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jon_curtis - n/a
27-Oct-06, 01:50 PM
anyone know where i can get stainless leading edge tape by the meter?



also, with two bladed prop on a rotax engine, do you have to place the prop in a certain phase with the firing sequence?



shouldn't be thinking of putting the rotax on my new craft, but its there and it looks fun! certainly after i read the sort of thrust im going to get with this thing!

jar2 - n/a
27-Oct-06, 02:19 PM
Jon,



I haven't been able to get stainless prop tape - I use the 3M plastic tape - which is very effective. What make of prop do you have - you may not need tape if it's a Ultraprop.



On using a prop with a Rotax I quote (from www.powerfin.com):

"Rotax has set a limit for how much inertial mass is allowable on the A/B-box and C/E-box. On the A/B-box they want propellers with no more than 3,000 kg/cm2. A 72" – 3-blade Ivoprop ultralight propeller is about 4,500 kg/cm2. The same Warp Drive is over 10,000 kg/cm2. Powerfin propellers are 2,500 kg/cm2 for a big three-blade model and 1,800 kg/cm2 for a two- blade model."



May not apply to you of course!

jon_curtis - n/a
27-Oct-06, 02:54 PM
hi john



got a two blade 60" ivo prop, its also adjustable pitch which is nice.



its the set up that was on a microlight so assume its ok!

Don83000 - n/a
28-Oct-06, 01:39 AM
Hi Jon you can get 4" wide tape by at 2-60 mtr from Trident Racing Supplies on 01327 857822

jar2 - n/a
28-Oct-06, 07:54 AM
.. or Windsports Centre Ltd on 01751 432356.



If enough people start using props I'd be willing to buy a big roll of tape direct from 3M and selling it on at cost - let me know!

hovmart - n/a
1-Nov-06, 03:11 PM
stainless prop tape...

TOLL FREE ORDER LINE: 1-800-LA-ROTAX (1-800-527-6829) General Inquires: 863-655-5100





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Lockwood Aviation Supply :: Propellers :: IVO Prop Propellers :: Prop tape, stainless, precut



Prop tape, stainless, precut #21377

Prop tape, stainless, precut

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FanBoyz - n/a
14-Nov-06, 12:04 PM
A contact tells me props are the current trend, replacing fans, is that the way things are going?

Keith Oakley - n/a
14-Nov-06, 06:16 PM
All UK racing craft in recent years have used multi bladed fans and all of the 120+ craft from all over the world at the recent world championships in France used fans bar a very small no of North American craft - so no prop trend there. However a number of UK people are interested in using props on cruising craft, largely US hull designs, and mainly on grounds of perceived lower noise levels.

Keith

jon_curtis - n/a
14-Nov-06, 06:33 PM
"and mainly on grounds of perceived lower noise levels"



not exactly keith! in my mind, reduced noise levels is a bonus of props!



the reason im going to use a prop on my next craft, is due to a props higher effiency!

there is no hiding from the fact that a prop is a better thrust producer than a fan for a given horse power.



any reducting in noise levels is never bad thing too! http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif

quahogwi - n/a
16-Nov-06, 01:23 AM
Here in the USA we see it this way ... Props (2 blades)will give you greater top end speed, but is slower getting up out of the hole. A fan, such as MultiWing 9-blade, will not give you as much top end speed, but you'll get up out of the hole much faster.



Also, a 2-bladed prop is good for thrust only and is practically useless for providing lift air. Again, here in the USA hovercraft with props have seperate fans for lift. Some use a mule drive off the same engine, while others use a second engine up front to power the lift fan.



Dave Brown

Green Bay, Wisconsin USA

Keith Oakley - n/a
16-Nov-06, 07:41 AM
Which agrees with the logic of the racing fraternity being keen on fans since racing (certainly in UK on our tight courses ) is more about acceleration whilst cruising (eg for miles along the Scottish coast) offers the distances needed to build up to high speed.

Hovertrekker - n/a
16-Nov-06, 01:52 PM
Although Barczynski's F2 craft certainly has no problem with acceleration. I've wondered how an F1 Pintail would work with a 2 blade wood prop for thrust. Cons: tips speeds would have to be slower or the leading edges and tips tend to shred pretty quick, harder to change the pitch obviously. The Hascon and MW fans are probably able to handle wear and tear better, but the thrust increase would probably be significant. Has anyone ever tried it? (not that those craft need to go much faster http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif )

team black - n/a
16-Nov-06, 05:48 PM
Although Barczynski's F2 craft certainly has no problem with acceleration.




True, but on a VERY big course. It would struggle somewhere like Blackditch, which is small, tight and very techinical

Ian Brooks - n/a
16-Nov-06, 09:06 PM
Hi



Regarding propeller performance debates, so far as I can make out there are three main factors:



1 - fans run in ducts. This gives them the 'duct advantage', which can be anything from a 20% to 100% static thrust improvement



2 - propellers are typically larger - this gives a static thrust advantage due the larger mass flow at lower exit speed - something like 40% to 60% improvement.



3 - neither are really designed for static thrust at low speed. Microlight props are the nearest to an optimum for hovercraft. Under some conditions it seems that fan blades can be very in-efficient, presumably due to some parts of the blade stalling. This seems to affect low powered installations particularly, and may also be a reason for increased noise.



Taking these factors together - which is best? The truth is, it seems to depend on the details. A good ducted fan will be better than a poor propeller, and a good propeller will be better than a poor fan.



In the end, a well designed shrouded propeller should win the arguement - the problem is that the propeller couldn't be a regular prop designed for unshrouded operation, as the tips are designed to do very little, being there to reduce vortices forming at the end (like the winglets on airliner wings).



However - there does seem to be a body of evidence suggesting that propeller driven craft have the potential to be quieter than fan driven craft, for reasons that are not altogether clear just yet.



Just my opinions...

Ian

jon_curtis - n/a
16-Nov-06, 09:23 PM
nail on the head ian!



the fans are designed for aircon and industrial applications, in static installations. and props are not really designed to be ducted.



perhaps the optimum ducted thruster might be found from something like an airship fan, designed for that application. im gona have a look on the net to see whats available lol.