I thought I'd run this by some of you to get your opinions. While trying to get my new Saito 72 adjusted correctly I noticed 2 things on my DPM Ultimate 40.

1. The carbon fiber aileron interconnects vibrate while the engine is running, in fact they move back and forth fact by about 1/8" in the center as a result at full throttle.

2. When advancing the throttle from idle to full the elevator halves flutter a bit due to vibration. They calm as the engine nears peak RPM.

The prop and nose cone are balanced, and were checked again this evening to be sure. I am not sure I can do anything about the aileron interconnects, but I was thinking the elevator halves pull-pull cables are not tight enough. There is certainly no slop in the control surfaces, though. The LHS owner checked the plane over and specifically the cables last Wednesday and saw no probs with it.

Should I be worried about this? The elevator is what really bothers me.

TIA

Sorry I can't answer your specific question, but my buddy's DPM Ultimate 40 broke the forward cabane attachment point (on the underside of the upper wing) fairly early; he had like maybe 20 flights on it total.

He's still waiting on the part. From what I've been reading here regarding DPM "support" after the sale, he may be waiting quite a while longer. Too bad, because it is really a nice model. I would like to have one. But I think I'll pass, in favor of some company who returns calls/messages.

Steve, after having my Goldberg Ultimate for two months now and about 20 flights. I would suggest you take a serious look at it if you are looking for a new Bipe. It's basically the same plane, but in a size between the DP40 and DP120. In the last few years I have built about every kind of plane you can think of and the CG ultimate is as good as it gets. On top of that they include a complete parts list and one call gets you service.

I built the CG Ultimate many years ago, with an OS 120 Surpass. You're right, it is a classic model that flies great. I sold mine only because I was tired of dicking around with that miserable, non-functioning DuBro fueling valve.

I agree that it is sized "just right"; however, I have an S-10 pickup with a fiberglass bed cover these days, and that severely limits the size of what I can carry back there, since I've only got 19" of vertical clearance.

I keep looking at the GP 40-sized kit. I've got a Contender to finish first, but that GP Ultimate is definitely on my short list for a next project.

Are you sure it's vibration? Is the rest of the plane vibrating? Could it be control flutter? Maybe try sealing the hinge gaps with some tape or covering.

Yeah the entire plane vibrates, but only the aileron interconnects and the elevators show it. The fuse acts like an echo chamber even.

All the gaps are sealed with clear monokote already.

I am confident the 4 stroke Saito 72 is to blame for this. This is my fist, and likely last 4 stoke. It just vibrates too much. I have tried 3 different props as well. All the props are balanced.

Four strokes can be a handful vibration wise. Your particular engine might just be one of the "shakers". I would check the specs. DP recommends no larger than a 63 4 stroke and has said that the YS 63 is too much for the plane. Your 72 is significantly larger. A recent review of this model used a Saito 72, and the magazine included a DP comment at the bottom stating that the engine was larger than he recommended. DP tends to design on the light side and when he recommends an engine size range I would seriously consider it unless I was prepared to beef up the model significantly. The plane's a good one, you might want to try a 56.

I well knew the specs when I got the plane and engine. I had also read several times the review here in RCU Mag as well as watched carefully what everyone was using for power. .50 2 strokes and .63-.72 4 strokes are all I have seen used, accept for Dave Patrick. I was concerned about getting a 4 stroke, and my concers have become reality. What a mistake. It vibrates a lot and is very finicky to get adjusted correctly.

The DPM Ultimate 40 is well over 5 lbs. I cannot imagine a .45 size 2 stroke in it. What a slug it would likely be. The only .45 I have is a Viper Q500 that weighs 4.25 lbs and it is just adequate.

I have always over powered my planes. My previous Ultimate was a .40 size running a .60 on a tuned pipe which weighed 4.75 lbs ready to fly, and it flew great.

An intersting note on Dave Patricks addendum to the RCU review. DP said the Saito 72 would add considerable vibration, well he was right. He also said it would add considerable weight, mine was still tail heavy. I have the 1450 mah battery on the firewall and 1/2 oz of weight on the nose to get the CG at 1.25" in front of the rear cabane. DP recommends 1.5" to start and then move back slowly, I'm not adding the additional 2 oz to it though to get the CG where he recommends. My .45 is 3 oz lighter than the Saito.

If you're running a 60 with a pipe on a 40 sized plane, no engine in the listed accepted size range will satisfy you. The 4 strokes are generally not hard to set up and adjust, just a little different than 2 strokes. Saito engines don't seem to be much different than others, I have four (56, 80, 100, 120) and although the 80 required physical mods to run correctly, the others didn't. Engine vibration was no more than other 4 strokes ( I also have an OS 52, 91 and YS63, 91 and 120), but that is more than 2 strokes in general. I would let others who have 4 strokes look at it, if it indeed vibrates more than normal, I would send it back to Horizon. If not, then you may not want to accept that much vibration. If you're having trouble adjusting it, the source of the problem may be that it's lean or rich. You may just want to go back to 2 strokes, it should be fun and isn't worth aggravation.

The 60 on a pipe was when I was 19. I wouldn't go that far now anyway. Nowadays I care a little bit more about safety. That was pushing the envelope. Now I have kids, and have grown up a bit. Back then I kinda flew the prop and wanted things to be wild, now that I have gotten back into RC I'd like to learn to really fly well, and under control.

I agree that I made a mistake getting the Saito 72 4 stroke for the DPM Ultimate 40. The vibration I will have to see about, the aileron interconnects and the elevators are all that concern me. I have tried tightening the elevator pull-pull cables a bit more to see if that helps. Course accelerating slowly it also does not vibrate the elevators. The interconnects vibrate from idle on up, and it gets worse as the rpm increases.

If I had the money I think I'd get either a Saito 56, or more likely an OS 50SX for it. My wife, the boss, said NO not right now at least.

The adjusting thing I hope I just have to be patient and get used to the 4 strokes. This is my first 4 stroke, after owning at least 50 different 2 strokes. The Saito runs good and accelerates great, but it won't idle under 3000 rpm. Maybe I need more time for break in. I have about 1/2 gallon through it now.

Since you likely know more about 4 strokes than I, will the OS type F plug help the idle any? Do I just need to let it break in some more? Also I put an exhaust diverter on it and lost about 500 rpm, is that normal? I've never run a diverter before.

TIA and sorry if I was a little snippy earlier Jim.

A Saito 56 would fly this model well, but it would not have any reserve power. My pal's has a YS 63, which is equal in output to your Saito 72 (practically speaking). Unlimited vertical, etc., etc...

Do not let this one bad experience sour you on four-bangers. While I have only owned one Saito, the 72 is one of their better ones. You could indeed have one that has a bad out-of-balance crank, or whatever.

You could also have an airframe problem (broken motor mount, cracked firewall, etc.) that is not readily apparent.

Four strokes are cool. They do take a bit more attention than two strokes, but sacks full of people find that extra effort more than worth it.

I would try your engine on another airframe (a test stand would be too rigid for you to really notice what's going on) to see if it shakes that one as bad. If so, send it back to Horizon with a detailed letter of explanation. They have an excellent track record regarding standing behind their products. If not, then you know to scrutinize your model more closely.

The early 72s had a problem with busting the crank case. This was due to insufficient strength in the case webs to handle the increased power output. That has supposedly been addressed. The fact that there are many, many happy users of this engine speaks for itself.

If you blow off four strokes because of this bad experience, then you might be robbing yourself of some additional modeling enjoyment.

Also, Chris, the OS F is the plug of choice for mst four stroke applications.

And you engine should improve its idle after a gallon or so. The proper propellor is also important. Most new four stroke users tend to under-prop their engines.

A well-broken-in Saito 72 will swing a low-pitch (4 or 5) 14 inch prop, and this is what you want to best utilize the torque of your engine. The APC "wide" props are true stump pullers. The time and money invested in trying out some different props can be very educational and productive.

It can also be aggravating, but if this was too easy we wouldn't enjoy it as much, eh? I just finished spending many weeks and over $50 trying different props on my YS 63/SIG SE, just to discover that the initial one I put on there is the optimum. Oh, well... some days you get chicken, and some days you get feathers.

The pull-pull cables should have slack removed but don't need to be "tight", in other words you don't need to have a lot of tension on them. If you're willing I would stick with the four stroke for now. I really like them and still fly two strokes but the sound and torque of the 4 strokes are nice. If you continue to have problems, stick a two stroke in it. Like I said it's about fun not aggravation. You can keep the 72, work with it some and put it in something else later.

I'm gonna play with the Saito 72 a bit more. If I want to fly the plane I haven't much choice at this time.

I have an OS type F plug I will try next time I have a chance to tinker with it.

I have a 12x8 and a 13x6 APC prop for the Saito, and have considered trying a 14x4 or 14x5, but I'll prbably fly it first with the 13x6. The engine seems to run a bit smoother with it, maybe it's just my imagination though.

I have also wondered if changing the clevis' on the aileron interconnects to plastic would help reduce the vibration on them. I have some I am gonna try.

I finally got the radio programmed correctly last night. Hopefully in the next few weeks I'll get a chance to go fly it. Flying time is rare for me, in fact I've only been twice this year.

I had one of the first Ultimate 40s and flew if for an entire season before selling it. Mine had a YS63 in it and it was a perfect engine/airframe combination. I used all of the standard DP hardware on mine and also had some concerns with vibration before the first few flights. I sealed my control surfaces, replaced some of the linkages with tighter connections and tightened my pull-pull connections ever so slightly. There still was a bit of vibration, but it didn't hurt a thing in flight. That little plane was rock solid and a real performer with the YS63/APC 13x6 combo. I too suffered a sheared off wing attach fitting on the upper wing center, but I had replacement parts within 3 days from DPM and never had a problem after that. Even the tail control surfaces on my big DP Ultimate and DP Edge have a bit of vibration during runup, but once you get in the air, it is not an issue. I say fly the thing w/ the Saito and you might be in for a pleasant surprise. Mine weighed in at 5 lbs even with an empty tank and you'll never find the kind of stability and control authority in any other plane of this size. It flies as good as my CG Ultimates did, but the light weight just made it a little trickier in wind. Good Luck.

rongreg13

Thanks for the reply. I may just go ahead and fly it. That'll tell for sure if it's okay. Since it seems I am not the only 1 with the vibration issue and it has been fine for others I will just get the engine set right and see how it goes.