chuckitt@earthlink.net wrote:What Prop Blades are those and what is the diameter.
Thanks, Chuck
Saturday April 11, 2015
Lake Wales, Florida
Chuck:
Direct answers first; the blades (six of them) are cast short Falcon models. The diameters of the discs using short three blade hubs with the short blades are 60 inches each. There was a big discussion as to whether to use short Falcons, Power Plus or Signature Blades. Plum and Andrew wanted wider blades so we settled on the Falcon model. After first runs on dry ground and now on water, it looks like the Signature series would have been the better choice. Perhaps we can get a new set of short Signatures soon for later tests. The reason is that the engine (a SBC ZZ 383, in fact the actual one from the original Concept Boat.) is topping out against the pitch load at just 4000 RPM +/- due to the thick airfoil and wide tip areas of the six blades.
The belt ratio is 1.6 /1 so at the current 4000 RPM we were seeing just 2500 RPM on these short blades. The system is designed for 3200 propeller RPM with the engine at about 5200 RPM. There is a dedicated new propeller design of my newest designs ‘in the can’ for the Dual Sync Waterline Drive that we have dubbed ‘The Talon’ blade. It has the proper pitch distribution, tip thinness and over all width to create a minimum of drag at 3200 RPM. (So far, it has not been worth the added costs of a dual set of new molds, left and right, until the rest of the boat features have been proven.) A sixty inch disc diameter at 3200 RPM yields 571 miles per hour of tip speed. For comparison a 78 inch Falcon disc at 2500 RPM yields 580 MPH tip speed.
Crateengines.com shows an HP & torque graph for the newest (450 HP @5200 RPM) ZZ-383. At 4000 RPM that engine would be developing bout 325 HP. Using our several year old ZZ-383 (originally 425 HP @ 5200 RPM) we are likely only developing about 300 HP. So currently at 3800 RPM and less moving on dry sand and grass ground we are moving this large work boat with only about 300 or less HP using the Dual Sync Drive.
Yesterday, after some tweaking in the morning, Plum and I set out looking for some water. We went east out Road 60 from Lake Wales and got some 93 octane gas at the Sunoco Station but they didn’t sell diesel for the dually. So we continued on out to the Citgo station just west of River Ranch. We decided then to go for ‘Thomas Landing’ on the west side of Lake Kissimmee and put in at their ramp. The boat floated OK (see picture). Note how heavy Plum is as he weighs down the dock while holding onto the boat. He encouraged me to go along as safety pilot and I weigh as much or more than he does. We estimate this large utility airboat (8.5‘wide X 20’ long with full ½ inch polymer bottom) with us, weighed gross at about 2800 lbs. or nearly one and a half tons. Plum with his great courage would be the ‘Test Pilot’.
We shoved off and idled out from the dock and headed north along the weeds and shoreline. The boat came up on plane easily and we held a steady planning speed that Plum estimated about 30 to 35 MPH. The engine tachometer showed 2300 to 2400 RPM at this steady cruise range. Props were (1.6:1) at about 1500 RPM. Plum commented that these were “aircraft type numbers”. Yes the noise was such that we could talk to each other with no ear muffs. The Transom was laying out flat with the airflow from the props and we were cruising along.
Plum saw an airboat trail running toward the shoreline and took it, slowing a bit as the water thinned out and soon we were on a nearly dry trail along the receded shoreline with some wet areas here and there. Our wide boat was running the dry edges of the trail and Plum kept her going with RPMs up to about 3500 for a quarter mile or so until we found an opening to lake water again. As we found open water, I told Plum that “we are getting a long way from the truck” so he turned back towards the dock. Running along the outer edges of the grass and reeds he began to throttle up for a speed check. I was looking at the tach which was beginning to pass 3800 RPM when the un-mistakable loud band and sound of metal going through the props happened. Plum later guessed we were going about 45 MPH.
With his ‘nerves of steel’, Plum reduced the throttle to a steady planning speed and headed back to the dock about half a mile away. We cruised on in and as he came to the dock open water area he throttled down carefully watching behind him as the variable geometry Transom rose to the up position with the boat settling into displacement of the water. It worked as it was designed to do.
Shut down alongside the dock, we found that two of the propeller blades leading edges had sustained major strikes and some damage. We discussed running some more anyway to get some pictures but decided against doing so until we determined what had gone through the port side prop. I backed the trailer into the water at the ramp and Plum drove the boat up onto it. I hooked up the winch and with a little help from Plum and the engine nosed the boat on up to the stop and secured it. Plum stayed in the seat as I pulled on up the ramp to level ground. As he rode up the ramp he saw laying by his left ‘go ahead’, the piece that had hit the prop and had it in his hand as I got out of the truck to help secure the boat.
It was a piece of the top support bracket that holds the radiator in place. There are two such brackets and this one had only been ‘lightly tack welded’ and not finished welded as the units were built. We then looked and the other one was also only tack welded, but a little more firmly. Our decision to not run some more for pictures was a good one. We may have lost the radiator through both props if we had. It’s an easy fix on the boat and repair or re-casting of two blades to have us in the water again.
First impressions are that we are so far pleased with the numbers and will be continuing the testing program as time permits.
David Wine
Water Walker Props, Inc.
Figured since I had a little break at lunch that I'd upload a few teasers of the boat during a some testing and tuning. I'm hoping I'll be able to pull out early enough to see her hit the water this afternoon. Dont forget to get all of the lunch sacks out of the hull before running it this time guys!!!! 
That is very impressive, indeed. 
