Strut depth

[Foolwitools]

Hi Guys!

Sorry to have to ask this guestion again, but beeing that I have a brain that is 1/2 concrete ( hard as a rock and nothing soaks in ) and 1/2 mush ( I have to put up with my wife an two adult daughters ), I don't exactly remember ........

I have a 44" round nose.............. I want to install a thru-the-bottom adjustable strut for the new flex drive shaft.

If I 'member correctly, I want the center of the adjustment to be as deep as the bottom of the sponsons.

My sponsons are about 1 3/4" deeper than the flat portion of the hull. So I want the prop centerline to be about the same distance from the bottom of the hull at the transom..... Right??

Then, where do I want the prop (as to fore and aft ) in relation to the transom? Should the prop extend beyond the transom or be well in front of it??

The important facts:

Late 70's Glass 44" Pinkert "Thunderboat"............ Running a mild K&B .82 with an AB "84 Muffled" pipe.........using a 1/4' teflon lined flexable stuffing tube and flex shaft with welded 1/4" propshaft......to an octura long alum streamline strut with lead/teflon bearings........ turning an octura 1460, 1462,1465, or 1470 prop......and a Speedmaster 6" wedge rudder.

I just want to end up with a dependable pleasure boat, but I want it to be legal.

Comments, suggestions, directions all welcome. Tis time I'll print the responces so I won't have to ask these questions again!!

Thanks, Bob the Fool :blink:

 

[missbudpilot55]

OK Bob let's see where do I start, as most of the old round bow boats designed had a bottom that arched up slightly at the nose 5 to 7 degrees, I set all of my round nose hulls up with the bottom of the rear section of the hull parallel with the surface of a table, meaning if the "break" in the bottom is at or slightly forward of the rear of the sponsons, measure from the height of the tunnel bottom at the rear of the sponsons and the transon edge should be the same height off the table. I usually put about 2 to 3 degrees of down thrust in the strut as well. Leave enough adjustablity in the strut to go down about 1/4" and up about 1/4", this way with strut adjustablity you can control the amount of air getting under the hull, to much and blow over, to little and the sponsons will ride too wet. The strut can be positioned so that the rear most part of the drive-dog does not protrude past the transom, to be leagal in IMPBA (not sure about NAMBA), if done in that fashion the prop will stick out past the transom. I prefer it that way as it gives a good rooster tail and lets the prop unload quicker. I have in the past put the prop under the hull and found that if you have to slow down to much to make a start, the boats is off plane and usually stalls or the prop cavitates and you miss the start. The older round bow unlimiteds channel a lot more air under the hull that the pickle forks, turbine & pre-turbine models, some of our for-fathers in full size racing built under the hull spoilers to limit the air flow, ie Chrysler Crew, Thriftway-Too, Hawaii Kai, just to name a few, but unfortunately a lot of 1/8th scale modellers leave them off of the boat, because the hull bottom is not judged in static display.... less to replicate & detail I guess.

Hope this starts you in the right direction, good luck Bob, enjoy your scale...............

 

[Foolwitools]

Thanks a bunch, Bill

Just what I needed to know.......

now how about center of gravity............ and why are the fuel tanks so far forward? The tanks in this hull are way up under the deck in front of the engine bay.

Tanks....er, Thanks!!

Bob the Fool :blink:

 

[missbudpilot55]

Thanks a bunch, Bill

Just what I needed to know.......

now how about center of gravity............ and why are the fuel tanks so far forward? The tanks in this hull are way up under the deck in front of the engine bay.

Tanks....er, Thanks!!

Bob the Fool :blink:

Bob, I put my fuel tanks in the sponsons if you can get them there, with the back of the tank as close to the sponson bulkhead as possible, that way once you get the boat in the right riding mode as the fuel is exhausted, it will not affect the balance much at all. If you can't get them in the sponson, under the deck in the same region of the hull as the rear of the sponson is good. I am going to get Walt Barney to build my next set of tanks for the Chrysler Crew I am building, and they will be under the deck not in the sponson, a lot easier to service them if necessary, especially on a wooden hull.

Any other tips just ask my freind............. B)

 

[Don Ferrette]

Late 70's Glass 44" Pinkert "Thunderboat"............ Running a mild K&B .82 with an AB "84 Muffled" pipe.........using a 1/4' teflon lined flexable stuffing tube and flex shaft with welded 1/4" propshaft......to an octura long alum streamline strut with lead/teflon bearings........ turning an octura 1460, 1462,1465, or 1470 prop......and a Speedmaster 6" wedge rudder.

I just want to end up with a dependable pleasure boat, but I want it to be legal.

Hey Bob if you want to be legal for 1/8th scale class racing you need to drop a .67 in. B)

 

[missbudpilot55]

Late 70's Glass 44" Pinkert "Thunderboat"............ Running a mild K&B .82 with an AB "84 Muffled" pipe.........using a 1/4' teflon lined flexable stuffing tube and flex shaft with welded 1/4" propshaft......to an octura long alum streamline strut with lead/teflon bearings........ turning an octura 1460, 1462,1465, or 1470 prop......and a Speedmaster 6" wedge rudder.

I just want to end up with a dependable pleasure boat, but I want it to be legal.

Hey Bob if you want to be legal for 1/8th scale class racing you need to drop a .67 in. B)

"Oh no", I sure missed the motor on that one, thanks, old buddy....

 

[Mike Hughes]

Like Don said. The only class that would be legal for is Sport X. There is a namba class for it, but it usually only runs at nats. It can run in the large engine hydro classes but will be out class.

Mike

 

[Foolwitools]

Thanks you guys!!!

I'm only using an .82 because I have a new one sitting on the shelf. Yes, I know that .67 is what I want to be race legal.

I figure the hardware setup is the same.............. So if I ever want to go to an IMPBA event, I just have to find a .67 and a few smaller props.

Thanks again !!!

Bob the Fool :blink:

 

[Dasboatman]

Hi Bob, I thought I would post a pic of the hull so everyone knew what you were talking about. The hull was never intended to be a Scale boat. We ran a whole bunch of them in Miami in the 70's, mostly with OPS 60s without tuned pipes, that were converted for marine use with Octura Kool Klamps, 45 size Octura flywheels, solid shafts running in ball bearings, throwing Octura 1465 props. Probably the most fun I've ever had in boat racing because the boats were equally capable, and plenty of assistance was available, mostly from Don Pinckert, to get a new boater running competatively. CHEERS !!! Bob