FLYBOY

My Feedback: (11)

To the guys making landing gear that are working, what cloth and how much are you doing?

I made some 40 size that turned out nice, but am curious what you are using. I used some heavy CF, but it doesn't have anything that will tell me the weight, and some light glass, but again, nothing to tell me the weight. Just curious what people are doing. I did 1 layer of CF top and bottom and 6 glass layers in the middle, but the glass is really light. Too light I think. I am guessing it is 1 or 1.5 OZ glass cloth from the feel of it. The surfaces turned out like a mirror though. They look good.

davidfee

What you've got there looks about right. You may find that they are a little flexible, being that thin and with only 1 layer of carbon... but they might also be perfect. The carbon looks to be something like 5 or 6oz. The finish looks great!

-David

davidfee

If your gear is too flexible, you might try using some unidirectional carbon. It doesn't look quite as cool as the bidirectional fabric, but it has the fibers all running one direction. With the fibers running lengthwise, it will result in stiffer and stronger gear. You can always use the bidirectional on the outside for that cool carbon look.

-David

FLYBOY

My Feedback: (11)

Ok, cool, thanks for the info. I think you are right on the cloth. The way I got the shiney look is to put clear mylar on as the last layer and then peel it off when it is all set up. Is there a better way to get that shiney smooth look without the mylar?

davidfee

Unless you want to go to the trouble of a "real" mold, then Mylar is the way to go.

nice work,
-David

FLYBOY

My Feedback: (11)

Thanks. Made a good mold, with a good epoxy finish, but just can't get the clear mirror finish like I can with mylar. Don't understand why it doesn't give the clear finish from it, but this works.

davidfee

Have you polished the epoxy-surfaced mold? Wet sand with 600 and up to the finest sandpaper you can find. Then flip the sandpaper over and use the paper backing. You can use polishing compound after the sandpaper. Once the mold is polished and cleaned, then apply the wax, allowing it to haze, and then buffing between coats. You should get a very deep, glossy finish which will transfer directly to the finished part.

-David

Ed Smith

Now there is a sanding freak if ever there is one!!

Ed S

FLYBOY

My Feedback: (11)

Ok, thanks. I will do that. Have to re-do the mold anyway. It looks like some of the epoxy pulled from the face of it. We used a wood mold and the guy that made it originally screwed it up, so I put a few coats of epoxy on it, but I think it would be better at this point to make a mold like you said instead of screwing around any more with this one. I have gotten about 5 good gears from it though. Useable, but not perfect like I want. I will keep playing with it. I have a very expensive heli mold that I want to pull, but I want to learn on other stuff. I built a full scale moldless aircraft, but man, this is way different. I thought I knew what I was doing but I am a major rookie. It is fun though. I switched to west epoxy instead of the hexcel I was using. Heck of a lot cheaper. Save the expensive stuff for the Long EZ. I will probably bug you some more at some point.

Thanks for the help though. I appreciate it a lot.

cnbhome

My Feedback: (2)

On the flexability of the gear the strength of CF comes from its tensile strength meaning it does not stretch. By using a separator such as a glass filler and making the structure thicker you can gain resistance to the flex and still only use one or two layers of CF, keeping the cost down. The thicker the structure the stronger the part because you are trying to stretch the long fibers on the outside and compress the epoxy on the inside of the bend. It is all a balancing act.

CB

FLYBOY

My Feedback: (11)

The ones in the picture are 2 CF layers, one on each side and the last one I did was six layers of glass. I think it is like 3/4 oz or 1/5 oz. I don't remember right now. Anyway, the flex is good for a 40, but it would need to be stiffer on a larger plane. I am going to try my rutan uni cloth on the next one and see what it does for stiffness. Will require less layers because it is 5.7 oz I think. Might be a train wreck waiting to happen, but what the heck, I am learning. I broke two of the gears I made just to see where they would break and how much force and they took a lot, but both broke at the bend where it starts down off the fuse. I am thinking I need more radious on the gear.

davidfee

Bingo! That's exactly right. The larger radius will reduce the stress concentration at the bend.

-David