spend2much

My Feedback: (1)

While we are here freezing we also save $$$ buy not going out burning fuel and crashing. And in the line of work I am in, we stay late and do side jobs to make extra. OH and don't forget.... more RCUniverse time!!! Our research months.

bob27s

My Feedback: (19)

Yeah, this is suppose to be building time Tony

Wife and I are expecting the new baby in two more weeks..... my building season has been pretty non-existant

HaveBlue

I can relate Bob ..Ive only just got back into planes the last year or so because of the same reason or I should say three of them over the last 8 years.. hence I occupied what little spare time I had with 1/5 scale road cars..less hassle , cheaper to run and not much space needed for working on or storage!!!..but now..its been great being able to get back into planes..a real fun time indeed(most of the time anyway..apart from when things go wrong!)

Bob.R

My Feedback: (2)

Bob,

I'd usually wait two weeks to offer my congratulations, but in two weeks you won't have time to visit RCU. So, congratulations in advance!

Bob R

bob27s

My Feedback: (19)

thanks

HaveBlue

Thats a damn good point Bobber, I think Bob will have his hands full when the time comes and might not have the time to visit RCU..so Bob..a round of congratulations from down under..another bundle of joy..hope all is well with your new addition to the family(and I'm not meaning any new speed plane that your into!!)

contrates mate!

MustangAce

My Feedback: (3)

Bob its been a pleasure learning from you. Don't be a stranger [&o]

smitty9969

My Feedback: (7)

Congrats to you and yours.. Take care and thanks for replies.. Really makes for some excellent conversation at the flying field, and being a bi-cultural / lingual field, sometimes we need all the help we can get..
Smitty

Mike James

Yep, that's a beauty... should be a screamer.

Nice work!

JohnVH

My Feedback: (38)

Just an obvious question for you guys, is the Jett90L truely worth the extra money over a, say, OS, or whatever other brand of the same size? Im considering one, and wondering if the double plus price is noticable?

JasonWilliam

What a beauty. I'm in awe.

I second John's request for details on the Jett. I'm considering the 90L for my BTE Delta Vortex project. The Rear Exhaust really lends itself well to this bird, but I'm having a hard time justifying the 2x price tag.

Bob.R

My Feedback: (2)

Is a Jett worth 2x? I suppose the answer depends on what you want out of a motor. I've owned two Jetts prior to the 90 FIRE. They start on the first or second flip of the prop. They idle reliably. They respond to throttle input, both up and down, precisely and quickly. They are durable. They have the best "sport motor" performance on the market. The only requirements are that they should be properly broken in, they should be properly propped, i.e. not overpropped, and they should not be run lean. If motor "aesthetics" mean anything, then the BSE motors are works of art. These characteristics make the Jett worth 2x to me. A scratch built plane involves a significant amount of time, effort, and money. When I go to the field to put one of these planes in the air, I want to know that I can depend on the motor, and I know I can depend on the Jett. I have no affiliation with Jett, but I do have admiration for anyone who can survive in the business of making specialty equipment for the modeling enthusiast.

JohnVH

My Feedback: (38)

What Im looking for is a 90 size engine, that will freaking haul the mail. I have lots of engines that start on the first flip, run reliably and all that.. I want power. SO... how does it compare? Anyone ran the tach with it side by side with a normal engine?

rcalbuquerque

My Feedback: (171)

I have tached a OS91FX with tuned pipe 10/10 apc 15%powermater fuel at 14100rpm... the Jett will do over 16000 with same prop and will hold up better to the higher rpm's

JohnVH

My Feedback: (38)

Now thats what Im talking about!
Thanks

HaveBlue

I have bought a jett90l for one of my projects too, I havent run it yet , but I sure hope its gonna be worth the price tag , but from all accounts I have read I find it hard to imagine that I will be dissapointed!!

Bob.R

My Feedback: (2)

JohnVH, if rpm/$ is how you value your motors, then get an OS ducted fan motor and bolt a prop on it. If the things I mentioned a couple of posts up are important, then get the Jett. And yes, the Jett FIRE 90 with the right timing and the right pipe (talk to Dub) will turn a 10x10 APC at 16K.

bob27s

My Feedback: (19)

Just as a heads up...... Dub has a variation on the 90L engine in testing. It evolved from an idea that he and I hashed around for a while, which was to build a specialized 'small prop' 90 engine for speed applications, now that the 100 and 120 can easily fill the big-prop nitch for scale/aerobatics stuff.

Engine will be the BSE-90XL. Side exhaust, special 90XL muffler. Designed for nothing larger than a 12x6 prop. Higher timed, tuned for higher rpm. On the muffler, this thing will get to 16K rpm on a 10x10 prop, and somewhere just over 15,000K rpm on an 11x8. Most promising so far has been the 11x9 - just a bit over 14,500.

The intent here was an engine optimized for the prop jets, and also for aircraft like the GP Toni.

As noted, its in development. Gotta work out a few things. You get top end sometimes at the expense of other qualities. The top end is really promising, and so far the tweeks to the midrange have worked out nicely

JasonWilliam

Bob, I recently sent Jett an email asking for a bit of help in selecting a Jett. I'll post it here also since it seems like those that frequent this thread are extremely knowledgable and might be able to help also.

bob27s

My Feedback: (19)

Hi Jason.....

Thanks for the note. I seem to recall seeing that one.

The Delta Vortex is an outstanding airplane. I have flown a few of them in the past couple of years. Flys very well. Bruce makes a good product. It is pretty quick, however, its not a real speed machine. Thick wing. Most folks had fixed gear on it too, although adding retracts can increase the speed quite a bit. Where the engine comes into play here is more for take-off and vertical performance.

The SJ-90L side exhaust engine would give you performance beyond what you might find with a ST-90 or OS91FX. Very user friendly, easy to maintain, and it uses the tuned muffler rather than the full pipe. Prop selection would be somewhere from 12x6,7,8 in size, depending on where you fly. Engine RPM with these props will be in the 14K range. Most of the folks I have seen with the ST-90 power had 13x8 or 12x9 props up front. The plane seems to like the 12" blades. No more than 13" dia though.

Utilizing a BSE FIRE-90 will give you a little bit more power, plus the nice look of the rear pipe. In this installation, you would want the engine set up with a quiet pipe, and tuned to run best with a 12x8 to 12x10 prop (somewhere in the 12.5K to 14.0K rpm band). The advantage of the FIRE setup here, is that the engine/exhaust can be tuned to run with a prop best suited for the aircraft. This pipe and prop combination will give you a fairly quiet installation, and also give you pleanty of performance. Once you know the rpm the pipe is set for, you can try different props, just stay within the top-end rpm window.

As noted, the plane is not condusive to extreamly high speeds that you might see with a Diamond Dust, Whiplash or Magnum. It is wise to keep this in mind. The Jett 90 will get this plane moving about as quick as its going to in any case. Just do not expect 150 mph from it.

This link here shows a BTE vortex with one of the older FIRE 95 engines on it. Does look nice.
http://www.deltavortex.com/neil.htm

My personal recommendation if you wanted the Jett engine, would be to keep it simple, and stick with a SJ-90L and a 12x6 to start with. It is worth keeping in mind, that the muffler is longer than some others out there. You may have to accomodate it a bit while building the wing (See Bruce's photos with the ultrathrust muffler...same sorta deal)

Other than that, using an OS91, Mag 91 or ST-90 will give you good performance too. All worth considering. Bolting on a jett-stream muffler to any of those will give you a performance boost above stock, and may be more economical.

I hope this has been helpful

Bob

I hope this is helpful
Bob

JasonWilliam

Very good info Bob, thanks. You've given me a lot to think about.

That site you reference was actually my inspiration for this bird. I'm just so in love with that rear exhaust I'm finding it hard to consider other options.

You mention mounting a Jett muffler for increased performance. I assume we're only talking 2 strokers? In other words, does Jett have an option for a Saito .91? I'm trying to figure out how to deflect the current muffler as the plane is just covered in oil after a flight. I was considering a piece of copper pipe welded on... but if Jett has a muffler to increase performance of this engine, and perhaps aid in the deflection, I think that would solve my problem wonderfully.

Thanks again Bob!

bob27s

My Feedback: (19)

happy to be of help.

The jett stream mufflers are for 2-stroke applications only.

Of note..... something to consider.

The Delta Vortex almost always comes out nose heavy. Bruce makes sure to note that in the instructions, and on the web site. You end up adding a bunch of weight in the tail end. The thought came to mind... what if you could avoid that by putting a much lighter engine up front.... this might be the ticket...

If you want something very different, Dub has the FIRE-60L engine. It is "40" size, but packs a heck of a wallop. Recent improvments to the engine design now make it more suitable for higher-rpm + higher torque applications. (part of the XL engine development effort).

I can't help but think that the new 60L FIRE, pipe, and using an 11x6 prop will end up with Delta Vortex that will balance without added weight, ends up weighing a full pound (16 oz) less ready to fly, and will have power and performance that exceeds that of a regular OS 61FX. Tuned properly, this engine will turn a 10x7 prop over 17K rpm. and can push an 11x6 upwards of 15K rpm.

I can get you more info on this off line by email if you are interetested.

Bob

JasonWilliam

Yes please Bob!

I'm emailing my address to you now.

I'd also like to understand why the 60L is better for this application than the 65 or 76?

Thanks agaiin Bob. I look forward to hearing from you.

bob27s

My Feedback: (19)

Main reason is the 60L is a small-block engine. Same size and weight as an OS .46

The .76L and 90L will out perform it on larger props.

Just considered it to help with the CG issue with the Delta Vortex. Its a healthy little engine.

Bob.R

My Feedback: (2)

Well, after a 5 month layoff due to a highly inconvenient work schedule, it's back to really important things, like trying to finish this ballistic pattern ship. At this rate, it ought to be done some time in 2007.

I tried Nelson System 3 paint. Very different stuff, and I probably should have experimented first with a less complex model. I finally got the mist coat process down, but I still haven't figured out how to handle removal of masking tape - argh. Anyway, it is a reasonable 5 foot paint job, so on to covering the wings and stab with Ultracote.