So sad you got bad experience with your, DV....
YES I am back after two years in hospital i flown my DV yesterday it rested hanging in my kitchen ceiling, but either i am sick I decided to fly it again, as usual he performed incredibly well....
I am now building some specials thinks for my neveuw (my sister' son), let's say the double whammy is on the building board and also a venture resised for a saito 150, to build this special venture i ordered a wing kit ( four star 120) to sig and I making the fuse myself.
for people building DV i would recomand to not buy the ARF, buy the kit it's more interesting and give you the possibility to make every kind of modifications.


I am now actualy in contact with Bruce to find clues to start and put in flight the double pulso double whammy, the resized venture is a easy challenge


salmonbug

PS: the four star 60 size kit is not a Bruce Tharpe design, and i have to admit i don't understand the design of the wing, i got one in my hands to build it for a fellow and think that the wings integrety is a bit overkilled

Thought I'd post a couple of pics of my Delta Vortex that maidened today. Started June 15, 2007 and flew first flights today, July 17. I was really lucky that the kit assembled very straight. No twist or out of true in the wing at all. I only needed three clicks up trim after take off to fly hands off. During construction I moved some things aft, used hardwood and epoxy aft of the cg in some places(because I knew it would need some weight aft) which resulted in a 21 1/2" CG with no added weight. I presently have one of the Delta Fighter 90 ARFs and didn't like the accessibility associated with the single access panel underneath. I built three access panels on top. These hatches have hardwood frames and sub spars that run from W-2(L) to W-2(R). One hatch is for the tank, second for the servos, and the third magnetically held hatch covers the air receptacle and charging jack/elec switch. Under the mount for the air receptacle and elec switch is the receiver and air tank. It has Spring Air retracts with 3/8" struts, Hitec digital elevon servos, Hitec servos for all the rest. The nose wheel steering servo is programed to only work when gear is down.

A couple more pictures.

Sitting in the driveway after first flights.

one more marstepiece...............

Nice job.

Your making me want to start on mine. What was the final weight?

Can you still get Spring Air's as I thought they were closed??

Pete

As I mentioned just above, I have been flying a Delta Fighter 90(Vortex ARF from a few years ago) and it required 16 oz of lead in the tail. I decided to use some heavier materials and liberal epoxy aft of the CG. With the retract gear and all other equipment ready to fly less fuel, it weighs 9 1/2 lbs. It balanced perfectly at 21 1/2" forward of TE.

Oh, Spring Air is alive and well. Go to http://www.retracts.com/. I bought the 700 series with 3/8" struts. Presently the supplier for the 3/8" struts is not that great and I'm changing to the 7/16" ones for the main gear as the quality is supposed to be better.

The last month has been a bit frustrating. First, the Spring Air retract gear was substandard and had to be replaced with Robart struts still using the installed Spring Air retract actuators. Then I had problems with the engine wanting to die when slowing in the pattern for landing. Bubbles were seen between the needle valve of the the OS91FX engine and the carb. The engine had the old/original needle valve design which was prone to bubbles. I then ordered a Cline Fuel Regulator and a new OS91FX and they were installed this week. Ran two tanks of fuel through it yesterday for breakin and flew it three times today for its first flights with the new engine and fuel system. After a few more engine breakin flights I hope to have a good report. The plane flies beautifully and now if the engine stays stable, which it was today, she will be perfect.

I can't understand why modeleres have so big troubles puting in flight this easy airplane, the 91 fx is known to be a bad engine, but mine work well as soon you use good fuel and don't have any fuel feeding troubles

Thought I would update my Delta Vortex build and experiences. This aircraft has retract gear which made the fuel tank location to be back in the center of the wing as the nose gear took the original fuel tank location. The fuel tank is about 11" to 12" behind the engine. The original configuration had an OS 91FX installed. Tank distance and the old style needle valve(bubbles) didn't run reliably. Next configuration was a new OS 91FX with a Cline Fuel pressure system to correct the tank to engine distance. It ran but not well. It is my opinion that the OS 91FX venturi style carb is not really compatible with a pressurized fuel system. Now I have installed a new YS61 pumped two stroke side exhaust engine. Yesterday the first test flight went very well. I have also changed the radio system from 72Mhz to the 2.4Ghz JR R921 receiver with a JR X93903 transmitter. During the radio change I used a five-cell battery that replaced the four-cell battery. The battery is in the very aft bay between the rudders. The YS 61 seemed to weigh exactly the same as the replaced OS 91FX. The 16 oz Hayes fuel tank was reduced to a 13 oz Hayes tank. All of these changes obviously shifted the CG aft just a bit. When flying inverted before the changes, a bit of forward stick was required to maintain level flight. Now little if any forward stick is required when inverted. So the CG is now just about perfect. With all controls centered for the first test flight after the engine and radio changes, no trim whatsoever was required after takeoff. The plane is built perfectly straight and is now balanced very well CG wise. Hopefully, after all these months of engine, fuel and landing gear hurdles, she will start to be a good and reliable flier. A couple of pics of the new YS 61 pumped two-stroke engine.

Nov 20, 2007 Update: Six flights now and not a single fuel issue. I think the fuel issues are over and many nice flights awaits this Vortex.

OS sometimes sucks really bad. You just have to admit it. [&o]

At least the 91's do. When I do my DV she will get a Webra 91[8D] It will cost more but what the heck it's only money

Pete

I think I am a lucky guy, my only 91fx is flying on my dv (see above in the thread the building of this bird), this bird is now loging 500 flights aproximatly with the same 91 fx in the nose. The engine start at the first chicken stick hit and never stopped in flight, I never had to change any part of the engine.....
but i have to admit that before the first flight i performed a extensive carrefull breaking in of the engine.
the engine is still pulling my old dv in unlimited verticals.
I think the secret is in the fuel I use, home made mixture.....
Actualy I am very sick and don't have a lot of time to go to the field, I worked in the passed in a major european rc compagny as designer and test pilots, I have tons of birds home, but the dv is still my favorite


DV is my avatar on RCU, it's because the DV has been been design by one one of the best guy in the model world, I flown most of Bruce's design, they are simply perfect..... (Bruce shorten the nose of the the dv on the next batch, lol)

I builded for the the third time a spacwalker coming from sig, again the maiden flight turned bad (i was not in comand), the fuse broken in hard landing, if Bruce has still contact with sig, I would recfomand to modify the fuse, in fact this fuse is made in two parts with a weak point, but i Think that Sig is not going to modify the kit, we are in the ARF destination; too bad

Strange to hear about problems with the FX91. I have 3 of them, one with a tuned pipe on a patternship, and have nothing but good things to say about this engine. I have modified mine (the tuned pipe one) by installing a Perry pump inside the backplate with incredible results. The engine never runs lean and the "bubble problem" disappears entirely.

If anyone is interested in making this modification, please see below:

1) Remove the backplate and drill a hole in the dead centre the exact diameter of the pump pulse input tube. The best is to ask a jeweler shop to do this, it cost 5 Dollars and a perfect job was done.
2) Insert the pump into the backplate with the pulse input tube protruding slightly through the hole.
3) Fill up the backplate around the pump with silicon rubber to both secure the pump and make a good seal.
4) When the silicon is dry, cut off the slightly protruding tube with a razor blade.
5) Reinstall backplate and connect fuel tubing as per the Perry Pump instructions.

NOTE: The blue hard plastic tube used for remote pump installation is not used as the pump now receives it's pulses directly from the crank case. MUCH more efficient!

When you start your engine, you will notice that it needs a lot of leaning out due to the higher fuel pressure, but once you have set this, the engine is MUCH more friendly with a far greater distance on the needle from too lean to too rich.

Since doing the modification, the engine has not even approached getting hot, & has not had one deadstick in over 400 flights. Many of my friends that fly pattern with tuned pipes, and many more flying with the standard exhaust have tried this and I have not heard one complaint. I cannot understand why more people haven't done this as all I did was take a look at the Heli version of the FX91 which comes standard with the Perry Pump in the backplate and copied the idea for a fraction of the price!

As soon as they come back into stock I will be ordering & building a DV. All of your posts in this thread are most inspirational & have given me many ideas as to personalising my aircraft. Example: Mine will have a side mounted FX91 with a Macs tuned muffler going beneath the wing, a cowl, and a canopy.

I really don't understand why this engine have a so bad reputation, I enterly agree with you !

SirLance, could you post some pictures of your pump mounted on the engine?

Many of the folks having problems with this engine are trying to run it with the fuel tank 12" or so behind the engine without assistance. No engine, other than a pumped/pressurized engine will run properly under such conditions.

I wish YS would bring back some of their pressurized two-strokes, but with muffler tuning and a thirst for 5% nitro.

Or, if they don't want to do the muffler tuning thing, include a muffler like the Ultrathrust or Jett high performance mufflers.


Ed Cregger

I know this is an old post, but the topic is still current.

Hi AirbusDrvr, no problem, I will photograph the installation on Sunday night after I have flown the aircraft. I would do it tonight but I need to take the cowl, prop & spinner off to get to this part of the engine. Nobody can complain if they have fuel feed problems on a non-pumped motor if the tank sits more than 7 inches from the engine, the exhaust pressure in the tank then becomes very erratic and varies very greatly between a full & almost empty tank, and of course the attitude of the aircraft whilst in flight. You are then risking the motor getting very hot during at least part of the flight. The problem (?) with OS 2 strokes is that they are very tolerant of running lean and most times you will not feel or hear it, but when it is overhaul time have a look at the piston, you can easily see the burn marks near the exhaust port.

From all I have read on this thread regarding the construction of the DV, a lot of people seem to put the tank further back for one reason or another. In many cases this will unfairly give the OS 91 (which seems to be the preferred engine for this aircraft) a bad name for the reasons given above. I have also read many threads on RCU that say that the normal (non-pumped) carbs on OS 2 strokes cannot handle the extra fuel pressure. This is so very wrong!!!! I have installed this mod on everything from the OS32 up to & including the FX160 and it works every time. The advantages of installing the pump right in the backplate are that a) the pump is much more efficient as the pulse comes directly from the crank case into the pump, b) there are no pressure pipes to develop an air leak causing loss of pressure and immediate engine stoppage, and c) there are no modifications needed to the aircraft, the old exhaust tank pressure line just becomes the tank overflow.

Looking so forward to finally getting my DV, I am going to need a LOT of advice as I am not a very good builder!

SALMONBUG:

Could you possibly post a video of the "flat spin" described earlier in this thread? (I think that was in one of your posts).

I have a Delta Vortex that I bought severely damaged at a regional swap-meet/auction that's held every year in Perry, Georgia. My Vortex had been crashed, and the engine box was completely destroyed. The leading edge of both wings was missing from about half-way back on one side and one-third of the way on the other, and there ware several broken and damaged ribs. Fortunately though, the spars were all intact and undamaged. I downloaded the instruction manual from the BTE web site, and using the photos and descriptions there I repaired all the damage and rebuilt the plane. Then I stripped it completely, added my own custom navigational lights, which include blinking strobes on the verticle stabilizers, landing lights and wing tip lights, and then recovered it. (I only paid $30 for the plane, and it had 4 Hitec BB servos in it, two of which were high-torque!) I've got an OS91FX with a tuned pipe on it, and it really scoots.

Anyway, I've got over 20 planes now, from warbirds to giant scale 3D planes, but the Vortex is still one of my favorite planes to fly. I take it to the field almost every time I go, and it's one of the most popular from the spectator standpoint, too. I've read how other guys have managed to get their planes to do some kind of flat spin where the plane spins around on a wing tip, but I've just never been able to get mine to do it. I'd love to see a video so I could figure out how to do it. If you have one, or could make one, I'd really appreciate it.

Thanks,

David

I THINK THIS THREAD WILL BE IN A VERY SHORT TIME BE ALIVE AGAIN

Are you building another one ? hehehe hopefully it will be different from the already very good looking one you've built years ago.

Hi Salmonbug,

Again, thankyou for your patience, and it seems that the DV kit is winging it's way from Belgium tonight on it's way to me here in Johannesburg care of Fedex! Thankyou sincerely for your help in sourcing one!

In answer to your question re the high altitude in JHB & the choice of an engine, I have lain awake at nights thinking about this factor. The way I see it, I have two choices. I could opt for the new OS 120 2 stroke with which I have had some experience and it is very powerful. Although by not much, it is a heavier engine which will add to the problem of getting the cg correct. The 2nd option is to use the FX-91 but with a tuned pipe like in my 90 size patternship. With a tuned pipe length of 460 mm and swinging a 15X8 APC prop, the engine is actually pushing out slightly more hp than a standard 120 at this altitude. Yes, the longer exhaust does add a few grams but towards the back of the aircraft where we need it.

My 90 patternship weighs nearly 5 kgs and this setup (with the pump mod described earlier) has terrific vertical climb.

Your comments in this regard will be very welcome!

Thanks again & Kind Regards...................Lance

woops who said is the kit coming from me ?, lol [>:]