



and here is the frame design, stolen directly from the 1952 Silver Streak Clipper I used to own. It had a central spine, steel C-channel crossmembers, a carriage bolt in the tip of each one and an aluminum C-channel plate to build the sidewalls on.

[Hersbird]

I'm still on this as well, lately been thinking more about doing a 5th wheel where the slider hitch design could tuck it up to the truck better, except I don't actually have a pickup anymore. There was a $995 "handyman" special 5th wheel down at the local big RV lot's annual winter clearance that looked pretty good. It didn't get so tall as the newer ones and I thought just cutting the side walls down and tapering the roof down to the floor might be pretty easy compared to starting from scratch. It would lose the rear door and rear booth, I would lower it and take all the stuff off the roof. putting a radius on the side edges of the roof would be better but more difficult.



Then there is the hybrid style with the tip outs front and back. I thought those tip outs might actually make a good platform for a boat-tail add to an existing one of those. Heck even the front tip out looks like it might helpf fill the SUV to trailer gap.

[skyking]

Originally Posted by AndrzejM

You should share some drawings... Good thinking anyway!

I know, I really need to do that.
In this post you can see the old roof profile:
http://ecomodder.com/forum/showthrea...tml#post258401

That section view met my interior size need, but now I see the light. If I add height to the section so it becomes more of a body of revolution, It will have less drag with more frontal area.
Now it will be limited by the size of garage door I want to drive it through.

[Grant-53]

A super slick trailer design is the one used to transport sailplanes.