DQX wheel

[traditions]

Has any one tried a DQX Michigan wheel.I have alot of slip with my boat and was wondering if any one has one and how smooth it was.

 

[F/V First Team]

How much slip?

 

[badabing]

i just put one on my novi boat so it may be a tough comparison since i repowered and don't have anything to base it against but it is very smooth but i have a 2.88 to 1 gear and rarely turn up over 1400 rpms for my 8 or 9 knots oh and its a 36x31

 

[traditions]

I cant remember what Mark said the exact numbers were,but he said it was alot of slip.He didnt recomend the DQX because of the thin blades and having a cage.I need a new wheel anyways and thought I would try something different and maybe get rid of some rumble.I tried a 2 1/2 to 1 gear this spring and lost 2 knots at criuse so I went back to the 2 to 1.The slower turning wheel was smoother but when your top speed is 11 knots you cant afford to lose 2.

 

[Powderpro]

I've always used the bronze Michigan dyna-quad and have been real happy with their performance, but I've wondered the same thing about the DQX. I don't know if I would pick up some performance by going to the DQX? My last boat had 88.8% efficiency with the dyna-quad. 28" prop pitch, 1220 rpm shaft speed=100% efficient speed of 32.35 mph. Actual speed of boat was 28.75 mph. That's impressive efficiency, don't know if a DQX would improve those numbers??

 

[F/V First Team]

My good racing prop was 125%

I really miss that wheel

 

[BillD]

Has any one tried a DQX Michigan wheel.I have alot of slip with my boat and was wondering if any one has one and how smooth it was.

I know it's not apples to apples but I run Dyna Quads and DQXs on the Blackfin.

20X20.5s.

Ran the quads 2008,2009... are now the spares.
Put DQXs on in 2010.
Last season 2011, smacked a wodden block with the starboard DQX last Sept after hurricane, changed out to the Dynas for balance of season.

Put DQXs back on this season.

The boat is remarkably more responsive, smoother and the prop wash with a DQX blades @ 2600 rpm 1.53 gears is something to see.

I'll take the DQXs over any other 3 or 4 blade prop on my boat.

Not a comparison to a single screw keel boat, but,,,,

FWIW,

Bill D

 

[Nighthawk]

My good racing prop was 125%

I really miss that wheel

Negative slip is impossible. You will never get near 100% propeller efficiency no matter what the prop is. If you can get slip into single digit percentages life is good.

Propeller Calculator / Prop Calculator

 

[gmarine25]

Negative slip is only possible if you have a fair current.

 

[CEShawn]

I think I was able to pick up about .7kt going to the DQX from the regular dynaquad. Boat definitely seems sluggish when I go back. I am running a GM26 with 200HP Volvo. I think I have this in an excel file somewhere when I compared the two. I just used it to hit the same speed and burn less fuel. I am oversea's still and not sure I have that file with me...

 

[F/V First Team]

Negative slip IS possible when you cup the blades of the propeller and the tech running the computer when scanning it didn't realize what was going on.

It was hilarious the level of excitement going on in that shop when I picked the propeller back up. He was going to "radically change the industry" with what he had discovered.

 

[Nighthawk]

That would be a true miracle because it is impossible from an engineering standpoint. Cup can help a propeller get a better bite and thus reduce slip but it cannot get you to negative slip, ever.

A shop can't tell you anything about slip during tweaking, scanning or testing in the shop The only way to measure slip is on the boat and then run the numbers on a slip calculator or use old school math. If you get a negative number for slip, one of the inputs is wrong plain and simple. In many cases the true pitch of the propeller is unknown or the gear ratio entered is wrong. Many gears are called 2:1 when in fact they are 1.86:1 (example). The true and exact gear ratio must be inputted. And then there are marine tachometers which are notorious for being off. If you really want to be precise a handheld phototach must be used. Then there is the speed input which we all know can be less than accurate but lets say you have very accurate GPS speed as your input, did the boat get run both ways to account for current, wind and sea state?

If you get true slip numbers into single digits, be happy.

 

[Powderpro]

This is an interesting discussion. From my somewhat limited experience of building 5 boats, I have first hand experience in seeing the various efficiencies of 1-24" diameter prop, 3-26" diameter props, and 1-28" diameter prop. They were all bronze michigan dyna-quads from the same machine shop. Obviously the most efficient prop was the 28" diameter with the slowest shaft speed of 1220 rpms wide open. There are a lot of factors that go into prop efficiency, the weight and design of the hull being at the top of the list.

The 37' boat with the shaft speed of 1220 rpms with 28" diameter had prop slip of about 11.5%.

The 34' Calvin Beal with a shaft speed of 1500 rpms with 26" diameter had prop slip of 17%. I think the combination of the 2" smaller diameter prop, a higher shaft speed, and a slightly steeper shaft angle all contributed to the 5.5% more prop slip versus my 37' boat. I could have reduced the prop slip by slowing the shaft speed if I had used a 2:1 reduction, used a 28" diameter prop, and going with a slightly longer shaft thus reducing the shaft angle. It sounds like going to a DQX could have reduced prop slip even further.

 

[Nighthawk]

Yes, a good discussion. Propeller selection is a significant contributor to performance, smoothness, vibration and fuel economy. After a boat is built it is the only real variable you have to play with. In the Downeast world without a lot of exact comparison success stories it becomes even more difficult. When you think about it there are very few boats built that are exactly like another one due to the miriad of variables from hull weights to power to gears to shaft diameters, skeg boats, built downs, rudder sizing etc. Prop matching then becomes unique to most all builds and although you may have some near "sisterships" for a starting point it's always going to be a compromise because nobody is going to explore 32 different props and test them precisely to find the one perfect match. Unlike grabbing a few props and spending a few hours trying different ones on an outboard, it's not so easy (and gets very expensive) on a new inboard boat.

The advantage the DQX has over a DynaQuad is due to the EAR (expanded area ratio). In 23"-32" diameters the DQX has a .81 EAR where the DynaQuad only a .69. What that means is that the DQX has 15% more effective blade area when comparing identical sized propellers between those two models.

Another choice from Michigan that I believe would be a good one to try is the Michigan M-500 (five blade) with a whopping .86 EAR.

Most propeller manufacturers use DAR (developed area ratio) to indicate blade area ratio, Michigan chooses to tell us EAR instead which will be a bit higher number than DAR due to the way the measurement is calculated. So if comparing blade area ratios between different prop manufacturers just be aware that it's not exactly an apples to apples comparison (a propeller will have a slightly higher EAR than DAR).

 

[Powderpro]

I'm going to check into how much more $$ the DQX is over the Dynaquad. I'm assuming that since the DQX grabs more water and is thus more efficient, I will have to reduce the pitch of the DQX over what the Dynaquad would be. And if that's the case, the top speed of the DQX vs. the DQ may not be any different?

On my next boat I was thinking I would start out with 30" of pitch on a DQ. If I go with a DQX, should I drop it to 29" pitch? And if there is less pitch, then even if it were more efficient, it would not translate into a faster top speed. But, the cruise may be a little faster? What do you guys think??

 

[captainlarry84]

??

On a keeled boat you will gain nothing with a DQX. As you rob Peter to pay Paul you lose pitch, which is what moves you forward. You need to figure out your current propeller efficiency before investing in the wheel. Also the same about of metal is used in both the DQX & DQ. Which means that a DQX is slightly thinner than a DQ. That is also something to consider. The QDX on vee bottom boat with wheel clearance and other issues maybe be worth the investment. But on a keeled boat it is a toss up

 

[traditions]

Thats what I was told,1 inch less of pitch for the dqx.They also have a dq486 that is even more skewed,for use in shallow draft boats with a tunnel.It would be nice to hear real world comparisons,like Bill,but he has a strut set up,so not a good comparison on my application.I looked back at some older post on noreast about dqx wheels,and some said that the top speed wasnt any more,but cruise was better,and better on fuel.I know when they first came out with prop scan they were saying how much more efficent they were.When I had the wheel I have now scanned it used to whistle when I was idleing in the harbor.I am going to make some more calls tommorow.

 

[Nighthawk]

The DQX on vee bottom boat with wheel clearance and other issues maybe be worth the investment. But on a keeled boat it is a toss up

Agree, the advantage of high DAR/EAR props is much more beneficial when the hull is limited to smaller diameter wheels. On a DE that rarely seems to be the issue. My suggestion to help with your excessive slip would be to get some real accurate numbers (rpms, speed) and at the end of your season take the prop to Larry at Accutech in NH. He is top notch and will improve your propeller performance. He has the latest scan equipment and is very skilled with propeller performance.
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