Fans, Props

I will be making a 54 inch prop with a 50 degree pitch, as per the 54-50 plans from UH. The material is Pine 1X 6 that I got at a local lumber yard, managed to get some with a good grain and little to no knots. The first step was to look through the stock lumber and set up the cuts so that the imperfections will be cut away. Here I have just indicated the leading, trailing edge and the rotation of the prop.
I then cut all lumber to length, I added a extra inch to all measurements just to be sure. 3 at 55 inch, 1 at 41 inch, 1 at 31 inch.
I applied a generous amount of epoxy to all surfaces. I used a line that I had drawn earlier to line the boards up. I will wrap this in plastic as to not glue my clamps to the prop.
Do you think I used enough clamps. I did not use threaded rod for the clamps but rather carriage bolts

This is a picture of the epoxy that was squeezed out with the clamps, I used a belt sander to take this down. I guess I could have used less epoxy, but I wanted to be sure of a good wood blank.
I determined the center of the prop, this is what all measurements will be taken from.


This picture shows the first line, This is the top flat area 1 3/4 root, 1 1/4 tip. You will also notice a compass line around the center for the hub and a arrow to depict rotation.
This line shows the front leading edge, I think it is 3/4 root, 5/8 tip.
This is the final line, this is the trailing edge and is drawn with the UH prop plans.

I do not have a ban saw so I used a reciprocating saw to connect the trailing edge to the leading edges. The cuts are 1/2 inch apart and get close to the line. I will Finnish the cut with a hand saw.
Now the fun part, remove all that wood that is not needed. I used a chain saw to remove the bulk of the wood.
Then I used a chisel to get closer to the line.
This picture shows the contour of the blade after I used a belt sander to get close to the line. This is a simple process of slowly removing wood until the grooves from the lines I cut disappear.
I used a chain saw to remove the wood to blend the blade into the center hub.

This is what the prop looks like after it has been roughed in. I will clean up the leading edge and trailing edge with a orbital sander later.
I will be making a UH 26inch 20degree lift fan. The first step is to cut all pieces to length. I made all cuts so that the blank will be about 27 inch in diameter. Here I have laid out the first layer, there will be 3. The wood used is clear pine 1X6. Make sure that any imperfections are positioned to be cut away.
This is a close up of the second layer after it has been positioned and glued. You will notice that I used a couple of staples to hold the boards in position. If you do not do this the layers may float around during clamping. I also put one staple at the tip of the Fan blades.
This is the Fan after it has been clamped. I have wrapped each of the blades in vapor barrier so that the epoxy does not stick to the clamps.
I have marked the center with a X and drilled a pilot hole. I then used a compass to draw the end of the fan at 13 inch, and the end were the plywood caps will go at 5.5 inch. This will be the root of the wing. The measurement for the Top Flat is 1 3/4 root and 1 5/8 tip.
This picture shows the leading edge 9/16 at root and 7/16 at tip.
This picture shows the trailing edge which was drawn from the UH plan template
Now I made multiple cuts to connect the lines that I had just drawn.
I used a chisel to remove the excess wood. I then used a belt sander to take the wood down to the line.
Here I have finished 2 blades of the fan.
This picture shows the airfoil shape that was created on the blades.
The fan is capped with a 11 inch disk. I cut this with a router so that it is a true circle.
This is the fan just before I use epoxy to put the first disk on. If you look closely you will see a drill bit in the disk. I will be using this to center disk on fan.
This is a roller chain sprocket. If memory serves it is a browning H33/45. I will use this along with a S bushing to mount the lift fan to the 1 inch drive shaft of the Briggs engine.
In order to mount the sprocket to the fan I will need to drill 4 mounting holes and tap and die them. This is a guide I put together with a piece of paper and a compass. The holes are drilled on a 3 7/8 circle.
You can not see the sprocket under the die here, but I simply used a punch to mark the sprocket, then cut the holes, then used a tap and die to thread a 3/8 hole.
This is a picture of the sprocket on the fan,the bolts that I used here are too short. I will want to use longer bolts for final assembly and thread about a inch of the bolt through the sprocket then put a lock nut the end just to make sure nothing shakes loose. The S bushing is then compressed into the sprocket. The bushing is split, when compressed it tightens onto the shaft.
The picture shows the other side of the fan. Use the same template that you used on the sprocket to cut the holes into the fan. I found that when I matched the fan to the sprocket, the holes would only match up one way, this tells me that the holes are not exactly in position and may cause some balance problems.
other side.
Now we need to balance the fan. There are two ways to do this, I used both. The first is to use 2 level rails and a 1 inch steel shaft. Make sure you have all the hardware on the fan when you balance. The fan will rotate until the heavy section goes to the bottom. The goal is to be able to set the fan in any position and not have it rotate. When I did my fan I found that the heavy section was between two blades. I checked the blades and decided that too much material would need to be removed by sanding to balance the fan. I decided to use lead weights on the hub to balance but I did not know where to place them.
This is the second way to balance a fan. It is a different version of the gravity balance. What you see here is a string attached to a eye hook that is on a 1 inch wooded shaft. The S bushing is on the shaft.
This is the fan on the balance. You can also see a level bulls eye and 3 things that look like bullets, they are not. They are some lead fishing weights that I placed on the fan to balance it.
I moved the bulls eye to different areas of the hub and checked for balance. I found through trial and error that if I placed the weights were you see them the fan is in fairly good balance. I will drill holes into the hub in these positions and epoxy them into place.
This is a picture of the mold for the fishing weights.

This picture shows me applying a layer of 6oz cloth to one of the blades of the lift fan.

mailto:bruce.einarson@mts.net