Tunnel Hull Design

[aaron alberico]

Mark

Why is the 40x53 not enough prop for a nova?

Regards Aaron

 

[shoboat]

Aaron,

You guys can run whatever works for you, but we have found

that the Nova likes the X-442 B/C the longer blades throw

more water. There are quite a few Lynx owners that run them

and they all seem to like the set up. The ABC 42 x 55 works well

Also if you back cut it. We have started to work some other propellers

on the Lynx with some good results. The M-445 is showing some

promise cut down with a strong motor and pipe combination.

What have you guys been testing lately?

Keep Testing,

Mark Sholund

 

[aaron alberico]

Mark

Just asking as I run 40x53 on my nova o/b

And is very fast! I tried x442 mod same speed but did not handle as good.

Aaron

 

[shoboat]

Aaron,

What diameter were you testing on the X-442 B/C?

Some have found on their set ups that the boat will

transition better with a little less diameter on the 442.

The P-Spec electrics are giving us all new kinds of

propellers to try on our Nitro boats. The electric OB's

Like bigger propellers to take advantage of their power.

Just sharing some different ideas with you guys,

Mark Sholund

 

[Carl Van Houten]

Slideblues,

Always run the O/S or lower unit on the Lynx or a lower unit that has the same prop placement +/- 1/8".

-Carl,

 

[Slideblues]

Got cha

Thanks,

Gene

 

[RodneyPierce]

Carl, sent you a couple PM's if you get a chance.

 

[kesso2118]

James,

The Nova runs very well with a X-442 Lynx cut propeller.

The 40 x 53 is not enough propeller to take advantage of

the Novas powerband. Just our experience.

Keep Testing,

Mark Sholund

Mark,

Thanks for your suggestions, what are the details of the X442 Lynx Cut e.g. diameter, cut back, detongued??? Also, what do you suggest with the reduced X642?

The issue I am trying to resolve is understeer going into the turns at speed. At slower speeds around 40mph the boat turns well and can stay in Lane 1, however, with the stock Grimracer 40x53 the boat can easily do 50mph but will drift in the turn and the sponsons will not bite until about 3/4 of the way around the turn. This can be altered by entering the turn slower and applying power, however, I would like to be able to get the boat to bring the sponsons down earlier in the turn and be able to run tight on the bouys.

As I mentioned in my earlier post I was getting much better turning results at higher speeds with the mod X640 props. I guess my main question (and this is addressed to everyone not just Mark) is to understand what is causing the difference in the turning performance I am getting with the X640 compared to the GR 40x53, is it a difference in lift, if so, what is it, more lift or less lift?

Regards,

James

 

[Luca Gray]

Hi James

have you thought maybe it has got to do with boat design,

that you are having issue's turning!

also i think the x640 will have less lift

P.S guys great thread.

cheers Luca

 

[kesso2118]

Luca,

That's why I am following this thread, we are experimenting with hull design, however, the current version is very close. It is fast with fairly tame engines and is stable at speed and over choppy water.

When I use a stock ABC 40x53 or Grimracer 40x 53 the boat understeers but with a mod x640 or the GR40x52/3 it turns much better at the higher speeds, I am asking the question to try and understand the reason the props are performing differently????

Regards,

James

 

[Mike Larson]

James.... the 40/53 has the same trailing edge pitch/cup as the 640, at least per my guage... I hadnt blueprinted any farther on the 2 for comparison as of yet, but possibly and true to ABC to Octura course, the ABC most likely has more/steeper progression along the length.... ( I havent taken it that far as of yet).... experiment more with the back cut/barr cut and reduction, on either until they show up better.... ie: season to taste..... Mark's work around the 442 warrants notice, as I've good results around this also..... and... I almost always like to cup up a less aggressive starting blade, (442, 215, 1440,), than chew down and de cup a monster 640/40/53/642.... apologize accordingly, now, back to our regularly scheduled programming, i need a faster boat. Mike

 

[LarryConrad]

James.... the 40/53 has the same trailing edge pitch/cup as the 640, at least per my guage... I hadnt blueprinted any farther on the 2 for comparison as of yet, but possibly and true to ABC to Octura course, the ABC most likely has more/steeper progression along the length.... ( I havent taken it that far as of yet).... experiment more with the back cut/barr cut and reduction, on either until they show up better.... ie: season to taste..... Mark's work around the 442 warrants notice, as I've good results around this also..... and... I almost always like to cup up a less aggressive starting blade, (442, 215, 1440,), than chew down and de cup a monster 640/40/53/642.... apologize accordingly, now, back to our regularly scheduled programming, i need a faster boat. Mike

Yup, you sure do.

 

[RonShaw]

James.... the 40/53 has the same trailing edge pitch/cup as the 640, at least per my guage... I hadnt blueprinted any farther on the 2 for comparison as of yet, but possibly and true to ABC to Octura course, the ABC most likely has more/steeper progression along the length.... ( I havent taken it that far as of yet).... experiment more with the back cut/barr cut and reduction, on either until they show up better.... ie: season to taste..... Mark's work around the 442 warrants notice, as I've good results around this also..... and... I almost always like to cup up a less aggressive starting blade, (442, 215, 1440,), than chew down and de cup a monster 640/40/53/642.... apologize accordingly, now, back to our regularly scheduled programming, i need a faster boat. Mike

Mike,

I know where you can get a LeeCraft XTR-120........ Alfred Lanza!!!.......

 

[Kris Flynn]

OK, I have something for Rod or Carl.

I have a boat of my own design which has developed a tendancy to do a 'flat spin in the turns' and sometimes barrel roll. The Flat spin seems as though the rear end 'blows out' and the boat does a pivot on the front of the sponsons. Where is the first place to start with looking for a fix?

I have some ideas, 1 being obviously the 'rod blocks' and creating a section of less deadrise on the R/H sponson near the front (which I see now that Carl has something similar on the new warhead)

1 other thing I notice is that when it drops and hooks, it is usually just after I see some spray coming from the front of the tunnel section, so that must be dropping in and causing it to suck in also...

I have moved my Rod blocks forward about 3/4" and will try the boat again tonight...

Thanks

Kris

 

[David Kingston]

Kris - its just your driving mate.

 

[Bob Kensill]

Slideblues,

Always run the O/S or lower unit on the Lynx or a lower unit that has the same prop placement +/- 1/8".

-Carl,

I found the best speed and handling for my Lynx with a K&B 7.5 lower unit.

 

[Mark Poole ModVP]

Yep, I saw that engine/lynx run that day. Ran like it was on rails.

 

[Slideblues]

Hey Guy's

Thanks, Try'n to come up with a set of numbers for a sweet spot transom to drive dog,

Lynx for example,

Gene

 

[RodneyPierce]

Gene I can tell you that I'm at 6" to the prop hub face with my sniper 2 and thunder tiger. I was at 6.5 but that was too much and caused the boat to hook badly.

 

[Tim_Duggan]

Very much depends on the type of hull Gener. The sweet spot that is....