Original Posted By: JamesJboyer(at)aol.com
Spar splices may also be made using a hand held router. Every thing is neat,quick, and accurate, and the second scarf is exactly the same as the firstone.Basicly the fixture is two parallel pieces of wood 1x6x24" with a 6" webbetween them that is attached at a 1:10 or 1:12 slope. The spar blank ispositioned on the fixture with wood spacers to hold it away from theparallel sides and held in place with C-clamps at a suitable distance backto clear the router base plate. Use a thin shim of wood under the C-clampsto avoid marking the spar.Make a base plate of 1/4" plexiglas (lexan, ect.) as wide as the base plateand long enough to span the two parallel pieces when the router is over toone side or other of the fixture.Set the router bit to a depth of 1" and lightly cut a mark on the slopedweb,use this mark to position the spar blank for scarfing.Then reposition the router to take 1/8" depth of cuts and finish up with a1/16"final cut.Rodger ChildsOne piece wing Piet in progress________________________________________________________________________________
Pietenpol-List: Spar Splices
RE: Pietenpol-List: Spar Splices
Original Posted By: owner-pietenpol-list-server(at)matronics.com
Rodger,I must be slow, but I can't visualize what you are describing. This methodof spar splicing using a router obviously has merit, but for some reason, Iam confused.Would it be possible to take a picture of the fixture and setup and scan itinto a computer file and send it as an attachment to email? Or perhaps makea crude sketch and do the same thing to get it on the computer?Speaking only for myself, I'd certainly learn something of benefit and wouldprobably use it on my project. Perhaps others feel the same way.Thanks Very Much,Mikemikehi(at)molalla.net-----Original Message-----
Rodger,I must be slow, but I can't visualize what you are describing. This methodof spar splicing using a router obviously has merit, but for some reason, Iam confused.Would it be possible to take a picture of the fixture and setup and scan itinto a computer file and send it as an attachment to email? Or perhaps makea crude sketch and do the same thing to get it on the computer?Speaking only for myself, I'd certainly learn something of benefit and wouldprobably use it on my project. Perhaps others feel the same way.Thanks Very Much,Mikemikehi(at)molalla.net-----Original Message-----
Pietenpol-List: Spar Splices
Original Posted By: "Michael Hinchman"
Michael,Ah, the limitations of my budget, I don't have a scanner yet. But I couldsendyou some sketches by snail mail if you like. I was able to take the fixturefroman idea to a usable part in about an hour and a half. The scarf for my sparswere made to a 10:1 slope.Imagine an " H ". This is what the fixture looks like when viewed on end.Now stretch out the two verticle sides so that the center web is muchlonger. Sort of, no, just like a piece of structural steel "H" beam onlymade of wood instead and 24 inches long.Now rotate the " H " 90 degrees so you look at one side of the 24 inch long" H ". The web is now hidden behind the face of the side and runshorizontal. Mentally move the left end of the horizontal web up to the topof the side face and the other end down as necessary to achieve the required10:1 slope.The spar will lay flat against the horizontal web which is on a 10:1 slopein relation to the top of the " H ". The router will track on the top of thesides of the " H " and cut the desired angle for the splice. Four sparblanks, cut on an angle, one end only, and all the same. Should take about 2hours to cut all angles.Send your address to me at ---> childsway@indian-creek.net and I'll get offa detailed sketch of what it all will look like.Best wishes,RodgerOne piece winged Piet in progress.________________________________________________________________________________
Michael,Ah, the limitations of my budget, I don't have a scanner yet. But I couldsendyou some sketches by snail mail if you like. I was able to take the fixturefroman idea to a usable part in about an hour and a half. The scarf for my sparswere made to a 10:1 slope.Imagine an " H ". This is what the fixture looks like when viewed on end.Now stretch out the two verticle sides so that the center web is muchlonger. Sort of, no, just like a piece of structural steel "H" beam onlymade of wood instead and 24 inches long.Now rotate the " H " 90 degrees so you look at one side of the 24 inch long" H ". The web is now hidden behind the face of the side and runshorizontal. Mentally move the left end of the horizontal web up to the topof the side face and the other end down as necessary to achieve the required10:1 slope.The spar will lay flat against the horizontal web which is on a 10:1 slopein relation to the top of the " H ". The router will track on the top of thesides of the " H " and cut the desired angle for the splice. Four sparblanks, cut on an angle, one end only, and all the same. Should take about 2hours to cut all angles.Send your address to me at ---> childsway@indian-creek.net and I'll get offa detailed sketch of what it all will look like.Best wishes,RodgerOne piece winged Piet in progress.________________________________________________________________________________
RE: Pietenpol-List: Spar Splices
Original Posted By: owner-pietenpol-list-server(at)matronics.com
Thanks, Rodger. Your second explanation was easier for me to "see". Still,if you feel like making a sketch, I'd be grateful. I don't own a scannereither, but the various places I work do, so I take advantage of that whenneeded.My mailing address is:Mike Hinchman31722 S. Goodtime Rd.Molalla, OR 97038Thanks again,Mike-----Original Message-----
Thanks, Rodger. Your second explanation was easier for me to "see". Still,if you feel like making a sketch, I'd be grateful. I don't own a scannereither, but the various places I work do, so I take advantage of that whenneeded.My mailing address is:Mike Hinchman31722 S. Goodtime Rd.Molalla, OR 97038Thanks again,Mike-----Original Message-----
Pietenpol-List: Spar Splices
Original Posted By: Gary Gower
Re: Pietenpol-List: Spar Splices
Original Posted By: "Richard Gillespie"
Subject: Re: Pietenpol-List: Spar SplicesI think I see what you have done. Are you scarfing each piece of 3/4inch stock, building a 29 foot strip and then laminating a stack ofthese into a spar, or are you laminating a stack of 3/4 in stock intoa part of a spar and scarfing the parts together?The reason I ask is that the joint that Bernard describes is scarfedthe wrong way according to standards and practices. The epoxy thatyou are using is happiest when the load is applied across the gluedsurface in shear and not in tension or compression. Bernard's is intension and compression and through bolted for extra safety.This means that the scarf joint should be across the face of the spartapering from 3/4 inch thick to zero over the length of ten or twelvetimes 3/4 inch or 7 1/2 to 9 inches. You would probably need toaccomplish this with a plane. What is described using a router seemsto be tapering the joined pieces on the edge from 4 3/4 inches to zeroover a length of 47 1/2 to 57 inches.I'll bet that joining pieces of spar material the "wrong" way to buildup a spar is plenty strong. Bernard seems to have never had one fail.But, since the standards for aircraft construction differs on thispoint, I would recommend building up your spar in this fashioninstead.Mike BellColumbia, SC________________________________________________________________________________
Subject: Re: Pietenpol-List: Spar SplicesI think I see what you have done. Are you scarfing each piece of 3/4inch stock, building a 29 foot strip and then laminating a stack ofthese into a spar, or are you laminating a stack of 3/4 in stock intoa part of a spar and scarfing the parts together?The reason I ask is that the joint that Bernard describes is scarfedthe wrong way according to standards and practices. The epoxy thatyou are using is happiest when the load is applied across the gluedsurface in shear and not in tension or compression. Bernard's is intension and compression and through bolted for extra safety.This means that the scarf joint should be across the face of the spartapering from 3/4 inch thick to zero over the length of ten or twelvetimes 3/4 inch or 7 1/2 to 9 inches. You would probably need toaccomplish this with a plane. What is described using a router seemsto be tapering the joined pieces on the edge from 4 3/4 inches to zeroover a length of 47 1/2 to 57 inches.I'll bet that joining pieces of spar material the "wrong" way to buildup a spar is plenty strong. Bernard seems to have never had one fail.But, since the standards for aircraft construction differs on thispoint, I would recommend building up your spar in this fashioninstead.Mike BellColumbia, SC________________________________________________________________________________
Pietenpol-List: Spar Splices
Original Posted By: vistin(at)juno.com
We are using 1 inch wide spars and these are routed as indicated in thePietenpol drawings. When looking down on the top of the spar, one isable to see the splice joint going from the front face to the rear face overa run of 10 inches. There are also plywood plates on the front face andrear face of the spar that are centered over the splice glue line. Theseplates are radius'd on the outside face as per FAA call out.My building partner who is an A&P assured me that he could cut thescarf joints for one spar with a spoke shave and plane in 8 hours andget the scarfs nice and flat for gluing. Many times he had done this heassured me, and I could too. I wondered. I could make one scarf, perhaps.But 4 matching ones? I really wondered about that. But I knew that arouter and fixture could do the job and make each scarf the same as theothers. And matching slopes are the MAIN thing here. So that was theroute(r) I took and got good matching scarfs each spar blank.I think the scarf joint that Bernie used way back when must have beenused in civil engineering or even ship building but I couldn't bring my selfto go that route, although it works. However, the "aircraft way" is thebetter way to go.RodgerOne piece winged Piet in progress________________________________________________________________________________
We are using 1 inch wide spars and these are routed as indicated in thePietenpol drawings. When looking down on the top of the spar, one isable to see the splice joint going from the front face to the rear face overa run of 10 inches. There are also plywood plates on the front face andrear face of the spar that are centered over the splice glue line. Theseplates are radius'd on the outside face as per FAA call out.My building partner who is an A&P assured me that he could cut thescarf joints for one spar with a spoke shave and plane in 8 hours andget the scarfs nice and flat for gluing. Many times he had done this heassured me, and I could too. I wondered. I could make one scarf, perhaps.But 4 matching ones? I really wondered about that. But I knew that arouter and fixture could do the job and make each scarf the same as theothers. And matching slopes are the MAIN thing here. So that was theroute(r) I took and got good matching scarfs each spar blank.I think the scarf joint that Bernie used way back when must have beenused in civil engineering or even ship building but I couldn't bring my selfto go that route, although it works. However, the "aircraft way" is thebetter way to go.RodgerOne piece winged Piet in progress________________________________________________________________________________
Re: Pietenpol-List: Spar Splices
Original Posted By: "Mike Bell"
Good point Mike!That's the point (or similar to it) that I was making regarding therecommended 1:15 (or preferred 1:20) splice (scarf) angle foud in some ofthe more recent literature. You are right- the scarf should be along thelong axis of the rectangular spar. Also a 1:15 or 20 may be impractical ifdone in the wrong axis because when you multiply 15 (or 20)times a depth of4 or 5 inches, the length (15 x this dimension) is LONG. depending on wherethe splice is, it may not even be possible.On my plans, it looks like the useable distance is about 20 inches betweenthe cabane strut mounting brackets. So if you take that as the controllingparameter and calculate the glue area,for the splice as shown in the plans,you have a glue area of about 20.55 square inches _________________( 1 x / (20*20) + (4.75)*(4.75)) This is a slope of about 1:4.2.! If you put a splice in the long axis , you have a glue area of about 95.1square inches ______________( 4.75 x / (20*20) + (1)*(1)) This is a slope of about 1:20. ( More likethe current recommended slope.)Therefore if you are depending on the glue coverage to be the saviour, ofcourse the splice with the largest glue area is the one you want to use.But, the clincher here is the placement of the two bolts in the methodproposed in the plans. So all this slope angle stuff is now chunked out theproverbial window - we arent comparing the same construction techniques arewe. So a person could do some serious calcs to determine the compression andtension loading, shear capacities of bolts, likelihood of bolt holeelongation, probability of splitting , compression failures or otherfailures. But not me.... I agree withmost everybody on this group thatPietenpol's method is just fine - it just doesn't comply with currentstandards - Is that a problem??? I don't know. Doesn't bother me too much.Each builder should decide on his own.I agree that the "new standards" of construction should probably be followedWHEN POSSIBLE OR PRACTICAL. Many times a change was developed over the lasttwo or three decades as a result of improved engineering analysis methods,access to computer modelling, improved materials, or empirical forensic(sp?) data. People a lot smarter than me have determined that some thingwill offer a higher level of probability of safety.I dont doubt one bit that Pietenpol's spar splice will work. I've flown aPiet with that type spar splice. It flew great - didn't break off. But wecould also surmise that a spar with 4 - 5/8 inch carriage bolts and no glueat all "would fly". Probably not very long. (Actually, it probably would).Lots of other things were built into WWI and WWII era planes that by todaysstandards aren't acceptable not only to amateurs but professional builders.Not much casein glue around these days. Nor stitched linen. Nor big radialsor bailing wire.I also agree that we have to be careful not to put too much trust in the"experts" as JimV seems hesitant to do in his response to my e-mail to thegroup last night. My main concern is that we have so many NEW andINEXPERIENCED builders (Like Me - I ARE ONE.!) building planes. A highlevel of attention to detail and playing the safe bets statistically maykeep more people safe. We have a wide range of abilities in our hobby thesedays - and we have thousands of planes under construction.Some of our builders have multiple planes under their belts and are lightyears ahead of me as a builder. I would NEVER tell you guys not to dosomething. I would never "diss" Pietenpol. I would only offer a suggestionto those building to DO RESEARCH if in doubt - there are "experts" out there(Look at your own EAA resources). Some change is good - some may not benecessary. Seat belts for instance werent put into cars until some bodyhad a brainstorm to hold people in place and not let them be ejected from avehicle. That was innovative - different. But has proven statistically tosave peoples' lives. I think the aircraft industry most likely has improvedsome ways of doing things that also may be worthy of research by usbuilders.Just my two cents.Not meant in any other way than to stimulate ideas amongst us.Bert (who hopes to get back on the Air Anvil project this weekend)Original Message -----
Good point Mike!That's the point (or similar to it) that I was making regarding therecommended 1:15 (or preferred 1:20) splice (scarf) angle foud in some ofthe more recent literature. You are right- the scarf should be along thelong axis of the rectangular spar. Also a 1:15 or 20 may be impractical ifdone in the wrong axis because when you multiply 15 (or 20)times a depth of4 or 5 inches, the length (15 x this dimension) is LONG. depending on wherethe splice is, it may not even be possible.On my plans, it looks like the useable distance is about 20 inches betweenthe cabane strut mounting brackets. So if you take that as the controllingparameter and calculate the glue area,for the splice as shown in the plans,you have a glue area of about 20.55 square inches _________________( 1 x / (20*20) + (4.75)*(4.75)) This is a slope of about 1:4.2.! If you put a splice in the long axis , you have a glue area of about 95.1square inches ______________( 4.75 x / (20*20) + (1)*(1)) This is a slope of about 1:20. ( More likethe current recommended slope.)Therefore if you are depending on the glue coverage to be the saviour, ofcourse the splice with the largest glue area is the one you want to use.But, the clincher here is the placement of the two bolts in the methodproposed in the plans. So all this slope angle stuff is now chunked out theproverbial window - we arent comparing the same construction techniques arewe. So a person could do some serious calcs to determine the compression andtension loading, shear capacities of bolts, likelihood of bolt holeelongation, probability of splitting , compression failures or otherfailures. But not me.... I agree withmost everybody on this group thatPietenpol's method is just fine - it just doesn't comply with currentstandards - Is that a problem??? I don't know. Doesn't bother me too much.Each builder should decide on his own.I agree that the "new standards" of construction should probably be followedWHEN POSSIBLE OR PRACTICAL. Many times a change was developed over the lasttwo or three decades as a result of improved engineering analysis methods,access to computer modelling, improved materials, or empirical forensic(sp?) data. People a lot smarter than me have determined that some thingwill offer a higher level of probability of safety.I dont doubt one bit that Pietenpol's spar splice will work. I've flown aPiet with that type spar splice. It flew great - didn't break off. But wecould also surmise that a spar with 4 - 5/8 inch carriage bolts and no glueat all "would fly". Probably not very long. (Actually, it probably would).Lots of other things were built into WWI and WWII era planes that by todaysstandards aren't acceptable not only to amateurs but professional builders.Not much casein glue around these days. Nor stitched linen. Nor big radialsor bailing wire.I also agree that we have to be careful not to put too much trust in the"experts" as JimV seems hesitant to do in his response to my e-mail to thegroup last night. My main concern is that we have so many NEW andINEXPERIENCED builders (Like Me - I ARE ONE.!) building planes. A highlevel of attention to detail and playing the safe bets statistically maykeep more people safe. We have a wide range of abilities in our hobby thesedays - and we have thousands of planes under construction.Some of our builders have multiple planes under their belts and are lightyears ahead of me as a builder. I would NEVER tell you guys not to dosomething. I would never "diss" Pietenpol. I would only offer a suggestionto those building to DO RESEARCH if in doubt - there are "experts" out there(Look at your own EAA resources). Some change is good - some may not benecessary. Seat belts for instance werent put into cars until some bodyhad a brainstorm to hold people in place and not let them be ejected from avehicle. That was innovative - different. But has proven statistically tosave peoples' lives. I think the aircraft industry most likely has improvedsome ways of doing things that also may be worthy of research by usbuilders.Just my two cents.Not meant in any other way than to stimulate ideas amongst us.Bert (who hopes to get back on the Air Anvil project this weekend)Original Message -----
Re: Pietenpol-List: Spar Splices
Original Posted By: dpilot