Sylmar Hang Gliding Association

Tired of constantly retouching up my basebar I decided that it was time to try and design something that looked like the Wills Wing skids they (wills wing) are basically giving away. I've researched making (molding) the product with a silicon mold that I did from my molding clay mockup. After the silicon mold was created, I used casting resin to make a prototype. The skids a still pretty rough looking (need some better sanding and maybe a touch of paint. But they slide on (snuggly) and don't seem too fragile. The base bar was scratched once again this weekend while setting up in our rocky area (hence the motivation to solve the problem).



I'm in the testing phase right now to see how well they hold up (expect no real issues). Designed them to be removable. Some Moyes pilots in Sylmar have just glued skids onto the bottom of their basebars. They work well and I haven't seen anyone break one yet.



If these skids hold up, then I have a person (OP) that is going to CNC a few to see how well we can make them.



Comments welcome.

OP, I'll have one ready for you when you want it. I hope we can make a few slight modifications with little trouble. The skid doesn't sit flat at the moment (has a slight lean to it). But they slide on well.

Any beta testers want to test a set?

Get me your prototype, or a sketch and I can have some prototypes done by the weekend.

I see what WW has done: http://www.willswing.com/news.asp?newsSeek=624

That's easy for me to do.

Good idea.

My solution:

#1 Stainless steel self adhesive tape.

Didn't last long.



#2 Aluminum "shell", made from discarded downtube. The downtube has

the same profile, as the basebar. Attached with thin automotive double

sided VSB tape.

More than 2 years now, and going strong.

OP wrote:Get me your prototype, or a sketch and I can have some prototypes done by the weekend....

I have the exact profile in pdf if you want it to convert to CAD.

PLZ send it over.

Both Moyes and WW if you got'em.

OP wrote:PLZ send it over.

Both Moyes and WW if you got'em.

Need a valid email address.

Vrezh, I'm trying to completely eliminate the scratches on the base tube altogether. Only by getting above the ground does that appear to be possible.

So, I'm going the skid route. Removable and easily replaceable.

Did some testing on the skids I created, they work OK, but I want some more resistance to the sliding when they are on and the base bar is resting in the skids. The base bar will slide inside the skids even though the tolerance is very close.

So, I'm going to pour a rubberized mix that will hopefully yield a bit more resistance to the sliding and potentially grip the bar with enough flexibility that the skid can slide on when not resting on the ground but prevent the bar from sliding inside the skid when the base bar is resting on the skid.

The rubberized mix is supposed to have the consistency of a break pedal or other hard rubber like the bottom of a shoe I'm told. The current skid is made from casting resin.

At around $25 dollars for the Wills Wing skids, it seems like a steal.

I am hoping to sell a few if they turn out well, although I realize Moyes could always start producing them and basically make anything I produce immediately obsolete.

Chip,

Have you considered using an adhesive caulk to secure your skids? A rubberized (or siliconized acrylic) caulk applied to both sides of the joint may well solve you movement problem. You could use a clear caulk, and it could always be removed pretty easily later.

RM

I'm designing the skids to be removable much like the WW skids. They slide on from the inside handle area as shown in the picture.

The casting resin is strong enough, just allows the basebar to slip when resting on the ground. The rubberized solution should give me the flexibility and grip I desire.

http://www.aeromarineproducts.com/make- ... e-mold.htm

I desire to cleanup my basebar one last time and then have the skids protect the bottom of the basetube from scratching the bottom from there on out

Let's just duplicate the WW effort. Use your mold and technique to get the external shape and size. Deeetch got me the internal shape. I can design it with a press fit such a rubber mallet would be required to install/remove. I've got 24/7/365 access to machine tools that can cut them out faster than a mold can.

Just because the resin has a durometer/shore of approaching that of a brake petal doesn't mean it has the strength, self lubricity or over all wear resistance to make a usable part. WW uses Delrin for good reason. Think cutting board material but better. Super strong, wear resistant and slick engineering polymer. WW's 2006 price was 10.5$/pop. Like the price of oil, plastic goes up in a similar amount. I can almost guarantee that they now charge more.

There are stronger and more exotic materials available. PEEK is the first that comes to mind. Approaching the strength of aluminum, peek is very strong. However it is super expensive, and not as wear resistant.

Put an add on the OZreport/Hanggliding.org and get a large order together and let me know how many to make. Setting up the machine to make one part is nearly the same hassle to make 100 parts.

In the event you get orders for 100s of them, I'll have an injection mold made. A plastic injection mold for shooting delrin of this complexity is made for about 1500 bucks. After that each part costs just a tad more than the price of the material in less expensive pelletized resin.

TL;DR (too long; didn't read):
Get me a napkin sketch of the external shape you want. I can make as many as you want for less than the WW price.