Sun Mar 20, 2005

 I epoxied on a 1/2" foam backing onto the dash to strengthen it and give the top something to glue to.

I have been warned about hot wiring polyurethane foam.  I've been told it gives off toxic gasses.  I have done research online and found that hot wiring polyurethane foam can produce isocyanates.  Here is an excerpt from US Department of Labor ( http://www.osha.gov/SLTC/isocyanates/ ):

"Isocyanates are compounds containing the isocyanate group (-NCO). They react with compounds containing alcohol (hydroxyl) groups to produce polyurethane polymers, which are components of polyurethane foams, thermoplastic elastomers, spandex fibers, and polyurethane paints. Isocyanates are the raw materials all polyurethane products are made of. Jobs that may involve exposure to isocyanates include painting, foam-blowing, and the manufacture of many products, such as chemicals, polyurethane foam, insulation materials, surface coatings, car seats, furniture, foam mattresses, under-carpet padding, packaging materials, shoes, laminated fabrics, polyurethane rubber, adhesives, and other polyurethane products.

Health effects of isocyanate exposure include irritation of skin and mucous membranes, chest tightness, and difficult breathing. Isocyanates are classified as potential human carcinogens and are known to cause cancer in animals. The main effects of overexposure are occupational asthma and other lung problems, as well as irritation of the eyes, nose, throat, and skin. The following commonly asked questions link to resources that provide useful safety and health information about isocyanates."

I have read on several sites that it is common to hotwire polyurethane foam with proper ventillation.  I know it works because I have done it before not knowing it was toxic.  Another thing I read is that it only gives off fumes with hotwire temps between 300 and 400C.   I have also read it is  common to use a flame torch to seal this type of foam after it has been cut and shaped.

I believe if I hot wire the foam outside and have the fumes go downwind with the help of a fan I will be ok.  But don't do what I am about to do without researching it yourself and knowing the risks involved.  Don't take my word for it.  After all I don't do this for a living.

The plan:  I need to shape the foam behind the duct and on top of the dash to match the curve of the dash going down to the nose.  My plan is to attach a hot wire to the nose of the craft.  I'll put some 1/8" ply between the wire and the craft at the front part in front of the lift duct.  I'll attach the power wires to the hot wire just before the foam on the lift duct and just behind the foam on the dash. 

Thu Mar 24, 2005 

I worked on the controls.  I have a new design that is using control cables.  I am planning on having one cable that attaches to the arm at the back of the control shaft and running to the rudders.  The second cable will run from the front of the shaft and will control the trim wing.  I used uhmw plastic as bearing blocks for to hold the emt to the 3/4"x3/4" supports.  The uhmw works very well as a bearing.  It works much better than the flimsy metal emt clamps I found at home depot.  I couldn't find any heavy duty ones that fit.  The uhmw works much better and really makes for some smooth controls.  It did take a few tries and the better part of a day to make ones that worked though as you can see from the last picture.

Sat Mar 25, 2005

The last picture shows all of my failed rudder attempts.  I gave up on it for the day and moved on to the front of the craft above.

Sat Mar 26, 2005

Second and Third pictures show the underside of the cockpit top around the dash.  I sealed the exposed foam with a coat of epoxy so I can paint it with any kind of paint later.   I am happy with how the dash turned out.  I used a 1/4" round corner bit on my trim router to round the front edge of the dash.  I plan on fiberglassing the top of the craft and under the dash.  I'll use some lite weight bondo to smooth everything out.

Second last picture shows my workbench.  This is after I cleaned it... :)

Last picture shows the bottom of the craft.  I have it up on a saw horse at the front so took the opportunity to take a picture.  I have decided to just coat the bottom with epoxy and then paint it.  This will give the foam some protection from the elements.  I'll attach the front foam top pieces to the cockpit tomorrow.

Sun Mar 27, 2005

The front part of the cockpit is on!

Mon Mar 28, 2005

Wed Mar 30, 2005

Thu Mar 31, 2005

Fri Apr 1, 2005

Well I have definitely left the domain of the UH plans at this point.  This means I really have to think everything out. When you work from the plans construction goes pretty fast as you aren't engineering anything.  The good news is that  I have pretty much got everything planned.  The controls, rudders and console are designed.  The cockpit console is going to consist of Choke, Key Start, and Throttle Kill Switch.  The dash will be finished smooth and I will attach a GPS mount to it.  The rudders will have stainless steel bolts with the heads cut off and the ends rounded as pivot points.  These bolt ends will ride is some uhmw plastic.  This makes the perfect non squeak bearing.  I never liked the design of wood dowels riding in a wood bearing block.  Can you say squeak!

Sat Apr 2, 2005

Sun Apr 3, 2005

I drilled the mounting holes for the thrust prop.

The hole I had the throttle cable in on the throttle arm was too far away from the hole and I didn't get full travel.  I drilled a couple of holes closer to the pivot point.  I used some silicone tubing over the cable where it clamps to the engine. 

I have decided to mount the choke control on the seat in front of the stick.  I bought the longest cable I could find at that's about as far as it will reach.  I may mount the throttle key switch beside it.  I extended the stock wiring key switch harness by about 2 feet today.  This will allow me to mount it on the console under the dash.  I still need to flush trim cut the overhang on the seat sides.  I'll use the flush trim bit on my Makita router to do this.

Mon April 4, 2005

Tue April 5, 2005

Sat April 9, 2005

Third and fourth pictures - I used the trim router and flush trim cut the seat top with the sides of the seat. Fiberglassed the seat top with 6 oz cloth.  It took a fair amount of epoxy.  I put fillets into the ladder structure underneath the seat and painted it with a thinned down epoxy to water proof it.  My seat needs to be able to hold a fair amount of weight so I am reinforcing it. 

The next pictures show the lift duct.  I used a razor knife and a sponge sander to start bring the foam inside the duct to the right shape.

I started work on the prop filling it and getting it ready for fiberglassing with 6oz cloth.

In the last picture I am reinforcing the seat structure. I epoxied to pieces of 3/4"x3/4" to the top stretch of the seat.

Second and Third from last pictures - I shape the inlet radius use some emery cloth on a roll and a razor knife.  In these pictures I have just given it a coat of light weight spackle.

Please go on to page 15