Thank you very much for putting things in perspective, Mark. If the cumulative weight of all the materials adds up to just a few ounces more with the 5048-45, then I'm sure not going to worry about going with a stronger spar. Please forgive my ignorance--in a couple of weeks my garage will be full of spruce and I'll start getting a much better sense of things. -Seth Jersild
On 1/22/2011 11:00 PM, krnet-requ...@mylist.net wrote: > Send KRnet mailing list submissions to > kr...@mylist.net > > To subscribe or unsubscribe via the World Wide Web, visit > http://mylist.net/listinfo/krnet > or, via email, send a message with subject or body 'help' to > krnet-requ...@mylist.net > > You can reach the person managing the list at > krnet-ow...@mylist.net > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of KRnet digest..." > > > Today's Topics: > > 1. Weight of 5048 wing vs. 5046 Noob questions > (Seth and Karen Jersild) > 2. Re: Weight of 5048 wing vs. 5046 Noob questions (Mark Langford) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Sat, 22 Jan 2011 12:27:27 -0600 > From: Seth and Karen Jersild<jersi...@gmail.com> > Subject: KR> Weight of 5048 wing vs. 5046 Noob questions > To: kr...@mylist.net > Message-ID:<4d3b218f.5080...@gmail.com> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > Hello All, > > Next month I'll start cutting wing spars for a KR2S, and now I'm doing > my usual last-minute dithering between different options when I have to > make important decisions. I'll have enough wood to construct 5048-15 > airfoil spars. > > Since I might ultimately go with a smaller engine, I'm going to be hyper > weight-conscious in every decision I make. I think I understand the > advantages of the 5048 airfoil (strength, efficiency, more gas in the > wings if you want it), but I'm wondering whether the total weight of the > thicker wing (more wood, more glass, more glue etc.) is something worth > thinking about for someone who wants things light. I have no experience > regarding the weights of the materials I'll be using. I know the 5046 > is generally used by people who have already built stock RAF48 wings, > but would the 5046 wings also be lighter than the 5048 in any > significant way? > > I know it's difficult if not impossible to compare since so many other > factors are involved in performance, but I'd also be very interested if > someone who has flown planes with both 5046 and 5048 airfoils could give > me their subjective "general feel" impressions of any differences > between the two (takeoff, climb, cruise, approach, stall etc.) if any > were noticeable and could reasonably be attributed to the different > airfoils. > > Any feedback would be greatly appreciated! > > -Seth Jersild in Illinois > > > > ------------------------------ > > Message: 2 > Date: Sat, 22 Jan 2011 13:02:42 -0600 > From: "Mark Langford"<m...@n56ml.com> > Subject: Re: KR> Weight of 5048 wing vs. 5046 Noob questions > To: "KRnet"<kr...@mylist.net> > Message-ID:<03083975E804468785776FA8051FBEFB@base> > Content-Type: text/plain; format=flowed; charset="iso-8859-1"; > reply-type=original > > Seth Jersild wrote: > > >>I'm wondering whether the total weight of the > thicker wing (more wood, more glass, more glue etc.) is something worth > thinking about for someone who wants things light.<< > > The main difference between the AS5046 and the AS5048 is 1.7 inch or so of > thickness (I'm too lazy to go look for the exact number). The spar caps are > the same thickness, so the only structural weight difference is in the > vertical spacers between spar caps and the thin plywood on both faces. It's > literally a few ounces. Easy enough to calculate if you really want to > know. The difference in fiberglass is going to be immeasurable. And given > that you're going to be tapering from AS5048 to AS 5045 on the outer wings > (I hope), you can cut the tiny weight gain in half. And if you're as serious > as seem about weight reduction, you can make your spar caps thinner and > reduce weight further over the AS5046 and still have the same strength, > since the taller AS5048 would be something like 18% stronger due to the > increased spar cap distance. You'll have to do a little homework on how > much thinner you can make them, but the airfoil website at > http://www.krnet.org/as504x/as5046inst.html mentions the exact number on it > somewhere, or back at http://www.krnet.org/as504x/ . Checking those links > show me that there are a lot of dead links there from my shift over to the > new domain, so I'll try to remember to fix those tonight. > > >>> I'd also be very interested if >>> > someone who has flown planes with both 5046 and 5048 airfoils could give > me their subjective "general feel" impressions of any differences > between the two (takeoff, climb, cruise, approach, stall etc.).<< > > I don't think you're going to find anybody that's done that. I'm having a > hard time remembering if there's even one plane flying with the AS5048/45 > yet, but there probably is or are. I think any difference will be minimal, > and like you said, it'll be lost in the noise of other flight > characteristics of the particular plane. > > Go for it! > > Mark Langford > ML at N56ML.com > website at http://www.N56ML.com > -------------------------------------------------------- > > > > > ------------------------------ > > _______________________________________________ > See KRnet list details at http://www.krnet.org/instructions.html > > End of KRnet Digest, Vol 353, Issue 23 > ************************************** >
