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PostPosted: Tue Apr 20, 2010 8:24 am
by Shannon
Hi Pete, the other day I purchased a pressure washer with a 6.5 Honda. Nice little engine. After a bit I was having visions of it turning a prop Haa Haa !

Each little pound is going to make a difference. P-tips for example would shed around 2lbs total right there. Combine this with other small changes and it starts adding up. I think (based on what you are showing us) a guy needs to go with upgrades so the engines can be pushed a bit harder. I'd love to see the engines putting up some "race" power. I'd love to see RPMs push over 5,000 static !

One thing I was curious about is the total weight of your Pod-Screen ? A bare bones Mike M. pod-screen adds about 6lbs. I'd probably do a little open air testing just to see how (or if) it changes things much.

When I went with a new type seat I did away with the original set-up and added two new spreaders. One was placed under the seat just behind the axle/cross tubes and another behind the seat serving as the front gas-tank bracket holder. Additionally two new "J" brackets were added on each side of the seat as well as two new straight "seat-support down tubes".

PostPosted: Tue Apr 20, 2010 8:31 am
by Shannon
Here's a little sketch from years back I scanned and saved.

PostPosted: Tue Apr 20, 2010 11:41 pm
by peter
Hi Shannon...I got up again today a couple of times, and your'e absolutely right...I'm dissapointed with the amount of thrust these props are giving at my t.o. rpm...I have over 4800 rpm on the rt engine, and over 4600 on the left and although GSC have a good reputation for making good props, I get as good or better performance with the 10x31 Clarks at the same rpm...go figure...
I tried to get a few figures on climb, and it is disapointing...the first run, air a bit thermally, showed only 75'/min, at a bit under 35 on the halls....the second was a bit better at 150' at 30mph...temp 50 degrees....I know I can climb better with the Clarks at that rpm, and I'm sure the hondas would just run away with them...The rt. engine on climb was almost 5000, and the other not far behind, probably close to 4800....way too fast for those stock motors....
I guess I'm faced with getting alum. flywheels and con.rods too but I'm dissapointed I'm not getting more thrust at lower rpm...I was originally hoping for takeoff power at 4500 and cruise at 4200 but it ain't going to happen with these props...I'd love to try a set of P-Tips, to see how much more efficient they would be but I'd need 5000 rpm for them. It would be real interesting to see how fast these motors as they are could turn them...
You know, even throttled back to 4600, I'm only showing a bit over 35, maybe 37 or 8, and at that throttle setting I'd be at 43 or better with the 185/Clarks....Something funny going on here...the plane hasn't changed that much...gained 12lbs total motor and props forward of the CofG, but that is really the only difference in the new setup....could the trim change bog the plane down to that extent?....seems to me it's either that or the props....I'll tell you though, I'm not comfortable about the way it flys.
I guess I had better put it back in the barn, do the engine mods and install the other seat, and get the CofG back....maybe the tinytachs and pressure reducers will have shown up by then....I don't want to give up on this because I'm certain these motors are capable of getting the job done.....I can always put the 185's back on for now... new seals and bearings, and running strong when I took them off.
Thanks for posting the info on the seat Shannon...I was a bit leary of moving the f10 but I see how you have done it...mine will be quite similar I think when I'm done....Appreciate the way Glen made the pod and I think the weight is 4lbs, and maybe a pound for the windshield and mounting hardware...I know..all forward ha ha...

PostPosted: Thu Apr 22, 2010 6:05 am
by gdewsbury
I weighed the fairing before Pete got it and it was 4 lb 9 oz. My own windshield made with 2 mm lexan is 1 lb 5 oz.

PostPosted: Thu Apr 22, 2010 8:21 am
by Shannon
Hi Glen, Not bad, pretty light ! I should have pointed out that by removing the pod you would get to see how removing ~6lbs forward changes things. Doing this would give some easy and quick answers.

Pete I guess this is to be expected with an experimental project. Personally as I stated earlier I just don't think the engines have what it takes to run 34x12 props. That's just too much length-pitch-mass for stock 6.5hp @ 4800 static. Remember it takes 9.5hp to run the 34x10 P-tips @ 5000+/- efficiently.

A lot has been learned here and now it's just a matter of going to next level. Costs and time are always the limiting factor. Personally I'd be thinking about putting the fresh 185s back on (with P-tips) while leisurely modification-testing was being made to the 6.5's. I think Chappy was on the right road with the notion to use Billet Flywheel, Race Rod, Flat Piston, advance ignition, ect. Again I personally would also be looking hard at the Tilly carb set-up too.

PostPosted: Sat Apr 24, 2010 12:05 am
by peter
Hi Shannon and all....Got the old seat out and a good start at getting the new one in....the front of the old seat was ahead pretty far it wonder I had such little clearance back stick...full back stick gives me tight against the ruddervator bracket/control horn up deflection the way it's supposed to, but now I'll have a bit more ballroom so to speak....just measured where the rivets were installed on the old seat front attachment, and they were 4.5''...looks like they should be at 3.5''according to the manual.
I'm going to give it one more go with the C of G back a bit to see if that improves performance any with the clones...if I'm not satisfied, I'll either put the 31/10's on or concider the p-tip's more closely...I know I can drive the Clark's with the clones to at least 5200 which is t.o. power for the rotax's.....but that requires the alum. flywheels that I haven't ordered yet.....Chappy,...if you don't mind, what ones did you get and who did you order them from? Did you get the ones with adjustable timing, and what is the weight?

PostPosted: Mon Apr 26, 2010 11:04 pm
by Chappy
Hi Peter,

I've been away for three weeks, and of that, got to spend four days at Sun 'n Fun. Been trying to catch up on stuff today.

Great to hear you have been up in the air; sorry the results haven't been quite what you were hoping for! From my experience with the Lazair, it does not like flying with the CG forward! The rudders create lots of drag trying to keep up the wing's angle of attack, and I suspect that having the center of mass too far forward on the wing doesn't help either. The wing just doesn't work as efficiently that way. You need to get the CG back some from where it is now (just don't go crazy like someone we know).

Also, the clones may have a tiny bit more displacement than the Rotax, but they only fire every other rotation compared to the Rotax and that puts them at a power disadvantage. On the other hand, the Rotax is a very low output engine for it's size, so that's working in our favor. I hoping bumping up the compression and advancing the timing will "wake up" the clones. I bought the $99 aluminum Honda flywheel from, part number7848864. They are supposedly 2-3 pounds lighter than the iron flywheel (before cutting off the fins). I plan to eventually cut off all the cooling fins, but will hold off until I know we can get enough power to pick my big butt off the ground. That way I can use it in some other application. It has the keyway advanced about 4-5 degrees over the stock iron flywheel and also the aluminum billet flywheel that everyone sells. I got one of the 4 degree offset keys too, but it was not what I thought it would be. I thought I was actually going to get an offset key, but what it is is just a milled off stock key. Crap. There's nothing to keep the flywheel from slipping back and retarding the timing, plus if it moves it could damage the flywheel or crankshaft. I plan on using low strength Locktite when installing the flywheel and so-called offset key, and hope I can get the darn thing apart without damaging stuff when I need to.

Also, I plan to eventually try the carb off the Rotax in place of the float carbs. That requires a different little manifold (about another $50US with gaskets). But I think the most important change to be made is to get a more aggressive camshaft into the engine. As you know, these engines make great torque at a very low rpm, but the problem is that with a stock cam, the torque begins to fall off above the 2500 rpm peak. That kills the horsepower rather quickly as we wind the engine up. The trick is to keep a fairly low peak torque rpm, but keep the torque output flat as long as possible. The cam can help do that. Unfortunately, it's the most expensive part at over $100US. All told, I have about $500US in engine parts (for one engine) not counting the engine, carb, velocity stack, prop, prop hub, and mounts. I hope my old Aymar 35X10 props work out, but they may need a bit more pitch. Add in a $350 genuine Honda GX-200, and the cheap engine thing is no more. But if there's enough power and they are reliable, I'll be satisfied.

I found some aluminum cut-offs and engine mounts to play with at the show, along with some hardware. I saw only one new UL design and it was interesting, called the Lucky Stars II and met the designer/builder. This is something like his seventh or eighth design, and he says even though he's designed yet another plane, he loves this on so much he hasn't had any motivation to build the next design. Other than John Moody and a few buddies that brought John's Easy Riser and a pair of Eagles, there sure weren't many Part 103 legal ultralights in attendance this year. It was really rather depressing for me. Ultralighting in the US, at least the commercial part anyway, seems to be just about completely crapped out.


PostPosted: Sun May 02, 2010 11:53 pm
by peter
Hi Chappy...thanks for the update and the info on the flywheels...I'm going to order those and also con. rods tonite...I also like your thoughts on the tillotson carbs, although my present setup seems to be working better now with the idle up close to 2000 flooding out now.
I finally finished installing the new seat thanks to Shannons' info,..haven't had a chance to get some new balance data, but I will when the weather improves and I can move the plane back out of the barn....I must say the seat sure feels more comfortable and natural than the old banana though.....I'd say it looks better too, if it's possible to have an eye for that sort of thing...I may just test fly it down the runway to see how it feels.
I didn't have to move the tank back any, what with the more upright back of the seat...I had intended to have a couple of pics of the installation to post...sorry...I'm sure hoping the CofG change will get the wing flying the way it is supposed to....I'm sure I have enough power and thrust for better performance than I'm getting with my present setup....anyway, I'll know the first nice day..
Great to see the old Sun and Fun stuff and also the legal Hawk....thanks guys..........Cheers ....Pete

PostPosted: Thu May 20, 2010 8:54 am
by peter
Hi Guys...Got up yest. for the first time since replacing the seat and I am pleased to say the performance is vastly improved...climb a bit close to the mid 40's...maybe 43 @4600...and I've got some float now on flare...The plane just feels /flys like it should now, and I feel quite comfortable now with it's performance...just made me smile when I was slowly gaining altitude when I thought I was flying level. I was up for one an a quarter hours, and the motors never missed a beat...I replaced the 1/8'' gas lines with 1/4 to the tank, and safety wired all the connections, and installed 1/8'' return lines to the tank to solve the idle flooding problem. I've got the bilit flywheels in now, by the way, they are 2lbs each lighter,but didn't do the rods, my thinking was that if I couldn't get enough power then I would change them along with any valve work I had to do.....I'd love to try a set of 36/10 p-tips Shannon, I think I have the power to drive them to 5000, and I'm sure they are a lot more efficient than those heavy GSC's. I'm going to install trim tabs when I get a chance...needs just a tad forward stick now... But it flys good enough and I'm looking forward now to some good flying in the coming months...The motors are noisier than I would like, but I think a lot of that is the props roaring away.
Chappy..the gross weight for the complete motor setup, including prop and nacelle, ready to bolt on to the wing is about 38lbs. It appears, so far at least, that these motors are able to do the job, and I think with a better set of props, my engine mods are sufficient, at least for my 160lbs, to do a quite satisfactory job....Fuel burn is not too shabby either..looked like a bit more than a quarter tank in an hour and a quarter...bonus.
Got a bit of video from the cockpit flyin over the farm I'll try to get posted.............Cheers Pete

PostPosted: Fri May 21, 2010 4:58 pm
by Chappy