payneinthe

Google's cache of HPM's website says $500.

krazik

http://web.archive.org/web/20040208081800/....com/index2.htm

They're still around but seem to not have interest in having a new fangled interwebsite.

drewchie

Gracias

kitwetzler

So I bought an Ebay wing. at 85 it produces enough downforce to noticeably deform the trunk. I suspect it also produces a lot of drag which is less than bueno. Good thing I bought that spare trunk! I was surprised, I would've thought that a wing making a lot of drag would deform like you were pulling it backwards (front mounting point up, rear mounting point down), but both go down.

I'm gonna drop some bar stock into the trunk as reinforcements.

Pics later, but it's UGLY

rlaifatt

Spraying foam filler into the channels under the lid helps stiffen it a lot also. Available at Home Depot.

kitwetzler

good idea, thanks!

guess I shouldn't have cut holes in them...

krazik

just bolt all the way thru the lid and the underside supports with a metal plate to spread the load on top. No foam needed.

mikegarrison

As you found out, it doesn't quite work that way.

There is a center of pressure, around which there is no moment. But that center of pressure moves. The structure doesn't move. So moments do get generated. However, the moments are small compared to the lift.

jzr

Mike, I think he's referring more to the resultant forces acting at the mount/trunk interfaces and not so much what's going on at the wing/mount interface.

Kit, the lift/drag ratio for your wing at the speed/angle/postion you're giving it will produce a net force that is both downward (-lift) and rearward (drag). With a high lift wing the sum of these two forces will be in a direction that is (very roughly) 30 degrees back from vertical. This net force originates from the center of pressure Mike describes. For most wings the COP is about 1/4 to 1/3 chord (chord is the length measured from front to rear, called the chord) behind the airfoil's leading edge, though its exact location changes with angle of attack and other airflow characteristics. With the multi-element stuff like Bomz has the resulting COP is trickier to find.

Whether the forward trunk mount is in compression or tension depends on the actual angle of the resultant lift/drag vector, and how that relates to the angles of the forward and rear trunk mounting points in relation to the center of pressure.

Solution: Use lots of beefy metal everywhere; if you can jump up on down on it, and shake the whole thing like a crazy caged gorilla* you're probably okay!

*gorilla part optional

mikegarrison

Yeah, guess so. I'm more conversant with wings where all the structure is inside the wing.