We can Rebuild it.... Make it Stronger.... Faster!....

    Welcome to the latest episode of the Six Million Dollar Viper!  The last article- "Viper Damage"- pretty much covered how to put a big gaping hole through the side of a perfectly good hovercraft. I also explained my "on river" temporary "fix" to get the craft home again.

    I forgot to mention an important conclusion in the past article - If you fly a hovercraft long enough then you are eventually going to hit something and damage it. I really can't think of any "long term" hovercraft pilots that have never damaged a craft. That said.... Let's pick up where we left off....

    I arrived home at 3:30 AM. I parked the truck, trailer, and wounded hovercraft under the security light next to the barn. I climbed out of the truck, and my glasses instantly fogged over.  Welcome home to Missouri..... or is that.... Misery ? We were in the middle of the worst draught in history, and it was still 85 degrees even at this hour.

    Since I wasn't supposed to be home for another three days I went upstairs and told my wife I was back- she knew from 31 years of prior experience with "Dixon's Law" that this was a "Bad Thing". Bad or not- all I wanted to do was take a quick shower and go to bed. I finally made it to bed and fell asleep.

    With a roaring V8 powered Pickup Truck spraying gravel the "Hay Boyz" came accelerating up my driveway at warp factor 6 and made a hasty retreat to their hay bailing equipment parked in one of my pastures. I slowly pieced together what was going on through the stupor of my five hour sleep.... Being from the suburbs of Chicago it still seems bizarre to actually make money by NOT cutting the grass... go figure? I have a crew come in and bail 60 acres of hay - they do all the work.... COOL!

Hay Boyz Toys

    The "Hay Boyz" are in their early twenties. They have been farming all their lives- so when the "New guy" comes out and Videos them doing the haying.... well.... They think I'm a putz. I can see it written all over their faces. Oh well.... I got work to do on the hovercraft so I might as well get to it. I washed the craft and then removed all the skirts. The skirts were so full of mud that I individually washed all them and then hung them out to dry.  In the 100+ degree heat it only took a half hour for them to dry, and I packed them away-  I knew I wouldn't be using them for a while. I started the motor to let it dry out and let it idle for a while and then I shut it down. One of the "Hay Boyz" saw me working on the craft and came over to check it out.... I explained how the craft works and I started it up again for his benefit. The craft can't move very far without skirts so I warmed it up for a minute I revved it up to top rpm for a second or two..... right exactly at that very same moment my young farm hand decides to walk directly behind the fan to get a "better" look.

    You know those movies of people being blown away backwards in hurricanes? That's exactly how it looked. Basically knocked him flat before I could back off of the throttle. I killed the motor and he sheepishly came over to me after getting up. Seizing the moment I looked at him and said "See... You guys know everything about farm equipment, and I don't. I know about THIS stuff and YOU don't."

    We both had a good laugh and I don't think I've been a "putz" since. I heard him telling his partner about how "cool" it was later that day. Maybe this could become a new event at the "X" Games!

    In the early part of 2003 I wrote on page 13 of the "Viper Project" -

    I do need to correct a self induced problem. I have too much thrust... never thought I would say it, but it's true. The Viper was designed as a cruising craft with a 582 Rotax.... I strayed from the plans and upped the horsepower from 64 to 92. My fault entirely and in my opinion not a design flaw.

    Basically the problem I have created is that I have so much thrust that I can literally fly the craft over the centerline and off of the cushion... While cruising at 45 mph with my wife on board I did a quick burst of full throttle and almost instantly drove off the cushion and planted the nose in the water... The Viper has VERY benign plow characteristics... I knew this and did it on purpose... just an experiment on a calm flat section of water. Even at 45 mph it just slows down- speed boat style...

    So what I have basically done is taken a perfectly good cruising craft and made into a "high speed" craft. I have discussed the problem with Michael Nell and he has given me a simple and elegant solution-

     I figured since the craft was already damaged and I needed to work on the hull that I might as well incorporate the new changes at the same time. I put in an order to Nell Fabrication in Australia for the parts I would need. I took a good look at the rest of the craft. The ugliest thing on it was my custom exhaust which I had meticulously sprayed black with special "high temperature" paint. The paint lasted about 3 outings and started flaking off.... Ugly..... Just plain UGLY! Something that expensive shouldn't look ugly so I pulled it off the craft. That exhaust header is UGLY too! I removed it as well. I stuffed oiled rags into the exhaust outlets on the cylinders and duct taped them in place. I covered the craft and put it away. I decided that I wasn't going to ANY work on the craft until I had all the parts needed to complete the job!

    I really didn't know what to do with the exhaust parts. I knew that the high temperature paint didn't work. I called a few "hot rod" shops around the area to get suggestions. They suggested having my exhaust parts "Ceramic Coated". I did some research and came upon "High Performance Coatings Inc." They are at: http://www.hpcoatings.com/ on the Web. I had a few email "conversations" with them and finally made a "confirmation" phone call with exactly what I wanted done, the cost, and the time frame. I shipped out my parts the next day. A few days later I was talking to my friend Gary Jensen ( http://hovercraftsales.com/ ). I mentioned that I sent my pipes out to HPC to be ceramic coated. Gary told me that he had used HPC on the exhaust system of his "Drag Racing" Z28 Camaro!  He highly recommended them.... COOL!

    Two weeks later I heard someone blowing their car horn outside on the driveway- it's still over 100 degrees outside so I'm hibernating in the house seeing how cold the air-conditioning can get before I walk down to the lake and do some fishing. I looked outside and it was the Mail Lady. I went out to see what she had.... It was a package from Australia! I ran the package back into the house and checked it's contents. Everything was there except one important thing,,,,, We'll get into that a little later....

    Marine plywood seems to be a commodity that continuously eludes me. I need 3mm Marine plywood to do my repairs. The local lumber suppliers are as baffled as I am as to where to buy it. If I needed 5/8 (16 mm) no problem. I finally used the "Glen-L" boat building website and used their list of suppliers to locate the closest marine plywood dealer- "Glen-L" has an interesting website with lots of good building information. The closest place to Kansas City that carries Marine plywood is "Cedar Tree Inc." in Des Moines, Iowa. I got their email address off of their website and asked about the availability of the 3 mm marine plywood.... No problem they had at least nine sheets in stock. I probably needed less than 1/2 sheet to do my repairs, but since the stuff is so hard to come by I ordered two full sheets and made arrangements to pick them up the next day. The next morning after a few hours of driving in the nice air conditioned truck my wife and I arrived at Cedar Tree Inc. My wife was spirited away by the owners wife and into their home. I walked over to seperate building where there where a couple of people working on restoring an old wood boat it was a 17 ft. "Carver Commander". The owner jumped out of the boat and led me to his Marine plywood supply and we pulled out the two sheets I had ordered and put them in the back of my truck. We went into the house to find our wives drinking tea. Nice people..... and really easy to deal with. They carry epoxy, fillers, 3M Sealant, and four different types of Marine plywood fro 1.5 mm (Yikes... that's 3 plys and only 1/16" thick!) on up to 18 mm (3/4" and 13 plys). Remember I mentioned we were in the middle of the worst drought in history? Not in Iowa.... For some perverse reason it rained on my nice new plywood until we hit the Missouri border... It was over 100 again by the time we were home. The plywood was dry by the time we got home and I put it away in the barn.

    Another two weeks goes by and UPS is in the driveway blowing their horn- it's still over 100 degrees outside so I'm hibernating in the house seeing how cold the air-conditioning can get before I walk down to the lake and do some fishing. I went out to see what he had.... It's a GIANT package from HPC!

    All I can say is WOW! I mean I packed the exhaust parts really well when I shipped them to HPC- these guys packed them at least twice as good as I did. It took me almost a half hour to get the two parts unwrapped. First they were foam wrapped and then bubble wrapped over the top of the foam. Then they were taped together and dropped into an oversized box full of Styrofoam "peanuts"- Impressive, but not nearly as impressive as the change the ceramic coating made to the looks of the exhaust parts ! It's too late to start working on the craft today so I grabbed my 5 weight fly rod, walked down to the lake, and "played" with my fish.

Ceramic Covered Exhaust

Ceramic Coated Exhaust Manifold

    It's going to be over 100 degrees outside so I'm hibernating in the house seeing how cold the air-conditioning can get before I walk outside to unwrap the hovercraft and move it from the mechanics shed to the barn. It's times like this that I really miss the workshop that I had at my old house. I don't have any kind of shop yet at this house so I'm going to have to do everything outside in the elements. The barn is the nearest source of power. I started out by disconnecting all the  wires going to the motor, the fuel lines, throttle cable, and rudder cable. I built the Viper so that the Duct, fan, radiator, and engine assembly all come out as a single unit that is held in place by four bolts....

    Back at my old shop it was really easy to work on the craft. I would suspend the craft from the roof, drive the trailer out from underneath it, lower the craft onto furniture dollies, and then winch the motor / duct assembly  off of the craft, and then roll the craft away... easy!

    Well.... Back on the farm.... You know how Harley Davidson Motorcycles have achieved "Cult" Status in most parts of the civilized world? This is "Farm Country". The "Cult" item of choice around here is the John Deere Tractor- Don't believe it? Just go to your local "Cracker Barrel" Restaurant and look at all the John Deere stuff. That's just a teaser.... You can't imagine the amount of JD stuff in a real "Farm" Store!

    So.... I got this here Genuine 1978 John Deere 1530 Diesel Tractor with a "Front End Loader" (aka.... big hydraulic bucket on the front of the thing!) I tied the motor assembly to the bucket.... You can figure out the rest.... MUCH Easier! With the motor assembly removed it's an easy task to lift each end of the craft while my wife slides a few five gallon paint buckets underneath to hold the craft up off of the trailer. The buckets give enough height that I can easily work underneath the craft. They also have enough stability that I can work inside the craft while it is suspended.

    While I was sitting on the river doing my emergency repair I had already formulated a "Plan" on how to repair the craft. First order of business was to cut out all of the damaged plywood- and to go a few inches past the damage to avoid possible delaminating plywood that might be hidden. I ended up with some pretty big holes in the side of the craft!

Hull side hole

Cockpit Side

    The next step was to cut plywood "backer panels" to fit inside the plenum to cover each of the two holes. I cut the panels oversized so they would overlap the holes by 3 inches. I put those panels aside and then cut exact sized pieces of plywood to fit inside both of the holes. The job of sanding the around the holes on the inside of the plenum was NOT a fun time, and took a couple of hours to complete. I managed to finish just before dark and put everything back in the barn and covered the craft.

    I spent a day or two not working on the craft due to the intense heat.... The picture doesn't lie! It was taken just behind my house in the early afternoon.

Did I mention it was HOT?

    I was finally lured into thinking it's cool outside.... It's actually still 89 degrees, but it surefeels cool compared to the last few days. I mixed up a cup of West Epoxy and "Colloidal Silica" filler to the consistency of glue. I had intentions of gluing the hull side "backer panel" into the plenum.... By the time I walked from the barn to the craft- about 20 feet- The cup of thickened epoxy was already feeling warm in my hand. As I tried to brush it onto the inside wall of the plenum it just rolled off the brush in clunks. I set the cup down on the back of the trailer and grabbed some rags to clean up the inside of the plenum before the chunks of epoxy adhered and hardened. I decided to abort the mission for yet another day! The cup of smoking epoxy had gone majorly exothermic and I had to wear gloves to remove it from the trailer. I set it on the concrete apron going to the barn where it merrily smoked, hissed and crackled.

Smokin West Epoxy!

    My Bad! I figured I could work fast enough with the supplies that I had on hand. Unfortunately I was in too big of a rush to realize that all I had on hand was West Number 205 hardener..... Hehehe.... Using "Fast" hardener on a 90 degree day- there's nothing even remotely intelligent about that..... It was the heat..... I swear it was..... Honest!

    Now I'm back to my favorite pastime- looking for stuff that I need, but can't find. I've given up on trying to use local sources to find anything. What I need is some different hardener for the epoxy. I check the West Epoxy website and sure enough there's a marine supply in Kansas City that carries their product line. I drive to "Boaters World" and sure enough there's the West display with most of their product line. After a little bit of poking around and looking behind other cans I manage to grab the last can of "209 Hardener" in the store. The 209 Hardener is "extra slow hardener"- at 95 degrees it gives you a "pot life" of 15 to 20 minutes with a solid cure in about 6 to 8 hours. It's not any good below 70 degrees....

    I finally managed to glue in the backer panel to the inside of the hull that I had been working on previously! I coated both the inside hull and the actual panel itself with thickened epoxy and sandwiched it together. I held it all in place with a sheet metal screw every two inches around the perimeter of the cutout- This bent the panel to the proper shape, and eliminated any voids between the panel and the hull. The excess epoxy that had oozed from the edges was cleaned up before it had a chance to harden. The backer panel now covered the hole from the inside of the plenum. I glued the fitted panel and placed it in place in the opening on the outside of the hull, and again temporarily screwed it into place. I let the epoxy set for 24 hours before I removed the screws. I sanded the outside of the hull around the patch and then wiped it down with lacquer thinner. I mixed up a small batch of epoxy and thickened it with micro-balloons. I used a putty knife to force the mixture into all of the screw holes and then allowed the epoxy to cure again. Once cured the areas that received the micro-balloon / epoxy mix where sanded again. I mixed up another batch of epoxy and placed a piece of two inch wide "S" glass tape across all of the panel to panel joints.

Finished Hull Patch

    One patch complete.... one to go. The second patch was made pretty much the same as the first, but was a little more difficult. The first patch had easy access to the inside of hull through the hole in the cockpit wall. The only access to the plenum side of the cockpit patch is through the air feed holes..... Patience is a really good thing during times like this! The craft was finally taking shape.... 

    OK... now for the changes I needed to make to cure my self induced handling problems. The "Magic" fix involves swapping out the current 9 blade Multi- Wing fan for an 8 blade unit..... Doesn't make any sense until you actually sit down and analyze it. Normally on an "integrated" (Single engine, single duct) craft reducing the number of blades on the fan would increase thrust, and reduce lift (less blades forcing air into the plenum's splitter plate to create the cushion volume)

New Fan Hub and Blades

    So what do I have to gain by going to an 8 blade fan when I already have too much thrust? Ahhhhh..... Magic..... The 8 blade hub is physically bigger than a 9 blade hub- which makes the blades shorter- which makes the tips of the new blades wider in front of the splitter! Cool! Once all the math is done you actually end up with more lift (15-20%) with a thrust reduction of about 5%. In addition to ordering the new fan assembly I also ordered a set of Carbon Fiber Stators which can increase the thrust by as much as 20%. So all said and done I increased the lift by 20% and increased the thrust by maybe another 15%. What was missing in my package Australia? The instructions for mounting the Stators. I emailed Mike Nell and got an immediate response. Mike wanted to be sure that I had the parts in front of me before he explained how to mount them. They can only be installed one way, and as Michael explained- Stators are easy! The entire fan swap and stator installation took about a day, and some time for the epoxy on the stators to set.

Stator Parts

New Stators Mounted

    We aren't done yet! Now we have more lift, but we need to redirect that lift to where it will do the most good. This, unfortunately, requires making the air supply skirt feed holes around the back and sides of the craft smaller and the skirt feed holes at the front of the craft bigger.... Making 14 holes bigger is easy! Mark out the holes with a sharpie and carefully "freehand" cut the holes to size using a router.

Bigger Front Holes

    Making the remaining 54 holes smaller is where the challenge came in. I went into mass production. I made 54 pieces of 3 mm marine plywood that measured 4" x 4". I marked the center of each piece then used a "Hole saw" to  cut the proper sized hole in each. I sanded each piece completely with 100 grit sandpaper and used an air gun to remove the saw dust. I connected a string to the trailer and then slid all 54 pieces onto the string and then tied the end of the string to a nearby fence. I sread the pieces out along the string and then gave each piece two coats of epoxy to seal it.

"New Holes"

    I decided to mount the "new holes" from inside the plenum- I would rather have the air pressure  pushing the plywood against the inside of the plenum instead of having the air trying to push the new pieces off of the craft to who knows where. Getting 54 pieces into position inside of the plenum was another little bit of tedium. I used a bead 3M 5200 Marine Sealant on the perimeter of each piece  and then handed it over the back of the craft ( where the duct usually sits) and grabbed it through the existing air feed holes. I just passed it from one hole to the next until it was in the proper position. I managed to hold it in such a way as to not glue it to anything until it was in place. Once aligned properly with the old hole I anchored the "new hole" in place with two permanent Stainless Steel sheet metal screws.

"New Holes" Glued and Screwed

    Now the craft was complete except for re-assembly- which took less than a day. The following weekend I attended a Hover Rally in Cedar Rapids, Iowa. With all the changes I had made I had no idea how the craft would perform. I didn't have a chance to do any testing before hand, and I kind of guesstimated what the pitch on the new fan should be set at. I guessed wrong. The craft flew, but not as well as expected. The fan was under pitched when I first arrived. I cruised for a while with a few other crafts and finally returned to the launch ramp. I figured I might just as well try to sort out the fan pitch while I was there. I removed the rudders and stators and re-pitched the fan to the maximum possible. This seemed to be closer to what I needed, but it played havoc with my jetting. Two Stroke Motors are such a pain sometimes! I re-jetted, but never really got it right. I was also having intermittent tachometer problems, but it appeared that the re-pitched fan was pitched a bit too much now. It was getting late so I left for home.

    The next day I took a trip to a nearby town to the local dirt bike shop to pick up a few main jets that I was somehow missing from my collection. Surprisingly this shop actually carries every jet you could ever need... In stock! Go figure? No such luck when I lived in the Chicago area....

    Once home I tested the craft on the trailer and re-routed the tachometer lead. With the tachometer working properly I could see that I was only getting 3500- 4000 rpm at maximum throttle- Obviously the fan was pitched too much. I removed the rudders and stators and de-pitched the fan blades about a sixteenth of an inch and tested again. This time I got full power out of the motor- it was still jetted too lean in the midrange, but it zoomed right up to 6900 rpm and stayed there while being governed by the fan. I reassembled the craft and after a few minutes I had the jetting perfect.

    There ARE some advantages to living in the boonies on a 60 acre farm.... I took the Viper out for a "test run" on the official 1 mile long Dixon Test Track. The craft worked AWESOME and had lots of power! The test track water sections aren't really long enough to get to top speed, but short bursts of 45 mph were easy.

    I had originally planned to attend the Big Springs, Tennessee hover rally, but I reconsidered due to the driving distance. There are quite a few hovercraft pilots in Missouri and we decided to have our own rally near St. Louis on the Meramec River the same weekend. The Meramec is a great river to cruise on and we all had a lot of fun. The Viper has a lot of performance and surprised a few people on the cruise. I still haven't gotten a top speed number because of cross wind conditions on the river, but I cruised for over 15 minutes at speeds over 48 mph- with a LOT more throttle in reserve!

    The stators have made a big difference in the side to side balance of the craft- before I had stators the left side of the craft would ride high under acceleration and higher power settings. The stators now keep the craft flat. The HPC Ceramic coating is also an excellent addition- First it looks a LOT better, and it also runs a lot cooler, and cools off much faster than the stock pipes. I made the mistake of accidentally touching the coated pipe while doing an adjustment.... It was hot and uncomfortable, but I didn't get burnt.... enough said!

    So That's about it.... The craft is back in one piece (the patch still needs paint!), runs good, and has all the performance I could ever use. What's next? Maybe a trim wing, but for now a little ballast seems to work fine so I probably won't bother. Sometime this Spring I'm planning on doing a "Viper Video" filmed on the 1 mile course here on the farm..... Hummm.... how about an "Ultralight" Formula 25 Craft?..... We'll see....

Later!!! 

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