Author Topic: Construction of the Pathfinder LE kit by RSM (Read 25556 times)

Peter Nevai · « **on:** July 07, 2011, 11:38:20 AM »

Hi every one I will be placing the step by step construction process of the Pathfinder LE kit by RSA (Gordon Delany Design) in this tread. The process shall be a long one due to business travel and my limited shop tools and building space.

I like to start of with the small stuff that I can knock out fairly quickly by hand. I had the wife mail me the hardware pack from the kit via APO so I could get my hands on something. So I'll start off with the bellcrank. The kit comes with a nice 4 inch carbon fiber bellcrank as shown in the pictures below. But being one for not leaving well enough alone, I modified it. Using some stuff laying around I fabricated the mod to the bellcrank as shown. I used a piece of powder coated aluminum electronics chassis hole cover left over from some equipment we were installing it was roughly 1.25 X 5 inches by roughly 1/16 th inch thick and using a hacksaw blade wrapped with a rag I cut it to the approximate shape shown, using a file I then got it to the final shape. Next I bent in the Z bends and drilled two holes in the aluminum using pin vice and a drill bit large enough to fit the pin vice and to accept the two phillips head screws that came on the plate, and the proper width to fit into the two eyelets in the bellcrank.

I did not want the Leadout grommets to ride on the bare screw threads so I scavenged two electronic D connector nuts (The ones that secure VGA / DB-9 etc cables on to the PC ports) Threading the nuts onto the two phillips screws I used a file to file down the nut corners and reduce the diameter enough so they fit into the leadout grommets freely. You can see these hand made bushing in the photo they are the two round threaded brass pieces.

I did not like the bellcrank bushing that came with the Carbon crank. It is a soft plastic that seemed to me would get heavy wear from the raw surface of the hole in the carbon crank. Besides I never much cared for plastic bellcrank bushings. So I figured if I was going to replace it I might as well replace it with something worth while. Long ago I discovered the tons of neat miniature parts you can scavenge from old obsolete computer hard drives. So I pulled a discarded one from a refuse pile. This was an old 60 gigabyte 5.25 Maxtor Hard drive. I opened it up and found what I was after. The heads on most of these drives ride on a sealed shoulder mount ball bearing assembly. I popped of the heads and salvaged the bearing along with the sealed motor bearings. With the nice stainless shoulder bearing assembly in hand I enlarged the hole in the bellcrank and fitted the Bearing, It is secured with a Snap ring explicitly for this purpose as it is used to hold the bearing in place in the Hard Drive.

You can see the bearing in the photos as the round stainless item with the circlip below it. Final assembly is inserting the phillips screws into the aluminum plate, Threading and tightening the two brass ferrules on the screws then inserting the aluminum plate assembly into the holes in the bellcrank arms. Secure the screws to the bellcrank with nuts as shown, insert the bearing and secure that with the circlip.

There you have it a customized Ball bearing precision Composite bellcrank assembly. A bonus is that the hole in the bearing is a perfect fit for the metal bellcrank post supplied in the kit. The bearing make the bellcrank rotation smooth as silk, the bushed leadout scheme does helps with this also. It places no angular or twisting forces on the leadouts without any binding.

While there is no absolute need to modify the kit bellcrank in this way, It is a part of my process so I include it. The biggest drawback to this part is my finger tips are raw and sore as hell. But if you have more than a 6 inch ruler, a pair of pliers, a set of jewlers files and access to some power tools (dremel) etc then so long as you have all the raw materials you can knock this out in 2 hours. It took me almost 8.

Wynn Robins · « **Reply #1 on:** July 07, 2011, 02:23:59 PM »

whilst I like the concept you are adding complexity and additional weight for no real gain......

Peter Nevai · « **Reply #2 on:** July 07, 2011, 02:50:52 PM »

Quote from: Wynn Robins on July 07, 2011, 02:23:59 PM

whilst I like the concept you are adding complexity and additional weight for no real gain......

It is no more complex than other split arm bellcranks out there (The tom morris Brett Buck Bellcrank or some of Windy's units) I like using that type of leadout attachment, it binds less, wears less and the leadouts always have a straight pull no matter the orientation of the bellcrank. The motion of the bellcrank is silky smooth low friction, no matter what amount of tension is placed upon the leadouts. ( comes in real handy when you have minimal line tension, it can make the difference between loosing the model or not) Which is the result of the ball bearing pivot. The added weight is located in the best place possible (very close to the CG) and can be more than than compensted for by selecting lighter weight components in other (Asthetic) places like wheel selection, spinner selection, etc. Of all the elements in a CLPA model, The control system, next to the engine the control system is the most critical. The last model I gave this treatment to (A Vector 40 kit) had control surfaces that were so free and smooth that they would flutter in the mildest breeze.

Note: The bellcrank as is in the kit is more than adaquate and is of better quality than most, but if you are going to the trouble and expense of retrofitting the kit with CF pushrods, Titainium ball links and adjustability up the wahzoo, this happens to be one spot that could stand some improvement. Until you try a control system using a ball bearing bellcrank pivot, you can't make a comparison. Also with this system there is no noticable chnage in control geometry as there is no wear on the bellcrank bushing or bellcrank pivot hole. There is no play either vertical, horizontal, or lateral in the bellcrank. While I did not measure it play in any direction of the bellcrank at the bellcrank pivot is undetectible without a dial gauge.

Besides, I had the time, I was bored as hell (You think Muncie has nothing to do? Try Kabul... Well avoiding potential terrorist, insurgents, road side and suicide bombs can lend a bit of excitement to life).

John Miller · « **Reply #3 on:** July 07, 2011, 04:18:34 PM »

Peter, did your wife also send you any other parts or sub assemblies from the kit?

I like your approach to building so far. Personally, I like to construct all the smaller sub-assemblies before the wing and fuselage. I don't know about others, but for me, I get slowed down building the small stuff if I've got the wing and fuse built. It seems to take forever for me to get them done at that time, whilst, if I build them right up front, they're waiting for me to install when I've finished the bigger stuff.

Whatever way you decide to go, keep us informed, and watch your backside.

Wynn Robins · « **Reply #4 on:** July 07, 2011, 07:07:03 PM »

what do you intend securing the nuts with? Loctite? mechanincal means? I would like to see you have those fixed for good on there - pretty easy otehrwise for one to come loose.....even nylocks may do the trick.

Peter Nevai · « **Reply #5 on:** July 08, 2011, 10:26:10 AM »

Quote from: Wynn Robins on July 07, 2011, 07:07:03 PM

what do you intend securing the nuts with? Loctite? mechanincal means? I would like to see you have those fixed for good on there - pretty easy otehrwise for one to come loose.....even nylocks may do the trick.

I am of two minds on this, I can either loctite or epoxy the nuts or mushroom the screw ends so they can not spin off. Mushrooming the ends is the most secure method but makes it really difficult to take apart should a leadout need changing. Loctite or epoxy is easier to get apart but is not as secure.

Note, the brass bushings are threaded, they thread up on the screws and are tightened against the aluminum plate. Even if the nuts come off the screws will not fall out because they are still attached to the aluminum plate (held in place by the threaded bushings). Remember the brass bushings started out life as brass nuts that fit the screws. The aluminum plate is also secured to the bellcrank by the C clip that holds the bearing in place, there is zero chance that the clip will come off accidentally. (It is a real bear to get off with tools). So even if the nuts should fall off the screws attached to the aluminum plate still act as pins to retain the leadouts and the C clip now keeps the plate securely attached to the bellcrank proper and the screws still seated within the holes in the arms.

Because of this redundancy I think I will use loctite to afix the nuts to the screw threads, perhaps with a drop of epoxy to be safe.

john e. holliday · « **Reply #6 on:** July 08, 2011, 11:18:57 AM »

Everybody has their way of doing things. I like your bellcrank set up.

Randy Powell · « **Reply #7 on:** July 08, 2011, 04:44:38 PM »

Yep, whatever works for you. I do it completely differently and it works for me. This seems like a good method.

Peter Nevai · « **Reply #8 on:** July 19, 2011, 12:41:02 PM »

The box it comes in. Much smaller than expected

Peter Nevai · « **Reply #9 on:** July 19, 2011, 12:58:01 PM »

The Stab and elevators.

This is where I ran into the first problem with the contents of the kit. The stab requires over 90 inches of 3/8th X 1/2 inch balsa stick to complete. The Kit is packaged with 2 36 inch pieces for a total of 72 inches. This is only enough material to complete the stab and one elevator half. Also the balsa strips that make up the ribs should be 3/32 X 3/8 inch strips. Mine was packed with 3/32 X 1/2. I contacted Eric and he promptly sent replacement pieces. He is going to make a change in the kit contents to include a third piece of 3/8th X 1/2 for the stab and elevator construction. But if you already have one of these kits Please note that you may also be a little short on the material.

Otherwise the Stab and elevators build up exactly like on the plans. When cutting the pieces try to use the top view of it that is on the Fuselage sheet. This one has the horn clips shown and you get a more accurate measurement. The view on the Wing sheet of the plans does not show the Horn clips and using that one your elevators will come out a tad on the long side. At least mine did. No matter as it is negligible and can easily be sanded to size.

The laser cutting on mine was OK, which means not great but not bad either. Many parts had to be cut free with the aid of a xacto knife while some of the thicker parts has significant burns. Nothing that made the parts unusable though.

The snapple bottles filled with water are used to weigh stuff down, like when laminating the ply parts to the ribs etc, and to hold stuff flat.

Randy Powell · « **Reply #10 on:** July 19, 2011, 02:12:31 PM »

I just figured you liked Snapple. The box looks fine except that it does have Gordy's picture on it.

Have fun.

Peter Nevai · « **Reply #11 on:** July 19, 2011, 07:15:34 PM »

Quote from: Randy Powell on July 19, 2011, 02:12:31 PM

I just figured you liked Snapple. The box looks fine except that it does have Gordy's picture on it.

Have fun.

I do like snapple it's the best stuff on earth. But as for a cheap way to weigh stuff down, you can't beat water. And as the building surface is a mirror on a 3/4 mdf back board (Old head board) I can't pin things down. So bottles of various sizes. Wait till I start jigging the fuse with the gallon containers.

Allan Perret · « **Reply #12 on:** July 19, 2011, 07:48:19 PM »

I am glad you mentioned the mirror. I was going crazy trying to figure out the gap down the middle of the 2 piece ribs. Whats the mojo you installing?

Peter Nevai · « **Reply #13 on:** July 20, 2011, 10:31:41 AM »

This is the Motor Mount crutch assembly. This is where I think I made a big mistake. The Plans and the FM construction article are very vague. I could not discern how far the engine bearers extended forward. It is not clearly shown on the plans and not discussed in the article. I made a guess that the maple mounts ended at the very front end of the plywood doublers. But now I think I was wrong. The supplied mounts are 10 inches long and if the mounts end at the front of the doublers they do not extend as far back as shown on the plans. They fall about 3/4 of a inch short. As you can see mine only extend past the rear bulkhead by about a half inch. They should extend about 1 inch further. I will fix this by cutting about 3/4 inch off the front of the mounts and splicing some back at the rear, to strengthen the fuse at this critical spot right over the wing.

When assembling your version use the Maple mount location on the plan starting from the rear end of the maple mounts lined up with the rear of the maple mount shown on the plans. Measure forward from that point. Do not try to estimate the locations of the parts from the front backward. This makes positioning the engine a bit more troublesome (As engine dimensions vary) but you will avoid the mistake I made. Also the balsa blocks provided with the kit are not referenced to the plan or called out on the plans or the construction article. Right now I have no Idea which balsa block is to be used where. The dimensions of the block do not seem to match with any of the outlines on the plans and the FM article is mute on this aspect of construction.

We will get to that problem later in this thread, and I hope one of the designers can shed some light on this subject. Otherwise the crutch squares up nicely and is straight forward in construction. It goes faster if you do all the plywood balsa laminating before hand and have the pieces all laminated and ready to go. The bulkheads are 1/8th ply with thin ply lamination's front and back. The nose ring gets the same treatment. At first these items feel too light and soft for this use, but I'll defer to the designers that this method is as strong as traditional engine mounting using solid PLY bulkheads and nose ring.

John Miller · « **Reply #14 on:** July 20, 2011, 11:56:22 AM »

Hi Peter, I'm not one of the designers, just the draftsman who worked closely with Gordan on the design. I took a look at the plan for the fuselage, and the top view shows the motor mount ending at the doubler. The Motor mount shows being slightly longer than 11 inches to conform to the shape shown on the side view.

Did you notice that the down thrust is built into the motor mount crutch?

I'm not in possesion of one of the kits, so I don't know about the balsa blocks supplied in the kit.

It's been our experience that the laminated nose ring, and forward bulkheads are as strong , or stronger than lite ply, and weigh less. Never seemed to have a problem with the laminations except in the case of my Bipe, where due to space considerations, i felt I neede a more solid nose ring, and went with birch ply for the part.

I'm sure Gordy will have a few comments to add, and correct me if I'm in error on any of this information.

Peter Nevai · « **Reply #15 on:** July 20, 2011, 01:36:44 PM »

Quote from: John Miller on July 20, 2011, 11:56:22 AM

Hi Peter, I'm not one of the designers, just the draftsman who worked closely with Gordan on the design. I took a look at the plan for the fuselage, and the top view shows the motor mount ending at the doubler. The Motor mount shows being slightly longer than 11 inches to conform to the shape shown on the side view.

Did you notice that the down thrust is built into the motor mount crutch?

I'm not in possesion of one of the kits, so I don't know about the balsa blocks supplied in the kit.

It's been our experience that the laminated nose ring, and forward bulkheads are as strong , or stronger than lite ply, and weigh less. Never seemed to have a problem with the laminations except in the case of my Bipe, where due to space considerations, i felt I neede a more solid nose ring, and went with birch ply for the part.

I'm sure Gordy will have a few comments to add, and correct me if I'm in error on any of this information.

Hee Hee, Don't want to take any of the heat?

Yes, I did notice the down thrust built in to the crutch design. It is slight but evident when the crutch is upside down as shown in the photo. When the tops of the bulheads are lined up with the tops of the fuse sides, It will have a degree or so of down angle relative to the centerline. I was unsure if the aluminum pads were to be inset into the maple mounts or laid on top. I opted to use some thinner material and epoxy them to the tops of the bearers. They are 1/6th aluminum pads and sufficent to prevent crushing the wood underneath.

You don't know what joy is until you have to use a loose hacksaw blade to rip saw maple motor mounts 8 or so inches, and keep the cut straight.

Thanks for taking the time to look the problem over. My Motor crutch mistake is not a serious issue, just an inconvenience. And was one of the reasons I started this thread so future builders of the Model will have a good reference to work from, one that may fill in the blanks in the FM article and potential discrepancies in the kit. The readers will note that I am assembling this model in sub assemblies. The Stab and elevators are one. The engine crutch is another. The vertical stab and rudder assembly is also sub assembled. This is how I am staging this build. You will notice that finishing touches such as sanding final shapes and small detail work has not been attempted yet. I like to group those tasks together so when that stage is reached it can be all done in one sequence. Also this way components can gather some hangar rash that won't impact the final stages while the sub components are awaiting assembly. For example If I ding the edges of the rudder before it is ready for assembly, no big deal, it remains in its rough form until right before it gets installed on the Fuse.

The next sub assembly will be the fuselage sides, they will be assembled and laminated then set aside until they are needed. Each fuse side is comprised of 5 pieces that have to be joined or laminated together in the kit. The plan shows the fuse sides being a single length.

Peter Nevai · « **Reply #16 on:** July 20, 2011, 02:03:49 PM »

The Vertical Stab and Rudder Subassembly. This went together without a hitch. Everything is at Zero (No offset in the rudder part). Historically when I ever put any offset it would be either sanding in a asymmetrical airfoil shape into the subassembly or installing the whole thing with a minute offset. Like my last model the Vector 40 there is no offset shown on the plans so this will be installed on the fuse also with Zero offset. One note however. This is a 6 piece unit. There is a little triangular piece that fits at the base of the vertical stab back where the rudder section joins it. I could not find this little piece anywhere, I fear it may have ended up in the pile of the scrap pieces. No worry though as there is enough scrap balsa left in the kit to build a entire 1/2A airplane. I just found a scrap piece with a right angle and trimmed it to fit the space.

I ended up gluing this sub assembly to the mirror work surface with CA and had to pry it up using a spatula.

Mark Scarborough · « **Reply #17 on:** July 20, 2011, 03:11:02 PM »

Peter,
I tape saran wrap to the glass to prevent parts from sticking to the surface when gluing them up. NOT the peal and stick kind, it seems a bit porous.

John Miller · « **Reply #18 on:** July 20, 2011, 05:21:21 PM »

The vertical stab and rudder are laidout this way to wind up with a stiff, warp resistant, structure.

john e. holliday · « **Reply #19 on:** July 21, 2011, 10:02:25 AM »

I guess that Eric of RSM Dist needs to put a disclaimer in his site about his kits being builders kits. I wonder at times how he keeps track of all this stuff. Have built several of his kits and am glad I had some experience behing me. Have the parts to build another HumBug and it will be powered right this time. Looking good on your build so far.

Peter Nevai · « **Reply #20 on:** July 21, 2011, 03:00:17 PM »

Quote from: john e. holliday on July 21, 2011, 10:02:25 AM

I guess that Eric of RSM Dist needs to put a disclaimer in his site about his kits being builders kits. I wonder at times how he keeps track of all this stuff. Have built several of his kits and am glad I had some experience behind me. Have the parts to build another HumBug and it will be powered right this time. Looking good on your build so far.

I knew from the beginning that this was not going to be a traditional kit (Like Brodak or Sig Kits) Brodak kits which are excellent by the way. I was told that the FM article would be absolutely necessary and it really is. But that is the purpose of this thread. To bridge the gap between a builders kit and one like Brodak puts together. Hopefully between the FM article and the Info contained within this thread a future builder will have a clearer path to successfully build this kit. It even supplements any info for people scratch building just from laser cut short kits. While it's not a step by step Glue this piece to that piece instruction it will fill in the gaps between the FM article and the Plans that are available from FM or supplied in the kit.

So far the construction process did not require much in the way of detailed explanation. But that will change when it comes to the adjustable leadout installation and construction. The adjustable leadouts supplied in the kit differ a good deal from the way Gordon installed and designed his on the plans. The Cowl construction is another area. I will note now, and again later.

The control system shown on the plans are Tom Morris components. They are not what is packaged in the kit. If you want to have the same setup as shown on the plans then you need to contact Tom Morris and order a set of controls for the Pathfinder LE. This is what I will be doing. The hardware supplied in the kit is good stuff, just it is not the same stuff as shown on the plans. I have verified this info from Tom Him self.

Peter Nevai · « **Reply #21 on:** July 26, 2011, 12:09:22 PM »

Here is the latest installment of photos. We have the Ribs that support the landing gear laminated with 1/32 ply ready to go. And you can see also the fuselage as it comes out of the kit. There are 5 pieces to each fuse side. The side doubler for the engine crutch, the side doubler for the stab mount area, the rear half 1/8th inch fuse side, the front half fuse half and a long thin triangular strip at the bottom (hidden by the tape)

Note: This is the method most use to but join sheet balsa. You true up the edges and then but them up against each other. Take tape and run it down the entire edge, taping the two pieces together. Flip over and run a bead of glue down the seam. Scrape off any excess then weigh down flat till it dries. Works like a charm every time. The tape keeps glue seapage to the un-taped side which you can face to the inside of the airframe. The little seepage on the taped side can be readily sanded out.

Here you can see first hand the SNIT Jig. (SN.apple I.ce T.ea) Hey you use what you have on hand! I put a small patch of Saran wrap on the underside of the bottles to give them good sticktion on the mirror surface. As long as the glass is clean the plastic wrap really clings to the smooth glass. While not as rigid as professional or task specific jigs, it works very well is infinitely adjustable and refreshing to boot.

I still have not figured out the balsa block configuration for the nose and cowl. I wish Gordy would comment on this thread and clear it up. It is completely neglected on the plans and has me scratching my head on how the top of the fuse under the canopy is supposed to go together. The plans only show the outline but no supporting description or detail.

NOTE: There are cutouts in the bulkheads for two balsa extension strips along the sides of the fuse. These are there to support the upper fuse sheeting and upper fuse bulkheads. The plans call out for two strips of 1/8th X 1/4 balsa stick to use as the extension strips. The cutouts in the bulkheads are too narrow for this. You can squeeze in a 3/32 balsa strip but I had to enlarge the notches to accept the 1/8th X 1/4 inch strips. I do not know if this is an error in the laser cutting, a miscommunication or some mod that was implemented later but never made it to the plans. At any rate it is a trivial modification that has to be made so prepare for it.

In addition the fuse bulkheads seem really fragile. Some being a mere skeleton's worth of balsa to form the fuselage shape. By that I mean rather wide and quite narrow with the grain not runnig in the optimum direction. I will highlight this in later photographs. I am seriously considering beefing up some of these bulkheads but of course that will mean additional weight.

John Miller · « **Reply #22 on:** July 26, 2011, 02:17:58 PM »

Greetings Peter. I took a look at the plans to try and figure out what was giving you questions in the nose,cowl area.

The cowl is pretty straight forward, with 4 pieces of 1/4" balsa that are identical, except for a relief for the nose wheel mount plywood. The idea was to capture the plywood by having the cowl parts laminated so that the relief makes a pocket that the edges of the nose gear plywood fits into.

As for the area on top of the fuselage, under the canopy, I formed mine so that the top of the balsa crutch, between the motor mounts, became the bottom of the cockpit, and where I mounted the pilot figure on mine.

Does this help?

Peter Nevai · « **Reply #23 on:** July 26, 2011, 02:36:29 PM »

Quote from: John Miller on July 26, 2011, 02:17:58 PM

Greetings Peter. I took a look at the plans to try and figure out what was giving you questions in the nose,cowl area.

The cowl is pretty straight forward, with 4 pieces of 1/4" balsa that are identical, except for a relief for the nose wheel mount plywood. The idea was to capture the plywood by having the cowl parts laminated so that the relief makes a pocket that the edges of the nose gear plywood fits into.

As for the area on top of the fuselage, under the canopy, I formed mine so that the top of the balsa crutch, between the motor mounts, became the bottom of the cockpit, and where I mounted the pilot figure on mine.

Does this help?

I'll have to post a close up photo of this part of the plans. Hi John!

I understand the area you speak of. I am confused about the area just above that and the section extending to the nose ring. This area is comprised I think by the nose block at the front shaped into what appears to be the instrument panel under the canopy. But then extends just above the fuse sides all the way back to Bulkhead 3. This piece is not part of the fuse side but some structure that sits right atop the fuse sides adjacent to the engine bearers. As the photo of the fuse shows the engine bearers and the balsa stiffener between them. I am confused as to what is used to fill the space between the engine bearers and the bottom of the canopy, from BH3 all the way forward to the nose ring. This mystery is complicated by the fact that there is no balsa block in the kit long enough to fulfill this area.

I understand the double 1/4 inch cowl sides, it is the front of the cowl (air inlet and venturi area) that concerns me, again complicated by the fact that there is no balsa block supplied that seems to fit the space up front between the cowl sides.

The plans show the cowl extending right up against the nose ring. The nose ring is not thick enough to support the dowels recommended in the article to secure the front of the cowl.

Note: The cowl width when assembled is a really tight fit over the OS 46 VF cylinder head. Much inside carving will have to be done so there is enough clearance around the cylinder head.

Peter Nevai · « **Reply #24 on:** July 26, 2011, 03:00:39 PM »

Here is the close up photo of the plans and the areas under question. Sorry about the quality. But it gets the point across.

The trouble with allocating kit materials to these areas is that I do not want to use up a piece of balsa block to this area only to find out later that, that particular piece was meant to be used elsewhere.

John Miller · « **Reply #25 on:** July 26, 2011, 03:44:59 PM »

OK, I better understand your questions.

In the area under the canopy, the block actually ends where the angle would make the base for the instrument panel. The small amounts of material going back to the back of the canopy are made fro scrap, and I should have marked it soo. I believe Gordy had a soft balsa block that went from the nose to the back of the canopy. He painted his canopy so it's all under wraps.

There should be a small block to fit between the cowl sides , behind the spinner ring. If it's not in the kit, be sure and make one out of scrap. You are correct, without it, the front of the cowl cannot be mounted as shown.

Peter Nevai · « **Reply #26 on:** August 01, 2011, 01:44:13 PM »

Starting on the wing. The great thing is are the guides and the built in tabs that allow the wing to be built without a jig. I followed the instructions in the FM article on how to set this up. The really really bad thing is that the bellcrank mounts are not cut properly in the kit. They are too narrow! I discovered this only after gluing the lower bellcrank mount on to the center ribs with epoxy. Because the mounts are cut improperly there will be insufficient contact area between the mounts and the upper and lower spar that caps the mounts!

I am upset that this error was make in the kit fabrication at such a critical part of the model. I am uncertain how I can now fix this deficiency, I can not afford for the bellcrank mounts nor the center section of the wing to structurally fail. As the parts have already been glued to the rear shear web spar and then glued to the 4 ribs, I would have to trash the entire assembly and cut new bellcrank supports as shown on the plan in the photo below. The supplied plywood supports are no where close to the parts shown on the plans.

This is a major fault please note this when constructing your kit!

I can probably fill in the space left by the too narrow supports but I fear that it will never have the structural integrity that a proper width pieces would offer. The killer thing is that the way the bellcrank mounting is designed there is not much in the way I can satisfactorily reinforce this area.

NOTE: In the photos you can see just how narrow the supplied laser cut bellcrank supports are compared with the drawing.

Peter Nevai · « **Reply #27 on:** August 01, 2011, 01:46:07 PM »

The plan drawing

John Miller · « **Reply #28 on:** August 02, 2011, 09:04:50 AM »

Darn Peter, that's a headache, but shouldn't be too hard to fix, even in place. Cut as shown on the plan, it's supposed to fit onto the spar, and put the joint in shear, but you know that.

I'm glad you like the self jigging features of the wing. Gordan tells me that goes back to Ed Southwick's Skylark construction.

john e. holliday · « **Reply #29 on:** August 02, 2011, 09:54:20 AM »

Make the bellcrank pivot long enough to extend past the surfaces of the center section. Then make ply pads to go over the pivet and butt up to the fuselage side. 1/8th inch steel wire/shaft should be enough to hold. I have a couple of wings in which there is no ply inside the wing itself. Also if you think that is not enough ply by itself, don't build an I-Beam wing.

Peter Nevai · « **Reply #30 on:** August 02, 2011, 02:24:19 PM »

Quote from: john e. holliday on August 02, 2011, 09:54:20 AM

Make the bellcrank pivot long enough to extend past the surfaces of the center section. Then make ply pads to go over the pivot and butt up to the fuselage side. 1/8th inch steel wire/shaft should be enough to hold. I have a couple of wings in which there is no ply inside the wing itself. Also if you think that is not enough ply by itself, don't build an I-Beam wing.

Read my mind John, Since I already epoxied all those parts in place and glued the ribs to the shear web spar at the back, I needed to come up with a alternate plan, else I would have to make new ribs, Spar etc. I took some of the scrap Ply and fashioned a couple of square pieces that filled up the empty places in the rib slot where the ply supports go. That taken care of I will do as you say. I was already planning to make ply pads on top and bottom extending to the fuse sides to help reinforce that area and in light of Matt Colans problems with his TP with the pull test I thought that would be prudent.

As the construction comes along I post photos of the fix.

Builders of this Kit should note this in their build process. The ply bellcrank supports are tapered far too much!!

DO NOT USE THE wing drawing itself to see if it conforms!!!!!

If you check it against the wing plan, then it would look like the part is laser cut correctly,

THIS IS WRONG

.

Use the separate section drawing located above the Wing Plan for the proper shape of this part!!!

I posted a picture of this part of the plan that shows the actual part outline!

Somehow when the parts were laser cut the part outline that is on the wing plan drawing was used for this and it leaves the part tapered much too thin at the ends. The Rib slots are correct however.

Peter Nevai · « **Reply #31 on:** August 02, 2011, 02:38:33 PM »

As a side note. Upon looking through the kit contents I think that the kit is short the necessary blocks to fabricate the wing tip blocks. According to the FM article there should be bocks hollowed at the leating edge of the wing tips. I only have one piece of 4 inch X 1 inch X 8 inch balsa block. And that would be needed to form the upper fuse nose block. (The area highlighted in the plans earlier in this thread) there is no significant left overs from this piece to make the wing tips.

I also have a block that is 2 inches X 1 inch X 6 inch block for the tail between the stab and elevator. I figure I would still need 4 pieces of 3 X 3 X 3/4 or 1 inch balsa block to fabricate the wing tips.

Am I correct in this assumption John? (John Miller) Please Confirm.

If so The kit is short these items and they do not even show up in the kits part list. I hate to hammer Eric on this sort of stuff, I have already found other balsa that was short in this kit and he shipped me those, so this would be another oversight. Perhaps George Delany needs to go over the kit contents and materials with Eric on this kits item by item so others do not have these issues. I find it weird that so far I have been the only one to report these irregularities.

John Miller · « **Reply #32 on:** August 02, 2011, 03:42:08 PM »

Greetings Peter.

I checked the parts you asked about. First, it appears that the plywood BC mounts were cut using the wing view, where the part of the mount is under the spar. The part shown on the smaller detail drawing, above the wing, shows thwe part in it's entirity.

The supplied block used at the tail would be fine, if it were 2 inches longer. The actual size that would work best would be, 1" x 1 1/4" x 8".

The wing tips will require 4 pieces of 1" x 3" x 3" balsa to make the tips.

I don't really know if any of the kits have been built yet, probably why you are finding these little problems.

Dick Pacini · « **Reply #33 on:** August 03, 2011, 06:56:46 AM »

I have one of the Pathfinder LE kits that I bought last year, yet to be built. I also have the magazine article for reference. I am very interested in this thread because I will face the same issues when mine goes from bones to bird.

It is also a bit disappointing to read that an expensive high end kit like this has its flaws. I was under the impression that laser cut kits were preceded by a prototype build to insure that all the parts were included and fit as designed.

Still, I think the Pathfinder is a gorgeous plane and well worth the effort required to overcome any shortcomings.

John Miller · « **Reply #34 on:** August 03, 2011, 09:21:31 AM »

I agree Dick. Peter is providing potential builders of this design with a great service. There were two prototypes built from the original plans, and cutfiles, but, there were some apparent minor changes going into kit production. Peter is also providing a service to Eric at RSM, by reporting these items to him. Eric's a class act, and will bend over backwards to make his products conform to his standards.

Here's some pictures attached of the two prototypes. I own one of them, and they do fly very good.

Peter Nevai · « **Reply #35 on:** August 03, 2011, 09:41:11 AM »

This is the shot of the wing under construction. The Shear web spar and the built in tabs work like a charm. Set it up exactly like the FM article says. The article says that you can install just about everything without removing the wing from the board except for the center sheeting. Although you would have to have the skills of s surgeon to apply the cap stripping and other components to the top side of the wing (REMEMBER THE WING IS BUILT UPSIDE DOWN) On advantage of building on a mirror you can see all stuff on the underside. This will make installing the top spars much easier since you can see reflected where the rib cut outs are and where you are smearing the epoxy on the center section components.

Also easy to spot if there are any gaps between items on the back side. Use a sharpie marker to draw your reference lines on the glass. In the kit the landing gear mounts are 1/8th ply. Study the assembly order subsection on the plans before you start sticking the pieces in. There is a very specific order to how the several pieces fit together. There are a total of 4 ply pieces for each main gear and 1 balsa filler piece. These are installed between ribs 3 and 4 (ply doubled) and then the main spar caps them. There is no detail on the meathod to construct the vertical section of the landing gear mounts. But this should be a simple task using some of the scrap plywood to fabricate it. Did I mention there is enough scrap balsa left over to construct a fleet Of 1/2a planes?

Also in the photo you will see the cowl, I'll get into more detail on that later, however it is best to mention that the nose gear wire is not bent according to plans. I did not sweat this detail but it does take a little tweaking to fit properly within the cowl. It does not conform to the outline etched into the plywood mounting pad. Since the nose gear is not bent according to plan you will need to create a bigger hole to pass the gear through the cowl bottom. This is because the angle at which it exits the cowl will cause the gear to deflect more upon landing. If the hole is too small the gear wire will smack into the hole sides and possibly cause your cowl to crack. I'll cover this more later. But be prepared for this or bend a new nose gear according to the plan.

Dick Pacini · « **Reply #36 on:** August 03, 2011, 10:47:30 AM »

Quote from: John Miller on August 03, 2011, 09:21:31 AM

Here's some pictures attached of the two prototypes. I own one of them, and they do fly very good.

John, I absolutely love the paint job on the original yellow one that was featured in the article. Did Gordan by chance sketch up a layout of the graphics, so a copy could be made?

John Miller · « **Reply #37 on:** August 03, 2011, 11:37:36 AM »

Hi Dick

As far as I know, he did not, but there are enough pictures available to let someone easily duplicate his trim scheme. I'm sure that he'll be pleased by your comments.

Peter Nevai · « **Reply #38 on:** August 03, 2011, 02:33:01 PM »

One of the things that are annoying me is that I have not yet settled on a graphics theme. Usually at this point in the construction process I have some inspiration as to where I want to go with it. Did the transparent thing with the vector and once I've been there I usually don't want to re visit it. The Pathfinder speaks to me of something else, although what that may be I have no idea. One thig is certain, it won't be a racing theme aka Gordon or similar. I have just not settled upon whether it should be a soft theme or a hard one. (Soft being curvy shapes, Gradient colors) Hard being angular and high tech. I was pondering military but that's been soooooo done already. Oh well something will come to me after I stare at the finished airframe for a while.

Peter Nevai · « **Reply #39 on:** August 05, 2011, 10:35:11 AM »

The great Tip debate.

The wing was coming along great. The included Rib spacing templates are a huge help. They get the ribs spaced and aligned properly. As you can see there are a ton of ribs and riblets (Sounds like a Sonny's BBQ menu) When I assembled the wing I got installed all of the ribs to the rear shearweb spar, and using the templates got the correct spacing and glued the rib tabs to the surface.

NOTE*** This wing has unequal wing panels the inboard side of the wing is longer than the outboard half. This is why the shear web and the templates are marked inboard and outboard. Keep this in mind and use the the correct spacing template on the correct side! I do not recall reading this in the FM article.

After getting the ribs fixed into position I attached the bottom spar (Top in this case as the wing is built upside down) I used slow cure epoxy to glue the spar from the center of the wing out to Rib #4 the second ply reinforced rib. I let this cure overnight and then I carefully glued the spar to the rest of the ribs using CA. This makes the whole process easier to manage, as this allows you to lift the spar up and glue each rib separately rather than trying to do them all at the same time before the CA kicks off.

I repeated the process then on the left half the top and bottom. With the spars installed it was time to add the riblets.

Not you will have to shim RBH 3 as the notch is too long. Something different between that half rib and the LG mounting blocks. Did you remember to install the PLY LG mounts to the ribs before installing the spars??? You need to install the block first the spar goes over them.

I had to trim a notch or two here and then on the half ribs but all in all they went in without a hitch. Here the Spacing templates come in really handy. Once the riblets were in I set the oven to 450 degrees and the cooking time........................... Oops wrong topic. With the half ribs installed I added the leading edge reinforcement strips. What seemed to be a spidery fragile wing now became a rigid structure. At first I had my doubts about the strength of this wing but after all the spars were installed it became solid as a rock. Looks like it will be really light weight too. Kudos Gordon.

Everything was going along swimmingly until I got to the tips. To accommodate my building surface I glued the tip plates to R 11 before adding Rib 11 to the ends of the wing. It just made it easier to square up the tip plate to the rib. Once done I popped them on the wing ends. This is where I ran into the problem, I started looking for the material to attach to the wing tip plates. Shown on the plans and in the FM article there were supposed to be some blocks for this purpose. Well no such blocks in the box. I contacted Eric and got a long response which I won't get into here about how Gordon changed the design. so the blocks were not necessary and that no block for this purpose were going to be supplied.

In my opinion this was a song and dance. Clearly all of the wing tip parts that are laser cut match the plans and the FM article exactly. Using the laser cut parts supplied you requires that the Blocks shown in the plans be used! The tip plates alone are not sturdy enough to make up the assembly and leaves you no way to mount the adjustable leadout guide. Not using the blocks requires you to completely redesign the way the tips are constructed.

To make a long story short as of this writting you have to order a piece of 1" X 3" X 12" long minimum balsa block to finish the wing tips as detailed in the FM article and illustrated on the plans. The photos I've attached validate this. You can use thinner balsa sheet and use a laminating technique with the layers pre-cut, simulating the hollowing process as well. This is how the Brodak Vector 40 wing tips are constructed. Up until this point I've been relatively happy with the quality of the kit. But the deficiencies have accumulated to the point where I caution that this kit is ONLY! for experienced builders with balsa stock and ply stock on hand. First it was the shortage of 3/8 X 1/2 stock, then the kit did not have any 3/32 X 3/8th stock, Then the bellcrank supports were cut wrong, the nose gear not bent correctly, 1/8 dia horns when the Flap and elevator ply mounting clips are designed and cut for 3/32" for starters.

Compared to the Brodak Vector 40 kit I last built the Brodak kit was a 10 this kit is down at a 5 at nearly twice the price. The best features of this kit is not really the kit but the design kitted, The consideration and forethought that Gordon put in when making the model easy to construct, strong and light. So far the execution of the kit it's self has been not more than OK.

Anyway, back to the construction, I am rapidly approaching the point where I am will have to form the leading edge sheeting. I dread this, as I still have not found a way to construct the forming buc's with the tools at hand. As I have to wait on the order of the balsa block for the wing tips, I guess I'll have time to figure a way to make those darn BUC's.

BTW. You will find a weird duplication. In the kit you get 4 ply landing gear pieces marked LG-1, a wider ones and a slightly narrower ones. USE the WIDER ones that's supplied. I think the narrower LG-1 piece is a error as I can not seem to figure out how it would be useful

Peter Nevai · « **Reply #40 on:** August 05, 2011, 10:36:13 AM »

More wing

Peter Nevai · « **Reply #41 on:** August 08, 2011, 09:38:29 AM »

All righty then,

Spent most of the weekend trying to figure out the wing tips with the material on hand. I do have a solution that works considering the lack if included blocks for the task. There is enough scrap 3/8th balsa sheet left (from the flap cut out) that can be edge joined and then used to laminate the leading edge blocks. The lamination technique should be familiar to those who have built the Brodak Vector 40. You cut the sheet to simulate the hollowing process while building up the height needed for the block. Then all you have to do is sand the outer contour. No actual hollowing needed as you fro cut the lamination's to mimic this. If you wish to carve and hollow the solution I have found has enough material for this. It is enough for 8 pieces of 3/8 inch wing tip that can be laminated into the four blocks that are required for the tips.

I'll post photos tomorrow. So make sure you save ALL of the scrap 3/8ths stock from the kit you'll need it.

I have yet to figure out how to mount the adjustable leadout guide, it is the one thing on the plan and the FM article that is not covered in any detail and the plan is very vague on this. Also vague is exactly where the leadout exit slot is to be. Is it above the leadout plate? Below? if it is vertically centered as shown on the side view the most of the Wingtip plate has to be cut away, leaving a bare minimum of support of the wing tip. Even as it is (un cut) the inboard wintip is very unstable and flexes a great deal. I can not imagine that cutting half of it away will help any.

Another item is that rib 8 through 11 are not laser cut correctly. The plan shows those ribs slotted almost the span of the rib with a 1/2 inch slot. This slot is for the adjustable leadout clearance. The ribs as supplied are cut the same as all the other ribs which have a central support (between the spars as seen on the pictures) and minimal material at the tops and bottoms. If the central supports are cut away then only a tiny portion of the rib would be left. I will have to reinsert the balsa knock outs back in these ribs and try to slot them while installed in the wing.

The problem with this is the Half ribs, If you examine the plan then it looks as if the leadouts would saw through the half ribs closest to the tip. The leadout spacing shown on the plans allows for only a tiny amount of adjustability if contact with the vertical parts of the half ribs is to be avoided.

In the end I think that the adjustable leadout solution shown on the plan and in the design will turn out unacceptable. Either the line spacing would have to increase or the limits of adjustability is far less than suggested on the plans. I am rather surprised that Gordon has remained so quiet and not made any comments on this thread at all. Makes one wonder.

The rest of you DO NOT remove the knock outs from the inboard ribs 8 through 11 glue them in and slot them as shown on the plans.

Note**** the provided Leadout guide has to be modified to resemble the one on the plans. You may wish to just fabricate a new one, it may be easier.

John Miller · « **Reply #42 on:** August 08, 2011, 12:04:05 PM »

Quote from: Peter Nevai on August 08, 2011, 09:38:29 AM

I have yet to figure out how to mount the adjustable leadout guide, it is the one thing on the plan and the FM article that is not covered in any detail and the plan is very vague on this. Also vague is exactly where the leadout exit slot is to be. Is it above the leadout plate? Below? if it is vertically centered as shown on the side view the most of the Wingtip plate has to be cut away, leaving a bare minimum of support of the wing tip. Even as it is (un cut) the inboard wintip is very unstable and flexes a great deal. I can not imagine that cutting half of it away will help any.

I regret that the plan and artical seem vague on the installation of the adjustable leadout assy. It's one of those things that one does almost by instinct, but that isn't how everyone does the same thing.

The inboard wing tip shows a notation to laminate 1/64" plywood, and shows the hidden dotted lines, where the 1/8" balsa was removed to create a 1/8" wide slot for the leadouts. There's a 1/4" X 3/8" balsa fairing strip attached on the top and bottom of the 1/8" balsa wing tip, between the trailing edge sheeting, and the tip block. In practise, it's easiest to laminate one side, leaving the area to be removed, glue free, and then remove the 1/8" balsa. Then attach the opposite 1/64" lamination. next, attachethe 1/4" tip fairing strips, on top of the 1/64" plywood laminations, so the tip becomes quite rigid once all assembled.

Another item is that rib 8 through 11 are not laser cut correctly. The plan shows those ribs slotted almost the span of the rib with a 1/2 inch slot. This slot is for the adjustable leadout clearance. The ribs as supplied are cut the same as all the other ribs which have a central support (between the spars as seen on the pictures) and minimal material at the tops and bottoms. If the central supports are cut away then only a tiny portion of the rib would be left. I will have to reinsert the balsa knock outs back in these ribs and try to slot them while installed in the wing.

The problem with this is the Half ribs, If you examine the plan then it looks as if the leadouts would saw through the half ribs closest to the tip. The leadout spacing shown on the plans allows for only a tiny amount of adjustability if contact with the vertical parts of the half ribs is to be avoided.

Mea Culpa, This was an oversite on my part. After several changes being asked for, I made the changes on the plans, but overlooked making the changes to the cut files. In my defense, I can only say that few people realize how many changes need to be made for what, on the surface, appears to be a simple minor change.

Before the change was made on the plans, when I built my version of the prototype, the ribs were lazer cut as they are presently supplied in the kit. When it was realized that the center supprt would interfere with the leadouts near the tips, I removed the center support on the interfering ribs, and added a 1/16" X 1/4" support further back where it would not interfere with the leadouts. Due to the fact that the grain runs 90 degrees o the rib, it seemed to make the affected ribs stronger in resisting the crush.

In the end I think that the adjustable leadout solution shown on the plan and in the design will turn out unacceptable. Either the line spacing would have to increase or the limits of adjustability is far less than suggested on the plans. I am rather surprised that Gordon has remained so quiet and not made any comments on this thread at all. Makes one wonder.

Gordan has had a death in his family, and is not paying a lot of attention to the internet at this time.

Actually Peter, the adjustable leadouts, as designed, work very well, and result in a strong and stable tip.

Note**** the provided Leadout guide has to be modified to resemble the one on the plans. You may wish to just fabricate a new one, it may be easier.

John Miller · « **Reply #43 on:** August 08, 2011, 12:53:40 PM »

I took another look at my files, and found that I had indeed made the changes on the cutfiles. What I cannot be sure of is which file was used to make the kit, or even if the changed file was sent to Eric. Because of a lot of changes being asked for, there were a lot of files flying back and forth, and I feared that the wrong ones may be used. I can see how it could easily happen, and I have to admit, that I may not have sent out the file with those changes. It's been a few years. It is what I feared and warned about, asking that older files be removed.

The simplest solution is either to do as you suggest, or use the solution I did.

Peter Nevai · « **Reply #44 on:** August 09, 2011, 11:31:11 AM »

Attached are the Photos of the inboard wing tip. I did the ply lamination's to the tip plate as suggested I applied them to the entire outside edge rather than just the spot shown on the plans. This keeps all of the balsa pieces the glued to them at the same base level. I did surmise that I would have to cut away the tip plate to slot for the leadouts. I'll do that when I flip the wing over. Here you can see the alternate solution to using one piece tip blocks. I edge glued the left over scrap from the Flap sheet to get sufficient width and marked the tip outlines on this piece. You may ask why am I doing this before installing the leading edge sheeting?

Because for me the leading edge sheeting is still a problem, and I want to get as much done before I beat my self silly with that. It is also easier to make the rib clearance modifications for the leadouts before the sheeting is in place. I want to make sure I have as much leadout adjustment possible without sawing ribs in half with the leadout wire.

NOTE:

The trailing edge sheeting supplied with the kit is not wide enough to cover the shear web! it is only wide enough if you but up against it. Wile this is not a issue with the top side of the wing. On the bottom the sear web does not extend past the ribs to but up against it. Either you ignore gluing the trailing edge sheeting to the shear web on the bottom of the wing or position it so it covers the shear web. That is what I did, so you will see in the photo that a portion of the trailing edge is uncovered by the sheeting. The sheeting still overlaps the trailing edge enough to get a good box structure with the sheeting glued to the shear web, ribs and trailing edge. I'll just use some scrap to fill in the 1/8th space where the trailing edge sheeting does not cover the trailing edge completely.

At the top of the wing you should be able to butt up against the shear web and retain the box structure along the trailing edge. We shall see if this is true when I flip the wing over and do the other side.

John Miller · « **Reply #45 on:** August 09, 2011, 01:09:14 PM »

Pretty creative us of scrap balsa to make the tip blocks. I like the idea.

As for the trailing edge sheeting, Gordan prefered having the sheeting cap the shear web, top and bottom. In my case, I butted the sheeting to the shear web on what will become the top of the wing, (bottom when jigged up) and capped the shear web on the other side. I installed both sides of the trailing edge sheeting, while still jigged up. My thinking was that It gave a better chance of keeping the trailing edge straight that way. It also made it easy to glue the sheeting on doing it that way.

I don't know if it really matters, as Gordan's wing came out just as straight as mine.

You did the tip as I did mine. It comes out pretty neat that way.

Allan Perret · « **Reply #46 on:** August 09, 2011, 03:04:19 PM »

Hey Peter:
Been following your build here with interest, because I have the same kit, not yet started it. I dont understand why you have a delima with the LE sheeting. Does the plan / design require a buck to mold the top and bottom sheets into one piece ? If so could you not just wet the bottom sheet, glue it in place from spar to LE using weights, flip wing over and do the same for top sheet ? Maybe I should just get the plan out for review. Not sure what materials and tools you have available where you are, but if I had to make a buck, I would make it from foam glued to base of something rigid, the same shape as the spar web, with root and tip half ribs for a carving / cutting guide.

Peter Nevai · « **Reply #47 on:** August 09, 2011, 03:07:12 PM »

I use a straight edge all the time to make sure things are running straight. I checked the TE on both the horizontal and vertical to make sure they remain straight throughout the building process, before gluing and after. Having done mainly Foam Wings in the past I am especially paranoid about warps. The mindset is that Foam Wings are inherently warp free and builtup's are inherently warp prone. This may not be true of built up wings but it helps to think that way.

Peter Nevai · « **Reply #48 on:** August 09, 2011, 03:13:16 PM »

Quote from: Allan Perret on August 09, 2011, 03:04:19 PM

Hey Peter:
Been following your build here with interest, because I have the same kit, not yet started it. I don't understand why you have a dilema with the LE sheeting. Does the plan / design require a buck to mold the top and bottom sheets into one piece ? If so could you not just wet the bottom sheet, glue it in place from spar to LE using weights, flip wing over and do the same for top sheet ? Maybe I should just get the plan out for review. Not sure what materials and tools you have available where you are, but if I had to make a buck, I would make it from foam glued to base of something rigid, the same shape as the spar web, with root and tip half ribs for a carving / cutting guide.

The dilemma is that, I have no way rough cutting the foam to the shape of the BUC templates. The Leading edge stiffener is only 1/8th wide so there is very little margin for error sheeting it in two half's, and would require attaching wet balsa to the wing skeleton. Now if there is any invitation to warps that is a VIP invitation. Plus as I can not make a mess (I don't own the property) Creating mounds of Styrofoam dust from sanding a BUC to shape is pretty much out of the question.

Mark Scarborough · « **Reply #49 on:** August 09, 2011, 04:33:27 PM »

I would not anticipate needing to soak balsa to form leading edge skins. They are not fully wrap around are they? I dont think I recall that.
I typically just sheet them with dry wood, at the VERY most I will get it in position , and mist lightly with a spray bottle of water, this swells the outside of the sheet and most times allows it to form right around the ribs