3 Blade GSC Prop on Parajet Compact

[irm750]

Finally got my crap together and took some pics of my gorgeous 3 blade GSC prop on my Parajet Volution Compact.

I wanted to be happy that it was going to work well before singing its praises as I had a bit of a challenge initially. I was gradually increasing the angle of attack and testing for revs on the tachometer. When I got to about 15 degrees the prop started to bang on the exhaust (eek). I wanted to go flying so re-fitted the old carbon fibre prop and put the GSC in the shed while I had a bit of a think. A couple of weeks later the carbon prop then started to hit the exhaust during starting (very dissappointing but glad to have spotted it BEFORE take-off!). This turned out to be worn exhaust mount rubbers and speaking with Gilo at Parajet this is apparently a known fault which is rectified on new models (yet another item for the pre-flight check!). I bought thinner mounts from a car parts shop (designed for MG Midgets!) which put the carbon prop well clear of the exhaust. I remembered the GSC languishing in the shed which I have subsequently fitted and incrementally adjusted up to 24 degrees for maximum dynamic thrust.

Am yet to fly it (hopefully this evening if the weather plays ball) but it spins up fine and tests out well on the tacho.

I have heard that original carbon props are in short supply, so once I am happy that it flys as well as it looks I will be importing a number of these as replacements. I should be able to sell them for £295 including postage to UK addresses.

Best regards,

Ian.

Rear View -

Hub View -

[norman]

I just picked up my 120cm prop. Beautifully made and excellent service from Rick at GSC.

I have yet to fit it as I have some mods to do on my Macro around the tank area before I bolt it on.

Would be very interested to hear how you get on Ian, the unit is heavier than the carbon of course but with props that isn't all bad.

[bathboy]

A couple of weeks later the carbon prop then started to hit the exhaust during starting (very disappointing but glad to have spotted it BEFORE take-off!). This turned out to be worn exhaust mount rubbers and speaking with Gilo at Parajet this is apparently a known fault which is rectified on new models (yet another item for the pre-flight check!). I bought thinner mounts from a car parts shop (designed for MG Midgets!) which put the carbon prop well clear of the exhaust.

Best regards,

Ian.

Ian,

As my prop is also very close, do you have a part number or dimensions of the thinner mounts?

Also, should we have an knowledge area for changes/upgrades for each make of paramotor as they are all still evolving?

Cheers

Paul

[pete_b]

Ian you say that you have set it for max dynamic thrust??

do you mean max RPM for the motor?

Dynamic thrust will lower your rpm and static thrust.

When I first put mine on I set it for max dynamic thrust (would only rev to 5500 instead of 7000) and had to run the length of the field to get up, but in flight the RPM was down to 3200 on fast trim.

I have now found a happy medium with enogh thrust to get me airbourne with a fast trim level flight RPM of 4500.

Reaction 27(20 kilos over weight)

Pete b

[irm750]

Hi Pete

With my carbon blades the motor revved to 7800rpm.

When I started, the pitch was 10 degrees and the engine was revving to 11,000rpm. I got this down bit by bit by gradually increasing the pitch until the rpm was about the same as with the carbon prop.

It is now at 24 degrees which gives a max engine RPM of 6800rpm which gives a reasonable static thrust. I have yet to try and fly it but am hoping that it will yield a greater dynamic thrust than the carbon prop.

Does this sound about right or am I barking up the wrong tree??

Cheers,

Ian.

[outkast]

looks a very nice peice of kit, sooner or later someone is going to design a variable pitch prop that can be adjusted in flight, it may well come to us footlaunchers via the trike route due to the wieght issue.

[Guest]

I got on to the production side of Parajet about this today....

What can I say..........

Excited.

Looks sexy, works well from reports so far...

SW

[irm750]

Hi Paul.

I don't know what the Parajet part numbers are, but my new mounts (you need 2) are approx 18mm thick as compared with the originals which are about 25mm.

You can get them from Partco or other motor factors locally and I paid a couple of pounds each. They are actually Leyland mini exhaust mounts and I had the complication of having to find nuts to fit on the threads which are imperial (the original Parajet ones are metric) but luckily my father in law has a garage which is an alladins cave which I regularly plunder!

You can get them from ebay complete with nuts -

http://cgi.ebay.co.uk/Universal-Exhaust-Mount-bobbins-nuts-suit-classic-cars_W0QQitemZ330265732531QQcmdZViewItem?hash=item330265732531&_trkparms=72%3A636%7C39%3A1%7C66%3A2%7C65%3A12%7C240%3A1318&_trksid=p3286.c0.m14

I am thinking of drilling either side of the mount and lock wiring across to prevent the exhaust leaving the motor mid flight if these mounts were to fail.

I would love to see an update section where manufacturers could list safety improvements made for each type of motor. It could save some costly failures.

Best regards,

Ian.

[Guest]

I would love to see an update section where manufacturers could list safety improvements made for each type of motor. It could save some costly failures

Great Idea for all manufacturers, for it is the Pilots who are the people to listen to.

Any good suggetions will be looked at by Gilo, Markus and Andrew for exactly this reason.

SW

[phatboy]

A quick way to put a safety across a rubber mount is to get a piece of webbing strap, burn 2 holes in it with a heated screw driver & put over each end of the bolts. If the mounting breaks it can not separate too far.

Paul

[norman]

An interesting subject this, and I bow to some of the experts we seem to attract. Take Phil_p with his extensive radio knowledge - awesome! Is there a prop man out there?

FWIW

Expect reduced thrust from the wooden blade unit, carbon is very light so doesn't absorb as much engine power simply rotating, then again it has greater rotational inertia. That's the conclusion I come to anyway - good bit of bullsh1t?.

Same RPM/same thrust? Similar perhaps, other manufacturers quote lower thrust output from their motors, Wood Vs CF. Carbon fibre can be modeled very precisely lending itself very well to props and aerodynamic surfaces. Simon W would be a man to listen to on this as he has considerable expertise in this area. I suspect the consumption would increase for the reasons given above as well.

CF against wood is therefore an interesting question, you pay more for carbon but get reduced consumption and more thrust. Wood props are easy to source and a lot cheaper.

Were I to follow through with the arguments I might use a wooden prop for training and consolidation, and when my technique has stabilized, decide which final unit would be for me. It comes down to skill and the wallet in the end doesn't it?

"The ground is hard, hit it lightly!" "Objects may be larger than they appear in this mirror" "do not fly inside thunderstorms." Gary Larson is an inspiration!

Darwin was right..... pilots do evolve over time. Only adapters and thinkers survive.... mostly.

[bathboy]

I would love to see an update section where manufacturers could list safety improvements made for each type of motor. It could save some costly failures

Great Idea for all manufacturers, for it is the Pilots who are the people to listen to.

Any good suggetions will be looked at by Gilo, Markus and Andrew for exactly this reason.

SW

Yere tis http://paramotorclub.org/forum/viewtopic.php?t=1871 I've added this info about the exhaust mounts.

Cheers

Paul

[Guest]

Perfect.

SW

[irm750]

I will use the webbing idea - Great suggestion, thanks Paul.

That's a good start with the new thread. User gleaned information and tips will be very valuable, but this would be enhanced significantly if added to by the manufacturer. If only we knew someone on the inside.........................

Best regards,

Ian.

[Phil_P]

On the rubber engine mount topic, I have just bought a whole load (6 off 38 diam x 25mm long, 2 off 38mm diam x 38mm long and 2 off 20mm diam x 25mm long) for the grand sum of £33.00 including VAT and postage, with next day delivery. I got these from www.fish4parts.co.uk

They aren't the 'waisted' variety and are round rather than the standard hex on my 'Adventure' but would seem an ideal replacement for the fitted ones.

The reason I've bought the two 38 x 38 ones is that I am going to try fitting these as the mounts on the left hand side of my engine in order to offset the thrust line to the right, to counteract the various forces that tend to turn you right. I know you can trim this out, but by reducing the cause rather than correcting the effects, I'm hoping to reduce drag.

[irm750]

Thanks Phil.

Certainly plenty of choice on there! (page 1 of 10 below)

http://www.fish4parts.co.uk/advanced_search_result.php?categories_id=800109&inc_subcat=1&sort=3a&page=1

Best regards,

Ian.

[irm750]

So I got to the field with my shiny new 3 blade GSC prop set more for dynamic thrust than static thrust (6800 max engine rpm as opposed to 7800rpm with carbon prop).

Got set up for a reverse in variable 4-6mph wind, warmed the engine, pulled up the wing and did my best impersonation of Usain Bolt. Unfortunately no gold medal and no take-off for this olympic effort. Managed a short hop before being planted back on terra firma with my legs going like the clappers!

I realised that I could not make a useful climb-out, and with discretion being the better part of running faster than your legs can carry you and breaking your jaw by falling on your face I throttled back and applied the brakes.

The extra weight of the prop compared to standard didn't seem to have any adverse torque reaction for the short time that I was airborne.

The good part about the adjustable prop is that you can, er, adjust it! I will give it a tweak for less pitch and increased revs and try again. Will obviously keep you posted as I am sure that there is some useful thrust in there waiting to be let out.

Best regards,

Ian.

[norman]

Ian,

What pitch did you have set? 10º - 11º was suggested to me as a good start.

[irm750]

Hi Norman

I set 10 degrees initially but this allowed the motor to rev to 11,000+ rpm compared to the original 7,800 with the carbon blades (only for a VERY short time as I didn't want to blow it up!). I then gradually increased the pitch 5 degrees at a time, testing the rpm at each stage.

My flight test setting was 24 degrees which yielded an engine rpm of 6,800 as I wanted to set it low to gain more dynamic thrust and hopefully increased efficiency in flight.

I will be reducing the pitch to bring the max engine rpm back to 7,800 and flight test again.

Best regards,

Ian.

[Mike]

Hi Norman, i was speaking to Simon about these three bladed adjustable props and he says that you have a set on your Macro. How are you finding them.

I also notice above that Ian is having problems setting them up. Have you any pros and cons about using these types of props. l also believe they are less expensive than the standard two blade variety.

Regards Mike

[Phil_P]

I've just succesfully fitted a GSC two blader to my Adventure unit. I made up an adapter plate with some 100mm billet off ebay.

I've found setting to be a doddle with the supplied protractor, but still a pain in the bum having to undo and redo all the nuts and bolts. Tracking seems to fall spot on very easily.

I'm surprised you are running such a coarse pitch. I'm down to 13.5 degrees on my tuned head/exhaust Solo 210, and I think it could still do with a degree less to really let the motor sing up to just over 7k RPM.

[norman]

Mike,

My Macro is with Parajet being serviced and having a mod done to make the tank strapping recede thus increasing clearance on the prop's downswing. I have developed my own view about the prop issue and am addressing it. While my kit is there I have left my GSC prop with Marcus to see if it will form an option for PJ to offer. As you know prop supply is an problem at the moment.

Personally I believe that training should be carried out using cheap (wooden) props and the CF version fitted after a level of expertise has been gained. Little to lose, much to save but again, that is just a personal view.

September is my month for flying, I hope to wrack up a fair amount down 'ere in Zummerzet.

[helimed01]

I replaced my exhaust mounts on my H&E 120, got them from internet company when I put a new exhaust on this year. During the first flight one of the rubber mounts got hot, melted and broke, luckily the exhaust did not move or hit the prop.

I resolved this by placing small washers x3 between the exhaust bracket and the mount allowing more airflow and reducing heat conduction. This has worked well.

I like the webbing backup idea.

Regards.

Whitters.