lamarkeiko

My Feedback: (1)

I want to strenthen my Four Star 120 landing gear from bending so easy. I have some carbon fiber cloth and 6 oz fiberglass cloth and resin. I came up with the idea of applying some layers of the cloth and resin to the LG to help stiffen it. Has anyone done this before, and if so, what was your methods and results? I't appreciate any opinions on this idea. I've never read this being tried before.

Thanks
Lamar

speedracerntrixie

My Feedback: (29)

It's possible to do but prep of the aluminum is key as well as.using a quality laminating resin. It must be sanded and very clean. Vacuum bagging would pretty much be a must. The other thing is you would want to encase the gear in CF not just add to the top and bottom. I would also suggest heat curing at 100-120 degrees.

foodstick

You could always run some wires from the top left to lower right and vice versa..forming an X . I always thought that looked good.

lamarkeiko

My Feedback: (1)

The method I was thinking about was to coat the inside LG surface with resin, apply a layer of 6 oz fiberglass cloth with more resin on top. Add a layer of carbon fiber cloth with more resin, then a final layer of fiberglass cloth and resin. Then use a small roller I have to work the resin well in the cloth, squeezing out all excess resin. Once that was cured, I would turn the LG over and repeat on the top.

speedracer, I don't really see the necessity of vacuum bagging. I built a cedar strip canoe using fiberglass cloth and resin, and all that was necessary was using a squeege to get out the excess resin. My biggest concern was attaching to aluminum, not knowing how well the resin would adhear to it. Possibly doing some roughing up of the LG surface before applying the resin.

foodstick, I have a plane in my hanger with the wires attached to the LG as you mentioned. It works fairly well, but I still end up breaking the wires from time to time with rough landings, and have to replace them.

Lamar

foodstick

I think your technique should help..

I have a friend that has put two different halves of gear back together the way you are wanting to do it. from two different crashes
His aren't pretty and he has re-broken them before.. but if you are beefing up good gear it should be strong...

Maybe you could just lay up your own gear using the aluminum for a mold? Multiple layers of glass with carbon in the middle of the sandwich ?

scale only 4 me

My Feedback: (158)

1- I would think the resin/glass would sooner or later crack away from the alum as the different materials would expand,contract and flex at different rates,
2- those gear have such an extreme angle, doubt that method would do much anyway,,
3- a wire or cable spreader bar is a much better idea IMO, I've don't that before and it works

good luck

lamarkeiko

My Feedback: (1)

[QUOTE=scale only 4 me;12149979]1- I would think the resin/glass would sooner or later crack away from the alum as the different materials would expand,contract and flex at different rates,
2- those gear have such an extreme angle, doubt that method would do much anyway,,
3- a wire or cable spreader bar is a much better idea IMO, I've don't that before and it works

good luck[/QUOTEThat is my main concern, the different materials separating from each other. I was thinking that as long as the top and bottom laminations are attached to each other all away around the edges, that the aluminum LG would be totally enclosed, and isn't going anywhere. Not quite sure what you mean by the extreme angle which gives you doubt that the method would not work. I did build an LG with the carbon fiber & fiber glass cloth once, using a 2012 Fly RC article instructions. It worked fairly well, and I still fly the plane with those LG. It's just a longer process of building a form and using many more laminations. The good side of building the new LG from scratch is the saving of weight. My original aluminum LG weighed 6 7/8 oz and the new carbon fiber/fiberglass LG weighed 2 1/2 oz. Maybe I should just use my Four Star LG as a form, and just completely make new LG. My Four Star LG weigh 7 3/4 oz.

Lamar

speedracerntrixie

My Feedback: (29)

Using a vacuum bag will do a couple of things. First it will compact the layers of cloth together tightly. This will greatly increase the strength of the composite layup due to the fibers nesting within one another. It will,provide a surface that will require far less prep for painting if you so choose provided you bag using peel ply and breather. Most important, it will remove any air bubbles you may have between the aluminum and composite materials. Those air bubbles is what would eventually lead to delamination.

lamarkeiko

My Feedback: (1)

I believe you are correct, but getting set up for vacuum sealing is more than I want to do for now.

Lamar

Jennifer Curtis

Wrap the fiberglass around the aluminum. Probably
one edge is tapered, most likely the rear (like if the .
gear was flattened out it is straight across the front,
and the back edge is tapered on each side from
the fuselage to the wheel). Start with the edge
of the fiberglass cut to match the tapered edge.
Wrap it around the front edge which is straight
and back around the tapered edge again.
End with one side with a complete overlap, thus
three layers, two on the bottom and one on the top.
Do this after epoxy already be spread on the aluminum
and work it into the fiberglass.


Put plastic wrap over the whole thing, and then
strips of wood over to hold the fiberglass against
the aluminum. Then wrap the whole thing with
string until the epoxy hardens fully.

Having the fiberglass wrap around the edges
will help to prevent delamination.

If you want, you can go another half way around,
for two layers on both sides. The more you go
around, the more the tapered edge will "skew"
the weave and make it difficult. Doing it like I
described above, only the last layer is skewed.


Jenny

GREG DOE

Lamar, My advice would be similar to what has already been expressed. Use wire bracing, possibly with springs, but if you want to fiberglass an aluminum landing gear, let me give you a few suggestions.
But first let me tell you about a solution that is employed for a slightly different full scale problem. The most popular home-built series of airplanes is the Vans RV's. The landing gear on most of these airplanes are a two piece steel tapered round gear leg, that is mounted in a "pocket" on the firewall. Some of the airplanes suffer from a sever shimmy, similar to the wobbly wheel on a grocery cart. Vans recommended solution is a fiberglass wrap. That's the simple description. In practice the repair is accomplished by constructing a wood leading edge, and a foam trailing edge, which is then wrapped in cloth. The glass can be sanded smooth for the finished fairing, or the standard aluminum fairing can be used over the glass reinforcement. This changes the resonance at which the gear leg vibrates, and generally cures the problem. I sight this an application where fiber-glassing is used to stiffen a landing gear.
Now, if you are still intent on fiber-glassing your aluminum landing gear, my suggestion would be to use fiber-glass sleeve, or "sock" material. Fiberglast.com calls it BRAIDED BIAXIAL SLEEVE, and they have it in both glass, and carbon. Of course the carbon sleeve material is probably more expensive then a new custom made landing gear; aluminum or carbon! Glass sleeve material would be my choice, since the difference in the weight between carbon, and glass on a project like this would be small. Several layers of sleeve would be used to get the desired thickness. Another option would be to use regular glass or carbon cloth wrapped around the landing gear, with the sleeve used to hold it all together. I would strongly recommend vacuuming bagging, and sealing is really not that difficult. You just need the right materials. Fiberglast Developments Corp. has a number of instructional videos on their web site that you could check out.
One final suggestion on making carbon fiber landing gears. I won't give a blow by blow description.
The procedure involves making a form that looks sort of like a piece of a gutter. It can be an inside, or outside mold. Cloth, usually carbon is layed up, and the whole thing goes in the vacuum bag. Think of the layup like a rack of ribs, and you saw off slices. The gears I make are a carbon/glass sandwich. As an example one gear I make is 5 layers of approx. 5.8 oz. per sq. yd. carbon with a layer of 9 oz. per sq.yd. glass in between each layer of carbon, for a total of 9 layers. Good luck, and be sure to let us know how the project turns out. Greg

SunDevilPilot

Do this.

http://www.flyinggiants.com/forums/s...ad.php?t=88397

speedracerntrixie

My Feedback: (29)

Or do a search on EBay for CF gears. Usually the correct size can be found.

CK1

My Feedback: (60)

I have used the B&B gear support on a few planes . It works well .
http://www.bennettbuilt.com/shop/Whe...doffs_316.html

MTK

Bingo.....
Or use the original ally gear as a mold to make a carbon and ply composite. Tape parchment paper to the ally and lay in 6 layers of carbon, alternating the layup from orthogonal to bias. Add 1/8" ply pieces to fit. Then cover the ply with 6 layers of carbon. Make sure the carbon overlaps the wood. Use a good laminating epoxy and also add several short strips at both knees. Add more parchment paper as release and back the parchment with pieces of wood that you can clamp against. Clamp the whole assy with hand clamps getting out excess epoxy.

You can use the ally gear and line that up with carbon. If you prep the ally well as Speed suggests, it will hold. For an even better hold, use primer first on the ally. The biggest problem with the ally gear is the inevitable bad landing wher the gear twists like a pretzel. The carbon will not survive that

lamarkeiko

My Feedback: (1)

Thanks everyone for the input and different ideas on reinforcing my LG. Jenny's discription on what to do is the closest to what I was originally thinking about trying. I'm going to give this all some thought and come up with something. I'll post what I come up with when I'm done. Here is what I have done before, that worked fairly well. I did this for a 40 size plane, so for a Four Star 120, it would take a lot more fiberglass & resin. http://www.flyrc.com/fabricating-composite-landing-gear/ I really don't want to build a new LG again.

Lamar

Greg Wright

My Feedback: (6)

Try buying some of these stand-off's from bennett and then you can bend a piece of Piano wire to stiffen the gear.

http://www.bennettbuilt.com/shop/Whe...doffs_316.html