Author Topic: 18 foot laminated blades  (Read 1130 times)

0 Members and 1 Guest are viewing this topic.

harrie

  • Sr. Member
  • ****
  • Posts: 365
18 foot laminated blades
« on: March 13, 2006, 06:56:02 PM »


The wood for these blades is tammerack, that grows in high moisture low areas along with our local Mn. cedar. It has a natural rot resistance like cedar, it is however alot heaver than cedar, and is more ridged.The mostly clear strips are 1-1/2"wide by 2" deep.The wedge shape piece was cut off the back side of each blade using a lumber cutting band saw. for sawing, the blades were fastened to a taper jig that sat on the bed of the saw to get the desired taper. 7/8" was left on the tip, and was sawed to nothing at the root.

the degree of slop on the front, was done with a skillsaw, with two strips of wood that was clamped to both leading and trailing edges. the leading edge strip was 1-1/2" deep the full length of the blade. The trailing edge strip was cut to a taper from one end to the other to get the desired pitch. The saw is on a flat guide, that sits on top of the strips, and is used to make continuous cuts, which also cuts thru the strips on both sides as you go. As you can see, I have the guard on the saw tied back, which is not safe, and is not reccomended. Fanman, has posted kind of the same thing, using a router, which would be alot safer, and result in the same thing. I would have done that also, but did not have a long bit.  

The blades after saw cutting, back one has been sanded, middle has had scrape between cuts knocked off with hammer, and front shows all the cuts.

Shows how alot of matl. was cut off back side of leading edge using a 10" table saw.

shows all three blades with one scrap piece of the back side of leading edge.

This is the tool that I use for doing the radius at the root. It cuts very fast,and is a flap sander sold at most hardware stores and will fit on 4 " angle grinders. I am very happy with the way they turned out, and will post the finished product with the construction of my new 16" duel rotor.


Great fun Harrie

« Last Edit: March 13, 2006, 06:56:02 PM by (unknown) »

Shadow

  • Sr. Member
  • ****
  • Posts: 473
Re: 18 foot laminated blades
« Reply #1 on: March 13, 2006, 02:34:44 PM »
Very nice!, I also used a flap sander at the root on my blades.It also works very nice for lowering knots.How long would you estimate it would take you to do a set of finished blades start to finish, using this method?
« Last Edit: March 13, 2006, 02:34:44 PM by Shadow »

harrie

  • Sr. Member
  • ****
  • Posts: 365
Re: 18 foot laminated blades
« Reply #2 on: March 13, 2006, 03:46:41 PM »
Hi Shadow, gosh, I guess it depends on how fussy you are, I being a carpenter by trade, and cabnet maker, im pretty fussy. it probley took me about 3 full days including the time to finish them. I was going to fiberglass them, but decided against it and used abut 4 coats of a rawhide product that they sell at home depot, 30 bucks a gallon. this is a clear coat, and is UV. resistant. it is also used on log homes and is a old proven product.
« Last Edit: March 13, 2006, 03:46:41 PM by harrie »

BigBreaker

  • Sr. Member
  • ****
  • Posts: 302
Re: 18 foot laminated blades
« Reply #3 on: March 14, 2006, 07:35:28 AM »
I wouldn't glass any wood blade unless it is to help with blade erosion.  Wood is a natural composite with strength that comes from a certain amount of flexibility.  That flexibility distributes forces through the structure to avoid focused stress.


Resin cured fiberglass is not flexible (in tension - its only real operative mode) and will either hold stiff across its backing structure (often foam) or break - catastrophically.  Wrapping wood with fiberglass with either make the wood redundant, because the fiberglass takes the load, or it will make the fiberglass useless because it fails while the wood beneath flexs with the load.


Even worse, the glass will break across a line of high load and the remaining glass will function to take the flexibility out of the wood away from that load line.  Now you have ruined the best thing about the wood - flexibility in the material distributing the load.

« Last Edit: March 14, 2006, 07:35:28 AM by BigBreaker »

picmacmillan

  • Hero Member
  • *****
  • Posts: 523
Re: 18 foot laminated blades
« Reply #4 on: March 14, 2006, 04:51:50 PM »
   below is an old article i had saved about blade design on props...might be some good reading if anyone is interested..if nothing else, it shows what a hard days work is about, and what true craftmanship looks like imho..pickster


http://www.woodenpropeller.com/Basic_Propeller_Construction-_Techniques.html

« Last Edit: March 14, 2006, 04:51:50 PM by picmacmillan »

picmacmillan

  • Hero Member
  • *****
  • Posts: 523
Re: 18 foot laminated blades
« Reply #5 on: March 14, 2006, 04:54:10 PM »
if link doesnt work go to www.woodenpropellor.com   pickster
« Last Edit: March 14, 2006, 04:54:10 PM by picmacmillan »