[orbywan]

Originally Posted by rickjames8

Hello,

Not sure if its better netiquette to reply to an old thread or start a new one, but as my question is about this original mod, I thought it would be best to reply here. If it's better to start a new thread, let me know and I'll do that next time.

Either way is OK RJ. If you make your own thread let me know, I'll subscribe to it, I'm interested to see what you'll do.

As far as your class C boat tail is concerned, do you think it would function the same if it just had the sides, and no back? This way you could have access to that space, and even place a cargo box or spare tire in there. Rear lights would simply be mounted to the edges. Any rear window would still let in light.

Just sides and no back is way more desirable than no sides at all. Mine is closed in the back, with a door, and is great for adding storage space. I have an extended hitch back there also which makes for super support for the back floor. I'm still adapting and building back there but I carry tons of stuff in the boat tail that I wouldn't be able to carry ordinarily.

Also, I've noticed that coroplast seems to be the material of choice for all boat tails. I have always enjoyed working with fiberglass. What is the main reason people do not use fiberglass? It has strength when it hardens, so you could save weight with a lighter frame while still having the structure rigid. I think in the end, the weight might be equal. Thats just a guess.

I think the reason you see so many coroplast mods is it is one of the best materials of choice for prototypes. It is easy to cut, shim, remount, take off and change the frame, or whatever. To me it is a temporary medium (except for the bellypans maybe) to work out the shape I want before I go to fiberglass or sheet metal or foam and fiberglass.

Lastly, how long do you think a boat tail on a RV would need to be to be very effective? I'm looking at 21-foot RVs primarily because I didn't like driving a longer one when I owned a big class A. I'd like to not add any more than 18 inches to the back, but would that get noticable results or be worth the effort?

Thanks,
-Rick

I don't know what the accurate answer is to the 18 inch question. Hopefully several of the experts here can answer that for you. If all else fails PM aerohead, he'll know for sure. My rig is 25 feet without the boat tail, and the tail is a little over 4 feet long. So far the added length has not caused me any problems and I take it some crazy places, everywhere from RV shows to off road locations like Cherry Creek in the Sierra Ancha's in Southern Arizona.

This afternoon I'll dig up a link to the study that NASA did on a 69 Econoline van at Dryden AF base back in the late 60's, I think you would enjoy reading that. A very interesting real vehicle (and wind tunnel) project on the particulars of changing the aero characteristics of a 'brick' shaped vehicle. Good stuff.