# Boat fiberglass on aircraft?

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#### KeithO

##### Well-Known Member
"Boat fiberglass" in the way understood by most people would be roving fed through a chopper which saturates it with polyester resin. The gun is usually mounted on a robot which is programmed to cover a mold with this material and there are workers who may have hand tools and rollers to help the material lay down. Several layers may be laid down in succession before the first layer has fully cured. Boats up to 28-30' may get made this way and the resulting hulls are heavy and relatively weak compared to "modern" composites with very strong and stiff facings over the top of fancy core materials.

On the other hand, racing boats, where strength and weight are very important, may use materials and processes very similar to that used in aircraft structures or formula 1 car design with Carbon fiber, aramid or S type glass in Unidirectional fabrics and high modulus PVC foam or Honeycomb used in the construction with epoxy resin, resin infusion or even pre-preg resin cured in an autoclave.

If you can find the information on the weave pattern and basis weight (weight per square meter for example) you can go and look for alternate places to buy the cloth. In so doing you have to make sure that the fiber sizing (coating) is compatible for the type of resin one plans to use. Ultimately the resin has to match the capabilities of the fiber being used and be of an appropriate viscosity to work in the kind of lay up you are doing. Thus infusion resins are very low viscosity whereas a hand layup done one layer at a time may need a higher viscosity to avoid having a dry joint because a very thin resint may just follow the easiest path downhill instead of staying in the cloth. Resins can be staggeringly expensive, the best thing to do is make samples of any critical joints and make sure that the layup schedule will work with the materials you are choosing before doing it full scale. If something goes wrong with a full hull infusion project, you will be out all of the reinforcement and core material + all the resin, not to mention probably having to pay a hefty disposal fee to get rid of the trash if you fail.

Depending on the source there are huge price variations on the re-inforcement as well as core materials. The more convenient the source the more you can expect to pay. The places that sell over run material from large composite manufacturers may be far cheaper but with more limited selection and possibly in large roll sizes.

#### Puggo1

##### Active Member
hi Marian,

as a mechanical engineer in industry, all materials irrespective of resource must be validated for each batch or invoice.
The means of validation differs
1. use standard certified materials with known and tested characteristics :ie 2024 aluminimum, then calculate the design loads with appropriate margins of safety. Note a certificate must be obtained when purchasing to avoid cheap copies.
OR
2. make small testing samples and test using a reliable/repeatable machine. The number of samples and tests depends on the repeatability of the sample manufacturing process and the testing repeatability. (you'll learn a lot by doing this and gain confidence in the manufacturing processes, materials, etc with minimal cost)
cheers
Puggo

##### Well-Known Member
Supporting Member
Can I use boat fiberglass on aircraft? I am thinking it has humidity, fire and low temp/high temp resistance.
There is a wide array of fiberglass cloths and resins used in boats, and yes, some is used on aircraft, depending on the application.

Do you know the specific glass & resins that is on the boat? If not, my guess is that the boat uses chop mat fiberglass, which has little to no structural value, and is held together with a vinyl ester or polyester resin. If this is the case, they're best used for molds, not flight hardware.

Many homebuilt composite aircraft use a matrix of fiberglass cloth (choice depends on application & load), a core material, and epoxy resin (again, the choice derived from the cloth used in order to ensure proper structural performance).

#### Norman

##### Well-Known Member
Chopped strand mat has been mentioned. Never use this stuff on an airplane! Chopped strand mat is held together with styrene which dissolves in polyester and acts as a plasticizer for that resin BUT DOES NOT DISOLVE IN EPOXY and effectively forms voids in the matrix. By "effectively voids" I mean that everywhere that the styrene is in contact with the fibers it will prevent the epoxy from bonding at all, the result will be that the fibers can pull out of the matrix.

#### speedracer

##### Well-Known Member
The stress strain characteristics of E-glass are much different than S-glass and it's not quite as strong. Sure you can use E-glass (the older EZs have E-glass spars) but the parts will be heavier and more flexible that an S-glass part designed to the same strength. Beats the hell out of wood though and way cheaper than aircraft grade spruce.
Older EZ's have E-glass spars? New ones do too. In fact, ALL the glass on EZ's is E-glass. Testing I've done show very little difference in breaking strength between E and S glass, but E-glass costs 1/2 as much as S-glass. At least in the Aircraft Spruce catalog.

#### Rik-

##### Well-Known Member
Boat fiberglass" in the way understood by most people would be roving fed through a chopper which saturates it with polyester resin. The gun is usually mounted on a robot which is programmed to cover a mold with this material and there are workers who may have hand tools and rollers to help the material lay down. Several layers may be laid down in succession before the first layer has fully cured. Boats up to 28-30' may get made this way and the resulting hulls are heavy and relatively weak compared to "modern" composites with very strong and stiff facings over the top of fancy core materials.

You have a very loose grasp on business as well as boat building. Glass and resins are sold by the pound, so under your analogy cost is not a factor in business and that's far from reality.

Chopper guns do not use "roving" rather they use a sting fiber from a roll that is fed into the chopper guns as a single strand and then blown with the resin onto the part that gets fiber glassed.

There are boat manufacturers that use polyester resins, vinylester resins, hybrid resins as well as epoxy resins. It all comes down to the $as does the cloth type and weights and being everyone wants a rot free boat, most use a core made from a Penske Board or similar or a foam core where it can be used in different densities. Fiberglass boats started roughly in the late 50's and fiberglass planes came along? Substitute composite for fiberglass as it's the same thing. People have mentioned "West System" resins and these were originally developed for........ It's all the same ****, just different shapes and applications. No black magic because one floats and the other flies. Well hopefully and respectfully to each at least. #### KeithO ##### Well-Known Member Chopper guns do not use "roving" rather they use a sting fiber from a roll that is fed into the chopper guns as a single strand and then blown with the resin onto the part that gets fiber glassed. What do you suppose that "string fiber" is called ???? Its roving, you are revealing your own ignorance. #### KeithO ##### Well-Known Member I'm pretty sure that unwoven roving is the cheapest fiber product you can buy because it has not been combined or woven/stitched into a more complex product. Thats why it and polyester resin form the basis of the cheapest hulls made out there and is obviously capable of automated application which any form of cloth is not capable of. But with random short fibers and plenty of (cheap) resin it is both heavy and weak for its weight and the polyester resin susceptible to breaking down when continuously in water hence the "blistering" issues. #### BBerson ##### Light Plane Philosopher Supporting Member 24 oz woven roving is common for boats and industry. Multiple layers of lighter fabric is used in aviation. #### Rik- ##### Well-Known Member What do you suppose that "string fiber" is called ???? Its roving, you are revealing your own ignorance. View attachment 128136 Go build a few boats and stop using google for your education deficiencies. Of course there's always an YouTube education waiting on line also for you. #### KeithO ##### Well-Known Member Roving is used for many things, including acoustic absorbtion material in mufflers. There is nothing wrong with knowing what the proper name for something is. Woven roving is of course a different product and is much stronger than CSM but difficult to wet out with anything but a very low viscosity resin. Its the stuff Jamie of "Island in Panama" fame uses to make his solar electric cargo catamarans, along with polyester resin by the 55 gal drum load. Hardly cutting edge stuff but he has built a lot of very specialized boats with it by himself in a very remote part of the world. #### Primaris22 ##### Member For non- structural components ( wheelpants,cowlings, fairings, etc) is it OK to use polyester? And also to use chopped mat for this? I would think polyester is what’s used at Vans…. But I’m not sure about the mat cloth. #### KeithO ##### Well-Known Member For weight, either bid (bidirectional woven fabric) or stitched 2 or 3 layer unidirectional fabric will always be the strongest and can thus be made the thinnest and thus lightest. CSM is both heavy and weak which means you dont want it on anything that is supposed to fly. Use it for tooling, with which you make your airplane parts from the proper materials. #### KeithO ##### Well-Known Member Many commercially made items use polyester resin. Its use in objects that stay submerged for a long time, like boats, has its problems but usually they appear long after the warranty has expired. I am pretty sure the KR series planes were built with fiberglass and polyester resin. It was really when Rutan started using extruded polystyrene foam where Polyester resin was an issue because it would dissolve the foam core. Thus the VariEze and LongEz had to use epoxy resin since it would not harm the core material that was being used. The other thing to watch out for is whether the resin contains wax to help cure it. This is usually used on the last layup. The previous layups may use a bonding resin without wax which remains tacky for a long time to promote a bond with the next layer. But if you used the resin with wax so that it fully cured and had no tackiness, it would be very difficult indeed to make a secondary bond to that layer because it is so difficult to remove the waxy layer and then one would also need a mechanical bond. Lots of education needed if one is not to screw it up. #### WonderousMountain ##### Well-Known Member For non- structural components ( wheelpants,cowlings, fairings, etc) is it OK to use polyester? And also to use chopped mat for this? I would think polyester is what’s used at Vans…. But I’m not sure about the mat cloth. If you've got some already it's probably okay to do those parts. Isopthalic is a cost saver, random oriented strand is okay, but not for the performance minded. #### Norman ##### Well-Known Member For non- structural components ( wheelpants,cowlings, fairings, etc) is it OK to use polyester? And also to use chopped mat for this? I would think polyester is what’s used at Vans…. But I’m not sure about the mat cloth. Yes you could use chopped strand mat for wheel pants but it's hard to get a really smooth surface unless you make a good smooth mold. Making a mold is both time consuming and expensive. For a one-off part it'll make your part cost about 3 times as much as that same part laid up over a Styrofoam core (don't use polyester on styrofoam). As has been said several times in this thread CSM is not as strong or rigid as cloth so for the same strength the part will be thicker and heavier, it'll also be a bit lumpy because the process of making the mat is kind of random by nature. Common weave AKA "bid" is okay for some compound curve surfaces but when you get to things with small radii twill weave really makes the work easier. Polyester could be used but it is somewhat brittle and may crack from stone strikes, it also shrinks a lot (7%) which will warp thin walled parts enough that the joint between the two sides of your wheel pant will eventually be noticeably bad. Don't use polyester on thin walled parts! Here's a video by a very experienced fiberglass airplane builder showing how to make moldless wheel pants. The one thing I'd add to the processes is vacuum bagging. Vacuum bagging sucks air and excess resin out of the part and also serves as a clamp to press the layers of glass together and press the whole stack tightly onto the plug so that your part comes out with the shape you intended. #### gtae07 ##### Well-Known Member I would think polyester is what’s used at Vans… From Section 5 of the build manual... Fiberglass parts supplied with RVs come in two resin types, polyester and epoxy. Polyester parts can easily be identified by their white or gray gel-coat surface. The "wet layup" epoxy parts are translucent green. Some parts (typically large parts such as cowlings) are manufactured from epoxy pre-preg cloth which requires baking in an oven to cure. These parts can be gray exterior, opaque green or pink. They are easily identified by the honeycomb pattern visible on the inside surface of the part. Polyester resin is not compatible with epoxy and can only be used on polyester parts. However epoxy resin is OK to use on either epoxy or polyester parts. Many builders have had good results with West Systems epoxy resin. #### Epoxydius ##### New Member Who are you buying that from? That stuff from Interglas geweb is$6.00 per yard in the USA.
I've been buying fiberglass and other reinforcement materials I need from Fibermax. They are relatively cheaper there than anywhere else I've looked and I'm totally satisfied.

#### wsimpso1

##### Super Moderator
Staff member
For non- structural components ( wheelpants,cowlings, fairings, etc) is it OK to use polyester? And also to use chopped mat for this? I would think polyester is what’s used at Vans…. But I’m not sure about the mat cloth.
I would not use polyester on anything in an airplane. It ”prints“ the fabric weave, has lower strain to failure than the glass fiber, crushes under fasteners, and has lousy behavior under thermal cycles.

In particular, I would never use it where it is exposed to engine or brake heat. Ever seen a cowling or wheel pants on a factory bird that are now kind of distorted and out of shape? Lots of polyester and a little glass…

The Vans cowlings are high temp epoxy cured at high temps, not polyester. Their cowlings look great for a long time. I can not say that about their polyester bits. There is a reason aftermarket pieces for Vans stuff are selling so well.

Billski