Guest ROM Posted October 31, 2007 Share Posted October 31, 2007 The discussion so far has been on fitting adjustable and inflight variable pitch props to Rotax engines. Has anybody fitted the Sensenich 2 blade ground adjustable prop or any other type of ground adjustable prop to a Jab 3300 engine or an inflight variable or constant speed prop to the same engine? If so what prop type and what were your experiences, the results and your thoughts on doing this? And what are the drawbacks and points to watch? We are keen to get experiences and opinions here as we are glider towing with a J230 and need to get the maximum out of a limited engine power. i believe that the Canadians and British Jabiru owners are throwing away the Jab props and installing the Italian GT props for better performance. We will also need to get any prop changes through Jabiru's system as it is a certified aircraft. Link to comment Share on other sites More sharing options...
facthunter Posted October 31, 2007 Share Posted October 31, 2007 certified prop. ROM, with regard to your last point, I don't like your chances. A wooden prop avoids the harmonics (vibration ) problem that can cause sudden blade failure, from vibration within the prop.(like a tuning fork which has a natural frequency) It is not caused by out of balance forces that can be felt externally, so you are not aware of them. Nev.... Link to comment Share on other sites More sharing options...
Guest ROM Posted October 31, 2007 Share Posted October 31, 2007 Yes, I am very aware of the cyclic and harmonic frequencies that arise from direct drive engines and that wood props can handle these. As an example, the Italian GT fixed, VP and CS props are all wooden bladed props so they probably don't have the harmonic susceptibilities that the composite props do. There are also other manufacturers with wood cored and composite covered blades on their VP and CS props. There are a stack of propeller makers out there and in the usual manner of all things ultralight, there will be a few makers whose products are tested, tried and completely acceptable. The rest could be anything from excellent to, politely put, very suspect! Unfortunately, as I discovered when I first started to explore the buying of an ultralight /LSA for our gliding club, the ultra light movement runs on a fairly heady mix of myth and rumour. If you want the nuggets of truth out there you really have to go digging with that proverbial, very large back hoe. So, I am digging for those nuggets, this time on the subject of propellers. I hope and would really appreciate it if some of the very knowledgable participants in this forum can supply me with those propeller information nuggets. Link to comment Share on other sites More sharing options...
Captain Posted October 31, 2007 Share Posted October 31, 2007 ROM Good post and it's a very interesting issue since the loose flywheel bolt issue was sheeted back, to some degree in some cases, to prop types. I too have been watching the OS J websites and forums on this subject and look forward to seeing the replies that are posted here. BrentC triggered a reasonable exchange on this issue when he went to a carbon fibre 3 blade a short while ago. Did you see those? Regards Geoff Link to comment Share on other sites More sharing options...
Guest ROM Posted October 31, 2007 Share Posted October 31, 2007 Yes, I had a look at those posts Geoff and was very interested in the experiences that a few people have had with these props on the Jab engines. Our real problem, club wise is that we have to conform with Jabiru's certification requirements but if the info can be put together then there could be a good case for some changes to Jabiru's certfied aircraft propeller configurations. Cheers. Max Link to comment Share on other sites More sharing options...
Guest High Plains Drifter Posted October 31, 2007 Share Posted October 31, 2007 Rom, What are the difficultys of getting a CAR 35 "one off" approval. HPD Link to comment Share on other sites More sharing options...
Guest ROM Posted November 1, 2007 Share Posted November 1, 2007 Haven't even thought of that yet! The thought of the paper work makes me shudder. Besides, we still have to find the prop make and type that is fully compatible with the Jab 3300 engine, will be very reliable, perform as advertised, has good back up, has a long TBO, is easily maintained, is easily repaired, and has no long term deleterious effects on the engine or airframe. There's a prop maker and prop out there somewhere that will do all of this on a Jab motor. The problem is to find it. This is where you guys come in! Link to comment Share on other sites More sharing options...
Guest High Plains Drifter Posted November 1, 2007 Share Posted November 1, 2007 ROM, The British or Canadian Jabiru owners may have gotten the GT approved in some way. That may simplifie the CAR 35's approval if needed. Their helpfull chaps and I find are always more than happy to take a quik phone call. Link to comment Share on other sites More sharing options...
Guest Flyer40 Posted November 1, 2007 Share Posted November 1, 2007 Hey ROM, I don't know anything about this subject and I don't know how helpful this is, but I noticed Lightning advertise the following prop options for use with the Jab 3300. Sensenich W58Fk-64 Sensenich W64ZK-51 Sensenich WC56FJ-56 Sensenich Carbon Fibre Ground Adjustable Link to comment Share on other sites More sharing options...
facthunter Posted November 1, 2007 Share Posted November 1, 2007 Possibilities. Sensenich have been around for ever. Carbon fibre may be less of a problem than metal which is the most critical. You can end up with a prohibited RPM, even in an approved engine/prop combination.. Nev... Link to comment Share on other sites More sharing options...
Guest High Plains Drifter Posted November 1, 2007 Share Posted November 1, 2007 I imagine tow plane operations would have a prop constantly working in a load and rev range that is not normaly imposed on it. HPD Link to comment Share on other sites More sharing options...
facthunter Posted November 2, 2007 Share Posted November 2, 2007 Harmonics. It's usually a small rev range that is prohibited. There can be more than 1 ,generally, only with big stuff. The POH will state them . AVOID operating the engine in the range(s) specified.. This relates to the propeller properties, (stiffness & mass distribution) and how it is affected by the pulses originating in the engine. They don't have to be direct drive always either. Whilst this information is not provided in general to RAAus type aircraft, the principles apply to all. There's a bit on the Hartzell site. Personally I wouldn't like to be a propeller builder. Nev... Link to comment Share on other sites More sharing options...
Guest ROM Posted November 2, 2007 Share Posted November 2, 2007 Glider towing usually is a full throttle operation but the towing airspeeds of around 70kts and engine revs are about the same as any normal full throttle climb out speed that would be typical for the type of aircraft normally used in towing. The time period for full throttle operation to the normal release height of 2000 feet AGL using say a low powered tug [ "low powered" compared to a say a Pawnee tug! ] is around the 6 to 7 minutes with a total tow time, ground to ground of around 9 to 10 minutes for a 2 seat glider. Link to comment Share on other sites More sharing options...
facthunter Posted November 2, 2007 Share Posted November 2, 2007 Glider towing. A fixed pitch sensenich with finer pitch and a bit more blade area (dia with CF) might be the go as your speed range is minimal, and if you got it right you would not need to vary the pitch after that. Still have to get max. revs though. They say it's easy to end up with a lot of nice unsuitable props on your shelf. Good luck Nev.. Link to comment Share on other sites More sharing options...
Guest ROM Posted November 2, 2007 Share Posted November 2, 2007 Yeh! A lot of nice unsuitable props, that's what worries us and that is the reason for this thread. We also have training and long distance flying as well as the glider towing so whichever prop, it has to cover a big operating range. Link to comment Share on other sites More sharing options...
Guest High Plains Drifter Posted November 2, 2007 Share Posted November 2, 2007 At least the superceded two blade wood props make nice wall fixtures - I keep an "Arrowprop", a "Catto" and a "Henry" hanging in the lounge room. Link to comment Share on other sites More sharing options...
rodknee Posted November 2, 2007 Share Posted November 2, 2007 http://www.jabiru.net.au/ Look under propellers Link to comment Share on other sites More sharing options...
Guest ROM Posted November 2, 2007 Share Posted November 2, 2007 Been talking with Jabiru about propellers for quite a while including today! The Sensenich and MT props listed there have not been cleared for certified aircraft, ie. those that are factory produced and are used for training, glider towing and etc. Link to comment Share on other sites More sharing options...
Ross Posted December 8, 2007 Share Posted December 8, 2007 Looking at the newest J230C at Narrandera recently and noticed that its Jabiru wooden propeller appears to have a leading edge insert quite different from the props on the other two J230Cs in the hanger. Does anyone know any more about this insert? Link to comment Share on other sites More sharing options...
TechMan Posted December 10, 2007 Share Posted December 10, 2007 Been talking with Jabiru about propellers for quite a while including today!The Sensenich and MT props listed there have not been cleared for certified aircraft, ie. those that are factory produced and are used for training, glider towing and etc. That probably because Jabiru don't want to authorise the use of other propeller brands on their aircraft. Being LSA, it is up to the manufacturer to authorise any modification on the aircraft. CAR35 engineers cannot be used for approval of modifications on Light Sport Aircraft. If you decide to say stuff it and operate the aircraft our a GT (for example) without the manufacturer's approval, then you are operating outside of the Special certificate of airworthiness and CASA undoubtedly has a whole range of penalty units that can be applied to that. Remember that the SCoA is a CASA issued document and has nothing to do with RA-Aus. If you breach the conditions of the SCoA, then you deal with CASA. Chris Link to comment Share on other sites More sharing options...
Guest brentc Posted December 22, 2007 Share Posted December 22, 2007 I spoke to Rod Stiff about props at my factory visit a couple of days ago. As I understand it, nobody out there that he is in contact with is able to produce carbon props for him in the bulk that is required (eg 35+ per month) and using technology that will not have the prop tearing apart when they test it. My carbon prop would be great, but the manufacturer wasn't able to produce enough of them in the timeframe required. Rod showed me that he is working on his own prop, however technology (build type )and time appear to be problem areas. Whilst it would be easy to say, 'just get the Sensinich' ones from the US of A, this does nothing towards the local economy and maintaining the building of an Australian built aircraft. Link to comment Share on other sites More sharing options...
facthunter Posted December 22, 2007 Share Posted December 22, 2007 Australian-built. Brentc, whilst the outstanding characteristic of the Jabiru is the quite remarkable fact that the design and production of the entire aircraft is done in Oz. The firm rightly deserve credit for their achievement. HOWEVER (that word again), The aircraft is exported to many countries, and has to compete in those markets, and here. Some components are not made in Australia. eg Electrical, (I would suggest,) & the alloy steels (Billet) for the cylinders and the crankshafts, are no longer produced in australia, and are probably sourced from Brazil. I don't pose this as a criticism, merely an acceptance of reality. The matching of a certified engine/prop. takes some effort. If this was DONE (by anyone), then the Jabs would be better for it. Until then, wood is the go. This no doubt limits the application of the engines, for some people. Nev.. Link to comment Share on other sites More sharing options...
Guest brentc Posted December 22, 2007 Share Posted December 22, 2007 Looks like they are going well overall ! Link to comment Share on other sites More sharing options...
facthunter Posted December 22, 2007 Share Posted December 22, 2007 Success story. Brentc, without a doubt. Nev.. Link to comment Share on other sites More sharing options...
Guest disperse Posted January 20, 2008 Share Posted January 20, 2008 Airmaster constant speed I was looking at there web site and claim the AP332 suitable for 6 cyl jab ..... price is a little quiet though... I've just started looking at the subject of variable pitch props and constant speed jobs.... I'm guessing you would have to allow $8000 for the prop and controler But then there is the whole harmonics thing too ..... Anyone in the know of approx prices ? Link to comment Share on other sites More sharing options...
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