Have you ever made a tail Wheel bracket??

[AirMcNair]

Hey guys, I woke up this morning walked out to the shop to have a smoke and looked at the Extra. I thought, I have a good amount of Composite fabrication under my belt and I should be able to build a tail wheel bracket myself... So I got to thinking, Most of the nice brackets are carbon fiber, The only problem is over time the carbon begins to either delaminate or crack because carbon is not meant to be flexible, So I though how about Kevlar, Kevlar is meant to be semi flexible after cured, My theory is that the flexibility of the Kevlar will keep the the bracket from breaking due to either a hard landing or time.. So with that being said, I had some 3" Kevlar striping from a different project, I grabbed my resin, Wax paper, Masking tape, Kevlar and some 2x4's. I first drew the profile and size of the bracket on the side of the wood. I then took a large band saw and cut the profile out of the wood splitting the 2x4 into two pieces. Once I had a good profile I sanded everything smooth so that I would have a smooth surface on the finished part. I then took a second 2x4 and cut it to the same length. I used the second 2x4 to hold the skinny parts of the mould together so they would not break apart during the clamping procedure. I then took two screws and screwed the two pieces of 2x4 together to make proper alignment holes with the crews as the alignment pins and clamps. (dual purpose). Once finished I was ready to lay up my part! I took Wax paper and used it to cover the two pieces of 2x4 where the Kevlar was going to be sandwiched between the wood. Now comes the fun part!! I pored a bunch of resin into a tub with tons of kicker, I then took the Kevlar and folded it over each other until I got 10 layers, soaked the crap out of the Kevlar and placed it on the wax paper on top of the 2x4 mould, Lined the male part of the mould with wax paper and proceeded on screwing the mould together, This cause all the resin to squish out the sides and pushed all my air bubbles out! LET CURE! Once dry I pulled the part and wax paper and Done!!! Now all that is left is cut to desired shape and drill holes... Hope it all works out!

[rdgood]

Airmcn,

Very interesting - got me hooked - please show us the finished assembly!!


Thanks,


Ronster

[AirMcNair]

Almost there! Here is the rough cut of the part. I have to round edges and sand still but I believe its going to work. There is some flexibility in it! should be perfect considering that the tail wheel only sees maybe 3-4lbs of pressure when sitting on ground. Ill have it finished tonight given I can find the parts I need
Chris

[why_fly_high]

I had thought about doing the same thing except just taking a sheet of aluminum and bending the angles I want in a break and then vacuum bagging the material to the plate. Could propably get 8-10 out of one lay-up pretty easily by just running the material after cure through a bandsaw.

Let us know how this turns out.

Dan

[AirMcNair]

OOPS.. Well I made it about 1.5" too short. I will build a new one tomorrow and post the new mould. I think I am going to take it down to 7 layers to increase a bit more flexibility. This is going to work well! One real hard thing I am having a problem with is how to cut Kevlar after its cured without getting frays on the edges . Ill be back.

[why_fly_high]

Kevlar is really hard to work with. One way is to cut it, run CA along the edge and then sand it, this works sometimes. Water-jet works best.

Dan

[AirMcNair]

	Quote: Originally Posted by why_fly_high
	Kevlar is really hard to work with. One way is to cut it, run CA along the edge and then sand it, this works sometimes. Water-jet works best. Dan

Funny you say that, Thats exactly what I did, Thin CA. It just looks like crap with it on there. Water-jet = Lots of fun

[Shawn Berkheimer]

Ok to answer the post title, Yes, about 80 to 100 per month. hahaha I have a couple of comments/hints but I don't want to step on any toes so if AIRMCN is Ok with me giving him some tips I will.


Shawn

[AirMcNair]

	Quote: Originally Posted by Shawn Berkheimer
	Ok to answer the post title, Yes, about 80 to 100 per month. hahaha I have a couple of comments/hints but I don't want to step on any toes so if AIRMCN is Ok with me giving him some tips I will. Shawn

Your tips are very welcome!!!!!!!! I am by no means any type of expert. Just sombody who likes to play
What ya got for me???

[Shawn Berkheimer]

Kevlar is a real pain to use and really rough on tooling. Thats why we don't use it and I really don't see ant benifit over carbon. You form is a good idea and that is pretty much how I used to make a tailwheel assembly that is now discontinued. Rather than using wax paper, try some 5 mil Mylar that has been waxed. It will leave a very nice glossy finish. If you can't find the Mylar you could cover the form with Monokote and then wax for the same result.

Delamination has to do with the process and not really the materials used. When you stack up multiple layers of cloth very small air bubbles are going to be trapped between the layers. This is what causes delamination when the part is flexed. This is why we have discontinued the tailwheel that used this type of construction. The replacement model uses continuous strand CF construction so delamination is no longer a concern.

I see that you have used polyester resin. Polyester when fully cured tends to be brittle. Do a test on the peice that you have already made and see just what it takes to break.

I am in no way trying to discourage you on your project. What makes this hobby what it is are guys like you that are willing to experiment. I do think that what you will find is that it will take much more time and effort then what you thought it would.


Shawn


R/C Blimp Productions - Home

[AirMcNair]

	Quote: Originally Posted by Shawn Berkheimer
	Kevlar is a real pain to use and really rough on tooling. Thats why we don't use it and I really don't see ant benifit over carbon. You form is a good idea and that is pretty much how I used to make a tailwheel assembly that is now discontinued. Rather than using wax paper, try some 5 mil Mylar that has been waxed. It will leave a very nice glossy finish. If you can't find the Mylar you could cover the form with Monokote and then wax for the same result. Delamination has to do with the process and not really the materials used. When you stack up multiple layers of cloth very small air bubbles are going to be trapped between the layers. This is what causes delamination when the part is flexed. This is why we have discontinued the tailwheel that used this type of construction. The replacement model uses continuous strand CF construction so delamination is no longer a concern. I see that you have used polyester resin. Polyester when fully cured tends to be brittle. Do a test on the peice that you have already made and see just what it takes to break. I am in no way trying to discourage you on your project. What makes this hobby what it is are guys like you that are willing to experiment. I do think that what you will find is that it will take much more time and effort then what you thought it would. Shawn R/C Blimp Productions - Home

Shawn, Thank you for the info!! I will take all your suggestions into effect. I have access to West Systems Epoxy. Ill go that rough. I think I will also try and make a crude vacuum bag and see if we cant pull the air bubbles out of the center of the laminates. This is going to take a few more days but hopefully will be worth it. If all else fails I guess I will call R/C Blimp productions
Thanks again for your assistance it is much appreciated!