Original Posted By: "ernest l. hagness"
To the group:Just some ramblings. Feel free to comment/critisize. Some of you may havepondered the Grega vs Piet debate and may get an insight or see something I missed.I'm starting to understand how needlessly overdone the Grega modificationsare after comparing the Piet and Grega cabane fittings and having a chatwith one of the aero engineers here. Most people, that see the Piet's tiny little strap cabane fittings, make remarks about how weak it looks. If you dosome crude math, the picture is different. If for argument's sake you considerthe loads to be shared equally between all eight cabane/lift strut fittings,and assuming a fuselage that weighs 900 lbs, the load on each cabane wouldbe just over 100 lbs at 1'G'. There are two straps at each cabane, so reducethat to just over 50 lbs on each strap.Actually, with the lift struts at about mid span on the wing panel, almost allthe lifting loads are transmitted through the lift struts, not the cabanes. (Infact, if there is more wing outboard of the lift strut than inboard, the loadon the cabanes is actually in *compression*. We had a Twin Otter that had awing root fitting fail completely and the airplane continued to fly withthe wing held to the fuselage by the fairings!). So the Piet cabanes are loaded to far less than 50lbs, probably less than 20 lbs that could be tension or compression depending on the flight condition. Pull 5 gs and the load goes to 100 lbs. What's the limit tensilestrength of a half inch strap of 4130 at the bolt holes? About 1000 lbs?The wing fittings would share most of the 900 lb load between them or about200 lbs per fitting, which would be 1000 lbs at 5 Gs. What's the tensilestrength of the 4130 strut fitting? 3 or 4 thousand lbs maybe? Same with the top fittings. The lift load on the wing root fittings is mostly acompression load trying to push the wing inboard against the center section,which is cancelled at the front fitting by the drag load trying to bend thewing aft. So the most highly stressed component at the center section isthe inboard compression load on the _rear_ wingroot fitting. The top cabanefittings are doing as little work as the bottom ones. The drag struts would probably be loaded the most.Look at the engine mount also. If the Model A is roughly 250 lbs, thereis half that or 125 lbs on the front end of the mount (since the other endis on the firewall) or 62lbs on each side. This load is split between thetop and bottom mount fittings at the firewall. Even at 5Gs there is not much stress on the engine mount fittings; even allowing for moment arms andwhatnot there would be no more than a few hundred pounds of shear load on each bottom mount bolt.This little excercise helped convince me what the oldtimers all say, thatthe stucture is adequate with mild steel and is actually much overdonewhen built using 4130. If you modify the fittings you are adding strengththat you will never be able to use. So while there *are* some design features of the Grega that may be nice tohave, (like the bigger ailerons), structurally speaking the extra beef in the Grega is just ballast.I'm sure all this is just preaching to the converted.RegardsJohn KahnTech PubsCanadair Regional JetBomabardier Inc.________________________________________________________________________________
Pietenpol-List: Re: Piet/Grega
Pietenpol-List: Re: Piet/Grega
Original Posted By: "ernest l. hagness"
John Kahn wrote:> > To the group:> > Just some ramblings. Feel free to comment/critisize. Some of you may have> pondered the Grega vs Piet debate and may get an insight or see something I> missed.> > I'm starting to understand how needlessly overdone the Grega modifications> are after comparing the Piet and Grega cabane fittings and having a chat> with one of the aero engineers here. Most people, that see the Piet's tiny> little strap cabane fittings, make remarks about how weak it looks. If you do> some crude math, the picture is different. If for argument's sake you consider> the loads to be shared equally between all eight cabane/lift strut fittings,> and assuming a fuselage that weighs 900 lbs, the load on each cabane would> be just over 100 lbs at 1'G'. There are two straps at each cabane, so reduce> that to just over 50 lbs on each strap.> > Actually, with the lift struts at about mid span on the wing panel, almost all> the lifting loads are transmitted through the lift struts, not the cabanes. (In> fact, if there is more wing outboard of the lift strut than inboard, the load> on the cabanes is actually in *compression*. We had a Twin Otter that had a> wing root fitting fail completely and the airplane continued to fly with> the wing held to the fuselage by the fairings!).> > So the Piet cabanes are loaded to far less than 50lbs, probably less than> 20 lbs that could be tension or compression depending on the flight> condition. Pull 5 gs and the load goes to 100 lbs. What's the limit tensile> strength of a half inch strap of 4130 at the bolt holes? About 1000> lbs?> > The wing fittings would share most of the 900 lb load between them or about> 200 lbs per fitting, which would be 1000 lbs at 5 Gs. What's the tensile> strength of the 4130 strut fitting? 3 or 4 thousand lbs maybe?> > Same with the top fittings. The lift load on the wing root fittings is mostlya> compression load trying to push the wing inboard against the center section,> which is cancelled at the front fitting by the drag load trying to bend the> wing aft. So the most highly stressed component at the center section is> the inboard compression load on the _rear_ wingroot fitting. The top cabane> fittings are doing as little work as the bottom ones. The drag struts> would probably be loaded the most.> > Look at the engine mount also. If the Model A is roughly 250 lbs, there> is half that or 125 lbs on the front end of the mount (since the other end> is on the firewall) or 62lbs on each side. This load is split between the> top and bottom mount fittings at the firewall. Even at 5Gs there is not> much stress on the engine mount fittings; even allowing for moment arms and> whatnot there would be no more than a few hundred pounds of shear load> on each bottom mount bolt.> > This little excercise helped convince me what the oldtimers all say, that> the stucture is adequate with mild steel and is actually much overdone> when built using 4130. If you modify the fittings you are adding strength> that you will never be able to use.> > So while there *are* some design features of the Grega that may be nice to> have, (like the bigger ailerons), structurally speaking the extra beef in> the Grega is just ballast.> > I'm sure all this is just preaching to the converted.> > Regards> > John Kahn> > Tech Pubs> Canadair Regional Jet> Bomabardier Inc.John, Thanks for sharing this good data with us . It gives me much peaceof mind knowing that my Grega is not going to break on me. I have neverseen any solid engineering data on this so I am making a copy to includein my airframe log book. Thanks. Ernie.________________________________________________________________________________
John Kahn wrote:> > To the group:> > Just some ramblings. Feel free to comment/critisize. Some of you may have> pondered the Grega vs Piet debate and may get an insight or see something I> missed.> > I'm starting to understand how needlessly overdone the Grega modifications> are after comparing the Piet and Grega cabane fittings and having a chat> with one of the aero engineers here. Most people, that see the Piet's tiny> little strap cabane fittings, make remarks about how weak it looks. If you do> some crude math, the picture is different. If for argument's sake you consider> the loads to be shared equally between all eight cabane/lift strut fittings,> and assuming a fuselage that weighs 900 lbs, the load on each cabane would> be just over 100 lbs at 1'G'. There are two straps at each cabane, so reduce> that to just over 50 lbs on each strap.> > Actually, with the lift struts at about mid span on the wing panel, almost all> the lifting loads are transmitted through the lift struts, not the cabanes. (In> fact, if there is more wing outboard of the lift strut than inboard, the load> on the cabanes is actually in *compression*. We had a Twin Otter that had a> wing root fitting fail completely and the airplane continued to fly with> the wing held to the fuselage by the fairings!).> > So the Piet cabanes are loaded to far less than 50lbs, probably less than> 20 lbs that could be tension or compression depending on the flight> condition. Pull 5 gs and the load goes to 100 lbs. What's the limit tensile> strength of a half inch strap of 4130 at the bolt holes? About 1000> lbs?> > The wing fittings would share most of the 900 lb load between them or about> 200 lbs per fitting, which would be 1000 lbs at 5 Gs. What's the tensile> strength of the 4130 strut fitting? 3 or 4 thousand lbs maybe?> > Same with the top fittings. The lift load on the wing root fittings is mostlya> compression load trying to push the wing inboard against the center section,> which is cancelled at the front fitting by the drag load trying to bend the> wing aft. So the most highly stressed component at the center section is> the inboard compression load on the _rear_ wingroot fitting. The top cabane> fittings are doing as little work as the bottom ones. The drag struts> would probably be loaded the most.> > Look at the engine mount also. If the Model A is roughly 250 lbs, there> is half that or 125 lbs on the front end of the mount (since the other end> is on the firewall) or 62lbs on each side. This load is split between the> top and bottom mount fittings at the firewall. Even at 5Gs there is not> much stress on the engine mount fittings; even allowing for moment arms and> whatnot there would be no more than a few hundred pounds of shear load> on each bottom mount bolt.> > This little excercise helped convince me what the oldtimers all say, that> the stucture is adequate with mild steel and is actually much overdone> when built using 4130. If you modify the fittings you are adding strength> that you will never be able to use.> > So while there *are* some design features of the Grega that may be nice to> have, (like the bigger ailerons), structurally speaking the extra beef in> the Grega is just ballast.> > I'm sure all this is just preaching to the converted.> > Regards> > John Kahn> > Tech Pubs> Canadair Regional Jet> Bomabardier Inc.John, Thanks for sharing this good data with us . It gives me much peaceof mind knowing that my Grega is not going to break on me. I have neverseen any solid engineering data on this so I am making a copy to includein my airframe log book. Thanks. Ernie.________________________________________________________________________________
Pietenpol-List: Re: Piet/Grega
Original Posted By: POWRACER(at)aol.com
Hello all,Discussion of the Piet/Grega prompts a further question? I have neverseen or heard anything mentioned about control surface flutter foreither a/c. Is it because of the slow speed that this is just not aproblem?Bob Bailey - Missouri________________________________________________________________________________
Hello all,Discussion of the Piet/Grega prompts a further question? I have neverseen or heard anything mentioned about control surface flutter foreither a/c. Is it because of the slow speed that this is just not aproblem?Bob Bailey - Missouri________________________________________________________________________________
Pietenpol-List: Re: Piet/Grega
Original Posted By:> John Kahn
John, thank you very much for the fitting (no pun intended) information. Iwas just going through the thought process, as I assemble the centre wingsection, that the cabane fittings look very flimsy and should probably bereinforced. Your expanation puts some sense into the fact that these planeshave been flying for so long without problems. When the centre section ishanging in place the first thought is WOW, those are really tiny fittings.It comes back to a repeated theme, build it as designed, its worked a longtime. Thanks again,-=Ian=-
John, thank you very much for the fitting (no pun intended) information. Iwas just going through the thought process, as I assemble the centre wingsection, that the cabane fittings look very flimsy and should probably bereinforced. Your expanation puts some sense into the fact that these planeshave been flying for so long without problems. When the centre section ishanging in place the first thought is WOW, those are really tiny fittings.It comes back to a repeated theme, build it as designed, its worked a longtime. Thanks again,-=Ian=-
Pietenpol-List: Re: Piet/Grega
Original Posted By: POWRACER(at)aol.com
Being a mechanical engineer myself, and I am very new at lookinginto the piet, I find your note on the cabane fittings ratherheartwarming. I have been helping some with the building startsefforts of John Fay, who has had his plans for eons, and am lookingat starting one myself. Two built together may take longer withall the side conversations, but enjoyable build is enjoyable building time anyway. The plans have no mention of a particular strength or type of steel for any of the fittings, which I also have done quick, notas in depth as your discussion, head calculations and concludedthen the same resulting answer -- mild A36 steel will suffice andnot have all the hum-drum expense of 4130.I wonder if anyone has done the next discussion. If the fittings are at this strength, is the real weak leak not in the fitting at all? The mounting at the fusulage (wood) may be such the place. Doyou know if anyone has made such analysis efforts? I believe some discussion on this might prove useful.David Scott102 Avalon DrWashington,IL 61571-2902djscott(at)heartland.bradley.edu--________________________________________________________________________________
Being a mechanical engineer myself, and I am very new at lookinginto the piet, I find your note on the cabane fittings ratherheartwarming. I have been helping some with the building startsefforts of John Fay, who has had his plans for eons, and am lookingat starting one myself. Two built together may take longer withall the side conversations, but enjoyable build is enjoyable building time anyway. The plans have no mention of a particular strength or type of steel for any of the fittings, which I also have done quick, notas in depth as your discussion, head calculations and concludedthen the same resulting answer -- mild A36 steel will suffice andnot have all the hum-drum expense of 4130.I wonder if anyone has done the next discussion. If the fittings are at this strength, is the real weak leak not in the fitting at all? The mounting at the fusulage (wood) may be such the place. Doyou know if anyone has made such analysis efforts? I believe some discussion on this might prove useful.David Scott102 Avalon DrWashington,IL 61571-2902djscott(at)heartland.bradley.edu--________________________________________________________________________________
Pietenpol-List: Re: Piet/Grega
Original Posted By: Greg Cardinal
> Being a mechanical engineer myself, and I am very new at looking> into the piet, I find your note on the cabane fittings rather> heartwarming. I have been helping some with the building starts> efforts of John Fay, who has had his plans for eons, and am looking> at starting one myself. Two built together may take longer with> all the side conversations, but enjoyable build is enjoyable building time anyway.> > The plans have no mention of a particular strength or type of > steel for any of the fittings, which I also have done quick, not> as in depth as your discussion, head calculations and concluded> then the same resulting answer -- mild A36 steel will suffice and> not have all the hum-drum expense of 4130.> > I wonder if anyone has done the next discussion. If the fittings > are at this strength, is the real weak leak not in the fitting at all? > The mounting at the fusulage (wood) may be such the place. Do> you know if anyone has made such analysis efforts? I believe > some discussion on this might prove useful.> > David Scott> 102 Avalon Dr> Washington,IL 61571-2902I would use 4130 anyway since there just isn't that much steel and the 50% additional tensile strength is there with no weight penalty. I thinkthere is only a couple hundred dollars of steel in the fittings if that. By theway, there is a huge cost saving by using round lift struts instead of streamline tube, about 1/3 of the cost. There is minimal effect on cruisespeed, only a couple of knots, and you can fair them anyway.I would make the nonstructural brackets like pulley fittings from aluminum.The plans show a steel strap that connects the strut fittings togetheralong the bottom of the fuselage, which is supplemented by the hardwoodcrossmember. I guess one could almost think of the fuselage as resting in apair of steel slings formed by the lift struts and carrythrough straps. Possiblythe only really highly stessed bolt-to-wood joints are the lift strut tospar fittings and maybe the engine mounts when you add thrust and gyroloads to the loads from weight. And the landing gear depending on how smooththe pilot is!There is mention in the mailbag articles on the website of a fellowthat did a stress analysis on the airframe and concluded the only criticalitem that must be added is jury struts to raise the negative G limit abovethe 1.5g compression strength calculated for no-jury-strut lift struts.It would be nice to have a summary from the stress analysis that gives thecalculated maximum load on a given fitting and the tensile strength of thefitting as made from the plans. That would probably stop most people fromadding meat to the fittings.I like the way the design, in its old fashionedness, distributes loadsthrough mulitple paths. eg. I think a lot of people are concerned by havingonly two drag bays in the wing, until it's pointed out that the drift wiresfor the lift struts share those loads and also relieve the cabanes of much of the job of keeping the fuselage perpendicular to the wing. You cetainly wouldn't want to use a vee strut arrangment without redesigning the whole wing and cabane arrangement.The one item I think needs to be modified came from the Piet forum at Oshkosha couple of years ago, where there was discussion of a crash where thecabane drag struts collapsed and let the wing come down on the pax's head. I think the drag struts should be quite beefy to resist collapsing incompression in a crash. I see a lot of Piets with really skinny drag struts.I will make them from the same tube as the cabane lift struts.jk________________________________________________________________________________
> Being a mechanical engineer myself, and I am very new at looking> into the piet, I find your note on the cabane fittings rather> heartwarming. I have been helping some with the building starts> efforts of John Fay, who has had his plans for eons, and am looking> at starting one myself. Two built together may take longer with> all the side conversations, but enjoyable build is enjoyable building time anyway.> > The plans have no mention of a particular strength or type of > steel for any of the fittings, which I also have done quick, not> as in depth as your discussion, head calculations and concluded> then the same resulting answer -- mild A36 steel will suffice and> not have all the hum-drum expense of 4130.> > I wonder if anyone has done the next discussion. If the fittings > are at this strength, is the real weak leak not in the fitting at all? > The mounting at the fusulage (wood) may be such the place. Do> you know if anyone has made such analysis efforts? I believe > some discussion on this might prove useful.> > David Scott> 102 Avalon Dr> Washington,IL 61571-2902I would use 4130 anyway since there just isn't that much steel and the 50% additional tensile strength is there with no weight penalty. I thinkthere is only a couple hundred dollars of steel in the fittings if that. By theway, there is a huge cost saving by using round lift struts instead of streamline tube, about 1/3 of the cost. There is minimal effect on cruisespeed, only a couple of knots, and you can fair them anyway.I would make the nonstructural brackets like pulley fittings from aluminum.The plans show a steel strap that connects the strut fittings togetheralong the bottom of the fuselage, which is supplemented by the hardwoodcrossmember. I guess one could almost think of the fuselage as resting in apair of steel slings formed by the lift struts and carrythrough straps. Possiblythe only really highly stessed bolt-to-wood joints are the lift strut tospar fittings and maybe the engine mounts when you add thrust and gyroloads to the loads from weight. And the landing gear depending on how smooththe pilot is!There is mention in the mailbag articles on the website of a fellowthat did a stress analysis on the airframe and concluded the only criticalitem that must be added is jury struts to raise the negative G limit abovethe 1.5g compression strength calculated for no-jury-strut lift struts.It would be nice to have a summary from the stress analysis that gives thecalculated maximum load on a given fitting and the tensile strength of thefitting as made from the plans. That would probably stop most people fromadding meat to the fittings.I like the way the design, in its old fashionedness, distributes loadsthrough mulitple paths. eg. I think a lot of people are concerned by havingonly two drag bays in the wing, until it's pointed out that the drift wiresfor the lift struts share those loads and also relieve the cabanes of much of the job of keeping the fuselage perpendicular to the wing. You cetainly wouldn't want to use a vee strut arrangment without redesigning the whole wing and cabane arrangement.The one item I think needs to be modified came from the Piet forum at Oshkosha couple of years ago, where there was discussion of a crash where thecabane drag struts collapsed and let the wing come down on the pax's head. I think the drag struts should be quite beefy to resist collapsing incompression in a crash. I see a lot of Piets with really skinny drag struts.I will make them from the same tube as the cabane lift struts.jk________________________________________________________________________________
Pietenpol-List: Piet/Grega
Original Posted By: "Mckellars"
They are both great airplanes,but, let's face it, they are look alikes,but not the same airplane. The Piet was initially designed for the "A"engine. Any other engine requires modification. The Grega was designedfor the A 65. I do believe no mods are required with that engine.The Grega has a different airfoil from the Piet, the fuselage has plyits entire length & the fittings are different from the Piet.If I was to build again with a A 65, I would proably build a Grega.Please, I don't mean to start a controversy ( as has occured in the past). Take your choice, either way you will have a good airplane.Mike B Piet N687MB ( Mr Sam )________________________________________________________________________________
They are both great airplanes,but, let's face it, they are look alikes,but not the same airplane. The Piet was initially designed for the "A"engine. Any other engine requires modification. The Grega was designedfor the A 65. I do believe no mods are required with that engine.The Grega has a different airfoil from the Piet, the fuselage has plyits entire length & the fittings are different from the Piet.If I was to build again with a A 65, I would proably build a Grega.Please, I don't mean to start a controversy ( as has occured in the past). Take your choice, either way you will have a good airplane.Mike B Piet N687MB ( Mr Sam )________________________________________________________________________________
> Re: Piet/Grega
Original Posted By: "Craig R. Lawler"
> > To the group:> > Just some ramblings. Feel free to comment/critisize. Some of you mayhave> pondered the Grega vs Piet debate and may get an insight or see somethingI > missed.> > I'm starting to understand how needlessly overdone the Gregamodifications> are after comparing the Piet and Grega cabane fittings and having a chat> with one of the aero engineers here. Most people, that see the Piet'stiny > little strap cabane fittings, make remarks about how weak it looks. Ifyou do> some crude math, the picture is different. If for argument's sake youconsider> the loads to be shared equally between all eight cabane/lift strutfittings,> and assuming a fuselage that weighs 900 lbs, the load on each cabanewould> be just over 100 lbs at 1'G'. There are two straps at each cabane, soreduce> that to just over 50 lbs on each strap.> > Actually, with the lift struts at about mid span on the wing panel,almost all> the lifting loads are transmitted through the lift struts, not thecabanes. (In> fact, if there is more wing outboard of the lift strut than inboard, theload> on the cabanes is actually in *compression*. We had a Twin Otter thathad a> wing root fitting fail completely and the airplane continued to fly with> the wing held to the fuselage by the fairings!). > > So the Piet cabanes are loaded to far less than 50lbs, probably less than> 20 lbs that could be tension or compression depending on the flight > condition. Pull 5 gs and the load goes to 100 lbs. What's the limittensile> strength of a half inch strap of 4130 at the bolt holes? About 1000 > lbs?> > The wing fittings would share most of the 900 lb load between them orabout> 200 lbs per fitting, which would be 1000 lbs at 5 Gs. What's the tensile> strength of the 4130 strut fitting? 3 or 4 thousand lbs maybe? > > Same with the top fittings. The lift load on the wing root fittings ismostly a> compression load trying to push the wing inboard against the centersection,> which is cancelled at the front fitting by the drag load trying to bendthe> wing aft. So the most highly stressed component at the center section is> the inboard compression load on the _rear_ wingroot fitting. The topcabane> fittings are doing as little work as the bottom ones. The drag struts > would probably be loaded the most.> > Look at the engine mount also. If the Model A is roughly 250 lbs, there> is half that or 125 lbs on the front end of the mount (since the otherend> is on the firewall) or 62lbs on each side. This load is split betweenthe> top and bottom mount fittings at the firewall. Even at 5Gs there is not > much stress on the engine mount fittings; even allowing for moment armsand> whatnot there would be no more than a few hundred pounds of shear load > on each bottom mount bolt.> > This little excercise helped convince me what the oldtimers all say, that> the stucture is adequate with mild steel and is actually much overdone> when built using 4130. If you modify the fittings you are addingstrength> that you will never be able to use. > > So while there *are* some design features of the Grega that may be niceto> have, (like the bigger ailerons), structurally speaking the extra beef in> the Grega is just ballast.> > I'm sure all this is just preaching to the converted.> > Regards> > John Kahn> Tech Pubs> Canadair Regional Jet> Bomabardier Inc.________________________________________________________________________________
> > To the group:> > Just some ramblings. Feel free to comment/critisize. Some of you mayhave> pondered the Grega vs Piet debate and may get an insight or see somethingI > missed.> > I'm starting to understand how needlessly overdone the Gregamodifications> are after comparing the Piet and Grega cabane fittings and having a chat> with one of the aero engineers here. Most people, that see the Piet'stiny > little strap cabane fittings, make remarks about how weak it looks. Ifyou do> some crude math, the picture is different. If for argument's sake youconsider> the loads to be shared equally between all eight cabane/lift strutfittings,> and assuming a fuselage that weighs 900 lbs, the load on each cabanewould> be just over 100 lbs at 1'G'. There are two straps at each cabane, soreduce> that to just over 50 lbs on each strap.> > Actually, with the lift struts at about mid span on the wing panel,almost all> the lifting loads are transmitted through the lift struts, not thecabanes. (In> fact, if there is more wing outboard of the lift strut than inboard, theload> on the cabanes is actually in *compression*. We had a Twin Otter thathad a> wing root fitting fail completely and the airplane continued to fly with> the wing held to the fuselage by the fairings!). > > So the Piet cabanes are loaded to far less than 50lbs, probably less than> 20 lbs that could be tension or compression depending on the flight > condition. Pull 5 gs and the load goes to 100 lbs. What's the limittensile> strength of a half inch strap of 4130 at the bolt holes? About 1000 > lbs?> > The wing fittings would share most of the 900 lb load between them orabout> 200 lbs per fitting, which would be 1000 lbs at 5 Gs. What's the tensile> strength of the 4130 strut fitting? 3 or 4 thousand lbs maybe? > > Same with the top fittings. The lift load on the wing root fittings ismostly a> compression load trying to push the wing inboard against the centersection,> which is cancelled at the front fitting by the drag load trying to bendthe> wing aft. So the most highly stressed component at the center section is> the inboard compression load on the _rear_ wingroot fitting. The topcabane> fittings are doing as little work as the bottom ones. The drag struts > would probably be loaded the most.> > Look at the engine mount also. If the Model A is roughly 250 lbs, there> is half that or 125 lbs on the front end of the mount (since the otherend> is on the firewall) or 62lbs on each side. This load is split betweenthe> top and bottom mount fittings at the firewall. Even at 5Gs there is not > much stress on the engine mount fittings; even allowing for moment armsand> whatnot there would be no more than a few hundred pounds of shear load > on each bottom mount bolt.> > This little excercise helped convince me what the oldtimers all say, that> the stucture is adequate with mild steel and is actually much overdone> when built using 4130. If you modify the fittings you are addingstrength> that you will never be able to use. > > So while there *are* some design features of the Grega that may be niceto> have, (like the bigger ailerons), structurally speaking the extra beef in> the Grega is just ballast.> > I'm sure all this is just preaching to the converted.> > Regards> > John Kahn> Tech Pubs> Canadair Regional Jet> Bomabardier Inc.________________________________________________________________________________