Carbon/Kevlar rear luggage boxes.....It has begun....

Hi Erling,

I have gone over your thread a few times and I have a few questions.

1) Do you use Kevlar for abrasion only or is it stronger than fiberglass?

2) If the CF piece is to be relatively non-bomb proof (not a skid plate) would a 6mm fiberglass weave as part of the lavers be fine?

3) Would the West Epoxy system (105 resin/207 clear hardener) work well with CF and Fiberglass/Kevlar and be as flexible/impact resistant?

I have a bunch of leftover supplies from when I glassed a hot tub cover that I would like to use.

Thanks for the inspiration, photos and time!!!

Blair

Blair..... I would rather see you make a complete box set with pure Kevlar....It`s not very expensive as compared to CF...... I think you can save a little with the epoxy I use.... Unless you already have the 105. If you are making a top box rather than two sides... I`d say give it a go with glass...... If you manage to break it in a spill..... you have bigger things to worry about.......

Erling

Thanks!

I was thinking of staring with a small box, replacing my pelican first aid box that's just a bit small. It sits on the front of a pannier and the box frame. If it sees a crash :eek1

As for the epoxy, I have to see what is still viable and I have to consider what I can get across the boarder.

Blair

That will be a great starter project..... If you can`t get the 105..... Try e-mail the vendor I use... I believe he ships to Canada...... When you start.... if you you post it....make sure you pm me with a link to your thread, so I can look in........

Erling

Hi Erling,

I'm trying to figure out what the CF total's are for the various items that you have built.

Here's what I'm guesstimating...
1 pannier = 2.5sq yrds (21"x17"x8")
skid plate = 1.5sq yrd (looking at yours)

Am I close? Do you try to figure out the square inches/yards so you can order the amount needed with some extra?

Blair

I usually order in 10 yards at a time...... I have grown fond of " discounted" materials.... Since CF is so expensive. The 50 and 60 inch with are good for bigger projects... But I get the 40 inch with....
http://uscomposites.com/shortroll.html

The thing is.....It`s hard to estimate....Unless you know you will only be doing one project a year..... I find it easier just to stock it ...10 yards of 40 inch....at a time. I have to back to look to verify.... But I think HI have 7-8 layers in the skid plate..........plus overhang......( 4 of those are off course kevlar) Plan on a minimum of 10% overhang..... That way you won`t have to pull the fabric too much.... If you have done the project many times... you can get along with 5% overhang......but it`s a little risky. You can get a better idea if you cut out a sheet of fabric....like ...say bed linen.. Then fold it over the foam plug.... sit and watch how you want the pattern`s to layout.....then cut it to shape...... Lay it out flat on the floor....and measure the square....including the cut out material voids.... Then that will give you a better idea. Last thing you want ....is to run out of CF in the middle of the project.......

Erling

Its not just a simple calculation of area. Especially if you're making big parts, you're going to have a lot of extra left over because you can only cut so many patterns out of your 40" (or whatever) wide roll. Also, if you want to lay up at different angles (increases rigidity), you're potentially going to 'waste' even more fabric from the starting roll because the patterns may be even more difficult to arrange. Put another way, thanks to Murphy, if you size your fabric order based on how much you think you need, you won't buy enough.

If you're concerned with spending a lot of money on 'waste' CF (its not really, unless you don't ever plan to make anything else)...or really for anyone just starting out, I recommend learning with glass instead of CF--its literally ~10 times cheaper. For WELL under $100 you can get a ~1qt epoxy kit, a couple yards of glass, and enough wax and mold release to last for a long time. What you'll learn mowing through those supplies on silly things will more than pay for itself when you start to make CF production parts.

Make no mistake, composite work is an art form. You can't approach it from an analytical standpoint.

Well said......and very true......

Erling

Thank you both

We will see what I get up to

And I do have a quite a bit of 6-9oz fiberglass that I can play with. I made a cedar hot tub cover and covered it with glass and epoxy, I made some mistakes but that's how I learn.

Hi Erling,

Thanks again for this thread!!

Would you trust your skid plate to be dragged over a rock or log (repeatedly) without deflecting into the oil drain bolt?

Yes I would....without any hesitation. Not many believe it......and have to see for them self.... Once you get involved with impact.....um....ballistic testing........will you believe. Layup quality.....like resin to fiber ratios need to be observed though........ Your average 5-7mm aluminum plate will deflect by far faster than this layup... I don`t say this because I made it.....really.... That`s just the the way it is. But one of the greatest things about the composites.....is that you can just apply more layers where it`s needed. So if your in doubt.....give it a few extra layers on the bottom.......

Erling

I have been highly impressed by the quality of work displayed in this thread, and even more impressed by the willingness to share technical knowledge.

I chose the picture above to illustrate the sort of thing that gives me trouble. For me, making the tubing be the right shape and size to fit where you have would be difficult. I lack a good method for making a mounting point on the bike connect with another part somewhere else.

Would you kindly explain a bit about how you locate parts and pieces in 3d space?

Thanks....... I enjoy when someone that watched any of my threads....start their first project.... I don`t mind share the knowledge, and know how to help other get started. My fam and I are educators......and the thrill to see someone succeed in part because of what I did....is priceless. There are little knowledge out there.....and most of it is not written for the average Joe/Jane. As far as the 3d fabbing........ It really depends on the lines you want to achieve. The picture above......I first fabbed the flat bracket by pounding a piece of SS tube flat......drilled it....and mounted the flat piece on the sub frame...... Then I just rough measured the distance the pipe needed to go....... Cut said piece of tube..... Then slowly....and I mean slowly began bending the pipe. See once you bend it.... you can " un bend" it about 10 deg......at the very best. Hold it up.....re evaluate....bend some more....etc....When it fits roughly..... fine tune it... some more... Tac it with the welder..... remove the piece.....and weld it solid. I do make mistakes....but then you just throw the piece in the pile to be used for something else. If you are in the market....My 1 generation rack as pictured in this thread is looking for a new home.... If your interested...pm me...... Hope this shine some light on it....If not.... let me know.....

Erling

That is more or less how I do things too. It just ends up much less pretty when I do it. As I get experience(and appropriate tools), I am getting better.

Thank you for the thoughtful reply. It is much appreciated.

Absolutely.......Let me know if I can help any further......

Erling

This would have to be without a doubt the best profile pic ever macadamia. As we say here in Kiwiland, Sweet as !!

thanks!

I have been reading your fabrication threads during my convalescence from back surgery and am tempted to start a project of my own. One thing I am not clear on is whether the high temp epoxy or the kevlar cloth is structurally stronger than the cf or if they only provide heat and abrasion resistance. If you were to make a mounting system that needed to be strong over anything else, which materials would you choose?

Good question.... In general....Carbon fiber yields by far better torsional strength.... Ie...stiffer...etc.... whereas Kevlar will not be as stiff. Carbon fiber holds up very poorly to abrasive stress. Like this.... you lay down 5 layers of cf....1 inch wide....do the same with Kevlar.....you have a stick....well...ehh.... two sticks.... with same thickness and overall dimensions. Take the Carbon Fiber stick to a belt sander.....( asphalt simulator...)... you will grind it down surprisingly fast...... Take the Kevlar stick to the same belt sander.......after 1 minute of sanding.....you have only gnawed 1/8`th of an inch.......the CF stick will be by far stiffer.....and the Kevlar bend easier. So for the stiffness properties you use the CF....and for the rock not "gnawing" through the composites you use the Kevlar. Carbon is lighter than Kevlar....Kevlar is about 40% cheaper than CF..... So I enjoy a mix of the two products. Hope this clears it a bit ......If not.... Just fire away..... Hope your back get`s better soon.....

Erling

OK what about the high temp epoxy vs the regular? It sounds like the regular is a lot easier to cure but if the high temp is stronger i may want to go through the trouble.