A 12 X 8 3-blade should be fairly equivalent to a 13 X 8 or 14 X 6 2-blade prop. Any of the three should be a good match to your Magnum 91 4-stroke as long as you've enough ground clearance and the 3-blade just looks good on the T-28.

Regards,

Clay

Ive looked at everything on this plane and been impressed with the quality of everything except the plastic engine mount. I wanted to use the DuBro rubber isolation mount but it put the engine another half inch forward because of its thick isolators, and extra clearance need forward because of the four stroke carburator, hence a balancing issue. Im not to the point of balancing but does the plane tend to balance tail or nose heavy? I guess my question is has anyone had any issues with the stock engine mount? It just looks cheap.

I tried a 14 x 6 two blade against a 12 x 8 three blade MAS prop on the bench. They ran within 50 rpm's of each other. They may run different rpm's at wide open throttle with the plane flying in the air though. Don't know.

Outstanding information Balsa. I just got a few 3 blades for $3 a piece at a swap meet and right now I can't remember if they are 12 or 13's. My question though is what about the two strokes. I have a Magnum 91 2 stroke.

This info is from Master Air Screw. 12 x 6 or 12 x 8 should be O.K.

skysfallin, I don't use those stock two piece engine mounts. I used a GP 40-70 mount for my Saito 82 for this plane. The GP mounts are sturdy and they have slots that allow you to move the engine up or down on the firewall (if mounting engine sideways). That helps to center the prop shaft in the cowl opening...gives you some room for error. With the Saito 82, my plane balances on the recommended CG perfectly. What I have been reading is that with OS and Magnums 91's the plane has been nose heavy. With the Saitos it seems to balance on or very close to the CG recommended. Jon

Thanks, I was thinking about the GP mount, I have it in most of my other planes and I like the adjustability of it. I just wanted to try the rubber Iso mount the Dubro makes. It looks like such a good idea for reducing vibration.

Hello Maukaonyx,

I was able to balance my plane out perfectly without adding any weight. I have a 91 2 stroke. I am not sure if the 2 stroke is lighter than the 4 stroke or not. Just an FYI.

Joseph

Sorry, I could have been clearer in specifying 91 four stroke engines. And it just appears from our thread that the 91 and larger four strokes are balancing nose heavy. There is always an exception since these T-28's are not all identical, and we are all different folks assembling them. Thanks for the clarification though. Jon

Finally finished my T-28 today!!! I was waiting almost two weeks for the straight exhaust manifold (the coupler between the engine and the muffler) for my Saito 82. It never came and I might have got screwed by an online dealer, so today I went to Corvallis, about 50 miles from Salem, to a hobby shop there that had the part...I had called them to confirm yesterday. Brought it home and had to cut off about 3/8" from its overall 1.5" length. That makes the stock muffler fit inside the cowl. So here is a pic of the business end of my T-28. The needle valve extension is visible, and is not as close to the nose gear as it looks. They are about 3/4" apart. The stock muffler is completely inside the cowl and what you see is the rubber exhaust deflector connected to it. Might need a larger exhaust hole by the nose gear if I have any overheating problems. Looking forward to trying this baby out as soon as the weather permits here! Jon

maukaonyx, the plane looks great. I really like what you did to the cowling and the exhaust. the biggest thing i found was making sure the air gets pulled over the head. It looks like it will be pretty close with the baffle and the hole where the extention is at plus the hole around the landing gear. Also your head is exposed where my 2 stroke is completely enclosed minus the pitts muffler exhaust tubes.

If you don't mind my opinion or suggestion actually. Get the plane going and only take it up for a lap and land. then feel the engine and prop hub. Initially mine was on fire within a few minutes. Fortunately it didn't burn my engine up. I put the hole in my cowling to pull the air over the head and it is cool as can be everytime I run it.

I can't wait to hear your report.

Joe

Hi everyone,

First post, I've finished my T-28 a couple weeks ago. Made a few small changes that I copied from your posts, I'm using a Saito FA80 I bought from a guy in our club new in the box for $90.00, a good deal but it's weight is giving me a ton of grief.
It must be very light for this plane as it flew very tail heavy. To get it to fly level with no trims it took 6 oz of lead on the back of the motor mount. All you guys are saying yours balance fine. Is the saito that much lighter then the Magnum or OS 91?
I even put the battery under the fuel tank..

Any Ideas

Thanks
Carl

Hi Carl, welcome to the thread! Do you have space to mount lead farther forward on the motor mount? Or maybe you could use the heavy Higley hubnut if you aren't already. I'd try to do these things to reduce the amount of lead you have to add. If you can't, no worries, just fly and have fun. How much does your plane weigh with the lead added to balance at the recommended CG? Good luck! Jon

Hello Carl,

Welcome to the T-28 club I checked with the Saito site and the 80 weighs 540 grams which converts to 19.048 oz. while the Magnum 91 2 stroke weighs 24.8 ounces. So I am guessing that this is the reason for your plane being tail heavy and having to put 6 oz of lead on the firewall. Hope this helps you out. Tower Hobbies has a conversion program on their website to help you convert grams to oz and so on.

This is an amazing thread, didn't realize how popular this plane would be when I purchased mine. The difference in peoples building techniques etc is astounding. I flew mine with a 91 Thunder Tiger FS in the nose and it performed beautifully. I really enjoyed flying it. We have 3 of these full sized aircraft based in my town and it is wonderfull to see them in the sky. one is ex CIA that flew in Vietnam, the other is ex Navy Flying School and the 3rd on which is in the same colors as the RC version has only recently arrived in town. Don't know its history.

Great plane, great thread and a fabulous RC bird to fly and even better to sit in the real McCoy and dance around the sky.

Hi Guys,
Thanks for the quick reply and the nice welcome. I just snuck out with the wifes scale, it weights 8lb 6oz and i'm moving the motor foreward. Plus changing motor mounts to metal ones.
I'm still confused with cg105mm it balanced a little nose heavy.
I had to give it 17 clicks down elevator, added the weight and no trim and it flys OK.
It's not even close to the recommended CG, the CG now is 65mm..
Does this make any sence to you guys?

Carl

I have the saito 82a. It's 16oz without the muffler and the plane is slightly nose heavey @ 105mm, which I prefer. You may want to check and see if you have up thrust in you mount.

Just my 2 cents.

Carl, I agree with phatbob02. Methinks you are trying to battle the upthrust by adding nose weight. 65mm is way forward of the recommended CG. Personally, I would take out some of the nose weight and try to hit the recommended CG, or maybe 1 cm ahead of it for safety. Set your elevator about neutral. Try some washers or add a ply shim for downthrust. Smarter to try washers first since they can actually serve as some nose weight for you if that is still a concern. My Saito 82 on this plane was just right. It balances right on the recommended CG, and my AUW is about 7lbs 3 ounces. At over one pound heavier, I also think you simply got a plane off the assembly line that has heavier wood behind the CG than mine. Good luck whatever you do! Jon

Ok guys, I maidened my T-28 today!!! It was exciting as most maiden days are. It went well enough and I got in two flights, but I am not going to gush about how good the plane flies yet, because mine doesn't fly that well YET! I got it home in one piece and that makes it a good day, but I have some work to do to make it fly like I want it to. I'll just list the main points to report:

1. The Saito 82 is my first Saito and it runs like a top. I think the main problem people have with starting any engine is to make sure it is wet enough. I pinched the rubber exhaust extender shut and hand cranked the engine a good ten times at full throttle to get the plug wet, and it started pretty easily at high idle with a backward flip after energizing the plug. Not on the first flip each time, but it was easy enough. I have to say this engine idles better than any of my OS FS engines, but I still love em anyhow. This engine provides an abundance of power for this plane.

2. I built in a down thrust ply shim on the firewall. It is 3/16" at the top and tapers to paper thin at the bottom of the wedge, and is just slightly larger than the GP 40-70 engine mount. My protractor and calibrated butt says it adds about 3 degrees downthrust on the stock firewall. I think it is about right. At full bore and trimmed per #3 below, she stays level.

3. My plane still needed about 9 clicks down elevator to fly level. At this trim, the bottom of the stab and elevator are pretty flat (used my ruler to check). I am thinking the decalage of the ARF is a little off, and if I could do it over, when trimming the stab saddle in the fuse, I would sand it in such a way to drop the trailing edge of the stab just a smidge...maybe 1/16".

4. The plane flew real floaty like. Mine balances on the recommended CG. I am going to move the battery under the fuel tank near the fire wall. It is currently behind the bulkhead where the rear of the tank is located. If that is not enough, I will add a couple ounces lead to the front of the engine mount or get a brass prop nut.

5. I have new Tower TS-126 digital servos in the plane (except for throttle) and I think they might be slow...either the plane wanted to tip stall or the ailerons were moving too slow. Not sure, so I am going to make them faster by going to a 6V battery. That will help me in the CG department too, by adding another cell ( about an ounce per AA cell) to move behind the firewall. I checked my wings and they are flat to me, so any tip stall is not caused by wash-in. Just to be safe, I am going to warp in a little washout in each wing with my heat gun. I had to fly with six clicks of right aileron trim, and that could effectively create wash-in on the left wing. I am going to mechanically trim each aileron to be up perhaps 1/16" at neutral on the stick. Hope that makes sense.

6. The hinges that I used to hold the landing gear door to the wing...one of them cracked in flight due to vibrations in the air or landing gear flex on the ground. That door was flapping in the wind, which I did not notice till I landed the first time. I took both doors off for the second flight. I am going to use some tin sheet to replace the hinges. Gotta have them doors on, the plane looks so cool with them!

7. I applied flaps when I was a couple mistakes high, and they gently lifted the nose. Not too much down elevator will be needed to land with flaps, I think. I noticed the plane yawed a little to the right with more flap deflection. I think they move equal amounts, but I will figure that out later, since the plane lands so slow without flaps as it is, so I did not use them on landings today. Try to land with some throttle and speed since I think my plane was starting to tip stall on landing. It also seemed to be tip stalling a little in mid throttle tighter turns. That is another reason why I want to add some wash out and also trim the ailerons up a little.

8. The plane rolled pretty axially at WOT. That was good!

9. One cowling screw backed out about 1/16" after one flight. Others not as much. Re-tightened all for 2nd flight and they didn't loosen anymore.

10. Main wire gears are pretty weak. I didn't bend them on landings but I could see them really boinging around on all taxiing on our grass field. That may have contributed to breaking the hinge I used per #6 above. Next struts will be stiffer, IF I wreck the stock ones.

11. Testors Acrylic paints seem at least partly fuel proof to me. I got raw fuel and burnt fuel on the Robart landing gear covers (esp the nose one), and when I wiped them with a paper towel, no paint came off. That was good too!

12. I was disappointed to see a few wrinkles show up on just the black Oracover, and of course some are inside the canopy!! Argh.

13. There is probably something I missed, and will report on later, haha.

All in all, it was ok for me and it was promising, but I expect the plane to be better each time I fly and trim her out more and more. There is nothing that cannot be figured out and fixed. And she is still a real BEAUTY! Here are some pics at the field! Jon

Jon


That looks awesome sitting there. That painted cowl and gear make a world of difference.

That's one heck of a field. Mine's only 100 ft wide and surrounded on three sides by briar and swamp, but it makes better pilots.

You did balance your prop, correct?

I assume you had no over heating problems. I didn't think you would. The saito's run at 1/2 the rpm's of a 2 stroke and you're running it rich.

I can't wait to get mine out. Hopefully in the next month.

Hey Bob, I knew I forgot something!! Thanks for the reminder:

14. The Saito 82 had no overheating probs with the holes in the cowl per my pic in post #610.

It is indeed a nice sod farm we fly OVER. Our club rents an area for a 250' x 40' runway, pit area, and parking area. When the sod farm is like you see, it makes it ok to land short or long. During the months it is being harvested, tilled, irrigated, etc, we have to know how to land or pay dearly for it. I have seen many a plane wrecked by sprinkler heads and windrows.

Hope you get warm weather soon so you can fly yours too! Jon

You didn't balance your prop, did you?!! I knew that when you said your cowl screws were leaving.

I didn't cut a hole in the bottom but I did make the cowl scoops functional. We will see.

I may hit 50 here tomorrow. I have four planes I built this winter that need a maiden. I'm keeping my fingers x'd.

Hey mauk, (Jon)

Nice flight report. Glad you finally got around to flying that beauty. Nice flying field too,,,just watch out for the water.

Hello Jon,

Congrats on the maiden. I have to be quiet honest I have been skeptical of the doors all along wondering if they would snap or pull away from the wing in flight. I absolutely agree they look fantastic on the plane. I wonder if maybe you would have to run a piece of ply connecting two wing ribs for better support. Of course you have to paint them white. Or am I not understanding where the door come apart?

How was the taxiing with the plane? Did it roll down the runway or did it lift at half throttle? Correct me if I am wrong, which I am most of the time according to the house boss. Didn't you put 3 inch wheels on the rear and a 2 1/4 on the front?

Great report Jon. Just remember the end result happened. The plane went up and came back in one piece for you to fly another day. I have had the unfortunate luck of only 9 minutes life span. LOL. My trainer had a mid air with my plane. LOL Oh well what can you do. Anyway, looking great and time to get that 3 blade prop on there and you can park your plane at the local air base.

All T-28 pilots, what shade of red did you use & what kind of paint did you use to paint that yellow ring? Did you masked it off & left the black oracover on, or did you paint the black stripe on?