Original Posted By: "cdlwingnut"
Clif,Here is a repeat of a discussion that I posted on the Pietvair Forum a while back.My reason for using aluminum spars was not weight, not exclusively. Therewere other reasons far more important to me than that. (FWIW, I sent all of this to BPA a long time for inclusion into a newsletter article,but some how, it never made it to print.)-----------Here is a comparison of the weight of each type of spar. The aluminum weights comefrom the Carlson Aircraft website. It is assumed that the D&E spars are ofa similar weight. The weights of the wood come from the current online AircraftSpruce Catalog.-Aluminum spars weigh between 0.93 and 1.00 oz per linear inch. Therefore, usingthe 1 oz. weight times the total length of the 2 front spars (2 x 158.5) and0.93 oz. weight times the total length of the rear spars (2X158.5) is 317+295,or 612 ounces. 612 ounces equals 38 pounds, 4 ounces. You will be using 30 each5/16 X 1 X 5.5 plywood slats and 30 each 5/16 X 1 X 4.5 slats for attachingthe ribs to the spars (more on that later). A 5/16 X 24 X 48 plywood sheet weighs30 pounds, or 1.33 ounces per cubic inch. The slats would weigh approximately33 ounces or 2 pounds 1 ounce, for a total weight of 40 pounds, 5 ounces.The weight of any T88 epoxy used to attach the slats to the aluminum spars isnot included.(Note - I later weighed the following wood pieces - Blocks to fill the spaces betweenthe top of each spar and the bottom of each rib upper capstrip - 331 grams,Front spar spacers to go between the shear web of the spar and the verticalof the rib - 645 grams, Rear spar spacers to go between the shear web of thespar and the vertical of the rib - 504 grams, wooden Wing tips added to theend of the aluminum spar for attaching the wing tip bows - 710 grams, and WingRoot spacers to fill the space at the wing root where the three piece wing attachfittings bolt to the spar root - 803 grams. That all added up to 2992 grams,or 6.5824 pounds. roughly 1 pound more per spar than I had originally calculated.I had forgotten to add the four wing tips and the wing root spacers inthe original article. Oops.That made the total calculated weight of the four aluminum spars to be 44 pounds,13 ounces. Good thing I am a pilot and not an engineer.)-Spruce weighs 27 pounds per cubic foot. so a 1 X 6 X 158.5 solid spruce spar weighs14 pounds, 14 ounces, while a 1 X 5.5 X 158.5 spar weighs 13 pounds, 9 ounces.2 of each spar has a total weight (before any routing is done) of 56 pounds,14 ounces.-If you decide to use the 3/4 solid, unrouted spars, each 3/4 X 6 X 158.5 sparweighs 11 pounds, 2 ounces, and each 3/4 X 5.5 X 158.5 spars weighs 10 pounds,4 ounces. the four spars together weigh 42 pounds, 12 ounces.-If you build up your I-beam spars, a sheet of Aircraft grade plywood (7 ply) inthe size noted above weighs 50 pounds. If you add 631.5 cubic inches of sprucecapstrips for the flanges (1/4 X 1 X 2526 inches [158.5 X 4 flanges per sparX 4 spars]), the flanges weigh 9 pounds, 14 ounces. The built up I-beam, therefore,weighs roughly 59 pounds, 14 ounces. That does not include the weightof the T-88 used in the assembly.So what does all the math tell me? It tells me that aluminum spars are slightlyheavier than 3/4 spars and lighter than 1 inch or built-up I-beams. At most thedifference is roughly 12 pounds. If you are looking for lighter, then the aluminumis among the lighter of the bunch. A little bit lighter compared to some,and a lot lighter compared to other methods.___________YMMV.--------Semper Fi,Terry HandAthens, GARead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: longerons and plywood?
Pietenpol-List: longerons and plywood?
Original Posted By: Jack Textor
Two questions for you all1. did you steam your bottom longeron to get it to bend or did it bend ok withoutsteaming?2. does the plywood on the sides need to be from one piece or can you piece itfrom two or three smaller pieces?Read this topic online here:http://forums.matronics.com/viewtopic.p ... __________
Two questions for you all1. did you steam your bottom longeron to get it to bend or did it bend ok withoutsteaming?2. does the plywood on the sides need to be from one piece or can you piece itfrom two or three smaller pieces?Read this topic online here:http://forums.matronics.com/viewtopic.p ... __________
Re: Pietenpol-List: longerons and plywood?
Original Posted By: "Greg Cardinal"
Subject: Re: Pietenpol-List: longerons and plywood?Did not steam my longerons. I used full sheets for my sides. Would suggest notusing multiple pieces unless scarfed...Jack TextorSent from my iPad> On Mar 4, 2017, at 2:25 PM, cdlwingnut wrote:> > > Two questions for you all> > 1. did you steam your bottom longeron to get it to bend or did it bend ok withoutsteaming?> > 2. does the plywood on the sides need to be from one piece or can you piece itfrom two or three smaller pieces?> > > > > Read this topic online here:> > http://forums.matronics.com/viewtopic.p ... 865#466865> > > > > > > > > ________________________________________________________________________________
Subject: Re: Pietenpol-List: longerons and plywood?Did not steam my longerons. I used full sheets for my sides. Would suggest notusing multiple pieces unless scarfed...Jack TextorSent from my iPad> On Mar 4, 2017, at 2:25 PM, cdlwingnut wrote:> > > Two questions for you all> > 1. did you steam your bottom longeron to get it to bend or did it bend ok withoutsteaming?> > 2. does the plywood on the sides need to be from one piece or can you piece itfrom two or three smaller pieces?> > > > > Read this topic online here:> > http://forums.matronics.com/viewtopic.p ... 865#466865> > > > > > > > > ________________________________________________________________________________
RE: Pietenpol-List: longerons and plywood?
Original Posted By: owner-pietenpol-list-server(at)matronics.com
1. Did not steam the bottom longerons on NX18235.2. Plywood sides were each made up of two pieces that were scarfed together.Greg CardinalMinneapolis-----Original Message-----
1. Did not steam the bottom longerons on NX18235.2. Plywood sides were each made up of two pieces that were scarfed together.Greg CardinalMinneapolis-----Original Message-----
Re: Pietenpol-List: longerons and plywood?
Original Posted By: Steven Dortch
Subject: Re: Pietenpol-List: longerons and plywood?I started out steaming the lower rib member. However I discovered byaccident that the lower member does not need to be steamed. The curvatureis not that great.I didn't put plywood on the full rib on ANY of them. The root and tip ribshave extra vertical members and that is apparently all that is required.When I covered the wings, I put fabric on the surface of the root ribs.ChuckOn Sat, Mar 4, 2017 at 3:25 PM, cdlwingnut wrote:>> Two questions for you all>> 1. did you steam your bottom longeron to get it to bend or did it bend ok> without steaming?>> 2. does the plywood on the sides need to be from one piece or can you> piece it from two or three smaller pieces?>>> Read this topic online here:>> http://forums.matronics.com/viewtopic.p ... __________
Subject: Re: Pietenpol-List: longerons and plywood?I started out steaming the lower rib member. However I discovered byaccident that the lower member does not need to be steamed. The curvatureis not that great.I didn't put plywood on the full rib on ANY of them. The root and tip ribshave extra vertical members and that is apparently all that is required.When I covered the wings, I put fabric on the surface of the root ribs.ChuckOn Sat, Mar 4, 2017 at 3:25 PM, cdlwingnut wrote:>> Two questions for you all>> 1. did you steam your bottom longeron to get it to bend or did it bend ok> without steaming?>> 2. does the plywood on the sides need to be from one piece or can you> piece it from two or three smaller pieces?>>> Read this topic online here:>> http://forums.matronics.com/viewtopic.p ... __________