Fiberglass question

Desert Flyer

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Hello all, I recently purchased a Pitbull gyro kit and one of the first things I would like to do is "beef up" the fiberglass fuselage. The fuselage is somewhat flimsy and is quite thin in spots. I am not too concerned with adding extra weight, as I am not trying to keep it under the 254 lb limit.

When I was a child, I watched one of my older brothers cover an entire canoe with fiberglass and then paint it, so I am familiar with the general concept. However, I am sure to do the process correctly, especially on an aircraft, there must be a proper procedure (priming, etc.). In addition, I can see that there is a wide variety of clothes available in the Spruce catalog - which one is best?

Could anyone suggest a good text book to get that would explain the correct process for adding fiberglass to an existing fuselage (no mold creation necessary)? Or perhaps the process is simple enough that a good website could serve as adequate reference. Any guidance would be appreciated...:confused:
 

Cobra Doc

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Dan, there are a lot of good books and web sites. The best way to start is buy the $50 practice kit/book from Spruce and start playing. Or go to Home Depot and get an gallon can of Bondo Fiberglass resin and a packet of cloth. Read the instructions on the can, leave out a couple of drops of the hardener in our area of the county, and start glassing things up. Don't try glassing white styrofoam. It's almost as fast as pouring gasoline on it. I'll try to get you some good websites from my home computer. Just remember: fiberglass breaks. Depending on what you want to do, there may be other options.
 

Chuck Roberg

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I was looking at a pitbull gyro this last weekend. The fella had the pod off and yes it is quite light. I could easily pick it up with one hand.

But I don't think it needs any more beefing up. Fiberglass is quite strong. For this application adding more to it is only going to add more weight.

Ron flew a pitbull a while back. Lets wait and see what he says.
 

Desert Flyer

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Thanks for your thoughts. I wouldn't bother with trying to strengthen the fuselage, except that mine is so thin in spots you can see light thru it. All it takes is a slight push and it gives in about an inch or so. I can't see how I could ever paint it, because at the slightest touch the glass would give in and the paint would crack.

Just to be clear, I have no delusions of making the fuselage a structure so solid that it offers protection in a crash or that it is strong enough to mount things to it. I just want to make it solid enough so if I bump into it in the garage or when unloading it from a trailer, I don't have to worry about the paint flaking off.

I am also considering lining the interior with aluminum sheets using glue. That way the glass would have some solid support. As I said, I'm not worried about the weight as I am likely going with an 85hp motor.

I think Ron will tell us the Pitbull is a pile of junk and I am wasting my time!;) And maybe he is right! :D
 

Cobra Doc

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Use an epoxy primer and paint. Or any other paint system made for fiberglass. Talk to John Parker at American Airracing over at Reno-Stead. John may be a crotchety old ----, but he knows his stuff.
 
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Desert Flyer

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Cobra Doc said:
Use an epoxy primer and paint. Or any other paint system made for fiberglass. Talk to John Parker at American Airracing over at Reno-Stead. John may be a crotchety old ----, but he knows his stuff.
Hmmm, I wonder what he would charge to paint my fuselage? Maybe I'll give 'em a call next month. Thanks.
 

gyromike

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Dan,

You can put a plastisizer in the paint when you mix it that will allow it to flex without cracking.
The same thing auto manufacturers and body shops do when they paint bumper covers.
 

scottessex

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Most of your newer (i.e.last 15 years) paints are a flexible base, and require no additive for flexibility. Epoxy primer with base coat clear coat will give you a durable paint job that will last 20 years or better if stored indoors.
Don't worry about the fiberglass being thin, aircraft have been covered with thinner fabric for 100 years.
Unless it is a monocoque composite structure, the skin carries no load.
 

Cobra Doc

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OR, you can glass it up with a clear epoxy, instead of polyester resin, and use the expoxy tints and other color additves available from Composite Structures Technology. We don' need no stinkin' paint.
 

Rehan K.Janjua

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Hello Dan.

You can put some more fiber razin coating from the inside to make it a bit stiffer. Or another layer of thin fiber cloth at the points you want stronger.

Good Luck. Rehan
 

Caribean_gyro

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Dan I noticed on a build of a rotorway exec. that they use a small half of an aluminum tube ben and confrom to the fiberglass. then they cover it with 1 cloth of fiberglass. I like this APROACH IT GIVE FORM AND STIFNESS TO THE CABIN
CHUCKP
 

Zack

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Here is what we've been doing...

Here is what we've been doing...

Here at the Museum (EAA AirVenture Museum) we've been working on a fiberglass replica of SpaceShipOne made of fiberglass from the original Scaled Composites moulds. Here is the procedure we've been using. First, you have to make sure to rough up the area you intend to glass with about 40 grit sandpaper. You'll have to be very careful as it sounds like your Pitbull's body is pretty thin. Use a drop cloth to clean up all the dust from the area. For the glassing itself, we've been using the West System of #105 Epoxy Resin and #205 Hardener. Lay out a sheet of plastic over your tabletop, then lay out the sheet of fiberglass cloth you are going to use. Coat the cloth with the epoxy mix, making sure to get it down into all the fibers so that it is completely soaked. Then squeegee out all the excess epoxy. If you need to cut the glass, I recommend using a circular cutter - they sell them in places like Hobby Lobby or Ben Franklin's in the fabric section. Once you have your fabric cut the way you like, you'll need to use the expoxy mix to spread a thin layer over the area you sanded. Then pull your cut piece of fabric up off the plastic and smooth it down over the area you want to build up. Make sure to get it completely battened down. If you intend to put more than one layer over the spot, you'll need to use a piece of peel-ply on the cloth after its been epoxied - just place it over the wet cloth and smooth it down - this will save you from having to sand the area again before you put the next layer of cloth on. Or, before you cut the cloth you can put another layer over it and epoxy it as well, then cut the cloth so that it is made up of two layers. You should use a respirator or at the very least a dust mask when doing the sanding and fiberglassing.

Those are the basic steps. Hope this helps.

Zack

PS: Mark Forss of EAA's Tech Services Dept. gave us a short afternoon class that was video taped since I could not be there. I would be glad to send you a copy of the video if you'd like. Just shoot me an email and let me know - it's [email protected].
 
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Desert Flyer

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Thanks to everyone for giving their thoughts. Sounds like I've got a few options, but overall it seems like a reasonably managable procedure.
 

Doug Riley

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Dan, from what I know of the Pitbull the glass is merely a fairing. There's a conventional metal frame that actually carries the loads.

If that's an accurate description, then weight saving in the glass shell becomes your overwhelming concern. Glass and resin are REALLY heavy.

They also are really limber. It sounds as if the limberness (oil canning) is what's bothering you. Pasting on extra flat layers of glass will add lots of weight and little stiffness.

A better idea from both perspectives might be to add internal ribs. Use strips of corrugated cardboard folded into long "tent" shapes to make internal forms to glue onto the inside of the hull. Make yourself some cardboard stringers and perhaps formers. Then epoxy fiberglass tape over them.

Builders of fiberglass boats make pseudo-ribs and stringers this way. It's much more weight-efficient than adding flat layers.

P.S.: It's not unusual to be able to see light through fiberglass. Even thick boat-hull layups are translucent if you put a light near them. Hell, it's only PLASTIC.
 

Bob

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Great sujestion there Doug!
he could manage a strip of alass over the cardboard easy enough by dabbing the reson into the cloth till the cloth is clear.
the cardboard ribs could remain inside the fiberglass and the cardboard ribs them self wouldn't have to be tall at all to add alot of striength to the flat surface, sort'a like make a triangle tube with 3 sides taped togather, crazy glue it to the inside and put a strip of fiberglass cloth about 5"wide or so
over the thing....
wet the rib and area first with reson add the cloth ,dab in enough reson to saturate the cloth , let dry and paint it !

capital idea !
Bob........
 

Bob

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Dan I am not far from Reno now , I lived there for 14 years
but i was wondering where you were planning on flying out of , Stead or the one on the golden valley side of the mountian towards Pyrimid lake ? there was a glider school out there when I was living there a while back accross from the big new subdivision now
<Grin> ...
Reno is definately a great place to fly at ! no trees to get in your way ! hehehehe
C ya neighbor !
Bob..........
 
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Desert Flyer

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Thanks again to everyone for their suggestions. I'm not doing anything to the Pitbull until after April 15th, so I have time to ponder my options.

As for where I'll be flying: My plan was to trailer my gyro to some large playa flats north and northeast of Reno to do my flying - weekend trips. The Black Rock Desert is a good place, but it is awful crowded these days thanks to that Burning Man festival. Before that crowd came along it was almost always devoid of people.

But thankfully I know of at least two other large flats that would be ideal for flying. Both are in northern Pershing County and miles away from any people. Usually by June they are dry, flat and hard as asphalt - depending on how wet the winter was. Acres and acres of dry lakebed, surrounded by scenic mountains.

I plan to avoid airports at all costs.
 

plastic

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Desert Flyer said:
Hello all, I recently purchased a Pitbull gyro kit and one of the first things I would like to do is "beef up" the fiberglass fuselage. The fuselage is somewhat flimsy and is quite thin in spots. I am not too concerned with adding extra weight, as I am not trying to keep it under the 254 lb limit.

When I was a child, I watched one of my older brothers cover an entire canoe with fiberglass and then paint it, so I am familiar with the general concept. However, I am sure to do the process correctly, especially on an aircraft, there must be a proper procedure (priming, etc.). In addition, I can see that there is a wide variety of clothes available in the Spruce catalog - which one is best?

Could anyone suggest a good text book to get that would explain the correct process for adding fiberglass to an existing fuselage (no mold creation necessary)? Or perhaps the process is simple enough that a good website could serve as adequate reference. Any guidance would be appreciated...:confused:

It's not necessary to strengthen it but if you insist then simply glass on some foam strips inside to form small ribs. You wont add much weight but will add a lot of strength/stiffness.
 

Buckingdummy

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Desert flyer, I also recently purchased a pitbull and found out you want to be extremely careful getting in and out or you can collapse the side if you put to much weight on it and I only weigh 145 lbs and crunched it by leaning on it with one hand. I have a falcon ultralight that had problems with the fiberglass in the back of the fuselage not being stong enough to support the wings and engine over time or with a few bad landings. A previous owner of one of my falcons took triangle shaped strips of styrofoam along the problem areas and covered them with fiberglass. I am thinking about trying this on the pitbull to try and stiffen up the fuselage and maybe take some of the vibration out of it.
 
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