Thu Jul 12, 2001

6 hours

Wow.. what a day... I finally got up the courage to cut the hole for the lift duct.  My craft is two inches longer than a stock 13P.  I ended up putting the lift duct an inch and a half forward of what the plans called for to keep things to plan mechanically.

Pictured top right - I used a piece of 1/8 ply with radius 13.25" to draw a circle in the middle of the craft. 

Pictured 2nd right - You can barely make out the circle I marked.

Pictured 3rd right - Since the duct is at a 30 degree angle the hole is more of an oval shape (30 degree cross section of the duct).  I mounted the duct at a 30 degree angle using a 1" dowel.  I tried to mark the oblong shape as you can see in the next picture but the back half didn't come out very good.

Pictured 4th right - I used a reciprocating saw (Sawzall) to cut out the hole.  This looks about right lets try fiting the duct :)

Pictured 5th right - Getting closer... note the 30 degre angle at the front and back of the duct.  The Sawzall is not a precise cutting tool.  It did a pretty good job of uglying up my underside.  I will have to fix it later.

Pictured 6th right - Here is the duct in position at a 30 degree angle.  There is as much as 3/4" gap between the duct and the foam. 

Pictured 7th right - I decided on a method to attach and finish the duct.  I put on 1 layer of 6 oz fiberglass around the duct using epoxy.  Next I mixed up some epoxy cut with micro balloons (thick ketchupy consistency)  and spread it thick around the join to solidify the fiberglass where it wasn't touching anything.  I then covered up the joint with another 6 oz layer of fiberglass cloth.  After this was complete I mixed up a thinner batch of epoxy and microballoons and coated the outer layer of fiberglass.  I used a foam roller to smooth everything out.

Pictured 8th right - I put 3 layers of 6oz fiberglass cloth in between the red straps.

I wasn't at all happy with my ability to cut the hole using the sawzall.  I was using an 8" blade on it and it wandered like crazy.  If I had to do it again though I would probably do it the same way as I can't think of a better way. 

Next steps - I am going to build a 1" foam form about 2.5" from the duct wall all around.  I am going to use this form to pour 2lb/cuft 2 part foam.  After this is complete I am going to flip the craft over and pour two part foam between the outer duct wall and the foam down to the epoxy seam holding the duct in place.  After this is done I will cut the duct and shape the underside.  Then I will attach the inner skirt attach/ landing skids.

I had a question from a person asking whether or not I was going to make my end of August deadline.  The answer is yes I believe I am still on track for that date.  I am however not going to rush things to keep to that date.  It is an artificial deadline to keep me on track.  It is a method to keep me producing as is this journal.

Fri Jul 13, 2001

3 hours

I flipped the craft over today and started working on the underside. The joint around the duct at the top worked really well.

Pictured top right - Side view picture taken of the lift duct while the hull was upside down. 

Pictured 2nd right - another side view picture taken upside down.  Zoltan let me know if these are ok.

Pictured 3rd right - I used 2lb 2part urethane foam to fill in the gap between the lift duct and the hull.  This was the first time I worked with two part foam.  I found it worked best when I mixed small portions in a plastic container then poured it between the cracks.

Pictured 4th right - I used the Sawzall to cut away the excess duct.  I am getting pretty good with this tool now...

Pictured 5th right - Another view of the duct with excess ply cut away.

Pictured 6th right - I used the Sawzall to shape the rear of the duct.

Pictured 7th right - Another angleof the rear of the duct taking shape.

Sat Jul 14, 2001

3 hours

Today I removed the duct formers...

Pictured top right - I removed the duct forming discs.  I didn't use a single brad nail so removing them was very clean.  I used a rubber mallet to evenly knock it out.  Note the taper of the duct at the rear.  I am not sure if this is enough.  Opinions?

Pictured 2nd right - Duct from the front.

Pictured 3rd right - The craft upside down with the duct in place.

Pictured 4th right - I tapered the nose of the craft up to near the bottom of the top skirt attach strip.  Thanks Dave S. for pointing this out.  I would have missed it otherwise.

I drilled about 12 1/4" holes in one of the inner skirt attach strips.  I then started with a few dowels into the hull in some straights spots.  I started bending the attach strip and drilling the additional holes and filling with dowels until I got the bend.  It worked quite well.  There is a lot of pressure required to make the bend in the wood.  I am wondering if I am better off using numerous cut pieces to make the bend? 

Pictured 5th right - the inner skirt attach strip held in place with 1/4 dowels.

Pictured 6th right - another shot of the skirt attach strip held in place with the 1/4" dowels.

Sanding Tip from Dave Schneider - If you have a rubber sanding block with a curved palm grip flip the sand paper over to the palm part and you have a handy curved sander.

Pictured top right -  Here is some material I found at Home Depot.  It is a 7 or 8 foot length of thick light weight plastic or vinyl lattice.  I am thinking of using it to cover the wood landing skids.  It seems like it is pretty durable material and it is lighter than aluminum (cheaper too).

Pictured 2nd right -This is is how it looks after I cut one side off using a cheap table saw.

Pictured 3rd right - This is how it will sit on the landing skid.

Pictured 4th right - Another view of it on the skid.

Pictured 5th right - My garage is becoming a hovercraft factory much to my Wifes dismay.

Anyone have any opinions on this skid material?

Sun Jul 15, 2001

8 hours

I sanded smooth some epoxy and microballoons I applied around the edge of the bottom of the duct ply where it meets the foam.  I filled some more spots.  I think I will be able to sand and fiberglass it next. 

Pictured top right - I cut the other skirt attach/skid and fitted it beside the left skid.  I put the dowels in approximately the same place.  The skids start to straighten out near the fron 4-5" or so.  I measured the distance to the outer attach skids using a square and it is around 10.25" at the front.  The skids around the rest of the craft are all 11"

Pictured 2nd right - Here is one half of the thrust duct forming disc.  It was supposed to be 54 1/4"  (54 4/16") in diameter.  It worked out ti 54 3/16".  I won't re-do it I will just shave a little of my prop if need be.  This duct former was a pain.  I had to use to pieces of particle board.  I used the same router jig that I cut the lift duct with to cut this thrust duct former.

Pictured 3rd right - A front shot of the whopping 54 3/16" duct.  Dave do you have duct envy :)

Pictured 4th right - A view of the  from the rear showing the 2x4's I used to join the two pieces.  Now if I can just figure out how to get the other side on and centered.

I am finshed my vacation and am back to work tomorrow.  I will only be able to work on the craft after work and on weekends.

Sun Jul 15, 2001

Cont...

Pictured top right - I screwed the particle board to the other side and used a reciprocating saw to rough cut it a couple of inches close to the top former.

Pictured 2nd right - I needed to figure out how to center the duct so when I routed it that it would be in line with the top former.  I marked an 90 degree x on the top circle and translated the lines to the side and then down to the unrouted duct former.

Picture 3rd and 4th right - I flipped the duct and marked a 90 degree x using the lines as a reference.

Pictured 5th right - I drilled a hole to hold the router jig.

Pictured 6th right - Starting to route the circle.

Pictured 7th right - Ta Da!  The finished duct former and guess what?  The discs lined up perfectly!  The duct is actually closer to 54 1/8" diameter.  Dave suggested I use some duct tape to bring it up to 54 1/4".  I may pick up some counter top material if I can find some in 1/16" and try that.  I think that if I use duct tape and then ratchet the duct down with my tie down straps that the tape may just compress.  The other option of course is to just shave 1/16" off each end of the prop if I need to.  Dave made a good case against doing this.  If you ever loose a prop at a hover rally there may be someone there willing to lend you one.  If you have an oddball prop size then you will be out of luck.  This is true but may not apply to me too much here.  The only person I know even somewhat close to me that has a 13P is Greg in BC.   He is over 600 miles away and has a 42" thrust prop anyway.  I guess the other option is to always travel with a spare or two.

I went to home depot and found some 2' x 4' sheets of 1/16" formica (counter top material).  I am going to use this as a space around my discs to bring the duct up to 54 1/4" in diameter.  I did a test and it brad nails ok.  I will cut the formica into strips about 1" wider than the duct and brad nail them around the duct formers.  I will then pre-join 4 12" x 48" sheets of 1/8 ply to get a 12" x 192" long piece.  I will use epoxy and fiberglass cloth to join the seams.  I will then wrap the duct around the former and use the ratcheting tie down straps to hold it while I epoxy the seam.  I won't be able to sacrifice the tie down straps to the hovercrafts Gods like I did with the lift duct epoxying them to the duct.  This time I need to keep a relatively flat surface to wrap the foam around the duct. 

Mon Jul 16, 2001

2 hours

Today I fiberglassed the bottom of the duct where the ply meets the foam.  I fiberglassed all around using 2oz cloth.  At the very back where the taper is I used 4 layers of cloth.  Around the other 2/3's of the duct I used 2 layers.  It sure is hard to get fiberglass and epoxy to go around corners.  I ended up with little air bubbles at the bend.  It think this procedure would work better if I used some microballoons to cut the epoxy to thicken it up a bit. 

Pictured top right - This taper has 4 layers of 2 oz cloth.

Pictured 2nd right - The rest of the duct has 2 layers of 2oz cloth.

A few words about perfection.  I learned a lot from my father growing up.  I am thankful I inherited his mechanical genes.  He taught me a lot of positive things.  I also learned from his mistakes.  He is a perfectionist by nature and so am I to a lesser degree.  I have been able to control my perfectionist tendancies to what some say is reasonable.  This duct is not as good as I would like it to be.  I would have liked to have it perfectly round and sculpted so you couldn't visibly tell where the duct ends and the foam begins.  This would have however taken me quite a few nights of filling and sanding and shaping and for what?  I would have ended up putting extra weight on the craft and spent needless time perfecting a view that no one would ever see.  This is after all the bottom of the craft.  I will save my perfection for the cockpit/topside.

Wed Jul 18, 2001

Thu Jul 19, 2001

I am still not totally recovered from my illness.  I did go to work today so I thought I better do some work on the Hovercraft.  Probably not a good idea in retrospect as I am really beat now.

Pictured top right - I attached the landing skids.  I epoxied the ply base where the skids would sit and the bottom of the landing skid. I used a small syringe to shoot epoxy into the holes in the base as well as the skids.  I pushed the 1/4" dowels into place and tapped them flush with the top of the skids with a rubber mallet. I used 2 1/2" screws about 6 per skid to hold the skid to the base.  When the epoxy is cured I will remove the screws and drill the holes out to 1/4" and epoxy dowels in place.

Pictured 2nd right - I used some epoxy and micro balloons mixed to the consistency of ketchup to run down the outer edge.  A little added strength to help reinforce the bend

Pictured 3rd right - Here is where the skids meet at the front of the craft. I used a 1.5" screw to hold the point together.  I spread a fair amount of the epoxy and microballoons in this area to help reinforce the joint.

The 1/4" dowels worked really well to hold the skids in place.  I don't know how I would have done it any other way.  These skids are never coming off.

On a lighter note one of my  friends, another geek like myself, made fun of the simplistic design of my website.  Those of you in the industry realize it was quickly thrown together.  I told my friend Steve, who will remain nameless, that I built it with the intention of eventually replacing it with something spectacular.  Like most solutions of this nature eventually never comes.  So if this site gets too hard on the eyes you'll have to let me know and I will consider a rebuild.

Fri Jul 20, 2001

Sun Jul 22, 2001

Ok I think I am on the road to recovery.... I haven't been this sick since I was a teenager. 

I had a nice chat with Mike Jacobson tonight.  He was very helpful and infomative.  I really do appreciate all the help I have received from the people in the Hovercraft community on the net.  If I just had the 3 plan sheets and construction book I would be making a lot of mistakes.

Anyhow I think I will finally be able to make some progress this week.  I am just about finished the bottom of the craft.  I will attach the air splitters to the skids and find some material to attach to the bottom of the skids.  Then I need to fiberglass the outer attach strips as per plans.

I will also start the thrust duct.  Should go smoothly as I have the duct formers already complete.  Stay tuned... I was down but not out. 

Tue Jul 24, 2001

Very rainy here today. I can't get my craft turned over. I really can't work on anything else with the rain as the garage has junk in it that I usually put on the driveway when I start working. I bought my gas tank (6 gallon plastic boat type) and some fuel line today. I found a really good source for light weight and inexpenisve boat seats at the local Canadian Tire store.   I found a few that would look good. 

Sat Jul 28, 2001

7 hours

Pictured top right - Today I decided to install the lift fan mounts.  Here is my first cut.

Pictured 2nd right -I used a dremel with a router like cutting attachment and cutting bit.

Pictured 3rd right - Here is the first hole cut.  I did the back freehand.  They turned out pretty sloppy but workable.  It will all be covered with fiberglass anyway.

Pictured 4th right - trial fitting the lift fan after cutting the two aft mount holes.

Pictured 5th right - I decided to mount the front of the mounts recessed 1/4" into the duct wall.  I used the dremel and this level to run the dremel beside to obtain a straight cut.

Pictured 6th right - The right mount is in and the left mount is about to be placed.

Pictured 7th right - The mounts are in place.

Pictured 8th right -Here is how the fan will sit in the lift duct.  I discovered my duct is not perfectly round.  It is definately within tolerances though.  I may be able form it when I pour the foam around the outside.

Sat Jul 28, 2001

Cont..

Pictured top right - Here is how I clamped the mounts.  I was in 1/16 th of an inch just by eye balling it!

Pictured 2nd right - a closer view of the clamping of the mounts.

Pictured 3rd right.  I placed the lift fan in the duct.  Rotates without touching the duct wall.  Typical clearance is 1/8".  Once I fiberglass the fan clearance will be a little tighter.  All in all I am quite happy with my duct now.   I spun the fan as fast as I could by hand and I could feel the air flow underneath...   

I can't find the bolts I need to secure the pillow block bearings in my UH shipment so I guess its off to Canadian Tire... again...

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