Dominator Project Questions

[Randall]

I just found this forum a couple of days ago and I've been browsing the forum for some help with an upcoming Dominator project.

I acquired a 4+ year old Dominator project last year and am getting around to starting working on it. I received a "rolling chassis" with nose, tail, rotorhead, some basic instruments, and the usual stuff. I also got an EA-81 engine w/o redrive. I'm trying to get it safely together and in the air with the usual caveat - minimum initial investment as possible.

1. After inspecting it, disassembling it I noticed that some of the parts appeared to under a little tension when assembled - meaning that to get all the holes to line up on some of the triangulated intersections, one had to really push/pull the parts to get the holes to line up. I'm concerned about this. Should I be? I'm tempted to re-fabricate the mast, boom, and cluster plate.

2. What do I need to be concerned with about the rotorhead? I'm not sure who's rotorhead it is or what model if there's such a thing. I'm not inclined to just trust the previous guy and use this one unless they're pretty much all up to the task at hand.

3. Should I use the EA-81 vs. something else? Is there an engine that's better suited to the Dominator that I might consider? I've been using weight, TBO, powerband, and cooling as my primary criteria (I realize that some of these might be a bit subjective). So far the soob seems to fit the bill on all except the weight but I'm not sure that the difference in weight is going to make that much of a difference.

4. Instrumentation. What should I start with as minimum necessary instrumentation?

[ToddP]

1. After inspecting it, disassembling it I noticed that some of the parts appeared to under a little tension when assembled - meaning that to get all the holes to line up on some of the triangulated intersections, one had to really push/pull the parts to get the holes to line up. I'm concerned about this. Should I be? I'm tempted to re-fabricate the mast, boom, and cluster plate.

That one is tough without seeing the project first hand. If I was really concerned about fit, I would definately rebuild the part.




2. What do I need to be concerned with about the rotorhead? I'm not sure who's rotorhead it is or what model if there's such a thing. I'm not inclined to just trust the previous guy and use this one unless they're pretty much all up to the task at hand.

It would probably be easiest if you could take a picture of the rotorhead and post it here. Someone would recognize it and let you know who made it. (most likely). Then you could call the manufacturer and ask all the pertinent questions.




3. Should I use the EA-81 vs. something else? Is there an engine that's better suited to the Dominator that I might consider? I've been using weight, TBO, powerband, and cooling as my primary criteria (I realize that some of these might be a bit subjective). So far the soob seems to fit the bill on all except the weight but I'm not sure that the difference in weight is going to make that much of a difference.

The Direct Drive EA-81 is only going to make about as much power as a rotax 582 and weigh an extra 100 lbs. The EA-81 is a great engine with a drive reduction but pretty heavy when it only makes 60-65 HP as a direct drive.




4. Instrumentation. What should I start with as minimum necessary instrumentation?
Thats up to you. Basics usually include: Airspeed, Altimeter, Engine Tach, Rotor Tach, Water Temp, EGT. However people have flown with virtually nothing and others have flown with panels that could be used for IFR approaches.

Good Luck

[Randall]

Rebuild it is! I just wanted to make sure that I wasn't being overly paranoid.

I've attached pics of the rotorhead and soob.

From your reply, I assume that a soob with redrive is ok on the Dom in spite of the weight vs. say a two stroke alternative?

Also, considering that I don't know crap about he soob, does anyone have any suggestions regarding the carb/manifold setup? Specifically where to start? Should I scrap the carb (two barrel Holley something-or-other) and buy a new one or get a new or used carb/manifold combo? It looks like having the coolant routed through the manifold and the radiator cap mounted high on the manifold might solve a couple of problems. I'm just not sure that I can figure out the carburation with a new carb much less the existng carb.

Thanks!

Randall

[robertstodaro]

NOT SO FAST !!!!!!!


get ahold the local chapter president, he knows that machine inside out.

we'll be glad to help

[Ernie_B]

The head looks like a plans built model, with some personal mods.

[Thumpernator]

Randall,

Was the airframe set up for the DD EA-81? If not, then you're in for a major modificaton to the gear and engine mount.

BTW, you do not want a Dominator with a DD EA-81. It will be a 'Dog', just like Todd said.

Also, if the parts are not fitting without forcing the parts, then I'd also suspect how the holes were drilled, ie, nicking the interior walls of the tubing.

[robertstodaro]

It was originally set up for a belt redrive, prop below the engine, starter above block but under the tall intake manifold. I owned it for a year but never touched it.

[Randall]

Thanks everyone for the info. I'm looking at the RFI plans built PSRU or possibly a Sub4 if I can get one. I'm kinda of weighing experience vs. $ vs. time.

Looking at the engine mount, it appears to place the engine a little high to my eye compared to other Dom's with Soobs. I hope that the plans and builder's manual shed some light on the issue when they arrive. So far, I figure that I'm rebuilding the mast, main tube, cluster plate, and possibly the keel and replacing all the AN stuff for grins. Shouldn't be too much work - I hope! I have all the really funky-to-fabricate parts for the most part.

So Ernie, what would one do with the rotorhead? Am I worrying to much about nothing?

Thanks again!

Randall

[robertstodaro]

Randall


Your local area PRA chapter is having a meeting at Navasota airport Saturday.
(right in your back yard almost)

It's a perfect chance for you to talk to the guys who built major portions of your

project and if you want to sell your folding mast that might happen there.


Take a look at the Joe Sousa redrive, that was the way I was going to go with it.

Also if you can take a look at the Thumpinator web site, if its still online that would be a huge help to you.

Also,Don Bouchard will probably be at the meeting . He's known throughout the land (even in Japan by the Subaru company) as the "Subaru Guru". He's built about 7 gyros to boot.

The club has a set of Don's tapes on how to rebuild a Subaru engine for aircraft. So call Jeff Spralding and have him bring the tapes, Paid members can check them out.


There will probably be a real live flying Dominator there.

If you decide not to use that intake manifold, don't give it away, it's worth a couple of hundred dollars.

See ya there.

[Thumpernator]

Unless Souza has changed the gear ratio ( 2.5:1), you will have to use a Prince Prop, or equivilent. Believe me, a Warp Drive or one like it, will not turn fast enough to give you any type of decent performance. I know, because I tried it.

Since it was set up for the prop to go below the engine, you'll have to find an appropriate redrive. The Sub-4 drive will work and there is also a belt drive setup that I saw at the PRA Convention when it was in Dallas. That setup was really sweet.

If you go with the RFI setup, you're in for some major rework to put the prop above the engine. That is, unless they have a new model that I'm not aware of.

In my many years of homebuilding, I've found one thing to be a fact. You make the first part as close as possible to the plans. After that, each part is made to fit the previous part.

So, drastically changing the design along the way will cause you to have to back up.

[robertstodaro]

The redrive you saw in Dallas may have been the original for this machine.

That whole deal sank faster than the Titanic and left alot of ill will.

I won't use names here, but I'll discuss it in private if you think you might be buying one or putting a deposit down.

[Randall]

Robert, I figure that I'd use twin 39mm or so motorcycle carbs because I know squat about tuning car carbs. It'll also clean up the top of the engine a little. Later on, I might look at something else like EFI. That said, I'll probably hang on to the manifold until I get the soob started and then sell it. I also have some thoughts about the need for carb heat on the twin carb setup - or in TX it just might not be a problem. I'll try to make it out to the meeting. I don't have anything planned and my new bride has to work until 4.

Thump, I found out the hard way about changing one part and seeing the trickle down affect that it has on construction. I hope to tighten up the "tolerances" a little compared to where things are now. It seems like after rebuilding it using the same parts things would up with enough slop in the works to make things difficult to align - not impossible, but I was surprised at how differently everything fit back together. I hope to redrill the fabricated parts to better fit the welded/manufactured parts and the engine mount/shock tower. Regarding the RFI, I figured on coming up with an alternative engine mount to lower the engine to accommodate the redrive/prop combo. depending on what the plans/builder's manual says about it.

Randall

[Neil Hintz]

Have a look at the Autoflight reduction drive, www.autoflight.co.nz made by the same person that developed the SUB4. This Autoflight drive is being run by Ernie now on an EA81. you can get this drive in offset up or offset down , ratio 2.21:1 or 1.47:1 or 2.91:1 . This drive weighs in at 13kg with starter ,flywheel,and all relivent mounting bolts. Autoflight pricing is much cheaper than most other ( and all other gear ) drives. This unit has been running on a turbocharged SUB4 engine here in NZ for almost a year now ( using the 2.24:1 ratio on 72" warp drive ) This drive is much smoother than the SUB4 at idle and has an oil level window. Output flanges are Cad plated, stainless steel drive lugs, standard is Rotax fourstroke output flange but SAE1 and SAE 2 output flanges are an option. I have all these options available now, order through Ernie at RFD. These units are on the shelf ready to send. Also available are EJ units same ratios same price! Ring Ernie as I have an order ready to ship shortly.

Neil

[Neil Hintz]

Dont throw away the EA81 engine, it can be made to deliver 90HP at the prop flange ( on a calibrated dyno ) with a little work. Ernie is more than happy with the performance of this engine on a single seater ( with 90HP ) . I can give you the specs we developed at SUB4 on the dyno to get this engine to perform well. We used two 32mm Mikuni's with one each side above each head with a one inch crossover tube. Cam was changed, I'll give you the spec on that if you like or you can buy one off Ernie, also the manifolds particulars I can relay to you, or you can buy them off Ernie. Done properly this is as good as you are going to get as far as a value for money / perfomance package.

Neil

[Neil Hintz]

Forgot to mention the Autoflight gear offset is 79mm ( 3 , 5/16 )

[Bill Freiburger]

Neil,

I am currently building a Dominator from plans. And I would like to utilize a Sub EA81 engine.

I am also interested in your EA81 upgrade specs.

BTW you have a great website,

Thanks,

Bill Freiburger

[BUD ONEAL]

[I]I have the sub-4 2.21/1 on my 100 hp sub with a warp drive 68" prop three blade and it will hual my heavy carcass with out a wimper. I still use the weber two barrel carb with a high rise manifold built by "Jake Jacobes" of Copeland Fl.

[CLS447]

Bud, what pitch are you running on that prop & what is your full throttle RPM on climbout? Thanks

[Neil Hintz]

Hi bud, how are things going for you? Could you relate to us all the the performance of your Dominator with the Subaru 100 hp set up as a direct drive before you fitted the 16 kg SUB4 gearbox please, thanks.

Neil