TEARDROPS HAVE CURVES

[bobhenry]

The true airfoil design of a teardrop I have discovered is fairly simple to develop into full scale. I think I have found an almost fool proof production technique that gives results that are the true airfoil teardrop profile.This worked beautifully for the side profile on my 3x6 toy trailer but I'll use a 4x8 as an example. I have not seen a profile developed this way but if I'm stepping on any toes I will apologize in advance.

On a 4x8 sheet measure from bottom front up 2' and in 2' this is a pivot point for the front profile. Make a 2' compass using a narrow rip of plywood with a nail and a small hole for a pencil point exactly 2' apart. put the nail on the point just developed and starting at the 12 o clock position strike a semi circle arc top to bottom. Tear is now 4' tall.

make a second compass the length of your tear (in this case 8' )
starting at the 12 o clock position exactly 2' in from the top edge strike a long arc I placed a second sheet of plywood butted up to the bottom edge of my side profile and just a little ahead of it. the 2nd pivot point will fall at about the 4 o clock or 5 o clock position so make a long arc from about 3 to 6 o clock
go to the rear bottom corner and strike a second arc .Where these arcs cross is your pivot point take the long compass and place the nail on this new point and strike an arc from tail to the 12 o clock position of the front arc. I like the profile except for the pointy tail so I experimented and used the same 2' compass to bob the tail slightly making sure the arcs blends smoothly. Try it on paper to scale I have had several positive comments on eggbert my 3x3x6 motorcycle teardrop

I keep losing these pics so I am adding them here. 4 1/2 years later

[Steve_Cox]

Hi Bob

Got any of "eggbert"?

[toypusher]

Hi Bob

Got any of "eggbert"?

Yah! Pictures, pictures, pictures!!! .................Please?

[bobhenry]

He's in my album but having troubles getting my build pictures to scan I'll figure it out. Eggbert is a cargo Teardrop for my Goldwing. We have a 14' Ritz we leave at the camp grounds year around and Eggbert's job is to haul an arm or two full of firewood and a couple coolers of food and barley pops to and from so we can enjoy the bike and camp out too.

[angib]

A couple of points on your profile:



- By using a 96" radius for the back, it doesn't reach the horizontal at the front and so there is a sharp kink between the front and back curves.

- The front radius gives you that classic aerofoil look, but you lose 24" of floor length, which is now only 72" long including the galley. Of course a bit higher up you have quite a bit more length, but it means you need an odd shape to the mattress (out with the electric carving knife...).



If you reduce the rear radius to 78", the curve goes horizontal as it meets the front curve, so there is no kink between them.

If you switched to a 48" radius for the front bottom, you lose only 6 3/8" of floor length.

Andrew

[mikeschn]

Very nice Andrew!

Mike...

[Arne]

my opinion is the top should be sloped more than the bottom, which does not get as much air pressure... and it would look better.

[bobhenry]

A couple of points on your profile:



- By using a 96" radius for the back, it doesn't reach the horizontal at the front and so there is a sharp kink between the front and back curves.

- The front radius gives you that classic aerofoil look, but you lose 24" of floor length, which is now only 72" long including the galley. Of course a bit higher up you have quite a bit more length, but it means you need an odd shape to the mattress (out with the electric carving knife...).



If you reduce the rear radius to 78", the curve goes horizontal as it meets the front curve, so there is no kink between them.

If you switched to a 48" radius for the front bottom, you lose only 6 3/8" of floor length.

Andrew

The 96" radius is developed by intersecting a common arc from the bottom rear corner and the apex of the semicircle front so if the distance from the 12 o'clock position to this common pivot point is 8' the distance from the pivot point to the apex has to be 8' also and they WILL meet smoothly. I am using a torsion box floor and the profile is attached at the bottom of the floor so the bed deck can be extended forward approx 15" I wish I was computer savy enough to show you without my number 2 pencil Bob

[bobhenry]

my opinion is the top should be sloped more than the bottom, which does not get as much air pressure... and it would look better.

I didn't expect everyone to fall in love with this profile!
I liked it because you can start at the tail and wrap under the torsion box floor and continue up and over the top with aluminum or frp and mount it on a flat bed trailer with or without a floor. It is easilt removed to utilize the trailer as a utility flat bed. I also thought the fact that 2 rips of plywood or osb can turn your router into a radius cutter for smooth curves to help an inexperienced builder form curves like a pro. I have had positive comments on Eggbert and value everyones input.

P.S. Will the bottom half see any air pressure in the vacuum wake of the tow vehicle ?

[bobhenry]

A couple of points on your profile:



- By using a 96" radius for the back, it doesn't reach the horizontal at the front and so there is a sharp kink between the front and back curves.

- The front radius gives you that classic aerofoil look, but you lose 24" of floor length, which is now only 72" long including the galley. Of course a bit higher up you have quite a bit more length, but it means you need an odd shape to the mattress (out with the electric carving knife...).



If you reduce the rear radius to 78", the curve goes horizontal as it meets the front curve, so there is no kink between them.

If you switched to a 48" radius for the front bottom, you lose only 6 3/8" of floor length.

Andrew

My deepest apologies Andrew when I 1st vied your post the drawings were not showing I tried to develop a common point at 78" from the rear point and 96" from the top apex since you only specified the rear change. It just didn't work ! I redrew using 78" from rear and apex it looks good , real good , but I still like the round front just a personal taste

thanks for your insight and the wonderful cads work I'm jealous of your talent. Bob

[twdarty]

I'm building one like the eggbert, but 4 foot wide, for a biker. What would be a good price to ask for it? Terry

[bledsoe3]

I'm building one like the eggbert, but 4 foot wide, for a biker. What would be a good price to ask for it? Terry

I would start with the price of your materials. Then figure how much time it takes and what you figure your time is worth to you. Add them up and that's your price.

You might figure in a little for waste.

[Alphacarina]

http://www.angib.pwp.blueyonder.co.uk/t ... tear00.htm

Check out page 2 of the profile drawing for the Grumman2 (Sorry I don't know how to attach a pdf file)

They show the points for drawing 2 ellipses which make a very nice profile . . . . they even leave you with a short (almost unnoticeable) flatspot for installing the roof vent

Don

[bobhenry]

I'm building one like the eggbert, but 4 foot wide, for a biker. What would be a good price to ask for it? Terry

Labor = Material cost times 2 at least !

I have a complete blog of eggberts build I will try and P.M. you ( If I can figure out how) Are you intending to use the little harbor freight trailer or will your frame be custom built. I had severe handeling problems with the short tongued devil. I purchased 8' of 2 1/2 x 2 1/2 x 1/8 square tube and replaced the factory tongue . This lengthened the tongue by 2 feet and he pulls nice now. I kept the overall width within the width of the handlebars to keep from hanging a trailer wheel on something. Think about over all width not just the box.

[bobhenry]

Here is Eggbert with the lexan look ! The vinyl for his vinyl top is on order. His frame was just painted to match the Goldwing and his extended tongue works great.