Barry_DVRC

So my Diamond Dust is on the bench being built. Took a break to come and write this. I've two possible engines that can go in it. Webra Speed .28 or Webra Speed .40 both with pipes.

1. If I install the .28 will I be dissapointed with the final speed. I want 150mph+. I guess std servos will be OK?
2. If I use the .40 are there any mods required? Beef up engine mount, or servos?
3. What prop should I tune the pipe for?

Thanks

Barry

huey-pilot

My Feedback: (17)

Use the .40, but you still won't get 150 mph and probably be lucky to get 100 mph. My first Diamond Dust had a Webra 40, the engine lost it's compression with less than 10 flights probably due to the high rpm, then I installed a Nova Rossi turbo .21 rear exhaust with a tuned pipe and the speed increased by about 40%. On my second Diamond Dust I installed a K&B 6.5 rear exhaust with a tuned pipe for initial trim flights then I removed it and installed a Jett FIRE .60LX. I believe that the only engines that resulted in more that 100 mph are the Nova Rossi and the Jett. You need to get a lot of rpm on the ground to get decent speed. My Nova Rossi turns 28,400 on the ground with a cut down APC 7x8 propeller and the Jett .60 turns a stock APC 8.8x9 propeller at 19,600, both of these combinations are very fast. Be careful with this kind of rpm, I had a propeller failure with the Nova Rossi, the only damage was the throttle servo, but could have caused a serious injury if it had occurred on the ground with some one standing in the wrong area. If this is your first Diamond Dust you will probably like the Webra .40 and its easy to install a different engine later if you want more speed.

huey-pilot

My Feedback: (17)

I guess I didn't answer all of your questions, the engine mount is fine, just build it as shown in the plans. Standard servos will work with the Webra engine but I am using the recommended JR 4735 with the Jett FIRE .60LX and Futaba coreless servos in the Nova Rossi airplane, my initial flights with my first DD were with Futaba 3004's and a Hitec HS 81 on the throttle. Throttle servos don't last very long even using a nylon clevis and pushrod. I just installed a Futaba 3101 on one of the planes but I haven't had a chance to test fly the plane. For a propeller try an APC pylon prop with 8 inches of pitch and a diameter that will give you as much rpm as you think your engine can handle, you might try an APC 8x8 and then cut it down if necessary to improve the rpm.

Mike Connor

My Feedback: (5)

huey-pilot has some good advice except my prop experience is a little different. As SloMo's Delta thread suggest, I had better luck with a 9" prop over the 8.75" pylon prop. My only radar speed was 135 mph turning a static 16,000 rpm and APC 9x8. Using video and time I well exceded 150 mph with a Sport Jett 50 turning a 9x8 at 18,000+ statcic. Mine is a little cleaner then most DD's I see with a covered fuel tank and limited exposed linkage.

I used standard servos (JR 517) on my first Dust with out any problems but noticed a big difference on my second one with lighter and stronger servos (Hitec 225 BB). It will be nose heavy with a 40 engine and it flies best with the CG at the rear of the recommended range. I cut the engine mount out to the rear some and it still took 2 oz of lead in the tail. I was happy with the with the final weight of 2 lb 12 oz mt. Good luck, the Dust is a blast to fly.

pdxpaul

My Feedback: (1)

1. You will be disappointed with the .28 if you want 150 mph. To get 150, it will take a Jett or similar high performance or racing motor. Standard servos are fine with either of your motors. If going for 150, I would use stronger servos.
2. No mods are necessary for the 40.
3. I would tune for an APC 9x7. Readily available, and less expensive than the pylon props. You may break one every now and then landing. Hopefully, you can turn a 9x7 16k to 17k. I would expect 120 +/- mph.

There is a big difference between a 120 mph D-Dust and a 150 mph D-Dust, at least to me. The former is very fast recreational place. The latter is a missile.

Just my thoughts.

Paul

Barry_DVRC

Thanks for all the info guys. I think 120 is respectable for my first ddust. So looks like the 40 it is on a 9x7. I'll tune the pipe for the 9x7 and let you know what I get.

Barry

Cyclic Hardover

My Feedback: (3)

Very good thinking here. Although the average basic 40 on a plane is never very impressive, you will have your hands full with it on that DD. It s a good way of seeing how you like it without sinking alot of cash on it.

Barry_DVRC

Although I've flown RC for almost 30 years I suspect it will be a bit of a challenge. And I'm looking forward to it

Barry