Da-85 - Actual Field Results

[krayzc]

the 85 is a very smooth single in my book

[sherman89]

I must be doing something wrong, I can't keep the motor box together, every day I fly I have to glue the bottom plywood back on. I have used 30 minute epoxy, thin Ca, thick CA. The prop and spinner have been balanced. At low-mid rpm the plane vibrates very bad,after 4 gallons what should the rpm be with an Evolution 26x10 prop? This one is turning 6150 at wide open throttle. This my first DA and I am afraid to lean it out and burn it up.

[sherman89]

Well, I guess we will finally find out why this DA-85 was a shaker, I mean was, because, it is seized, tighter than a drum as the saying goes. Lawmboy ashless 32-1 on its fourth gallon, turning a tbm 26x10 at 6150 rpm, idle at 1550, vibration as bad as the first 5 minutes of running. We will see what DA wants to do on Monday.

[WangoTango]

	Quote: Originally Posted by sherman89
	Well, I guess we will finally find out why this DA-85 was a shaker, I mean was, because, it is seized, tighter than a drum as the saying goes. Lawmboy ashless 32-1 on its fourth gallon, turning a tbm 26x10 at 6150 rpm, idle at 1550, vibration as bad as the first 5 minutes of running. We will see what DA wants to do on Monday.

Sherman,
You may have had something wrong with the DA in the first place but take a look at that Evoloution prop too. I had one of the EVO 26-10's on my 3W-80 twin on one of the first runs we did with it. The hub of the prop was soft and came apart after two runs. I also tried a 24-10 Evo and it did the same thing. After only a couple of minutes of running the whole airframe was shaking like crazy, especially at idle. I do have a friend that is having success with his Evoloution prop (smaller size) and another that experienced the same shaking/soft hub. Both of the props I tried seemed real easy to flex. Just something to check.....
WT

[wildhare]

Yesterday I had an opportunity to do a direct comparison of the DA-85 to a DA-100. The two engines were installed in similar aircraft with pretty much identical setups.

The DA-85 has the MTW flex header and MTW TD110K muffler as sold by DA, the header is stock length, not trimmed at all. The DA-85 was on its 5th flight, so it has about a gallon through it. Not broken in completely, but certainly loosened up enough to run it at full output.

The DA-100 has MTW flex headers, also untrimmed, and KS-86-4 mufflers. The DA-100 has been flown quite a bit so I'd say it's as broken in as it's going to get.

I used the same gas in both engines, Pennzoil 32-1. I used the same prop, 27-10 bunny/xoar/tbm/bolly (all the same). They were run within 1 hour of each other and the temperature and air did not change. Both engines had been adjusted for maximum RPM, they were both at the point where they needed to get warmed up to get good throttle response.

These two engines are as close to identical as I could make them. The tests were done in Houston where we were at or slightly below sea level. I used the same tach for both tests. It is possible that the tach is not real accurate, I have noticed that my readings are consistently lower than some that I see on the various forums, but it has been consistent and I am confident that the relative readings of both engines is accurate, meaning that if it's off it's off for both engines the same amount.

The results were as follows.

DA-85 peaked at 5820 and settled back to about 5780 after it got warm.

DA-100 peaked about 5880 and stayed there, it did not change as it warmed up probably because it is more broken in.

The difference in the air is about the same, almost undetectable except for the fact that the plane with the DA-100 had more engine weight to pull around.

Is 100 RPM worth the difference in cost and weight? Probably not.

But there is one significant difference. The DA-100 was much quieter in the air, I was at a fly-in with several dozen other similar planes and probably the most remarkable thing was how quiet it was when the DA-100 flew. Of course with the canister the DA-85 was also very quiet but not down to the whisper level of the 100.

One other bnefit of the twin was that the cowling did not need to be cut, the plane's appearance in the air and on the ground is better with the twin.

The twin might have been slightly smoother also, this is something that's difficult to measure. Either engine was totally in the "super smooth" range. I'd be happy with either one in any 35% plane.

Tom Fawcett
Wild Hare R/C

[aerojack]

	Quote: Originally Posted by wildhare
	Yesterday I had an opportunity to do a direct comparison of the DA-85 to a DA-100. The two engines were installed in similar aircraft with pretty much identical setups. The DA-85 has the MTW flex header and MTW TD110K muffler as sold by DA, the header is stock length, not trimmed at all. The DA-85 was on its 5th flight, so it has about a gallon through it. Not broken in completely, but certainly loosened up enough to run it at full output. The DA-100 has MTW flex headers, also untrimmed, and KS-86-4 mufflers. The DA-100 has been flown quite a bit so I'd say it's as broken in as it's going to get. I used the same gas in both engines, Pennzoil 32-1. I used the same prop, 27-10 bunny/xoar/tbm/bolly (all the same). They were run within 1 hour of each other and the temperature and air did not change. Both engines had been adjusted for maximum RPM, they were both at the point where they needed to get warmed up to get good throttle response. These two engines are as close to identical as I could make them. The tests were done in Houston where we were at or slightly below sea level. I used the same tach for both tests. It is possible that the tach is not real accurate, I have noticed that my readings are consistently lower than some that I see on the various forums, but it has been consistent and I am confident that the relative readings of both engines is accurate, meaning that if it's off it's off for both engines the same amount. The results were as follows. DA-85 peaked at 5820 and settled back to about 5780 after it got warm. DA-100 peaked about 5880 and stayed there, it did not change as it warmed up probably because it is more broken in. The difference in the air is about the same, almost undetectable except for the fact that the plane with the DA-100 had more engine weight to pull around. Is 100 RPM worth the difference in cost and weight? Probably not. But there is one significant difference. The DA-100 was much quieter in the air, I was at a fly-in with several dozen other similar planes and probably the most remarkable thing was how quiet it was when the DA-100 flew. Of course with the canister the DA-85 was also very quiet but not down to the whisper level of the 100. One other bnefit of the twin was that the cowling did not need to be cut, the plane's appearance in the air and on the ground is better with the twin. The twin might have been slightly smoother also, this is something that's difficult to measure. Either engine was totally in the "super smooth" range. I'd be happy with either one in any 35% plane. Tom Fawcett Wild Hare R/C

Hi Tom, hey what % of header drop would you use for the DA85 on your 35% Sukhoi? I have a DA85 here and want to get a header for it to go on my Sukhoi and need to know what drop I need. Thanks!

[sherman89]

	Quote: Originally Posted by WangoTango
	Sherman, You may have had something wrong with the DA in the first place but take a look at that Evoloution prop too. I had one of the EVO 26-10's on my 3W-80 twin on one of the first runs we did with it. The hub of the prop was soft and came apart after two runs. I also tried a 24-10 Evo and it did the same thing. After only a couple of minutes of running the whole airframe was shaking like crazy, especially at idle. I do have a friend that is having success with his Evoloution prop (smaller size) and another that experienced the same shaking/soft hub. Both of the props I tried seemed real easy to flex. Just something to check..... WT

When the engine seized , it was turning a TBM 26x10, by the way, there is nothing wrong with the Evo prop as well, both props where balanced with the spinner and marked so that they were mounted to engine in the same balanced line. The DA-85 never did run right as far as I am concerned. It vibrated severly from the beginning to seizure. I believe the engine was not right from the getgo.

[Dan Bregar]

Sherman--As a potential buyer for the DA85 I sure am interested in what the problem is with yours. Please let us know when you know. I know there were some problems with the DA50 for a while after it first came out. I think it is all resolved now, but there is a possibility of some issues with the new DA85. I hope not but I believe there are only a couple hundred out in the field as of yet and for only a few months of service. Not trying to say anything negative about DA that's for sure. They make nice engines and they work hard on any issues that come up. The 85 is a new design and I hope the learning curve on the 50 will minimize any issues on the 85. Any how I'm sure DA will make it right and in short order also. They are good people to work with. Let us know what the deal is .

[Eury]

Does the 85 have the same prop bolt pattern as the 100?

[wildhare]

	Quote: Originally Posted by aerojack
	Hi Tom, hey what % of header drop would you use for the DA85 on your 35% Sukhoi? I have a DA85 here and want to get a header for it to go on my Sukhoi and need to know what drop I need. Thanks!

I used 50mm drop on a 35% Edge, I have not done it yet on a Sukhoi but my guess is25mm would do it. I think zero drop would put it too low, but if you have the plane you could mount the engine up and eyeball it to see where the center of the exhaust port falls relative to the tunnel.

You could also order both 25 and zero from DA and then return the one that you don't use.

TF

[sherman89]

	Quote: Originally Posted by Dan Bregar
	Sherman--As a potential buyer for the DA85 I sure am interested in what the problem is with yours. Please let us know when you know. I know there were some problems with the DA50 for a while after it first came out. I think it is all resolved now, but there is a possibility of some issues with the new DA85. I hope not but I believe there are only a couple hundred out in the field as of yet and for only a few months of service. Not trying to say anything negative about DA that's for sure. They make nice engines and they work hard on any issues that come up. The 85 is a new design and I hope the learning curve on the 50 will minimize any issues on the 85. Any how I'm sure DA will make it right and in short order also. They are good people to work with. Let us know what the deal is .

I have been practising for my first IMAC meet this coming weekend, I hope that DA will just replace it with a new one, I would willingly pay the overnight freight to get it in time to get ready for the IMAC contest on Saturday next.

[krayzc]

Tom (WH)

That was good scoop to let us all know about. I know I am just loving my DA-85 and it kicks butt to me for the weight, plus I have 2 other brands twins.

Eury same bolt pattern as I used my 3w adapter to drill the props for this and my BME motor.

[sherman89]

Desert Aircraft is taking care of business, they called and things are being taken care of.

[rede2fly]

this is good to here. i knew they would. see ya at the field rob.....

[wildhare]

	Quote: Originally Posted by krayzc
	Tom (WH) That was good scoop to let us all know about. I know I am just loving my DA-85 and it kicks butt to me for the weight, plus I have 2 other brands twins.

Here's a quick update. I spoke to Bill at DA today and toldhim about my setup and results. He told me that their experience shows another 200 rpm can be gained by using the KS 95-4 rear outlet muffler over the MTW TD110K that I was using, so I ordered one to test. I also ordered a Mejzlik 27-10TH which he said is the prop of choice.

I will re-run my tests when I get the new stuff. Stay tuned.

TF