New Landing gear brakes.

 Hello to all the readers of Kitplanes magazine!!   I was fortunate to meet Dean Sigler at the 2012 Experimental Soaring Associations  Western Conference in Tehachapi California. It was sure great meeting and seeing everyone over the Labor Day week end. From the emails I have received I see that the January edition has already made it to the subscribers base.

The first thing I realized when we went to the airport for the initial Taxi test, is that  I need brakes!!!! For the initial flight my buddy Ed was going to keep me from rolling into other planes and hangers, but in reality that's not really practical.
 With this new Grove spring gear, it quickly became apparent that I was going to have a axle bending problem. The axle is a 4130 steel tube 3/4" x .125" wall. I do not want to heat treat the axle, so I am using the 4130 in the normalized condition. That limits the stress to about 95 ksi in tension and 74 ksi in compression. The old landing gear design tucked up inside the hub and limited the bending moment because the point of load application was only 1.75" The new spring gear increases the cantilever distance to 3.57", That distance by the way is the point the axle is cantilevered to the point of load application which is the center of the hub. When brakes are added the distance increases by another inch.  The gear will almost bend now just sitting on the ground!!! To solve this problem I decided to make a sleeve collar that is 1.24" in diameter at the point of greatest moment. this will limit the bending in the axle back to the original design stress.  I bought some 3.5" diameter 7075-T6 round stock and proceeded to make a ton of chips.

Sleeve collar being turned

Here is the beginning of the Sleeve hub being turned on my Lathe.
This is my faithful 36" Grizzly Bench lathe. I've had this lathe for 20 years, and believe it or not I have moved this lathe all over the country chasing the latest and greatest aircraft design contract!! I'm getting too old for that stuff these days however!!

 This gear design is not only way too heavy, its also too damn expensive. As you can see in the next picture, 8 hours of my life was spent standing in front of my lathe!!
  

Chips and turnings

I filled that trash can 5 times!!
I have decided that the final design will be offered in two options, thanks in large part to all of the letters I have received.  I will offer the original retractable mono wheel as well as an  option  Taylorcraft style internal bungee landing gear.

sleeve collar and axle

This shows the outside of the sleeve collar, the part not shown is a flange that mates to the gear leg. In this picture its very apparent how far the axle would have had to extend. The inside face of the wheel bearing rides on the outboard face of the sleeve. The flange of the sleeve is bolted to the gear with 4 .25" dia bolts. The brakes that I finally adapted are from Azuza manufacturing. I purchased them online from Go Kart Galaxy
http://www.gokartgalaxy.com/

ask for Clint. These brakes are mechanically actuated so I ordered all of the cable , cable ends and fittings. I have plenty of excess cable that I think I can route the cable  to the actual rudder pedals. That will be the subject of the next blog entry.because I haven't designed them yet!!!

inside view of gear leg

The 3/4"l axle is welded to a 1/8" steel plate that is bolted to the inside face of the gear. I had to grind out a small recess at the very bottom of the gear to clear the actuation lever. I also had to flatten the lever and remove the 1/4" offset. The flange of the sleeve is also shown in this view.






  

Cable anchor bracket.

I added a bracket to attach the adjustable cable anchor. All in all this turned out to be a really clean installation. The cable will route along the trailing edge of the gear and will be attached to it with heavy duty nylon tie wraps

Drilling the axle hole

If you were wondering how I was able to accurately drill the 3/4" axle hole, this is how I did it.

New Landing gear cont.

I have finished the gear fitting installation to the fuselage. The first step was to locate the fittings using the gear as a guide. I loosely bolted the gear to the fittings and then located the fittings to the fuselage. Once located I back drilled the through fitting through the fuselage bearing blocks. I made a makeshift drill jig by drilling a 1/4" hole through a 2.5" thick block of aluminum. It was very critical to drill these holes perpendicular to the outer flange so the holes would line up with the inside flange. Normally the inside flange would be left un drilled or undersize so the final hole would open up both flanges. I was betting that I could drill a hole accurately enough so the drill would align with the inside flange.

homemade drill guide

I used to work in Wichita at Boeing Commercial aircraft, they had the most wonderful surplus yard I have ever seen. I bought a ton of forged aluminum block and plate stock. This is just a small little piece. There are commercial drill jigs, most notably the "Egg Cup " design. all of these will work, but I didnt have a 1/4" drill bushing for my Egg Cup. 


After the 1/4" holes were drilled, I chased then through with a 1/2" twist drill. Opening the holes up to just slightly under 1/4" (-.003) I then fabricated eight 1/2" diameter aluminum bushings. The 1/2" aluminum stock is slightly larger than 1/2" (+.002) this makes for a nice tight transition fit between the wood and the bushings. I sanded the outside of the bushings and then cleaned them with MEK.

cleaned bushing and epoxy adhesive

once cleaned, I coated the bushings with epoxy adhesive and tapped them into place. The bushings were made with the center hole undersize (.223") so that on final assembly they will be opened up again to .250" The adhesive is used to stop the bushing from rotating when it is drilled out.

installed bushings

the bolt loads are such that they needed to bear into the wood with greater area, this is the reason there are 1/2" diameter bushings.




The landing gear fitting is square and parallel to the landing gear. The fuselage has a slight amount of contour . The load path from the gear to the fuselage is through a mechanism called "Heel and Toe" The design condition is a 1G breaking load applied to the tangent edge of the tires. This creates a large moment that needs to be reacted by the two outer bolts on the gear fitting. Since the fitting is wider than the bolt pattern, the reaction will actually  be between the edge of the fitting (heel) and the opposite bolt (Toe) . Therefore the gap between the fitting and the fuselage must be filled with a material capable of withstanding compressive forces. The fitting is "Bedded" with a mixture of epoxy and cotton fiber (Flox) . Flox is mixed to a consistency of dough. I spread it under the footprint of the fitting and then installed the fitting. The inside of the gear fitting was coated with mold release wax so the fitting could eventually be released if needed.

flox bedding

once the fitting is installed, the excess bedding is scraped away.

When I installed the gear for a trial fit I saw that the clamp block was deflecting and bridging over the gear. To fix this I designed 4 more bushing that were exactly .003" taller than the thickness of the gear. They would crush to equal the gear thickness after installation

clamp bushings

after the clamp up bushings were installed, the bridging stopped and a more even clamp pressure was developed.

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New Landing Gear installation

My new gear finally arrived from Grove Aircraft.I have finished all of the fuselage structural modifications. I have built all of the attach fittings and I have prefitted all of them. The gear is designed to clamp up between two radius filler blocks. The purpose of this design detail is to limit induced bending into the fuselage. If the gear were to be clamped with just flat plates, every time the gear deflected, the gear moment would be transmitted into the truss.

new gear

this is one heavy chunk of metal!! Makes me want to think about a mono wheel again.

attach fitting and radius plate

This image clearly shows the radius plate. The gear is clamped with two 3/8" dia bolts. I plan on silver soldering the bolt head to the inside of the steel fitting. This is so the bolts wont rotate when they are torqued. there will be a 3/4" counter bore in the fuselage that the heads will sit in. There is a slight amount of contour mismatch between the fitting and the fuselage truss. I will assemble these fitting with a bedding of Cotton Flox and epoxy. The primary load direction is in compression, with the exception of the fore/aft braking load .

3/4" counter bores

The area under the counter bore has been padded up such that the width of the gear bearing plate is supported.

The attach bolts that pass through these pads are bushed with a 1/2" diameter aluminum bushing.

After the gear is installed, I will need to fabricate a fabric rib that will sit on the front and rear of the gear. An aluminum cover will connect the ribs and fair in the gear

New Landing Gear

I have been patiently waiting for my new Aluminum Landing gear from Grove Aircraft in San Diego. My friends Mike and Neal Lafrance actually own the hanger next to Grove..  Even with that kind of pull, I still have to wait 8 weeks for the gear. As Robbie explained it to me, its out of his hands because the gear has to go to a heat treat shop 3 times during its construction. I have 3 more weeks to wait!!! I decided that the simplest way to add a landing gear to the Prototype was to attach it to the outside of the fuselage in the same location of the old one. I needed to add some additional bearing blocks and increase the area of the two diagonal stiffeners . Truth be told, I should have done that for the original gear.My goal is to have all of the modifications done and the Fuselage recovered by the time I get the gear. I want to be able to just bolt it in and then flip the plane over.

reinforced gear frame

in this picture the extra doubler on the two diagonal members are shown. all of the vertical loading of the gear is reacted by these members. They also need to react the aft braking load by a heel and toe reaction between the gear fitting bolt and the back wall of the fitting. underneath the plywood is 1.5" of birch plywood bearing blocks. .

outer landing gear fitting

This picture shows the outboard fitting for the new landing gear attach fitting. There will be a narrower fitting that is bolted to the inside of the gear frame. Both plates will be welded to a .125 plate that will act as a bearing plate. I will have two 3/8" bolts permanently brazed to the 1/8" plate. I will counter bore into the birch doubler to clear the bolt head. Sitting on top of the plates will be a radius block. The gear will be sandwiched between two of these radius plates. The isead here is to limit the gear bending moment to the gear itsself. The radius blocks will act like two fulcrums.

Unfortunatly this new gear will add 8 lbs to the Robin and may put the prototype out of the part 103 category. I'm sure with the redesigned wing and the single cylinder 2 stroke engine, Part 103 will still be possible. After my talk on Labor Day, the universal opinion of everyone I talked to was to scrap the 2 stroke and Part 103. My Friend Murry Rozansky who is the ESA Treasurer, suggested that I look at the 23hp Briggs and Stratton Vanguard conversions. After some research, I have decided that this is the perfect engine to adopt. The Prototype is actually perfect for it from a weight and balance point of view. My CG will move forward to 22% at full fuel. 26% empty. The static margin increases by 10%. This engine will be far more reliable than the 2 stroke. I will however fly this plane on the MZ 34.

Just a quick update.

I took the Robin to the Airport for first taxi and I discovered a landing gear design error. I built the gear with a horizontal core of Spruce wood. Under the gear clamps, the wood crushed slightly and the gear released or started to slide out of the gear clamp. This is a basic design flaw and because of it, I have fired the designer!!!!

After I hired me back, I went back to the drawing board and started on an all aluminum spring gear. I will either build it myself or Have Robbie Grove fabricate it up for me.


In the mean time, if you are in the Southern California area, specifically Tehachapi on Labor Day Weekend, you are invited to attend the ESA western conference at Tehachapi airport. My original plan was to haul the Robin out for her first Public showing, but the gear problem took care of that plan. I will be speaking on the Robin design @10:30 am on Sunday.

If you can make I would love to meet any of the Blog followers.

Mark Calder

Final Prep

 

I am preparing for the first taxi and flight test. Its incredible how many little "final" jobs are left. I'm really up against a deadline, I am a guest speaker at the SSA western conference on Sunday Sept 2 at 10:30 am. I really would like to have a first flight before that speech!!!  If you are in Southern California on Labor Day weekends, you  are invited to the conference. I'm looking forward to the opportunity.
I started finishing out the design in anticipation of the first flight, I mean I really started getting serious!! The first problem is the canopy, the fwd hing idea is really bad. There were many reasons to scrap the idea, but the biggest was I couldn't run the engine with the instrument panel installed on the canopy. I finally got the engine running reliably. The gasket for the needle seat finally arrived and once installed, the engine rang smooth through the entire RPM range. I was able to put another hour running time on the engine. She should be fully broke in by now.

New Canopy hinge

I decided to hinge the canopy on the R/H side. I installed a 3 foot long piano hinge and a holding lanyard . The immediate result was to greatly simplify the wire routing. I removed all hardware related to the fwd hinge, and I realized the I needed a second latch for the fwd edge of the L/H side.  The existing design has a latch on the aft end of the canopy, but not one farther forward. I have calculated that there is about 100 lbs of lift on the canopy. To be safe and to keep the canopy from racking I decided to add a second fwd latch.

New fwd latch

 I used the existing latches and modified them for the Left side only. I added a compression spring to both latches so they will normally be fully latched. This eliminates the latch plate I had mounted on the inside of the longeron. I was worried that if I added a second latch plate it would make entry and exit into the cock pit difficult.

Rear latch

Another problem also reared its head and that's the need for a small sliding window to access the latches so the canopy can be locked down. I am adding that window as I write this. I should have it done tomorrow. I am adding the window right above the rear latch.

One of the cool things about being in the small world of aviation, is the small circle of friends you realize you actually have. My Friend Ed was in contact with a Pilot of Erickson Helicopter of Medford Oregon through his blog http://nc35447.blogspot.com/

Erickson was in the Midlothian Texas area setting a huge air conditioning unit on a local Walgreen's Warehouse.  Ed is actually from the Medford region and he had a number of mutual friends with Fran, but when the guys showed up here in Midlothian, the circle finally closed. Erickson has an operation in San Diego at Gillespie field. A few months ago I was there visiting my friends Mike and Neal Lafrance. This is where the circle closes, Fran is very good friends with Mike and Neal. Mike gave Fran a ride in his Luscombe a few years ago.

Fran Tebbe

I invited Fran to sit in the Robin.

If you guys are aver privileged to meet the guys from Erickson Helicopter, you are in for a treat. These are some of the nicest guys I have ever met!! I have to apologize because I am bad with names but another Erickson guy took a "ride" in the Robin

Mr Warren

There is Ed in the background















After the Erickson guys left, I decided to convert the Robin to a two place side by side

Gretta and Gracie

Eds girls Gretta and Grace took a quick ride in the Robin. Believe it or not, we were once this small.

Canopy Lanyard

So the final count down continues, I need to add the side window, finish the fuel door and route the Pitot static tube. Once that is finished, I will do one final assembly to catalog all of the assembly hardware and then break her down and take it to the airport

Seat Cushion and Citabria Cowl Repair.

I have been waiting for a copper gasket for the Tillotson HR carb needle seat. I have been waiting a month, and believe it or not, it actually arrived while I was writing this blog. In the mean time while I was waiting, I fabricated a new seat head rest and added a leather covered head rest and seat cushion. It really came out nice! Every one who has sat in this seat said it is extremely comfortable.

head rest and seat cushion

I fabricated a light weight head rest support from .020 aluminum  sheet.














 

Shoulder, lap and crotch harness

 Good view of the seat belts and adjustable rudder pedals. The read "Tee" handle is the Ballistic chute deployment handle.

Another view

Citabria Cowl Repair

This is the plane I have been flying at Big Q Aviation in Midlothian Texas http://www.bigqaviation.com/
The Cowl was getting pretty tired and while the wing was being rebuilt, it was decided to repair all of the elongated cowl fastener holes. Once a fastener gets loose, a "sawing" action occurs on the fiberglass holes and the holes start to elongate. Some of the holes were so badly elongated that there was just a thread left on the original cowl. That was the case for 16 of the fastener holes. The rest were just slightly elongated and could be repaired by filling with chopped cotton fiber and epoxy. The original Cowl was hand laid up out of fiberglass cloth and polyester resin. The basic principle of repair says you need to restore the existing structural capability. In the case of a composite repair, that usually means all of the original fibers plus 1 extra. The strength of the original material is the determining factor on what taper ratio will be used to scarf the ply's . High strength uni fiber repairs like on a wing spar will require a taper ratio of at least 100 to 1. The lower modulus materials used on the this cowl could be repaired with as little as 15 to 1. the minimum however per FAA guidelines is 20 to 1.

repair schematic

The basic idea here is to clear out the elongated hole, in this case a slot is opened up along the cowl edge.The edges of the cowl are then taper sanded at a 20 to 1 ratio.  A sheet of waxed .020 Aluminum is then bonded to the outside of the cowl with 5 minute epoxy. 7 plies of equal size semi circle doublers are then laid up into the tapered space. After they cure , the edges of the splice are taper sanded . The process is really simple, only the edges are sanded until a space in the middle equal to the original slot remains. After the splice is sanded, a final overlay ply is added (original ply plus 1 extra)

corner edge repair

 After the inside is repaired, a very slight taper is sanded into the outside surface, and a single ply of fiberglass is laid up. This way the repair is actually a double lap shear/Tapered scarf. This is a very good structural repair because all tendency for the tapered splice to Peel away is reacted by the over lay ply's.

Double hole repair

This is a good example of what the repair looks like after taper sanding. Its possible to actually count the ply's as they drop off. Notice how the center of the repair laminate has not been sanded.  

single hole repair.

 This picture clearly shows the internal taper sanding. One final overlay ply will be added over this repair.

overlay ply with peel ply

a very good technique is to finish the repair lay up with an overlay of Dacron Peel ply. This adds a professional touch and serves a very good structural purpose, the hard edge of the repair laminate is tapered out with a resin rich edge. This serves to smooth the hard edge and eliminates the tendency for the repair to peel away. After cure, the peel ply is pulled off the laminate. This material is the same Dacron I used to cover the Robin.

Squawk list burn down

I had a week off from work due to the 4th of July holiday, a few vacation days and a summons to appear for a Grand Jury!! I didn't get picked for the Grand Jury, but it sure wasted 1/2 a working day!! All of This means I got to work on my Robin for long uninterrupted periods. My original plan was to assemble the airplane at Midway Airport near Midlothian Texas, but cooling problems, traced to a bad head design, and carburetor leakage side tracked me from all of the small final jobs. The MZ 34 cooling issue was first on my plate, I discovered a few weeks ago that the head was retaining too much heat and when I tried to shut her down, she continued to run in diesel mode. This turned out to be a poorly designed head, why I had to pay for a new head, is beyond me and making me consider my choice of engine, but non the less, I received a new redesigned head from Compact radial engines and when I installed it, It seems to have solved the heating problem.

MZ 34 with new head

The new head has about 40% more cooling fin area, it does however completely screw up my old baffling system. I have not run the new head with a baffling system yet, or the cowl. If I have to, I will do the first flight without a cowl. The engine is cooling very well and it seems I may have to rethink my cowl design. I will however try to run it first with the baffle on to see how it behaves. After I got the engine running with the new head, I discovered that the carb was leaking gas when it was shut down. In addition, the engine was not running very smooth and it was almost impossible to warm start. I started doing some online research and came across a very good web site http://www.aerocorsair.com/index.htm. They also make a good engine!!! Anyway, I determined that the problem was probably an incorrectly set pop off pressure on the main float needle. The web site has a very good step by step troubleshooting guide and for this project I invested in an automotive cooling system tester. The web page shows how to modify this so you can set the pop off pressure. The Tillotson HR carb should have held 8 psi indefinitely. But when I tested it, it started leaking at 3 psi, this obviously was the root of my problem. when I applied the pressure tester to the fuel inlet as I mentioned, it immediately bled down to 3 psi. I then disassembled the pump housing and inspected the gaskets. Nothing seemed amiss. I then applied pressure to an alternate port and I noticed fuel leaking past the needle seat. When I pulled the needle seat out, I noticed a mangled copper gasket. It appeared that the gasket wasn't fully seated before the needle seat was installed. Of course I didn't have a new needle seat copper gasket in the rebuild kit, so I made one by hammering flat and then annealing a section of copper tubing. once I trimmed it and installed it, the carb held 8 psi and "popped off" ay 11 psi just like it should. I then ran the engine for another 45 minutes and almost finished with the ground break in.

Another nagging issue with the design, was the final design of the seat. All along I knew I needed to build a head rest, but I didn't think it would be a big deal. My friend Ed came over and we shot a series of  pictures with mocked up head supports. It became apparent that by just supporting the head, the pilot would be choked, because his upper shoulders were not supported. I decided to modify the seat to add the upper support. This was quite easy because of the way the seat was made.  sanded off a 4 inch wide section of the inner skin and exposed the foam core. I made two patterns out of Styrofoam and then clamped the seat the form blocks. I then lain up another ply of 8 oz fiberglass over the core. 

bonding supports

  The next step was to build a support from the roll over cage to the back of the seat. This part has to be substantial, as it will see heavy compression load in the event of a crash. I made the support and side ribs from .032 aluminum sheet.

upper seat support

I need to rebuild the triangular rib and adjust the flat pattern slightly. But this shows the support clearly. I will build a light weigh aluminum head rest on top of this. That will support the head cushion. The white color by the way, is protective plastic that will come off eventually.









Another project was to do the final rig of the ailerons and cut a cable exit slit in the wing.

Right wing and aileron

This is a picture of the right wing, the left wing was already finished.











Where the wing interfaces with the fuselage, there are slits that needed to be cut in the fuselage skin for the leading edge attach fitting and the aileron cables. I located the areas, added fabric doublers and then added felt seals.

Felt exit seals

I will touch up the paint after I am done adding the seals.

Leading edge felt seal

Before a doubler is added, the old paint is removed with a solvent wipe with MEK. It works quite well!!











I am continuing work on the seat support and head rest. Nest week I should have the final engine run with the cowl and baffle, hopefully this is all I will need to do before the first taxi test.

New head

I have been having overheating problems with my engine. I was completely stumped as to the reasons. I contacted Compact Radial Engines and Leon Massa told me that he had redesigned the head for the MZ 34. Turns out I was not the only one. The difference in the head is huge, there is at least 40% more fin area. One issue I was having was the engine started Dieseling on me, it wouldn't shut off. Initially I thought the reason was the smaller head, but when I started to strip the engine down to replace the head, I discovered the real reason. All of the head bolts were loose and a great deal of exhaust was blowing by the head gasket. This caused the head to fail to transfer any heat, and also heated up the head. Here is a picture comparing the old head (blue) with the new one.



as you can see there is a big difference. it still will fit under the cowl however, but I will need to rebuild the baffling. I am going to install the head and carb without the baffling, cowl and spinner. I may try my first flight in that configuration. I'm spending the next 5 days getting ready for the first taxi tests. I will update again next Sunday














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Fuel Tank Rebuild, new Trailer and Firewall rebuild

During the initial engine run up, a number of problems became apparent. The engine head was cooling properly, but the rest of the engine compartment was overheating. It also became apparent that I had too much pitch in the propeller. I reduced the pitch to the least angle available and I will use this setting for the retest. According to Leon Massa of Compact Radial Engines, the engine will really heat up at 6200 RPM. I have yet to see more than 5400 RPM. The tuned pipe I designed, was sized to start delivering a secondary boost at 6200 RPM. So hopefully the increased prop inflow will deliver more airflow for greater cooling at the higher output. The under cowl temps were getting too high after shut down, I recorded  300 degrees surface temp on the upper surface of the cowl. I have no doubts about the composite being post cured now!! As I outlined in the previous posts, I removed the fiberfrax from the firewall and then re-coated it with Fiber Frax and then a shield of .012 aluminum. I reinstalled the engine and added another heat shield between the exhaust and the fuselage fabric. Another problem with my original design was mounting the instrument panel permanently to the canopy. This turned out to be unsatisfactory because I cannot run the engine without the cowl installed. I am revising the design such that the instrument panel is on a separate hinge and will swing out of the way when the canopy is opened up. I have decided to use an original Fournier RF4D canopy in the future. I found a very good source who can make them for a reasonable price. Even though the canopy is thicker than the Lexan I am using, the elimination of the frame and housing will result in a net weight savings. Speaking of the Canopy Frame. I modified it to remove the solid bulkhead, this will interfere with the seat head rest, so I had to cut the foam core and complete a "corner Closeout"

the exposed pink foam shows the area I cut away.

the pink area was where the bulkhead was. I cut it out and then knife cut the pink foam away. I made a cut parallel to the existing laminate along the surface and then cut in at 45 degrees to remove a foam wedge approx .25" x .25" The exposed inside laminate was sanded with 180 grit paper to roughen it up so it can be secondarily bonded.

cut foam and sanded inside laminate

this shows what the edge looks like before dry Micro was troweled into the cut. Dry Micro was used, but that by itself has very poor adhesion properties. The technique here is to paint the surface first with raw resin and then trowel the Micro in.

Dry Micro

Dry Micro has a consistency similar to cool whip, its about as lite too. The key is that the mixture has a dull, non shiny surface.

laminate added

 
2 plies of 8 oz fiber glass was added over the micro and exposed foam. Its only necessary to wet out only 1/8" beyond the edge. In approx 12 hours the epoxy will be cured to a semi hard state that allows easy knife trim. after trim, the edges can be slightly rounded over because the micro will be exposed.
This is a common technique that is used to finish out a structural edge. Sometimes, the foam us routed out flush down to a 1/4" and unidirectional roving is added in place of Microballoon, this would greatly increase the bending stiffness of the canopy frame. It is not required on an Ultralight however.

The next big job was to redesign the fuel tank, again this is a temporary solution. I am going to adapt an off the shelf polypropolyene tank, this will offer the maximum resistance to Ethanol. Its unreasonable to assume that pure gasoline will only be available in the future. I need to talk to Leon about revising the carb and Engine seals.  I am really amazed what happens to epoxy when exposed to ethanol in gasoline. 20 years ago when I made fuel tanks similar to this for my old Wren, Ethanol was not used in fuel and I never had any issues. Because of this, I would NEVER consider buying a home built composite airplane that uses Mogas. Wet wings especially like the Lancair would be destroyed.

existing fuel tank mold

The rebuild started by laying up 3 ply's of 8 oz and one face ply of 120 glass in the existing mold. The mold was prepped with 5 coats of mold release wax. This mold is well seasoned, so 3 coats is sufficient

existing mold

3 plies of 8 oz and a surface coat of 120 glass were laid up.  All seams are overlapped a minimum of 1.5 inches

Bottom surface mold form

Instead of laying up the bottom surface on a flat plate, I decided to make a foam and Bondo sump. This will become the low point of the tank. This is a temporary one time tool.

lower surface mold form

I added bondo to fill the foam surface, and then sand able primer over the top of the mold form. 10 coats of mold release wax was added and then a coat of spray able PVA water soluble release. After the mold was treated, I laid up 3 plies of 8 oz fiberglass and one surface coat of 120 glass.



bleed air being added to aid the cure of the sloshing compound


After the bottom surface was cured and released, I bonded a glass bearing block into the base of the sump. This will be drilled and tapped to accept some barbed nipples for the fuel line and primer line.  I rough sanded the inside of the main tank and the bottom surface. I mixed up some epoxy and cotton Flox to a peanut butter consistency, its very important that this mixture have a shiny surface. I then bonded the upper surface to the lower surface.  After the tank bond cured, I drilled a 3/4" hole where the fuel gauge will go and started the sloshing process. I am banking on this sealant to give me enough life of this new tank for the flight test program. I will constantly check the tank for signs of ethanol degradation

And Finally!!! The reason I was late in updating this blog was a trip I made to Pearson Georgia to South Georgia Cargo. I got a hell of a deal on a 24' enclosed cargo trailer. I will convert the interior into a camper and a hauler for my plane. The trailer was sold thru Allpro Trailer out of Florida http://www.allprotrailers.com/  Ask for Brian Robison  brianr@allprotrailers.com The price was $3800 base , but I ordered 5200lb axles, the final price came to $4300. After my buddy Ed and I picked up the trailer, we immediately headed north to Wilson, North Carolina where Ed bought a very nice Piper J3F cub project. Ed started a blog similar to this, http://nc35447.blogspot.com/2012/06/data-plate-confusion.html  give him a visit sometime.

Robins new Home away from Home

Heating problems

I have been running up the engine. So far I have 45 minutes on it. A number of problems have reared their head. The wiring has to be re done. I need to eliminate the quick disconnect plug. The tach pick up wire needs to be rerouted away from all of the other leads. The tach is not reading properly. The pick up is inducing a signal into the adjacent wires, which in turn are inducing a second signal into the tach pick up lead. The CHT lead broke because there was not enough strain relief, the EGT never worked. I need to disconnect the instrument panel from the canopy, yet it still needs to pivot away when the canopy is raised. I'm going to make a secondary pivot for the Instrument panel. That should solve the problem and allow hard wiring direct to the panel and eliminate the disconnect plug. The second problem which is much more serious is excessive hear build up on the reduction drive mount. That in turn is conducting the heat to the back of the spinner backing plate. The spinner backing plate is room temp cured graphite epoxy laminate. As soon as it gets above 175 degrees, the plate gets soft and the spinner starts to wobble. I plan on solving this by three methods, I will post cure the spinner plate in the oven at 300 degrees. Hopefully that will raise the T/G (Temperature of gel) to near the hub temp. Next I will place a fiberfrax or Mica insulator between the hub and the spinner backing plate. Third I am going to drill some vent holes in the backing plate and in the inlet baffle. to direct some of the input cooling air toward the mount. There is no secondary air flowing in the rest of the cowl, this is causing high internal temps. Hopefully the internal duct I am ding to add will help this. It will take very little flow to solve this problem. Because of this, I decided to tear down the engine compartment and install a .012 aluminum heat shield over the top of the firewall fiberfrax insulation.
 

Existing baffle wearing thru the FiberFrax

 The actual engine head temp is running cool, it seems to peak around 425 degrees. The spec allow the head to see 500 degrees. Because of this, I should be able to redirect some cooling air toward the reduction drive mount.

New Aluminum heat shield

I am in the process of finishing the engine re installation. I should have this finished tomorrow.

Finally I have a third problem that is also equally serious. My Fiberglass fuel tank is starting to deteriorate. I attribute this to the ethanol that is in modern fuels. I never had this problem 25 years ago on my Wren. I also do not like the design of the fuel pick up on this tank. Another glaring error I made was the lack of a tank sump for the fuel pick up. I also need a fuel shut off valve. The tank head pressure is overcoming the reed valves in the pumper carb, causing the engine to flood while sitting. The other problem I discovered, was that the fuel filter and line needs to be routed on the inlet side of the intake plenum.The fuel was cooking off when the engine was shut off causing a vapor lock and making starting hot very hard. I started laying up a new tank and I bought a special fuel tank epoxy coating designed to protect against the ethanol in the gasoline.  Anyway, better to find all of this out on the ground then of first flight!!!
















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