Shoulder harness, ballistic chute and fuselage fabric.

I made good progress this Easter holiday. I started the installation of the seat and shoulder harness system. Because of the reclined position of the pilot, I realized that I need to add two crotch straps because the pilot would submarine under the lap belt. I bought my shoulder harness and seat belt from Aircraft Spruce. I need to find a source of the following shoulder harness fitting.

Davis Manufacturing Shoulder Harness fitting

For some reason I cannot get in contact with anyone at Davis Aircraft who made the original harness. If I have to I will buy a second shoulder harness and cut them down to make the crotch straps, but I would prefer to find the fittings and make up my own. I have a local Master Rigger who could sew up the webbing. But based on the response I am receiving form Davis, I will use another manufactures harness.  Anyway, if anyone has any Ideas I would appreciate an email.

planebuilder@yahoo.com


I laid out the parachute risers. The need to route around the main spar and around the landing gear. These are the hardest points on the Plane. The riser straps lengths are designed such that after they deploy, they will come to a point 12 feet in the air above the CG. 

main spar riser web instal

 I installed the riser strap with a liberal amount of fabric adhesive. The fabric will bond over the straps and then an opening will be pierced and then wrapped into the opening, further retaining the riser straps. This is an area I will revisit when I finalize the Robin Plans. There has got to be a cleaner way to attach the riser straps





 

Riser strap routing

I attached the Straps to the fabric standoffs.  The are non structural and sit outside of the longerons. The straps route over the longerons right next to a truss gusset. This particular gusset was increased in thickness to match the strap thickness. this way strap routing will be partially hidden.Notice that the risers route aft of the roll over structure. Everything that has fabric would be history if I ever have to pull the deployment lever.

bottom covering

 the covering of the fuselage starts with the bottom panel. Each successive panel will lap over the previous panel. All lap joints will face downward and be reinforced with a 2 inch pinked tape.

Side panel being installed

side panel was added after the bottom. Extra reinforcements were added at the wing carry thru and the the landing gear. This fabric shrinks very well with an Iron set at 260 degrees. One trick I learned watching the Stewart Video is to immediately wipe off the excess Eko bond right after application. This way a thick bond line is eliminated and a much cleaner fabric job is done.

Left side front view

The lower tape was also added. The fabric is coming out really nice and clean, I definitely learned some lessons from covering the rest of the plane.

Ballistic Parachute installation

I received my refurbished ballistic parachute from John Dunham at Second Chantz parachutes earlier in the week. http://www.secondchantz.com/. They did a fantastic job of reworking my 19 year old used parachute. I called John and asked if they had found a new case to repackage the chute. He informed me that this was the original case, but it had been thoroughly cleaned. The big delay was waiting for the sub contractor to fabricate the unique riser straps that the Robin will require.The deployment sequence had to be carefully thought out. The riser straps will rip away anything in their way. They need to be routed outside of the longerons and designed such that after deployment, the plane is supported by 4 straps that come to a point 12 feet in the air. The plane needs to sit level such that the main gear will be the first thing to strike the ground. All thought of saving secondary structure like the fabric and the fairings is ignored. A ballistic chute deployment is a serious action that is only contemplated when your life is in danger. Years ago, in my Hang gliding days when I was single, I participated in the Owens Valley Classic Cross country Hang Gliding race. This was run by my late friend Don Partridge. Don had a rule that all participants had to have a deployable parachute. This was in the days before ballistic chutes were ever designed. I launched that day from a turn out in a road 6500 feet above the floor of Death Valley. Truth be told, I had no business flying a hang glider at noon in Owens Valley. Every thing went smoothly until I hit the first freight train (thermal). I was pitched up violently 90 degrees. My audio vario pegged at 2000 fpm plus. I was barely ably to maintain control of my kite (Seagull 11 Meter) . I was tumbled end over end at least three times. Once I stabilized in a level flight attitude, I got hit by a monster thermal that bent both wing tips up at least 4 feet until each of them snapped. I then tumbled over and over at around 11, 000 feet of altitude. I cant tell you what I was thinking at this point, because it was all animal instinct. I do not recall my life flashing in front of me, but Hell after earlier Hang Gliding mishaps, it would have been a rerun any way!!. Finally I saw an open stretch of blue sky and I was able to deploy my hand held parachute. I was successful ( or I wouldn't be writing this) and the chute blossomed above me. From the time I deployed the chute until I landed on the ground, it was almost 1.5 hours. I was hit over and over by one thermal after an other. My flight profile took me from as low as 8000 Agl to over 14000 Agl. I drifted east away from Highway 395, my best estimate was about 20 miles. The only reason I was able to land, was because the sun had begun to set. I ended up drifting over a section of the ground that was in a shadow of the mountain west of me. Another requirement of the Cross Country Classic was the carrying of survival rations and water. This undoubtedly save my life the following day. I landed so late that I I decided I could not walk out at that hour. I made a very comfortable tent out of my wrecked 11 Meter. I rolled up in the Parachute and actually had a very restful night. The next day I started around 4 am and followed my shadow east. The sun was rising behind me and I knew that if I headed due west I would eventually intersect highway 395. This I did 4 hour later. I was at Highway 395 for no more than 5 minutes when a California Highway Patrol Car stopped and asked if I was Mark Calder? He informed me that 3 people had died the day before and that I was the last person missing!
Because of that experience, I am a firm believer in Ballistic parachutes.

The Robin has been designed from the onset for a Ballistic Parachute.

Riser straps

These are the riser straps that still need to be installed. They are made with shock resistant Nylon webbing. There are two sizes, one is designed to loop around the the main spar, the other is designed to loop around the landing gear. Each strap has a sewn in  loop that is stronger than the base web.

beginning the installation

I will take blind luck over careful planning any day of the week!! The chute will just barely fit under the roll over spreader bar with less than 1/8th of an inch clearance. If the wood intercostals were attached, it could not fit. The Chute is designed to mount to my roll over structure. I had an idea as to the dimensions of the chute but I was really guessing when I designed the roll over structure.!!

Business end

This is the business end of the chute. don't stare too long or you might not get a Second Chantz!! The mortar/rocket will shoot out between the roll over struts. The wood fabric fairing will be history if this lanyard is ever pulled. The riser straps will attach to a steel D ring on the R/H side of the package. The risers will rout around the outside of the roll over strut and outside of the longerons.

Deployment handle

 The deployment T handle is mounted forward of the stick and attached to the landing gear carry through. I debated where I should put this handle and my Friend Dan had a really good point, what if a left handed pilot flies the Robin, or I break my right arm. This way its centrally located. it will sit below the seat cushion.






 

Seat Belt  routing

 Once the chute was positioned, I could route the shoulder harness belts. They are designed to pass through the roll over cage and sit above the spreader bar. This way they are at the correct angle and will not cause the spine to be loaded in compression.

 

 The rest of the covered surfaces have been completed and final paint has been applied. The red color is spot putty that is filling pin holes in the fiberglass.

As I finish the paint, I am wrapping the surfaces in plastic. I have some kind of insect that loves to crap on  finished paint!! I'm tired of fighting with them, so I am wrapping everything as I finish.

Left wing about to be painted, Right wing wrapped

The right wing is fully painted. So far I have used less that one additional gallon of finish paint. I am a true believer I the Latex pint finish method. This is definitely the lightest way to cover an airplane!!

Weight and Balance (unofficial roll out)

Well the weather finally broke, I sat inside working on my new wing redesign until I saw the first glimpse of the sun. I quickly gave my buddy Ed a shout and he came over to help me assemble the Robin out doors for the first time. This will be the longest Blog entry to date, there are a ton of pictures. Most were taken by Ed who showed me all the cool features I never knew the I-phone had!!

Farmer Ed

My Buddy Ed from down the street. He and I drove 3 weeks ago to Phoenix to buy the Mini Max project and my Ballistic Parachute, My chute is back to the manufacturer Second Chantz http://www.secondchantz.com/index.html  Getting repacked and re armed. I should have it back sometime next week. That is the only reason the fuselage is not covered. I need to route the riser straps outside of the longerons and around the main spar and landing gear. Give ole John Dunham a call and he will fix you up with a nice Ballistic Parachute!!

Front view

The wings have two coats of  Latex UV barrier paint. I was following the process outlined in the last blog entry. I have used a little over 3/4 of a gallon so far. I will easily be able to finish all of the fill and UV barrier coats on the is airplane for under 1 gallon. I am really impressed with this finishing method. It sure is cheaper than the certified water based systems. I had allotted 18 lbs of weight for the complete cover and finish. so far I am just under 5 lbs. This became really good news later in the day when I completed the weight and balance.

a man and his plane!!!

Here I am with my other friend

Me and Boo

Me and You and a dog named "Boo"

Left quarter view
 I'm pretty sure I will need a larger rudder.

Right Rear Quarter view

looking down the L/H wing. We are getting set up for the weight and balance

Looking down the R/H wing









 

               L/H cowl view

My Friend Yuki Yoshi Ishihara of Chiba Prefecture Japan bought me this Propeller. I plan on Painting the words "Yuki's Prop" on it eventually. This is a CGS ground adjustable prop. It weighs 8.5 lbs. I will switch to a fixed pitch Spruce blade once I dial in the correct pitch. That will reduce my empty weight by 7 lbs.

   




 looking up

Exhaust side

I thought this was a pretty cool Picture Ed took.

leveling the Robin while Boo supervises

The plane was leveled and 3 scales were placed under the three wheels. The upper longeron is the level point.
Ed and I discovered a huge scale error under load. We spend some time calibrating the scales until we were assured they were accurate. That's what I get for buying $7.00 scales from Target!!

important first step!!!

Now this was a really important first step, literally!!! I rebuilt the inbd root leading edge of the L/H wing to add a walk way. It was solid as a rock!!

size 11's

You can see in this picture how 245 lbs is distributed over a fairly large surface area. The actual analysis however assumed I would place all of my weight on only one stringer. Over kill, but conservative and the step literally is rock solid.

An old designer once told me never to design for a skinny kid!! They never have any money!!

It is very comfortable in that cockpit. The profile of the seat is right out of a Jantar Ad in Soaring magazine. They claim its the most ergonomic seat shape ever designed. I believe them!!!

notice that the gear still has negative camber at full gross weight!!

Real Dummy

See if this Dummy looks just like

Fake Dummy

this Dummy!!!



(notice the gut)

Real Dummy again

The Jantar seat profile is really clear in this view. The Yarmulke really does its job. I definitely need to add some vents. It got hot really quick in that green house

Ed playing with his "Stick"

I asked Ed to work the controls and play with the Stick, I think he misunderstood me!!!!!

final weight and balance

So here is the end result of all of this fiddling around. I calculated the Neutral Point (NP) at 37.5% This is the point  around which all the aerodynamic forces are balanced. The center of gravity must be forward of the NP with a margin of safety Typically 10% to 15%

Well after all the sweating and sleepless nights here is the final numbers.
CG with no fuel  is 29.1% with a static margin of 8.2%

CG with fuel is 25.8% with a static margin of 11.5%

this is a good link to an online calculator   http://www.geistware.com/rcmodeling/cg_super_calc.htm

This is as close to perfect as I ever thought I could get. Now for the best news, the plane weighs 262 lbs with the 7 lbs extra weight prop hub. and with parachute it will weigh 276 under the 284 FAA part 103 weight allowance allowed for a Ballistic chute. With the light prop the empty weight will be 255lbs. The new wings will be at least 30 lbs lighter, that and some other weight improvements will easily allow for brakes and a starter on plans built planes.

Latex House Paint Covering method.

Big milestone today. I started finishing the fabric. I decided a while ago after some research that the Latex house paint system was the lightest covering method I could use. The major covering methods are mostly dissolved thermoplastic. All of these processes are heavy. The latex system I believe is also similar to the Stewart covering system,  http://www.stewartsystems.aero/default.aspx    in fact I am using their adhesive called Eco Bond. There has been a ton of research done on using Latex House paint. A friend of mine in Wichita, Duane Life covered  his J3 Kitten and I have always been impressed with the finish. A lot of good work and research has been done on this process, the most impressive is Drew Fidoe's blog http://www.bowersflybaby.com/tech/latex.html, other good sites are the reprint of Charles Threewit's article http://www.lazair.com/housepaint.htm   and this article in Ultralight News http://www.ultralightnews.ca/articles/housepaint.htm

Fresh Bloom

The process starts with a good base latex Acrylic latex enamel. I am using Sherwin Williams D-100 gloss exterior enamel The base color of my Robin based on my Friend Bills design is Gun Metal Grey. This may be too dark, so after the base UV coat is applied I may pick another lighter color if Bill decides I need it. The formula for using latex involves adding a viscosity modifying agent called Floetrol. This smooths out all brush and roller marks. Each coat is additionally thinned with standard windshield wiper fluid. The links give the ratios. 

The day started nicely with a fresh bloom in the flower box.  We had a few  85 degree days last week. Like I said earlier, Texas is wonderful in the spring, winter and fall!!!



  
I started with the ailerons. I figured they were the easiest to recover if I screwed up.

Single coat on Ailerons

 The procedure for finishing goes like this. After the paint is well thinned and mixed with Floetrol. it is rolled on with a foam roller. Right behind the roller you follow up with a foam  brush and push the first coat into the open weave. Let that dry and and complete the same process on the opposite side of the part you are working on. The second coat is put on with only the roller and is rolled 45 degrees in the opposite direction of the first coat.

Ed doing the Brushing duties

 Its amazing how well this covers. By the end of the day, all of the control surfaces and Horizontal were finished and I had used less than a quart of paint. The beautiful thing about that is its mostly water and it evaporates away.

Ailerons with second coat

 Depending if Bill likes this color, the next step will be a spray over coat at Eds house in his spray booth. At this point the fabric on the surfaces sounds like  a snare drum when you tap it. Its pretty exciting seeing it at this stage. 








 

Coating the elevator

 This is me doing the elevator. I tried to measure the weight gain at this point, but I found that my scales were not sensitive enough to measure the difference. I will know exactly when I reassemble everything an re weigh, but from the looks of it my weight gain will be measured in ounces. My estimate of the paint weight was 12 lbs. Based on that I was going to be 10 lbs over weight. 

Finished Rudder

 The Rudder was recovered after the trailing edge was replaced. Again, I could not measure any weight gain.

Wings

 This is another view that shows the wings. They came out beautiful!! Over weight , but very clean and smooth.

Horizontal with one coat

 The Horizontal came out beautiful. Its very smooth and very clean. I can hardly wait to fly this thing.

Parachute trip, revised rudder and covering.


So its been a very busy 3 weeks. I have been traveling on my job and last week end my friend Ed and I drove to Phoenix Arizona to buy a Mini-Max project, I was looking for a Second Chanz 550 or 600 ballistic parachute, This particular model weighs 13 and 17 lbs respectively. Because of the 30 lb weight allowance the FAA allows, this particular model will give me the 10 lb margin that the prototype appears to be overweight. I found a project for sale and one of the items was a model 600 ballistic chute. I called my Buddy Ed Gardner and asked him if he wanted to split the whole deal, he gets the complete project, I get the parachute. The final price was a really good deal, circumstances combined to force Mike Gurtler to part with his project.

Mike and his old Project

I got to hand it to my Friend Ed, he had a really good idea about how to pack the project, he bought 2 foot wide packing wrap, similar to Saran Wrap. We covered each section three times. That turned out to be the perfect number. We hit nasty weather coming back thru the mountains near El Paso. On the following day (Sunday) we were in ice, rain and snow all the way to the Dallas Fort Worth area

We spent about 2 hours packing the project in Phoenix.

Mike and me just before shove off

Ed and I drove my old 96 Chevy Z71 Pick Up. (219,000 miles)  I have had this truck since it was new and I have religiously maintained her,but 2 years ago I had to put in a new transmission. Other than that I have not touched her. I attribute her long life to the use of Mobil 1 oil . Anyway, she made the trip

ready to shove off

We both got one hell of a deal, I got a $3200 parachute and Ed got an airplane complete with all covering materials , engine and a brand new composite ground adjustable prop. I wont mention the price, but our gas was just about equal!!!
I accused Ed of being really anal when it came to packing up the project, well that turned out for the better, he decided to do one last walk around through Mikes garage and guess what!! There was my parachute sitting on top of a trash can!! That was the whole reason I bought half of this project. It would have been near impossible to ship the chute to me once I had left. The pyrotechnic would have to have been removed.

 I finished my Wing Walk and started covering the L/H wing. I then went back to the rudder. Turns out I designed the trailing edge too light. After I covered the rudder I noticed the trailing edge was scalloping and the fabric was losing its tension.

wing walk skin installed

This picture shows the wing walk after installation. The outer glass surface has been scuff sanded.

using the Multi-tool to cut off the training edge

So I used my muiti-tool to cut off the trailing edge. as you can see in this photo, its only .125" thick and .75" wide. This was actually unstable in torsion. After the fabric was shrunk, the trailing edge rolled over. I am modifying the trailing edge to be similar ti the rest of the airplane. I will detail the Trailing edge attachment in the next blog.

I prepped the L/H wing for cover, but will not actually be able to cover it until Tomorrow.
I tried to mount my new Ballistic parachute and discovered that due to the wing being overweight, I cannot mount the chute behind the pilot (at least not now) The weight and balance right now was the rear limit at 30% with no fuel and 22% fwd CG with full fuel. Still working on the chute installation. I am thinking that I will mount the wings after cover and then check the final balance. This will determine where the parachute goes

Wing Walk and some test photos.

I started modifying the L/H wing to reinforce the leading edge so I could add a wing walk. The redesign was pretty straightforward. I removed the existing wing skin with my multi-tool. That thing zipped right through the fiberglass. After the skin was removed, I reinforced the foam ribs with a ply of 8 OZ fiberglass on each face of the exposed ribs.

lateral stiffeners

I then slotted the ribs every 2 inches and inserted a wooden stringer. the Stringer was sized to react 250 lbs between the farthest span (6") so basically each stringer can support the weight of one step. In reality the load will be distributed between at least 3 members. The stringers were potted in with micro balloon and epoxy. Using the leading edge lay up mold, I laid up a 2 ply skin of .012 thick carbon fiber.

leading edge walkway skin

2 ply's of graphite and a single lightweight ply of glass comprise the walkway skin. The leading edge was taper sanded  to allow blending into the existing skin.


Right now the skin is curing after having been bonded 8 hours ago. Tomorrow I will be able to flip the wing over and finish sanding the skin in preparation for covering. I should be able to finish the covering tomorrow.

rib stitching

My airfoil is a Worttman 170 low speed laminar flow airfoil. It has a reflexed trailing edge on the upper and lower surface. Because of this, the fabric tension after shrinking will try to pop off the reverse curve surface. So I elected to rib stitch the trailing edge where the reflex is. Everywhere else on the wing, the fabric is bonded.

wing re test

The original wing test spar has been sitting out in the weather for over 2 years. The ultra violet radiation has attached the foam and the fiber glass. Periodically I retest the wing. The original wing was rebuilt after initial destruction testing and re mounted to the back side of my test stand. A 2 x 10 wood extension was added to increase the applied moment such that it equals the actual moment on the wing. This is a little conservative because the wood does not deflect similar to the wing. Because of this the stress is concentrated more toward the root, there is no relief that would normally occur it the complete wing was allowed to deflect.

anyway, this is a picture of the wing at just a little over limit load. There is 1200 lbs of force being applied. In the previous picture you can see my load cell that I designed. I made a piston with exactly 1 inch of area. I then bored a cylinder out of some scrap aluminum.I drilled and tapped into the cylinder and installed a 3000 psi pressure gauge. I filled the void with transmission fluid. The actual load now is a one to one read out. I calibrated the load cell at work on a universal testing machine one day at lunch. There is a little hysteresis error, but that was under 100 lbs. Close enough!!!