The blades were to made of a material called 'Hyfill', a sort of honeycomb.
Lighter and stronger was the hope, as it turned out, they were anything but stronger, bird strike tests had bad results.
Leading to more conventional fan blades, with all the re-designs, weight issues leading to delays.
There were other delays, on this the first R/R big high-bypass fan, until the mid 70's the L-1011 was the only application too, ending when BA
.211 747-236 aircraft.
In the mid 60's R/R were going to develop the larger RB
.207, (applications were the embryonic A300 and it's rear mounted engined UK rival, the BAC 3-11, plus later 747 versions).
At the lower (around 30,000lb) end of the scale, the RB
.178, (applications included HS
-178, very similar to the 757, in 1967! With a Trident style forward fuselage, and possibly the Vickers Superb, basically a double deck VC
-10, up to 284 pax).
.178 originally was a much improved R/R Conway, rather like how the original JT8 was improved to the -200 engine as fitted to MD
-80, but the project grew into a high bypass fan.
With no Vickers Superb, BEA unsure on future Trident developments, leading to the HS
-178, the RB
.178 stayed a technology demonstrator only.
The emergence of the L-1011, requiring an engine easier to develop than the large RB
.207, led to the middle path of the RB
.211 being pursued (this in part led to the original UK exit from Airbus, for 10 years from 1968), the final blow was the government axing the BAC 3-11.
But R/R's hopes of a easier entry to the civil big fan market were not at first realized with the RB
.211, in time of course it became a good engine, but delays and R/R bankruptcy delayed higher powered version for some years, which put the L-1011 at a serious disadvantage compared to the DC-10, whose higher powered CF-6 engines enabled longer ranged (-30) DC-10's to be offered much sooner than a similar improved Tristar.
Going back to the mid 60's, one reason R/R spent a lot of money (with could have made developing those other big fans mentioned above, quicker and easier), into buying out Bristol Siddeley, was because BS
were to be the UK part of a European consortium, to license produce PW
JT9D engines for the 747's on order by some European carriers, Snecma in France being another, so presumably BOAC and AF
747's would be included in this, at least.
R/R, already struggling to develop big fan engines, probably were alarmed at BS
assembled JT9's being called 'British Engines' and maybe knocking R/R out of the emerging big fan market.
So R/R brought out their major UK rival, ending any BS
assembled JT9Ds, in fairness, R/R at the time did need to expand their portfolio of products, BS
got them on to Concorde, Harrier to name two high profile projects, as well as plenty of others, not just in the aero engine range.
In the end, only PW
built JT9Ds, which in fairness to R/R, had more than their share of problems early on, these were all very new technology engines after all.