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  #1  
Old 05-20-2007, 06:52 PM
ckeze ckeze is offline
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Default kevlar

Quest: Can you mix kevlar and fiberglass? In my project most of the fiberglass work has been done.The winglets need to be added and my question is: Can you use kevlar to add the winglets instead of the fiberglass?
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Old 05-20-2007, 08:15 PM
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jpolenek jpolenek is offline
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Look up the thread entitled "BID Carbon fiber" for some discussion on mixing glass with other materials. Doesn't seem to be recommeded. Why do you feel it is necessary to stray from the plans in this area?


(BTW, can somebody tell me how to insert a link to another thread into a post.)

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Last edited by jpolenek : 05-20-2007 at 08:25 PM.
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Old 05-20-2007, 10:58 PM
kjashton kjashton is offline
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Quote:
Originally Posted by ckeze View Post
Quest: Can you mix kevlar and fiberglass? In my project most of the fiberglass work has been done.The winglets need to be added and my question is: Can you use kevlar to add the winglets instead of the fiberglass?
The winglet attach layups are some of the most critical layups on the airplane. Kevlar has lower compressive strength and higher water absorption than fiberglass. If Kevlar and glass are used in the same laminate, the glass may stretch but the kevlar may not and the laminate may gradually delaminate. Alternatively the Kevlar buckles at a lower compressive strength and fails the laminate. Personally, it would scare me to do anything different there -- and why would you need to? The plans materials work. Plus, Kevlar is a PITA to work with.

Not trying to discourage experimentation but this is not the place to experiment. Try making some Kevlar wheel pants first.
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Old 05-20-2007, 11:46 PM
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If you are planning on using Kevlar in the lower winglet (or on the outside angle if the lower winglet is let off) as a protection measure, it can be done but use it over the plans lay-ups. You will also want to apply a final lay-up of glass over the Kevlar to facilitate finishing. Kevlar fuzzes when you sand it.

As far as a total substitute for the glass....while is seems like a realistic option when looking at the warp/fill tensile strength numbers, it is no guarantee that this is a viable substitute. I haven't read where this is being used in our type of building. I do know that structures made of Kevlar experience a 30% reduction in weight but those numbers are based on boat construction.

I plan on using Kevlar as an additional barrier reenforcement for the lower winglet area and underside of the fuselage.
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  #5  
Old 05-21-2007, 05:15 AM
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i just saw the winglets in question, and he will not be using CV.
engineer/test pilot......not !
he got it at the ...test for leaks chapter 23? . less lower strake outer glass
its still a big finish no engine/dash/seats

he has no e glass and was just looking for some thing local.
150 miles round trip, and i got pulled over on the way home(no tic-it)
wish mine was as done
looks like he will need to foam fill over the st rake glass and re-glass
unless 1/4 to 1/2" mico is OK ?
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Old 05-21-2007, 11:07 AM
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I am not a fan of kevlar

it is very hard to work with and most report having to coat it with a layer of glass to sand and fill

It suffers from long term moisture degradation, I believe that that is why bullet proof vests have a 5 or so year shelf life.

for skid pads - fine stuff - for just plane plane building - glass and CF is the way to go
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Old 05-21-2007, 11:44 AM
argoldman argoldman is offline
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I believe that the main benefit of kevlar is weight reduction. Once the material has been saturated by epoxy, or water, I have been under the impression that the abrasion and puncture strength is greatly compromised.

However, I have been known to be wrong in the past. Anybody out there know more about this fiber????
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Old 05-21-2007, 12:10 PM
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Quote:
Originally Posted by argoldman View Post
Once the material has been saturated by epoxy, or water, I have been under the impression that the abrasion and puncture strength is greatly compromised.
I've read "composite construction techniques" and this was not mentioned, i believe the water degradation was. Course, this is from memory.

heh heh heh spell check suggested "compost" for the way i had misspelled composite, maybe i should have left it!
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dust

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  #9  
Old 05-21-2007, 04:24 PM
argoldman argoldman is offline
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Quote:
Originally Posted by Dust View Post
I've read "composite construction techniques" and this was not mentioned, i believe the water degradation was. Course, this is from memory.

heh heh heh spell check suggested "compost" for the way i had misspelled composite, maybe i should have left it!

Dust, you are trying to make an honest man of me.

As Rosanna Rosannadanna used to say on SNL----"never mind" about the kevlar/epoxy being weaker

Perhaps it is the sleep deprivation from training my Granddog.
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