Original Posted By: "John Carmen"
Keep in mind I am building a GN-1 which has a different method of attachingcabanes to wing center section.I'm having a bit of dilemma. I am using Skytec extruded aluminumstreamlined struts for cabanes and lift struts. The struts are hollow coredwith flats on the insides to allow a 3-6" piece of 3/4" x 3/4" solidaluminum bar to be slipped in which allows you to terminate the ends byhaving an inch or so of that bar stick out past the strut. You then bolt thestrut to the structure with that piece of bar.Problem is, a 3/4" x3/4" solid aluminum bar only allows me an AN3 boltbecause of edge clearance issues. As I recall, the rule is 2D from centerto edge (where D is diameter of hole). 2D of an AN3 is 3/8" which allowsproper clearance, but I feel I really need an AN4 to attach the tops of thecabanes to the wing spar center section fittings.Here's what I can do:1. Drill out to 1/4" for an AN4 anyway and disregard the edge clearancerecommendations.2. Taper a 1x1" bar to 3/4 x 3/4 and use an AN4 in the 1" portion (thismethod may look wierd)3. Use AN3's to bolt the tops of the cabanes to the wing spar fittings.(will 4 AN3's do the job of holding the wing center section in place?)4. use 3/4" x 3/4" .080 wall 4130 steel instead of solid aluminum bar anddrill for AN4's5. use 3/4 x 3/4" solid steel bar instead of aluminum and drill for AN4's (aheavy solution)No. 4 & 5 makes me wonder if edge clearance guidelines are different forsteel than aluminum...... are they??I need advice!DJ Veghwww.imagedv.com/aircamperMesa, AZN74DVThis email has been scanned for known viruses and made safe for viewing by HalfPrice Hosting, a leading email and web hosting provider. For more informationon an anti-virus email solution, visit .________________________________________________________________________________
Pietenpol-List: cabane bolt edge clearance
Re: Pietenpol-List: cabane bolt edge clearance
Original Posted By: "DJ Vegh"
DJI would make one hole 1/4 and the other 3/16. larger one inboard, andmake both bolts NAS1103. These bolts are under shear thus 1/4 and 3/16 NASshould be plenty strong enough. A NAS bolt will allow you to tighten morethus allow more binding force to the aluminum bar and strut. make the holeclose tolerance .247 and .186( use a reamer to final the hole). and usechamfered washers on the heads. And if you can get a piece of 7075-T6aluminum bar, it will be stronger than 2024-T6.How's this?John----- Original Message -----
DJI would make one hole 1/4 and the other 3/16. larger one inboard, andmake both bolts NAS1103. These bolts are under shear thus 1/4 and 3/16 NASshould be plenty strong enough. A NAS bolt will allow you to tighten morethus allow more binding force to the aluminum bar and strut. make the holeclose tolerance .247 and .186( use a reamer to final the hole). and usechamfered washers on the heads. And if you can get a piece of 7075-T6aluminum bar, it will be stronger than 2024-T6.How's this?John----- Original Message -----
RE: Pietenpol-List: cabane bolt edge clearance
Original Posted By: "Kevin Holcomb"
DJ,I would go ahead and use the AN4 bolt. The 2D edge distance is primarily aconsideration for riveted joints, where the spreading rivet can causecracking of the base metal if too close to the edge. I pulled out my oldrivet installation standard from my days in the aerospace business and foundthat for 1/4" rivets the standard edge distance was .50", but the"Engineering Minimum" was .40" for material .064" thick and thicker, and the"Inspection Minimum" was .37" for those conditions. The Engnieering Minimumwas the minimum value that could be specified on the drawing without havinga special signoff by the stress analysis group, but the inspection minimumallowed the shop to screw up a little bit and go a little below the minimumengineering standard. Bear in mind that this was for supersonic jetfighters. I think it will be OK for a Pietengrega.As John Carmen pointed out, these bolts are loaded in shear (double shear,actually) and I would be concerned about the aluminum piece shearing with a3/16" hole in it. Since the aluminum is considerably softer than the steelbolt, the bolt would likely wallow a hole in the aluminum and allow you wingto clunk up and down every time you hit a little turbulence. An AN4 boltoffers 33% more shear area than an AN3.Good Luck,JackKeep in mind I am building a GN-1 which has a different method of attachingcabanes to wing center section.I'm having a bit of dilemma. I am using Skytec extruded aluminumstreamlined struts for cabanes and lift struts. The struts are hollow coredwith flats on the insides to allow a 3-6" piece of 3/4" x 3/4" solidaluminum bar to be slipped in which allows you to terminate the ends byhaving an inch or so of that bar stick out past the strut. You then bolt thestrut to the structure with that piece of bar.Problem is, a 3/4" x3/4" solid aluminum bar only allows me an AN3 boltbecause of edge clearance issues. As I recall, the rule is 2D from centerto edge (where D is diameter of hole). 2D of an AN3 is 3/8" which allowsproper clearance, but I feel I really need an AN4 to attach the tops of thecabanes to the wing spar center section fittings.Here's what I can do:1. Drill out to 1/4" for an AN4 anyway and disregard the edge clearancerecommendations.2. Taper a 1x1" bar to 3/4 x 3/4 and use an AN4 in the 1" portion (thismethod may look wierd)3. Use AN3's to bolt the tops of the cabanes to the wing spar fittings.(will 4 AN3's do the job of holding the wing center section in place?)4. use 3/4" x 3/4" .080 wall 4130 steel instead of solid aluminum bar anddrill for AN4's5. use 3/4 x 3/4" solid steel bar instead of aluminum and drill for AN4's(aheavy solution)No. 4 & 5 makes me wonder if edge clearance guidelines are different forsteel than aluminum...... are they??I need advice!DJ Veghwww.imagedv.com/aircamperMesa, AZN74DV________________________________________________________________________________
DJ,I would go ahead and use the AN4 bolt. The 2D edge distance is primarily aconsideration for riveted joints, where the spreading rivet can causecracking of the base metal if too close to the edge. I pulled out my oldrivet installation standard from my days in the aerospace business and foundthat for 1/4" rivets the standard edge distance was .50", but the"Engineering Minimum" was .40" for material .064" thick and thicker, and the"Inspection Minimum" was .37" for those conditions. The Engnieering Minimumwas the minimum value that could be specified on the drawing without havinga special signoff by the stress analysis group, but the inspection minimumallowed the shop to screw up a little bit and go a little below the minimumengineering standard. Bear in mind that this was for supersonic jetfighters. I think it will be OK for a Pietengrega.As John Carmen pointed out, these bolts are loaded in shear (double shear,actually) and I would be concerned about the aluminum piece shearing with a3/16" hole in it. Since the aluminum is considerably softer than the steelbolt, the bolt would likely wallow a hole in the aluminum and allow you wingto clunk up and down every time you hit a little turbulence. An AN4 boltoffers 33% more shear area than an AN3.Good Luck,JackKeep in mind I am building a GN-1 which has a different method of attachingcabanes to wing center section.I'm having a bit of dilemma. I am using Skytec extruded aluminumstreamlined struts for cabanes and lift struts. The struts are hollow coredwith flats on the insides to allow a 3-6" piece of 3/4" x 3/4" solidaluminum bar to be slipped in which allows you to terminate the ends byhaving an inch or so of that bar stick out past the strut. You then bolt thestrut to the structure with that piece of bar.Problem is, a 3/4" x3/4" solid aluminum bar only allows me an AN3 boltbecause of edge clearance issues. As I recall, the rule is 2D from centerto edge (where D is diameter of hole). 2D of an AN3 is 3/8" which allowsproper clearance, but I feel I really need an AN4 to attach the tops of thecabanes to the wing spar center section fittings.Here's what I can do:1. Drill out to 1/4" for an AN4 anyway and disregard the edge clearancerecommendations.2. Taper a 1x1" bar to 3/4 x 3/4 and use an AN4 in the 1" portion (thismethod may look wierd)3. Use AN3's to bolt the tops of the cabanes to the wing spar fittings.(will 4 AN3's do the job of holding the wing center section in place?)4. use 3/4" x 3/4" .080 wall 4130 steel instead of solid aluminum bar anddrill for AN4's5. use 3/4 x 3/4" solid steel bar instead of aluminum and drill for AN4's(aheavy solution)No. 4 & 5 makes me wonder if edge clearance guidelines are different forsteel than aluminum...... are they??I need advice!DJ Veghwww.imagedv.com/aircamperMesa, AZN74DV________________________________________________________________________________
Re: Pietenpol-List: cabane bolt edge clearance
Original Posted By: "DJ Vegh"
Here is a bit of background that may help you. The Aerospace industryrequires substantiation of structures, and to show something is strongenough you need to know it's material properties. Years ago the USgovernment did the industry a huge favor by developing a handbook onmaterail properties for metals (MIL-HDBK-5.) This handbook gave bearingdata for 1.5D and 2D edge distance. It is of course conservative to use the2D values if you have a larger ED. However, if you want to use somethingless than 1.5D in a design you have to come up with your own materialproperties. As it is much more accepted, cheaper and quicker to use thepublished ones the industry demands at least 1.5D. At less than 1.5D therewill of course be some strength, but there is not an accepted chartdocumenting what that strength must be. Thus virtually anything designedwill require at least 1.5D. This is where the 1.5D rule came from. Itshould also be noted that this practice will keep you out of trouble as thematerial properties drop off rapidly as you get closer than 1.5D.For initial design, most manufacturers start with at least 2D. This isbecause you can upsize the bolts at least once and still have at least your1.5D provided of course the hole was drilled where it was supposed to be.In fact some manufacturers use 2D+.06 as an initial ED requirement as thatallows for the bolts to be upsized if the hole is miss-drilled, or if it islater determined that the bolts need to be stronger. The +.060 is two+/-.03 tolerances (one incase the edge is cut short and one in case the holeis drilled short). These rules exist to reduce scrap rates. The simplefacts are that in the manufacturing industry to be profitable you cannotavoid to throw away much of what you build. To cut scrap you design thingssuch that there is margin for imperfections in the manufacturing process (itis not reasonable to expect that every hole will be located perfectly anddrilled perfectly.)If you decide to use 1.5D, you need to first do the calculations andcarefully consider your design to make sure that it will be adequate. Also,when fabricating your parts be very careful as this is 1.5D as drilled(measured from the center of the hole to the edge of the part). Which meansyou must not oversize the hole and it must be located where you need it tobe. My advice is use at least 1.5D+.032 and be very careful.My advice, when possible build per print. At the very least the design onthe print has been tried before which often means more to me than a shelffull of engineering models.Kevin----- Original Message -----
Here is a bit of background that may help you. The Aerospace industryrequires substantiation of structures, and to show something is strongenough you need to know it's material properties. Years ago the USgovernment did the industry a huge favor by developing a handbook onmaterail properties for metals (MIL-HDBK-5.) This handbook gave bearingdata for 1.5D and 2D edge distance. It is of course conservative to use the2D values if you have a larger ED. However, if you want to use somethingless than 1.5D in a design you have to come up with your own materialproperties. As it is much more accepted, cheaper and quicker to use thepublished ones the industry demands at least 1.5D. At less than 1.5D therewill of course be some strength, but there is not an accepted chartdocumenting what that strength must be. Thus virtually anything designedwill require at least 1.5D. This is where the 1.5D rule came from. Itshould also be noted that this practice will keep you out of trouble as thematerial properties drop off rapidly as you get closer than 1.5D.For initial design, most manufacturers start with at least 2D. This isbecause you can upsize the bolts at least once and still have at least your1.5D provided of course the hole was drilled where it was supposed to be.In fact some manufacturers use 2D+.06 as an initial ED requirement as thatallows for the bolts to be upsized if the hole is miss-drilled, or if it islater determined that the bolts need to be stronger. The +.060 is two+/-.03 tolerances (one incase the edge is cut short and one in case the holeis drilled short). These rules exist to reduce scrap rates. The simplefacts are that in the manufacturing industry to be profitable you cannotavoid to throw away much of what you build. To cut scrap you design thingssuch that there is margin for imperfections in the manufacturing process (itis not reasonable to expect that every hole will be located perfectly anddrilled perfectly.)If you decide to use 1.5D, you need to first do the calculations andcarefully consider your design to make sure that it will be adequate. Also,when fabricating your parts be very careful as this is 1.5D as drilled(measured from the center of the hole to the edge of the part). Which meansyou must not oversize the hole and it must be located where you need it tobe. My advice is use at least 1.5D+.032 and be very careful.My advice, when possible build per print. At the very least the design onthe print has been tried before which often means more to me than a shelffull of engineering models.Kevin----- Original Message -----
Re: Pietenpol-List: cabane bolt edge clearance
Original Posted By: "Jack Phillips"
Jack and DJI agree that two 1/4 inch bolts not cause any problems as Jack indicates,but I feel that using a 1/4 and then a 3/16 above it will distribute theload better and eliminate a stress riser. We do have two struts and notmuch of a moment arm at the attach points and predictable dynamic loads,thus distribution of load to the strut should be primary consideration, overbrute strength.DJ, I think Jack's idea or mine would work just fine. Just make the holeclose tolerance to eliminate any "wallowing"----- Original Message -----
Jack and DJI agree that two 1/4 inch bolts not cause any problems as Jack indicates,but I feel that using a 1/4 and then a 3/16 above it will distribute theload better and eliminate a stress riser. We do have two struts and notmuch of a moment arm at the attach points and predictable dynamic loads,thus distribution of load to the strut should be primary consideration, overbrute strength.DJ, I think Jack's idea or mine would work just fine. Just make the holeclose tolerance to eliminate any "wallowing"----- Original Message -----
RE: Pietenpol-List: cabane bolt edge clearance
Original Posted By: clif
RE: Pietenpol-List: cabane bolt edge clearance
Original Posted By: DJ Vegh [mailto:aircamper(at)imagedv.com]
DJ,I'm a bit late on the cabane discussion, but I have a couple of commentsthat nobody's mentioned yet.1) Work out the stresses on the cabane struts. If it's anything like thePiet, you'll find out there isn't much. What there is is mainly compressiondown the spar. The reason for this is that the lift struts are mounted muchcloser to the center of the wing than in most high-wing planes.2) I personally wouldn't do anything close tolerance at that point.Pietenpol has a note on his plans (Hoopman 1934) to the effect that thecabanes should rattle. The reason is that there's a lot of bending momentat the joints, and it could (will?) fatigue. If the joints are loose andthe wires take up the bending moment, nothing bad happens.This is not professional advice--it comes from high school physics books.But the numbers are interesting.Gene-----Original Message-----
DJ,I'm a bit late on the cabane discussion, but I have a couple of commentsthat nobody's mentioned yet.1) Work out the stresses on the cabane struts. If it's anything like thePiet, you'll find out there isn't much. What there is is mainly compressiondown the spar. The reason for this is that the lift struts are mounted muchcloser to the center of the wing than in most high-wing planes.2) I personally wouldn't do anything close tolerance at that point.Pietenpol has a note on his plans (Hoopman 1934) to the effect that thecabanes should rattle. The reason is that there's a lot of bending momentat the joints, and it could (will?) fatigue. If the joints are loose andthe wires take up the bending moment, nothing bad happens.This is not professional advice--it comes from high school physics books.But the numbers are interesting.Gene-----Original Message-----