Lift Duct

In order to cut the templates for the lift duct, I welded a quick guide using some scrap metal that was sitting around.
This shows how I removed the glide plate from the router, inserted the metal guide that I had made and then used washers and some longer connection screws to attach the glide plate back on. This setup is somewhat fragile but worked good.

In this picture you can see the two disks that were cut using the guide and router pictured above. These disks have the exact same dimensions and were attached together using some scrap 2X6 ends I have cut two pieces of 1/8 plywood to wrap around this disk. The ply is 4 feet long and the two pieces are attached together with 6oz fiberglass.

This picture shows the two pieces joined with the 6 oz tape. Then the entire section is placed on the duct former and pulled tight with two ratchet tie downs

A piece of 6 oz tape was placed under the ratchets before they were tightened. The duct comes up flush under this fiber glass but naturally spreads out where the ratchet straps are not holding. I will be fiber glassing only between these straps, then I will move the duct former and straps closer to the edge of the duct.
I suspended the entire duct so that I may rotate the duct as I fiberglass
I put masking tape over the ratchet straps. I will not be fiber glassing them down.
If you look closely her you will see the fiberglass tape between the two ratchet straps, also the original fiber glassing to join the two pieces of plywood to form the duct.
This is the top of the Hull. The position of the duct was measured out. Then the skin was cut using the router jig that was used for the disk formers.
The skin was pried away to expose the foam of the Hull. The cut will be completed after the angle of the duct is determined, 15-20 degrees dependant on the engine. My plan is to draw out the exit hole on the bottom of the craft and use a cut away saw to remove the material that is needed.


Here we have made a 20 degree jig and have drilled a guide hole through the hull
Here we have flipped the craft over and have double checked our measurements on the bottom
Now we use the piece of the skin that was removed from the top to create a guide line for cutting
This shows the guide line
We have joined the two lines and now must ellipse the hole so that the duct will slide in. Had to think here a little bit, almost cut the hole the wrong way. You will eat more product at top/nose and bottom/stern,while keeping the duct centered.

The lift duct was slid into position, approx. 13 inch to top of center of duct. The foam I add will bring it up to the 15 inch outlined in the plans
The duct is centered and leveled
The duct fit in very tight, space was from 0 to 1/4 inch, I would cut away more material next time so that the foam is easier to pour in
This is the bottom and the foam that was poured into the gaps. This stuff seems to grow forever. Looks like I put a little (allot) to much in the crack.
This shows the top side
It is time to sculpt the lift duct. The duct is placed in at 20 degrees, the taper at the bottom stern of the craft goes to 60 degrees.
I cut a piece of wood at 30 degrees and using a long drill bit, cut a pilot hole. I will remove foam until I reach this hole.
This picture shows the portion of the duct that was cut away. If you look careful you will see a line (by the golf ball on the file) that depicts were the top of the hull is. Approx. 1 inch

This picture shows the guide lines I drew for foam removal, these were made from the center hole.
The foam is removed and sculpted
another view
Shows the taper
I placed the the skid plates in place. The gap to inflate the bag is 1 3/4 inch at its widest point, I do not know if I should taper this out. to allow more are in the bag. If anyone knows what to do here I could use the help.
I removed all the foam from the top of the craft, I will be glassing this.
I used epoxy and ground fiberglass to create a mixture the consistency of peanut butter. I then created a filet around the duct.
I am now putting fiberglass around the bottom of the lift duct. I am probably covering more area than I should, but my thinking is that the front of the craft will take the most punishment.
Just a different view. You will notice that I put tape around the inside of the duct so that I can use a knife to make a clean edge after it sets.
This is what it looks like after you epoxy. The epoxy makes the fiber glass clear, just a little shiny
Well a lot of work has been done to the craft before I could add more pictures to this section. What you see here is the top of the lift duct. I have cut 3 inch wide foam spacers and glued them to the sides of the ducts. I still have to put the engine mounts in, but once this is done I have plans of wrapping these spacers with plastic and filling the voids with spray foam. This will allow me to form the mouth of the duct.
Another picture of the spacers.
I have been putting the rest of the lift duct pictures into the cockpit section of the web site.
This is a picture of the lift engine and prop in place. I needed to install these components to position the air splitter correctly.
This is a close up of the air splitter, I put a piece of 1/2 dowel on the top edge so that it may wear better. This will be the edge closest to the lift fan.
This is looking up from the bottom of the craft. The splitters are positioned on the inner skirt attach strip and lead up to the lift fan. You want to position them as close to the lift fan as possible
This is a picture of the tip clearance. I measured the clearance and it is 3/4 inches at the end of the splitters and reduces down to 1/2 inch in the center.
This is a top view showing the tip clearance of the lift fan, it is 1/8 inch
A view from above showing the air splitter in position.
This is the air splitter after it has been sealed with epoxy, I had to use some 60z tape on one side because the gap was just too great.