Fiberglass concerns
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wbwoodward
- Posts: 8
- Joined: Thu Nov 06, 2014 2:03 pm
Fiberglass concerns
Are there any concerns or history of fiberglass delaminating in Express aircraft? Is fiberglass a common material in composite aircraft?
Re: Fiberglass concerns
1. Delamination is due to improper construction technique- My flying Wheeler is serial number 16, flying Wheeler # 3 first flew late 92 and has around 2300 airframe hours on it. I bought it, took it apart and rebuilt it. I found no issues with the glass at all. So to answer question 1- not that I am aware of that would be considered a defect.
2. Yes and no.
School time- there are basically 2 types of composite construction used in modern aircraft and other "fiberglass" items. Glass fiber reinforced and carbon fiber/ kevlar reinforced.
There are basically 3 types of resin matrices that are used with the reinforcing to make a panel, polyester, vinylester and epoxy. The esters use mechanical bonds- when you glass over something it softens the lower layer and "sticks" to it. Epoxies bond on a molecular level with actual strands winding around each other. BIG NOTE: Epoxies will bond to virtually anything, not so with the esters. Esters will bond to esters and thats about it. If you ever repair a spot or lay up a piece with epoxy, you will have to use epoxy there forever.
Now for a little more: Polyesters are typically not as strong as vinylesters and are usually heavier. Boats are usually polyester because its cheaper and readily available, and they dont worry about weight. Polyesters are susceptible to softening by different solvents particularly alcohols. Vinylesters are not.If you build a fuel tank with vinylester and run auto gas, you should be fine. Build it with polyester and it will start to dissolve and gum up your fuel system. Read about ethanol and boats and you can see what I am talking about. Lots of boats have the fuel tanks built in to the hull with the same glass that is used in the rest of the hull and polyester resin. When alcohol started to be mandated in the fuel, it started to eat the boats from the inside out.
There are essentially 2 types of reinforcement- glass and carbon/kevlar. Fiberglass is then broken down into categories like S glass, E glass, etc which are primarily the 2 we would use. S glass is finer and will require (normally) more layers to get the same strength as E glass. The glass is the same, but S glass is a little bit like 1200 thread count sheets, and is easier to work with but takes a little more glass. E glass is like using a flannel sheet- thicker, stiffer and in the glass world a bit harder to manipulate but faster to build thickness and strength. Carbon is strong and stiff, Kevlar is strong and a bit more flexible. More on this in a bit.
You can lay up any of the glasses with any of the esters relatively easily- the secret is in the prep work. Before you start to lay the material down, quickly clean the area with MEK, sand with 80 grit, and then really clean with MEK again. The MEK will remove any foreign materials, the sandpaper makes it smooth, and the MEK the second time softens the underlying resin for a better bond. It always requires several i.e. 3 to 5 layers minimum to make a good bond. Fiberglass composites only have strength in tension- meaning pulling along its length. Pulling at a 90 degree angle from the base material will usually result in pulling the layer off. The thicker your layup, the harder it is to pull off.
Carbon and/or Kevlar are different. These are usually pre impregnated with epoxy resin and kept in stasis until needed. Then the layers are placed in or on a mold and then cooked in an autoclave (oven) to cure. This is great for making the plane, but bad for any repairs. If for example you have a Cirrus and the line guys hit it with a vehicle and make a hole in it around 3 inches around. For fiberglass, this would be an easy repair- grind it down, add layers to lay the area back up, fill it, fair it, paint it done. With Carbon fiber, it needs to go to a shop with portable autoclave equipment, a larger area will need to be removed and an expensive and time consuming repair and heating process will need to be completed. Also, Carbon fiber is electrically conductive which will result in electrolosis. Some of the same precautions needed on boats to prevent galvanic corrosion must be applied to carbon fiber aircraft.
Carbon fiber has its place, but not IMOH, on smaller GA airplanes. Too much trouble for the payback.
I have much much more that I can tell you if you want to know- but the answers again are that I dont know of any "defects" in the construction of the Wheeler that would be caused by anything other than poor workmanship, and yes fiberglass is common in GA airplanes.
Feel free to call me at 239-896-7576 if you want to know more.
2. Yes and no.
School time- there are basically 2 types of composite construction used in modern aircraft and other "fiberglass" items. Glass fiber reinforced and carbon fiber/ kevlar reinforced.
There are basically 3 types of resin matrices that are used with the reinforcing to make a panel, polyester, vinylester and epoxy. The esters use mechanical bonds- when you glass over something it softens the lower layer and "sticks" to it. Epoxies bond on a molecular level with actual strands winding around each other. BIG NOTE: Epoxies will bond to virtually anything, not so with the esters. Esters will bond to esters and thats about it. If you ever repair a spot or lay up a piece with epoxy, you will have to use epoxy there forever.
Now for a little more: Polyesters are typically not as strong as vinylesters and are usually heavier. Boats are usually polyester because its cheaper and readily available, and they dont worry about weight. Polyesters are susceptible to softening by different solvents particularly alcohols. Vinylesters are not.If you build a fuel tank with vinylester and run auto gas, you should be fine. Build it with polyester and it will start to dissolve and gum up your fuel system. Read about ethanol and boats and you can see what I am talking about. Lots of boats have the fuel tanks built in to the hull with the same glass that is used in the rest of the hull and polyester resin. When alcohol started to be mandated in the fuel, it started to eat the boats from the inside out.
There are essentially 2 types of reinforcement- glass and carbon/kevlar. Fiberglass is then broken down into categories like S glass, E glass, etc which are primarily the 2 we would use. S glass is finer and will require (normally) more layers to get the same strength as E glass. The glass is the same, but S glass is a little bit like 1200 thread count sheets, and is easier to work with but takes a little more glass. E glass is like using a flannel sheet- thicker, stiffer and in the glass world a bit harder to manipulate but faster to build thickness and strength. Carbon is strong and stiff, Kevlar is strong and a bit more flexible. More on this in a bit.
You can lay up any of the glasses with any of the esters relatively easily- the secret is in the prep work. Before you start to lay the material down, quickly clean the area with MEK, sand with 80 grit, and then really clean with MEK again. The MEK will remove any foreign materials, the sandpaper makes it smooth, and the MEK the second time softens the underlying resin for a better bond. It always requires several i.e. 3 to 5 layers minimum to make a good bond. Fiberglass composites only have strength in tension- meaning pulling along its length. Pulling at a 90 degree angle from the base material will usually result in pulling the layer off. The thicker your layup, the harder it is to pull off.
Carbon and/or Kevlar are different. These are usually pre impregnated with epoxy resin and kept in stasis until needed. Then the layers are placed in or on a mold and then cooked in an autoclave (oven) to cure. This is great for making the plane, but bad for any repairs. If for example you have a Cirrus and the line guys hit it with a vehicle and make a hole in it around 3 inches around. For fiberglass, this would be an easy repair- grind it down, add layers to lay the area back up, fill it, fair it, paint it done. With Carbon fiber, it needs to go to a shop with portable autoclave equipment, a larger area will need to be removed and an expensive and time consuming repair and heating process will need to be completed. Also, Carbon fiber is electrically conductive which will result in electrolosis. Some of the same precautions needed on boats to prevent galvanic corrosion must be applied to carbon fiber aircraft.
Carbon fiber has its place, but not IMOH, on smaller GA airplanes. Too much trouble for the payback.
I have much much more that I can tell you if you want to know- but the answers again are that I dont know of any "defects" in the construction of the Wheeler that would be caused by anything other than poor workmanship, and yes fiberglass is common in GA airplanes.
Feel free to call me at 239-896-7576 if you want to know more.
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wbwoodward
- Posts: 8
- Joined: Thu Nov 06, 2014 2:03 pm
Re: Fiberglass concerns
Thanks for the info, Kevin. Very comprehensive. I may request your services for an inspection of a used Express prior to a possible purchase in the spring. You seem to be very familiar with the aircraft, with the builds and mods you have worked on.
Bill Woodward
Bill Woodward
Re: Fiberglass concerns
I would be glad to look it over for you- just let me know when and where.
They are great airplanes- At 8500 feet I get 150 knots at 8.1 gph ROP. Great useful load, good slow flight characteristics.
If you have any more questions, let me know.
KA
They are great airplanes- At 8500 feet I get 150 knots at 8.1 gph ROP. Great useful load, good slow flight characteristics.
If you have any more questions, let me know.
KA
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wbwoodward
- Posts: 8
- Joined: Thu Nov 06, 2014 2:03 pm
Re: Fiberglass concerns
OK, thanks, will do.
Bill
Bill