Original Posted By: "Glenn Thomas"
Pietenpol-List: What should a fiberglass cowling weigh?
RE: Pietenpol-List: What should a fiberglass cowling weigh?
Original Posted By: "Phillips, Jack"
Re: Pietenpol-List: What should a fiberglass cowling weigh?
Original Posted By: "Ben Charvet"
Ben,Jack Phillips answer is probably right on the money. "it depends". Heck, because of my weight I had to move the entire engine 4" forward to get a good CG., a big heavy cowling would probably do me good. But back to lightweight correctly made composite parts. You can make a composite cowling just as light as the AL on the cubbie BUT, lots of techniques and tricks involved. A) People who don't do a lot of composite parts always ALWAYS use too much resin. It makes the part nice and smooth looking, but makes it heavy. The resin doesn't make the part strong, the fabric does. I ran the composites workshop at Oshkosh for several years and the one key observation I came away with after watching 100's of novice potential composite homebuilders try their skills on trial composite parts.....homebuilders always want to use too much resin on their parts. One part by weight fabric to one part by weight mixed resin is a good laminate. 40% resin is better, but hard to do without vacuum bagging. B) Resin choice... Polyester resins tend to go on heavier than two part epoxies, making a resin rich heavy part. Polyesters resins belong on things like shower stalls not on airplanes. C) Carbon fabrics are lighter than fiberglass. Kevlar is lighter than carbon, but harder to work with. But choice of weave of fiberglass is important to get smooth finish without too much resin, open box weaves suck up a lot of resin. Try a tight closed satin weave like 7781, 3783 glass or 613 style in carbon. D) If you can, get a look at the first 10 pages of the instructions for a Longeze or Cozy. See if anyone in your EAA Chapter will let you read the intro by Rutan or Nat Puffer on how to get a lightweight composite laminate. Then try again with carbon weave 613 and epoxy to make your part on the plug, you'll be much happier with the result.Gordon----- Original Message -----
Ben,Jack Phillips answer is probably right on the money. "it depends". Heck, because of my weight I had to move the entire engine 4" forward to get a good CG., a big heavy cowling would probably do me good. But back to lightweight correctly made composite parts. You can make a composite cowling just as light as the AL on the cubbie BUT, lots of techniques and tricks involved. A) People who don't do a lot of composite parts always ALWAYS use too much resin. It makes the part nice and smooth looking, but makes it heavy. The resin doesn't make the part strong, the fabric does. I ran the composites workshop at Oshkosh for several years and the one key observation I came away with after watching 100's of novice potential composite homebuilders try their skills on trial composite parts.....homebuilders always want to use too much resin on their parts. One part by weight fabric to one part by weight mixed resin is a good laminate. 40% resin is better, but hard to do without vacuum bagging. B) Resin choice... Polyester resins tend to go on heavier than two part epoxies, making a resin rich heavy part. Polyesters resins belong on things like shower stalls not on airplanes. C) Carbon fabrics are lighter than fiberglass. Kevlar is lighter than carbon, but harder to work with. But choice of weave of fiberglass is important to get smooth finish without too much resin, open box weaves suck up a lot of resin. Try a tight closed satin weave like 7781, 3783 glass or 613 style in carbon. D) If you can, get a look at the first 10 pages of the instructions for a Longeze or Cozy. See if anyone in your EAA Chapter will let you read the intro by Rutan or Nat Puffer on how to get a lightweight composite laminate. Then try again with carbon weave 613 and epoxy to make your part on the plug, you'll be much happier with the result.Gordon----- Original Message -----
RE: Pietenpol-List: What should a fiberglass cowling weigh?
Original Posted By: owner-pietenpol-list-server(at)matronics.com
Sounds a bit heavy. Depending on how you did it you may have a lot of resinon the inside or outside or both. You might be able to sand a good bit ofit away before you get to the glass. Then again, you might have a lot ofresin inside the glass layers and might not be able to sand away much.Brian KrautEngineering Alternatives, Inc.www.engalt.com-----Original Message-----
Sounds a bit heavy. Depending on how you did it you may have a lot of resinon the inside or outside or both. You might be able to sand a good bit ofit away before you get to the glass. Then again, you might have a lot ofresin inside the glass layers and might not be able to sand away much.Brian KrautEngineering Alternatives, Inc.www.engalt.com-----Original Message-----
Pietenpol-List: What should a fiberglass cowling weigh?
Original Posted By: "KMHeide, BA, CPO, FAAOP"
HiIt seems to me it would make sense to wax up the existing cowl and use that as a plug to make a new female mold. Then different cowlings could be produced Knowing the surface area a layed up weight can be calculated. In the boat business we would use glass "cloth ranging in weights from 1 oz to 32 oz depending on the application. I would think a 3/4 oz mat and 18 oz roving with some local stiffners or some balsa core would be a good starting point. A lot of work for a few lbs of weight that will probably be in the right place anyways.Steve snowed in in Maine with more coming this weekend.________________________________________________________________________________Date: Thu, 13 Dec 2007 12:03:50 -0800 (PST)
HiIt seems to me it would make sense to wax up the existing cowl and use that as a plug to make a new female mold. Then different cowlings could be produced Knowing the surface area a layed up weight can be calculated. In the boat business we would use glass "cloth ranging in weights from 1 oz to 32 oz depending on the application. I would think a 3/4 oz mat and 18 oz roving with some local stiffners or some balsa core would be a good starting point. A lot of work for a few lbs of weight that will probably be in the right place anyways.Steve snowed in in Maine with more coming this weekend.________________________________________________________________________________Date: Thu, 13 Dec 2007 12:03:50 -0800 (PST)
Re: Pietenpol-List: What should a fiberglass cowling weigh?
Original Posted By: Steve Glass
Steve,Think using roving will absolutely make a very heavy composite part, never used in composite homebuilts for skins. Like the idea of using the current part as a female mold. Two plies of 6 oz. carbon with "hat sections" using 3 lb/cubic ft foam core where stiffeners are needed, does the trick. Carbon is stiff anyway, stiffen the edges where the two or three parts come apart is all that is needed on a 200 mph Cozy or Longeze. A Piete at 70 mph wouldn't need that much. Next time anyone sees a Longeze or better yet a Glassair on the flightline, give the cowling a good looking over. The skins are very thin with stiffener around the air outlet and inlet lips meet fuselage and along where the side piano hinge is laminated in. (pull the hinge pins and a couple screws to remove the cowl)Gordon ----- Original Message -----
Steve,Think using roving will absolutely make a very heavy composite part, never used in composite homebuilts for skins. Like the idea of using the current part as a female mold. Two plies of 6 oz. carbon with "hat sections" using 3 lb/cubic ft foam core where stiffeners are needed, does the trick. Carbon is stiff anyway, stiffen the edges where the two or three parts come apart is all that is needed on a 200 mph Cozy or Longeze. A Piete at 70 mph wouldn't need that much. Next time anyone sees a Longeze or better yet a Glassair on the flightline, give the cowling a good looking over. The skins are very thin with stiffener around the air outlet and inlet lips meet fuselage and along where the side piano hinge is laminated in. (pull the hinge pins and a couple screws to remove the cowl)Gordon ----- Original Message -----
Re: Pietenpol-List: What should a fiberglass cowling weigh?
Original Posted By:
Steve,Think using roving will absolutely make a very heavy composite part, never used in composite homebuilts for skins. Like the idea of using the current part as a female mold. Two plies of 6 oz. carbonwith "hat sections" using 3 lb/cubic ft foam core where stiffeners are needed, does the trick. Carbon is stiff anyway, stiffen the edges where the two or three parts come apart is all that is needed on a 200 mph Cozy or Longeze. A Piete at 70 mph wouldn't need that much. Next time anyone sees a Longeze or better yet a Glassair on the flightline, give the cowlinga good looking over. The skins are very thin with stiffener around the airoutlet and inlet lips meet fuselage and along where the side piano hinge islaminated in. (pull the hinge pins and a couple screws to remove the cowl)Gordon ----- Original Message -----
Steve,Think using roving will absolutely make a very heavy composite part, never used in composite homebuilts for skins. Like the idea of using the current part as a female mold. Two plies of 6 oz. carbonwith "hat sections" using 3 lb/cubic ft foam core where stiffeners are needed, does the trick. Carbon is stiff anyway, stiffen the edges where the two or three parts come apart is all that is needed on a 200 mph Cozy or Longeze. A Piete at 70 mph wouldn't need that much. Next time anyone sees a Longeze or better yet a Glassair on the flightline, give the cowlinga good looking over. The skins are very thin with stiffener around the airoutlet and inlet lips meet fuselage and along where the side piano hinge islaminated in. (pull the hinge pins and a couple screws to remove the cowl)Gordon ----- Original Message -----
Pietenpol-List: Re: What should a fiberglass cowling weigh?
Original Posted By:
Have similar concern. My cowling has a big oval opening on it that needs some kindof cover over it. (Opening is about two foot long and a foot wide.) My engineis a 125hp ENMA Tigre with a couple giant magnetos on the top of the backend of the engine.First thought was lay something about as thick as the clearance I need over themags and engine, then make a dam around the opening and use the shape as a malemold to make the big hood bump thing out of fiberglass. To be able to accessthe mags without removing the whole cowling the bump would have to sit on topof the aluminum cowling. Then there would need to be some kind of fasteners,that would attach the bump to the cowling, and a means of dealing with fiberglassnot expanding contracting at same rate as aluminum. Also the design is vintage1930's, but a glass bump is more 1970's.So, I started looking in to what it would take to make a bump out of aluminum,and watched some you tube video's on aluminum forming. Turns out compound curvescan be made with a good deal of effort, people that are in to that kind ofthing can make reproduction Ryan radial cowlings from sheet aluminum, completewith the bumps for each cylinder.I spent the last 2 days trying to take my aluminum leading edge for the centersection of the wing and polish it out like a mirror. (Plan on having wood polyurethanedand natural looking, and the aluminum shiny, rather than covering itlike everyone else does.) Its taken 3 times the work I thought it would and Iam only half done. Will have about a week in getting the center section prettyby the time I am done. Should make my plane distinctive, but I can tell younow there are no Luscombes or Swifts in my future.My point being that aluminum is light, and can be made pretty, but it takes a lotof work to make something curvy and nice out of it. Flat pieces rivet togetherquick, and paint pretty easy, but its hard to get something that looks reallynice without a lot of effort in the design or the construction or both. Thefactories tend to use a fiberglass nose bowl so they can have some compoundcurves, then make the bulk of the cowling out of fairly simple flat aluminum sheet.If you already sank the time in to making a mold and your cowling looks good, thenmove on to something else. When your plane is done you can always revisitit. How many hrs and $$ will it take to save how many pounds? Do you have bigflat areas on your cowling that could be replaced with aluminum? Maybe your curvypart could serve as a nose bowl. I have been looking for a simple aluminum hood scoop design made up of all flatpieces or with very easy to do compound parts. So far no luck. But rather thandwell on it I am moving on. JimRead this topic online here:http://forums.matronics.com/viewtopic.p ... __________
Have similar concern. My cowling has a big oval opening on it that needs some kindof cover over it. (Opening is about two foot long and a foot wide.) My engineis a 125hp ENMA Tigre with a couple giant magnetos on the top of the backend of the engine.First thought was lay something about as thick as the clearance I need over themags and engine, then make a dam around the opening and use the shape as a malemold to make the big hood bump thing out of fiberglass. To be able to accessthe mags without removing the whole cowling the bump would have to sit on topof the aluminum cowling. Then there would need to be some kind of fasteners,that would attach the bump to the cowling, and a means of dealing with fiberglassnot expanding contracting at same rate as aluminum. Also the design is vintage1930's, but a glass bump is more 1970's.So, I started looking in to what it would take to make a bump out of aluminum,and watched some you tube video's on aluminum forming. Turns out compound curvescan be made with a good deal of effort, people that are in to that kind ofthing can make reproduction Ryan radial cowlings from sheet aluminum, completewith the bumps for each cylinder.I spent the last 2 days trying to take my aluminum leading edge for the centersection of the wing and polish it out like a mirror. (Plan on having wood polyurethanedand natural looking, and the aluminum shiny, rather than covering itlike everyone else does.) Its taken 3 times the work I thought it would and Iam only half done. Will have about a week in getting the center section prettyby the time I am done. Should make my plane distinctive, but I can tell younow there are no Luscombes or Swifts in my future.My point being that aluminum is light, and can be made pretty, but it takes a lotof work to make something curvy and nice out of it. Flat pieces rivet togetherquick, and paint pretty easy, but its hard to get something that looks reallynice without a lot of effort in the design or the construction or both. Thefactories tend to use a fiberglass nose bowl so they can have some compoundcurves, then make the bulk of the cowling out of fairly simple flat aluminum sheet.If you already sank the time in to making a mold and your cowling looks good, thenmove on to something else. When your plane is done you can always revisitit. How many hrs and $$ will it take to save how many pounds? Do you have bigflat areas on your cowling that could be replaced with aluminum? Maybe your curvypart could serve as a nose bowl. I have been looking for a simple aluminum hood scoop design made up of all flatpieces or with very easy to do compound parts. So far no luck. But rather thandwell on it I am moving on. JimRead this topic online here:http://forums.matronics.com/viewtopic.p ... __________
RE: Pietenpol-List: Jack Textor's Control Horns
Original Posted By: "Jack T. Textor"
Jack,I was looking at the photos on your web page (www.textors.com) and noticed youhave some good looking control horns. Would you please share with ushow you formed the control horns.Chris TracySacramento, CaWebsite at http://www.WestCoastPiet.com ________________________________________________________________________________Subject: RE: Pietenpol-List: Jack Textor's Control HornsDate: Fri, 14 Dec 2007 08:28:10 -0600
Jack,I was looking at the photos on your web page (www.textors.com) and noticed youhave some good looking control horns. Would you please share with ushow you formed the control horns.Chris TracySacramento, CaWebsite at http://www.WestCoastPiet.com ________________________________________________________________________________Subject: RE: Pietenpol-List: Jack Textor's Control HornsDate: Fri, 14 Dec 2007 08:28:10 -0600
RE: Pietenpol-List: What should a fiberglass cowling weigh?
Original Posted By: gbowen(at)ptialaska.net
Hi GordonI understand what you are saying but the cowling is a structual part and not just a skin. 1 layer of 18 oz roving will weigh the same as 3 layers of 6 oz.There are many different ways to get the weight down. Does anybody else have some typical cowling layups? SendSteve
Hi GordonI understand what you are saying but the cowling is a structual part and not just a skin. 1 layer of 18 oz roving will weigh the same as 3 layers of 6 oz.There are many different ways to get the weight down. Does anybody else have some typical cowling layups? SendSteve