rm

My Feedback: (27)

Picked up a new motor to try out. EME35.

actual weights:
motor with spinner bolts, and cm6. 1004g
aluminum standoffs without bolts 52g
ignition 108g

length to spinner back plate, motor mount pattern, header bolt pattern, matches OS, so should be a drop in fit.

ignition is rcexel. has a rpm extension, not sure how that works. high voltage.

needle valves are upward, will have to do something with that, as well as throttle and choke.

black friday price was $239. reg $269. pretty good deal. included ngk cm6 plug, standoffs, and other stuff which all cost extra on the OS.

Included some rpm testing done by another chap, link to his thread
http://rccanucks.com/showthread.php?365-EME35-vs-DA35&

vatechguy3

My Feedback: (11)

Has anyone compared a da35 on the same pipe/prop combo as an osgt33?

Tony

MTK

Tony,

A guy at Flying Giants made a comparison between the two engines and claims more power from the DA.

My OS puts out more power for Pattern than required for any maneuver we fly in Masters or F3A. I never go to full power for anything. So, for me, the DA brings nothing to the table. If it was lighter, if it had outstanding throttle response and much better than the OS, or it was rear exhaust, I would buy one

EDIT-- I've mentioned this before but may be worth repeating. The heaviest pattern model I've flown on the OS33 was my Aesthesis at 11 1/2#. The plane was originally built for the ZDZ40 rear exhaust which at 40 ounces was a bit porky. I moved the firewall a little fore to accommodate. When I installed the OS the plane needed about 6 ounces of nose weight to balance reasonably. So the weight got out of hand. Still, the OS had no problem with this weight..... No different in throttle management to speak of than the more typical weights of 10 1/2# of Temptress and Delta.

vatechguy3

My Feedback: (11)

yeah the rear exhaust would be nice for sure, either from DA or OS.

tony

kenh3497

I don't want to run this thread to far off track.... I have a Supertiger S3250. Specs say 43 oz. without muffler. Mine has the backplate mount so I would have to say it might be heavier yet. I would consider converting it to a sparky for economy and reliability. YUP, more weight

Would the Tiger make a "suitable" engine for a 2M plane?

Thanks!

Ken

MTK

How much prop does it turn? The current crop of pattern planes really need at least a 19" to work properly. If it turns say a 19-11 or 12, at around 7- 7.5k, it would work okay even if the plane weighed 12#. If it turns a 20-21" prop, even better. It probably will need a pipe to get the mid range torque. I don't have any experience with ST so don't know capability first hand..... maybe someone else does and can chime in?

As I've stated before in this thread the GT33 turns the 20.5x10.5 APC at 7100 and the 20x10.5 at 7400, burning avgas. On premium autogas it will turn +300-400 rpm, same props. These are all very sporty numbers and produce incredible performance on an11# pattern plane.

Good of luck with it.

kenh3497

I don't have any experience with Tiger but from the manual is says 7300 to 7800 RPM. A "break in" prop 18 X8 is recommended and then up to a 20 X 8 is OK. I know with spark you can expect an increase in power just because you can control the ignition point MUCH better than a glow plug. I would expect the engine to go into an "older" air frame so maybe the power thing might not be as big a deal??? From what I understand these engines are know for their torque. Like I say no first hand experience.

Ken

PS. I was going to have it auctioned off this weekend but when I saw a ST 4500 sell for $40 or $45, I decided I WAS NOT going to give it away.

MTK

I just completed the rebuild of my first GT33. Straight forward.....piston plus ring and the piston liner were replaced as well as the retainer clips. I will run it in the newly modified Griffin....modified from electric that is. Modifications were extensive but resulted in a net loss in weight. The rudder, balsa firewall and landing gear mounts in the fuse saved about 140 grams. I opted for all pull-pull controls which removed a bunch of tail weight.

There is quite a bit more weight that can be saved in built up wings and stabs but I'll wait until I fly the plane before deciding on that.

MTK

I played with the engine today and with some coaxing, it finally fired. Had to richen both needles nearly 1/4 turn to get decent running without the engine wanting to cut out. Quite a bit of smoke but it was running smoothly and strong. Im sure that the needles will be leaned over time as the engine breaks in. Only an 18x12 on it right now which turns much too fast for my liking. The first 20-30 runs will be made with this prop to beak in the new piston, ring and sleeve.

I hope we have decent weather tomorrow for the Griffin maiden.

In meantime, R&D continues with a newly built 21x10.5 MDK wood carbon hybrid. I made a 21x10 MDK hybrid for a customer's YS185 about a year ago and wanted the same prop for my GT33. Based on information from Scott re: performance, I decided to narrow the blades about 10% more and thin them down another 10%. I had run the APC 21x10 wpn a while back on the 33 and got a respectable 6900 rpm. The engine did not bog down or overheat but it just sounded like it wasn't happy. Or it might have been my ears hearing things that weren't there. This much load wass unchartered territory.

Well, the new prop has narrower blades and is much thinner at the hub. I think the 33 should rev up a little more than it did with the APC, but of course this waits to be proven. Weight is a very nice 82.5 grams or about 45% that of the APC.

drac1

My Feedback: (4)

65% of the new APC Carbon

rm

My Feedback: (27)

pics ...........we need pics

MTK

I only have the all glass prop to measure against which weighs a whopping 195 grams. A beautiful piece of equipment tho and is worth copying or modifying to suit. So the part carbon prop weighs about 150?

I'll try to remember to take my camera for photos. Weather looks fly able so I'll head to the field soon.

MTK

After all the work to modify the Griffin and make it ready for gas, it felt good to finally get it in the air today. Geez it only took two years....of course, that's because of a bunch of health issues and several hospital stays.

Final rtf weight is 9# 13 ounces. With gasoline in the tank it tops off at 10# 4 ounces.....flies very light on its wing. The airplane flies true requiring only a click of up and two clicks of left aileron. Yaw stability is good. There is no roll couple and only a slight hint of down pitch couple. It's surprising it didn't become more popular. The wing could use a thinner tip section to enable easier snaps and spins. Maybe that's why, who knows. Don't know who designed this bird but he did a fine job overall. And Xtreme Composites did a good job in the build.

The 18x12 APC is a good break in prop providing a minimum of load and allowing relatively high revs...just what a new piston, ring and liner need. Of course with such a light weight, the plane flew very well at about 1/3throttle, or less than 6k rpm. With only 8 ozs gas on board I experienced a couple dead sticks but the plane floated in from long distance easily. A successful day and a very sweet flier.

EDIT: on second thought, I remember folks had wing failures due to a flawed spar design. What a shame. It probably doomed the design.

drac1

My Feedback: (4)

The 21 X 10 Carbon weighs 125.5 grams. 39.5 grams lighter than the 21 X 10 Nylon/Glass.

It spools up quicker and verticals are much better.

MTK

Not sure what prop you have. I have the 21x10 wpn which weighs about 195 as i recall. It's been a year or more since I weighed it tho.

Here are a few photos

Canopy was modified from electric full length to gas partial length like old times.
.
Chin cowl was cut from the fuse. Electric only planes apparently have done away with chins. Not difficult .


Pull-pull on elevator removes weight from the tail (servos and wire extensions). It produces better overall trim capability.

Engine offset 5 degrees to accommodate the header. As it turned out the model is so light, a lesser engine than the GT33, such as the DLE 35 RA might have been a better choice due to the rear exhaust configuration. No offset would have been required. It's just that the GT33 is simply the best for this type of thing. Your milage may vary, as always.
Even this engine is, after all, a rebuild. The failure was very strange; you just don't hear of gas engines chucking their circlips after a backfire. That's what happened to this one last year after terrific service for over 3 years (some 130 hours of operation)

The rudder was changed to a built up unit finished in Esaki Jap tissue and water colors. The rudder alone saved well over 1 ounce off the tail.

The landing gear was changed to my design. This type of gear simply plugs into sockets on the side of the fuse and is secured by those sockets. A single 4-40 screw holds each strut in place. I've written about this approach several times and have used the method for 6 years now..... It is lighter and much stronger than the stock mounting blocks. All up weight for the complete gear set including the fuse mount, pants, wheels and axles is about 6 ounces. The axle, pants and struts are constructed in monocoque fashion. Pants stay on even flying off relatively rough grass strip. Of course there are special design features built in that enable this kind of strength.


I added the near full depth center bulkhead just in front of the wing tube. Also added a pair of stiffeners along the radio cavity in the fuse near the top of the compartment. The shake at idle was better managed with these small but important mods. With wings on, the wing tip shake is almost nil. The thin foam I use to form the pipe tunnel floor should be visible. It is very light yet fully functional. The pipe does not attach to the pipe floor; pipe is attached to the outside fuse shell.

It's hard to see in this shot. The engine mount was deepened slightly to allow just about 1" of rubber. This helps the soft feel of the mount, snubbing vibes better. Notice that I had to grind the head fins a little to clear the chin cowl's center rib.


The mount has a large hole in its center aligning with a corresponding hole in the firewall. The balsa/carbon composite firewall weighed a scant 18 grams as I recall after the hole was cut.

MTK

A couple more photos


Building a wood/carbon hybrid is not difficult. I start with an electric woodie from Falcon or XOAR and shape it according to design specs I want.

There are three layers of carbon in this prop. Two are full length and the third covers only the center section out to the 3" station.
This blade shows what the prop looks like after laminating and top epoxy filler coat have been sanded smooth.

This blade is filled but as yet unsanded.

I use a braided carbon tube and epoxy to laminate. The scale and balancer are always on hand during this process

drac1

My Feedback: (4)

21 X 10 PN Matt. It's actually 10 grams lighter than the 20.5 X 10. I have a WPN but haven't weighed that.

MTK

Ahh....apples and oranges.
both are fruit and both make juice but different. I thought their 21x10 only came in one flavor. Maybe it did when I purchased mine, dunno. Apparently I have the wide blades.? No wonder my 33 sounded unhappy turning this prop.

MTK

RM,
did you determine the causes of the GT33 seizing?

The rebui!lt engine I just put into service seized again after 10 runs. It was the same failure mode....circlip popped off and jammed the piston. The failure occurred on the same circlip as the first time...the side of the screw port. There is an intake port on the path which does not have a rib support. A rib in the sleeve's intake port might eliminate the possibility of the circlip popping off. Or a different design is needed to retain the wrist pin.

Thats a serious design problem in my opinion. It's something OS needs to address.

drac1

My Feedback: (4)

Hi Matt,

It shouldn't be relying on the sleeve to hold the circlip on though. Did you replace the wrist pin?

rm

My Feedback: (27)

Yep, it's been the same clip in 2 motors. Not sure what happened to the 3rd with the top of the piston.

rm

My Feedback: (27)

I'm coming to the conclusion that anyone who competes with a combustion engine, no matter what type needs a backup motor, and 2 backups if u want to be sure.

MTK

Scott,
The wrist pin was not replaced. The piston and liner, ring, and both circlips were. Of course the piston and liner are both scratched and are probably toast.

I will contact Hobby Services to see if there's an OS fix for this flaw. RM and I can't be the only unlucky souls. The clips need a deeper groove and a larger diameter I think. Circlips holding wrist pins in place are not new technology. If the clips are breaking up, hydrogen embrittlement could be the culprit.

anyway, I just installed a new gt33 in the Griffin and hopefully 3 times a charm.

drac1

My Feedback: (4)

Maybe the edge of the circlip groove had rounded off a bit?? Just a thought.

MTK

Anything is possible. The piston originally had around 700 flights and then was badly damaged by the clip ingestion. The new piston had only 10 flights on it.

We'll see what Hobby Services has to say. The kid on the phone tried to be helpful. I'm sending it back for their evaluation. I know mine is not the only one with this problem