Topic: Prop testing - Your opinion please? (Read 8703 times)

craig dickson · « **on:** July 11, 2013, 09:03:17 pm »

Hi Folks
In trying to find the best prop for my BMPRS SC46 powered Crusader 3, I have narrowed it down to two props. I cannot decide which of the two gives best performance. Could you help me make my mind up by watching these 2 short video clips?
First is the Mocom 19-19 prop:
https://www.youtube.com/watch?v=ngJ6w5ferFU
Second is the AMPS 20-18 prop:
https://www.youtube.com/watch?v=t0Arvnoh1ws
Which prop delivers best performance in your opinion?
Cheers
Craig

john44 · « **Reply #1 on:** July 11, 2013, 10:45:11 pm »

Sorry Craig the video,s kept freezing when I viewed them,
impossible for me to tell.
Have you got a Watts-up meter you could put in circuit,
that would tell you which is more efficient.

john.

spearfish99 · « **Reply #2 on:** July 11, 2013, 11:54:18 pm »

Hi Craig
I think that the AMPS looks as if it is quicker , the boat certainly looks happier with that one.
Will be faced with the same problem myself soon as I am just finishing a Crusader 3 with an Irvine 46 for BMPRS racing.
Ian
BMPRS 151

Sparky · « **Reply #3 on:** July 12, 2013, 12:21:54 am »

Not being a fast boat type of guy (yet) !!,
It looks like the 18-20 has got the edge.

Good luck with the boat, whichever prop you pick.

cheers Vic.

Sparky · « **Reply #4 on:** July 12, 2013, 12:24:46 am »

18-20 ?? Sorry !! 20-18

Vic

derekwarner · « **Reply #5 on:** July 12, 2013, 12:32:48 am »

Craig....this is a very difficult task from 22,000 km away.....

[19x19=361] as compared to [20x18=360]
First A to B comparison appeard to have 19-19 with a higher audible note which did not necessarily make loading sense
Second A to B comparison visual appeared water speed faster with 20-18
I cannot think of a simple A to B test that would answer you question

...I can comprehend a totally complicated scientific A to B test ......but then it must include
two identical vessels [one with 19-19, one with 20-18]
two computers [to eliminate human input/error]
scientific weighing equipment [for input & resultant fuel]
electro telemetry equipment ..............
the assistance our Lord to ensure mirror like water for the tests

The other option could be is to purchase one of each prop .......flip a coin...& race with the first selected by the coin.......you know the rest of the story......Derek....

tigertiger · « **Reply #6 on:** July 12, 2013, 01:14:00 am »

Most mobile phones have a stop watch. You could try timing them in a range of water conditions you are likely to meet.

Martin (Admin) · « **Reply #7 on:** July 12, 2013, 11:25:45 am »

The AMPS prop looked quicker to me too but I think you'll have to do it the old fashioned way.
Fill the tank, run and time ten laps, bring it in, measure amount of fuel left, do the same with the second prop.

AMPS? Old Miller died years ago, where are you getting the props from?

Martin

spearfish99 · « **Reply #8 on:** July 12, 2013, 07:06:40 pm »

Craig,
The thought occurs, that if all us seasoned observers of boats can't tell you which is going better, then there ain't much difference!
As I said before, I think that the boat looks "happier" on the 2018, meaning that it seems to be riding cleaner and more settled. For racing that can often be more important than outright speed. I have always found that the faster your boat goes, then the opportunity for things to go wrong seems to increase exponetially, as does the mirth of fellow boating "friends" when it does!
P.S. If that prop is 30 years old, keep it for when you need it. If you bend it you probably arn't going to find another!!

craig dickson · « **Reply #9 on:** July 12, 2013, 07:58:36 pm »

Hi Folks
Firstly, a big thanks for your responses to this topic as I only posted it a day ago and did not expect such a response.

It appears that the consensus of opinion is that the old AMPS 20/18 prop comes out top from those two videos albeit by a small margin.
The AMPS prop is one that was purchased just over 30 years ago. It is the bronze cast prop with the brass insert for those of you that remember these. It has been kept in mint condition. Perhaps I should keep it safe but then it was made for winning races. Out of interest I can not even find a supplier that does a prop 20/18 size today which is a shame. The AMPS props for me were always my favourites and beautifully finished.
Martin, forgive me for being a plank, but how does the amount of fuel left in the tank say after 10 laps on each prop determine which prop delivers best performance?
Cheers
Craig

craig dickson · « **Reply #10 on:** July 12, 2013, 08:07:07 pm »

Quote from: spearfish99 on July 11, 2013, 11:54:18 pm

Hi Craig
I think that the AMPS looks as if it is quicker , the boat certainly looks happier with that one.
Will be faced with the same problem myself soon as I am just finishing a Crusader 3 with an Irvine 46 for BMPRS racing.
Ian
BMPRS 151

Hi Ian
I will look forward to seeing your new boat and having a race with you in due course

I have only entered mine in 3 BMPRS races since building it. The hull has exceeded my expectations as it gained first place position in each of these 3 races. Bernard Holder who designs and makes these hulls has immense talent that I am very thankful for.
Cheers
Craig

Martin (Admin) · « **Reply #11 on:** July 13, 2013, 07:32:19 am »

Fuel usage will indicate how hard your engine is working, engine loading.
Ie, driving your car down the road at 30 MPH in first or 5 gear!

derekwarner · « **Reply #12 on:** July 14, 2013, 02:26:26 am »

Craig.......just thinking outside the square

....the following could be considered to provide definitive answers for the comparison between the 19x19 & the 20x18 propeller's
1. attach a substantial restraining V rope to the stern of the hull
2. connect a tension spring balance [fish scales] to the pool wall & the V rope
3. gradually increase the throttle to max & record the load/strain as shown on the spring balance = thrust in kg
4. simultaneously with this, record the engine/coupling RPM with a digital rev counter..............
I have used a similar simplistic load/strain spring balance approach to understand & then define acceptable rotational torque on hydraulic distributors as attached to large [320 mm bore] expand collapse mandrel rotating cylinders as used in our steel industry..............
This was after our mathCAD engineering designers stated too many variables existed to provide an accurate calculation of the mechanical restriction within the distributors

.......Derek

spearfish99 · « **Reply #13 on:** July 14, 2013, 02:44:42 pm »

Quote from: craig dickson on July 12, 2013, 08:07:07 pm

Hi Ian
I will look forward to seeing your new boat and having a race with you in due course I have only entered mine in 3 BMPRS races since building it. The hull has exceeded my expectations as it gained first place position in each of these 3 races. Bernard Holder who designs and makes these hulls has immense talent that I am very thankful for.
Cheers
Craig

Hi Craig,
Everything that he produces seems to go well. Either very good luck or a very talented gentlemen, I know which I would go with!
As I am not either a very quick or talented builder, I have bought 3 of Bernard's hulls from various places in various states of completion , to give me a start. One is the Crusader3 for A class, bought with no mechanics but mounting posts everywhere. This is nearly complete for an Irvine 46. Another was a well used Crusader 2 which had raced for years in OMRA (don't tell Scoop) as an A class but at 48" long has just had a long stored CMB .67 installed.
The third hull is one you know as it featured in one of your Youtube videos with a Webra 40 installed. I have a 40 in my collection of Webras ( I am a fan like you and Gary) but rather fancy trying a Webra 61R as an alternative for B Class.

Talking of Webra's, I have just acquired a Webra 91 from Fleabay. I think that someone has had a good tinker with it as the keyway on the crank holding the flywheel in place is a bit iffy and I know this will sound daft, but I think they have turned the piston 180 degrees as when you look through the exhaust port you can see a cut out in the piston. On my other 91, you only see solid piston and I am guessing that what I can see is an induction port which should be on the opposite side of the cylinder.
Do you or anyone else know anyone who can/does service or repair old engines with a reasonable degree of expertise. This is a nice engine and I would like to be able to use it with confidence.

craig dickson · « **Reply #14 on:** July 14, 2013, 05:29:27 pm »

Hi Ian
I can't help you with anyone who I know specialises in engine servicing/re-builds. Perhaps someone else might chip in. The problem with vintage engines is getting decent spares/parts. What I would say is be especially attentive to the bearings in any second hand engines. With a recent Webra I acquired I thought the bearings were shot. However after leaving them overnight in a jar of Acetone they cleaned up pristine and a close look with a very powerful magnifying lens showed them to be in very good condition. The acetone was black with dissolved gunk!
Back to the original topic in respect of a couple of points made:
Martin:
Thanks for the explanation about fuel usage being a pointer. Can I deduce that the prop that uses more fuel (by loading the engine more) delivers more thrust? However what if one prop is not as sharp as the other? Would that lead to more engine load and give a false interpretation?
Derek:
Thanks for your alternative suggestion and consideration. I can see some sense in that from a practical and logical point of view. However, in a stationary boat we are running the propellers at 100% slip. This is of course very different to the boat running at full speed and with much less slip. Therefore can such a test provide results that are realistic?
Thank you all for your further input.
Cheers
Craig

derekwarner · « **Reply #15 on:** July 15, 2013, 12:53:14 am »

Craig.......I do understand a static motion test with rotating elements will provide erroneous results viz. [prop slip] .......& in reality using a spring balance to attempt to differentiate differences in two such closely matched component sets may be asking too much

Having said this.......the same principal with a more sophisticated load cell will confirm the power output able to be transmitted to the differing propeller geometry

With respect to needle bearing sets......could I suggest....
1. Used needle sets....wash them out & rotate slowly without lubricant & they sound like a bag of bolts & nuts
2. New needle sets.. .wash the preservation lubricant out & rotate slowly without lubricant & they sound like a bag of bolts & nuts
3. New needle sets....wash the & examine the needle surface under an electron microscope & the needle surface appears sand blasted like which is intentional to aid with maintaining a film of lubricity between the components

4. It would be a waste of time in attempting to measure such needle roller elements for wear
One would think that all needle bearing sets would be replaceable from an industrial bearing source & should be replaced when a second hand engine were purchased
Possibly best to reconsider....."flip a coin...& race with the first selected by the coin".......you know the rest of the story......Derek

martno1fan · « **Reply #16 on:** July 16, 2013, 08:20:43 am »

Fact is as your running submerged drive your never going to see maximum performance anyway,if you want a fast boat then get something with surface drive.
Mart

Martin (Admin) · « **Reply #17 on:** July 16, 2013, 11:57:32 am »

Quote from: craig dickson on July 14, 2013, 05:29:27 pm

Martin
Thanks for the explanation about fuel usage being a pointer. Can I deduce that the prop that uses more fuel (by loading the engine more) delivers more thrust? However what if one prop is not as sharp as the other? Would that lead to more engine load and give a false interpretation?

Now that you put it like that Criag, I don't really know.
Anyone know how it works on full size engines?

craig dickson · « **Reply #18 on:** July 24, 2013, 07:22:30 pm »

Quote from: martno1fan on July 16, 2013, 08:20:43 am

Fact is as your running submerged drive your never going to see maximum performance anyway,if you want a fast boat then get something with surface drive.
Mart

Hi Mart
I agree that for flat out maximum speed, the hulls with surface drives are the business. And when I next buy a mono hull with surface drive your company will certainly be on my radar.
However, I guess it depends on what type of racing and overall hull attributes are preferred. Three particular aspects of submerged drives appeal to me:
1 The lack of the rooster tail spray makes them much easier to see when racing especially when the hull is heading away from you. Submerged drive boats from my experience are easier to set up.
2 The solid propshaft is in my opinion much easier to maintain and less prone to problems/breakages compared to a flexi shaft for a surface drive.
3 The costs of the drive system (prop shaft, bearings, supporting hardware and propeller) are much lower than what it costs to equip a surface drive boat.
For any members new to IC power boats, I think these factors need consideration.
Finally in respect of a slightly faster submerged drive boat, this short clip shows my other boat that I am currently testing. Once the Zenoah engine is properly run in, and with the right prop and engine settings I think it will be reasonably fast enough for me:
But could it be described as fast??

https://www.youtube.com/watch?v=vBgWVYjqXsE

Thanks for your input folks

Craig

martno1fan · « **Reply #19 on:** July 25, 2013, 02:53:14 pm »

Hi Craig I was just pulling your leg mate

,the advantage of submerged drive is how they handle in rough water and also turning but you do lose a bit of top end speed although acceleration can be better.Biggest disadvantage is no rooster tail ,cmon if it aint got a rooster tail its just boring lol

.
As regards costs I don't think theres much in it to be honest and ive yet to break a flex but then I don't race,but if you want a flex that wont break get yourself a suhner cable they will not break very easily.Many prople break flexis because they don't run a large enough gap between drive dog and stinger some use 1/4" this isn't enough in my opinion and you need at least 1/2" especially with todays more powerfull motors.These are just my opinions but like I say ive never had a flex bind up and break on me.

spearfish99 · « **Reply #20 on:** July 25, 2013, 04:47:53 pm »

Hi Mart and Craig,
The last couple of comment are interesting as I have just acquired a Zenoah from Ebay. It was advertised locally and since the Paypal balance had some in from my currently selling off my model railway collection, I was tempted.
For £100, I have got a brand new ( i.e. never used since purchase in 2006) 260PUM and a semi completed 48" Huntsman kit . All complete with other hardware and the original bill from Prestwich Models.
This will be my first sparkie and I am trying to get my head around what needs to be be done. Bit confused by all the add on bits that you see advertised for relocating coils (why?) , different carbs etc. It has one of the cradle sort of mounts already fitted and I believe a 644 carb?
I already have a Aeromarine 56" Apache hull ( curse of Ebay again) which was previously fitted with a Zenoah or clone engine so that may make matters easier. I think that I will try and find someone who wants the Huntsman and the spare Prestwich racing style rubber mount set that came with it to offset the cost a bit for anything else I need ( or the bunch of flowers when the wife finds out that the garage has acquired another resident in spite of a ban!)

martno1fan · « **Reply #21 on:** July 25, 2013, 05:06:26 pm »

Hi Ian,sounds like you got a good deal,as regards coil relocating mounts you may or may not need one it depends ,most likely you wont

.
Your carb will work fine on a stock motor,basicly the main dif between that and the 257 many use is yours has the primer bulb and choke.
Anything you need let me know mate,you know im allways willing to help a friend

.
Mart
ps did you buy lees red and white apache ?

spearfish99 · « **Reply #22 on:** July 25, 2013, 07:22:08 pm »

hi Mart ,
Thanks for the offer, most appreciated
I bought the Apache off of a guy in Kettering about 12 months ago. He goes in for huge cabin cruisers and the like powered by Zenoahs and similar motors. He had taken the engine out of this when he bought it, to use in one of his boats and just wanted rid of the hull.
It has a pair of "homebuilt" rails in it which don't look good but are up to the job. The boat has lots of holes in the transom and from stuff that I have spare I can see that originally it had all Aeromarine fittings which I can put back. Colour scheme is a bit strange but effective: white hull, metallic grey deck and white cockpit. The grey deck has lozenge shape pieces of yellow tape randomly placed on it. Would be better if the yellow was sprayed on but I can always do that.
Been quite lucky on the Bay lately. A couple of months ago I picked up another Aeromarine 56" Apache for £50locally . It is probably a very good copy rather than original Aeromarine, as the hull is not joined to the top, with a big wedge of foam fixed in the front of the hull. Going to make reinforcing the joint there fun when I eventually get round to doing it. Neither of the hulls is as good as yours but they just came up at too good a price to refuse!
Now that I have retired I have been talking about getting a smaller car, then go out a keep buying ever bigger boats. Must be the start of grey moments, but the big ones are impressive. We holiday in the Lake District most years and I can just see one of the biggies going round on Windermere or Coniston. Unfortunately , her indoors does not share the beauty of this mental image!!!

craig dickson · « **Reply #23 on:** July 26, 2013, 06:01:33 pm »

Quote from: spearfish99 on July 25, 2013, 04:47:53 pm

Hi Mart and Craig,
The last couple of comment are interesting as I have just acquired a Zenoah from Ebay. It was advertised locally and since the Paypal balance had some in from my currently selling off my model railway collection, I was tempted.
This will be my first sparkie and I am trying to get my head around what needs to be be done. Bit confused by all the add on bits that you see advertised for relocating coils (why?) , different carbs etc. It has one of the cradle sort of mounts already fitted and I believe a 644 carb?

Hi Ian
I agree the engine itself sounds like a bargain. Just on relocation the grey coil: Most people relocate it simply because it can get in the way. Especially if using a bell crank for the throttle linkage and also with certain engine mounts that surround the crank case. Relocating it is a relatively easy but if you mount it above the red coil using a CNC bracket you will need to remove the red coil and make sure it is refitted with the correct gap between it and the flywheel.

Cheers
Craig

spearfish99 · « **Reply #24 on:** July 26, 2013, 07:03:57 pm »

Hi Craig,
Thanks for that. I do think that the throttle will require a bellcrank to operate reliably. The mount fitted to the motor does appear to have mounting points above the red coil which when measured are the same distance apart as the screws for the grey coil. I need to take some better pics of the motor to post on here to show what I mean by that. I will try and attach some from Ebay , if I can.
As I do not have any experience of Zenoahs and the fact that it is ,in effect, brand new, I 'm not in a great hurry to start taking it apart before I know that I am not going to upset anything.

News:

Author Topic: Prop testing - Your opinion please? (Read 8703 times)