fredo

Well, unfortunately another flightless day for me. My inspector never turned up, so tomorrow is another day.
There's one thing I've noticed today. I have one single stock tank in the middle and two smoke tanks working as fuel tanks.
I was all fueled up but since there was no show, ended up pumping the fuel back to my canister. While it was emptying, I noticed the main tank started imploding pretty badly. Thinking about it, it is the smoke tanks that are vented only. Don't know what is this going to do in flight.
Comments appreciated

gsmarino2000

My Feedback: (2)

Fredo,

How are your tanks plumbed? Do you have the vent line from the main tank in parallel with a "Y" so that the fuel suction & vent restriction is minimized, or are they saddle tanks plumbed in series? Mine is in parallel and it does this some (the front poly tank expands during fill and sucks in during de-fueling). It's not enough to cause any problems in my case and I have had zero issues in flight. My fueling pump has a higher flow rate than the engine pump in practice. Not sure what engine you are using but the pump on the K100G is capable of overcoming a fair amount of restriction.

If you have the saddle tanks plumbed in series, I would suggest changing to parallel. Use large tubing and low restriction fittings for the saddle tank and vent plumbing. Then you should have no problems.

Greg

fredo

Hi Greg
If you see page 47 post 1167 on this forum, there's a schematics that Mark drew for me. That,s exactly what I used.
Rear tanks are in paralell and their vent line is connected via T exiting below the fuse. But I can't remember if the entry from the rear tanks into the main are suppose to face up (same as vents) or down facing the bottom? I have a feeling I have plummed mine with them facing down. When I think about it now, it will keep imploding until the main tank is empty, because it's an enclosed space. Is that correct?
It's one year ago since I did this.

gsmarino2000

My Feedback: (2)

Fredo,

It's not supposed to be an enclosed space; it's vented through the system. Mine is essentially the same as Mark's schematic. The entry from the rear tanks into the front need to be at the top of the tank. You can either go through the stopper with two vent tubes going up to the top of the tank (this is what I did), you could "T" the rear tanks into a single vent line in the front tank (more restrictive), or you could use nipples on the top of the tank (least restrictive). Ether way the rear tank inputs should enter the top of the front tank like a normal vent line. The fuel path needs to be identical for both rear tanks so that they draw evenly and you get full capacity from both rear tanks.

The collapsing of the front tank (I like this term better than implosion) during defueling is simply due to the vacuum that your fueling pump has to create to overcome the resistance of sucking air into the vent system and fuel from the rear tanks into the front tank. With the three tanks this is somewhat torturous path. The way to minimize this is to make the vent path into the rear tanks and the entire fuel/vent path from the rear tanks into the front free flowing as described above. Also, you can also slow down your pump using a speed control which would reduce the collapsing effect. Jersey Modeler (probably the most common fueling system for jet pilots here in the US) has a optional version with an ESC. Or you can just stop your pump periodically and let the vent system catch up and then start again.

IMO the advantage of making the plumbing low resistance is that the engine pump doesn't have to work as hard to suck the fuel from the rear tank. That's why you wouldn't want to plumb the three tanks in series. The engine pump could probably do it but the ECM is going to have to run it a lot harder. BTW, the size of the fuel plumbing (including the tank lines and clunks) is probably more critical than the vent plumbing just because fuel flowing through the same size line is going to have more resistance than air.

Greg

fredo

Thanks Greg I was just freaking out a bit. After careful inspection I learnt my plumbing is correct. That deformation was only very temporary. I found the entry from the rear tanks inside the main is facing up as it should but ends about 3-5 mm short from the ceiling inside the main tank. I could be wrong but I think that short transition causes the tank to deform because of vacuum but as soon as those rear tank entry tubes are exposed, it's back in business.

On a better note, I had my very first turbine maiden today. I was a bit nervous at first but must say as soon as I took off, retracted UC
and flaps, I felt very comfortable with it. It was my first maiden ever, where I didn't have to do any in-flight trims what-so-ever. What a treat this plane is. It flies like it's on rails.Landing was quite greasy. Very easy to land.
Well done Jet Legend and thank you all forumers here for a very valuable inputs.

gsmarino2000

My Feedback: (2)

Congrats on the maiden, Fredo!

Greg

M3Baker

Fredo
Congratulations on a successful maiden! I'm so happy everything went well for you. You will love this jet.
Paul

erwin peters

Hello friends, has anyone installed an electrics retracts like Prolink or Electron on this plane?.
Regards
Erwin

barger

Arrived at my door this morning......By far the nicest airframe I have ever owned everything fits perfect the paint is flawless....very happy with my decision to buy this airframe😊...small 90mm jtm viper on floor electric edf on 10s.

fredo

Very cool. Love that Canadian scheme. Looks like you have a pro-wired version. Which turbine?

barger

Congratulations on your maiden Fredo.......Yes pro wired with factory hv servos,Kingtech k100g majority of my flying will be off thick sod farm turf so i hope the k100 will have enough thrust to get airborne.Also has the stock smoke sytem installed.A little worried that i wont be able to get up enough steam with the added weight of the smoke fluid.Any thoughts on the optimum configuration for thick grass would be appreciated.

Greg

fredo

I'm a bit lucky, we have our grass strip very well maintained. My take off run was a tad longer than I expected but without any problems. Yes, I have K100 as well, running on diesel.
I used about 15 degree flap. It all depends how high your turf is and how long is your runway. You may perhaps use a little bit more flap for take off. I did a few dummy runs to get the feel of it. I don't think you are going to be underpowered. You can always try short take off,
apply brakes, full throttle, release brakes. You can save yourselves a few metres of runway. Just 5 cents from a jet newbie. Others may have better ideas.

barger

I am running diesel as well... Runway is very long over a mile,Grass is cut short but well fertilized no earth showing all grass if you know what i mean.I think it will go just never flown turbine off grass or asphalt for that matter.

gsmarino2000

My Feedback: (2)

Very nice ... I really like that scheme even though I'm not Canadian. One thing I haven't seen before is the large single front tank. Looks like it nests in the "V" between the ducts and gets the fuel Cg back a bit vs. the original two tank setup.

Greg

barger

Thanks Greg I was wondering the same thing I had not seen the single big tank either That would be good because i want to get cg aft to help with grass takeoff.Also i test fit the k 100 in the engine bay and it seems to want to sit with the turbine exhaust inside the thrust tube! Is this correct ?I thought there is supposed to be a gap betwen pipie and turbine exhaust!??

gsmarino2000

My Feedback: (2)

That bellmouth is new, too. Place the turbine nozzle the specified distance (I think 25mm for a K100G) from the point the actual pipe starts. So yes, the nozzle will be partially inside the bellmouth. The only caveat is that there needs to be enough space for air to get around the turbine. This can be a problem with some short nozzle engines like Jet Munts but should not be an issue with a K100.

Greg

barger

Ok great thank you Greg

FlyEng

My Feedback: (5)

Anybody know the volume in that new single large tank? Is it the same, less, or more than the original two tank arrangement?

barger

I will look tonight when i get home from work to see if it is on it somewhere.

Greg

barger

This is my first plane with air retracts and I know nothing about them and even less about the digital controller. Is there a way to control the speed of the up down and what about the air brakes do they just grab or can they be programmed to gradually come on?

Jgwright

These are some of the best ARTF retracts and brakes available. They are designed just to be connected up to the receiver and do not need to be messed about with. As we all know retracts can be a pain but these are as reliable as any available. My brakes needed nothing to be done to them. I would not put flow restrictors on the air lines of the retracts just use them as supplied.

John

barger

Ok great thats good to hear thank you for the info John

barger

Its not stamped on the tank anywhere like dubro tanks......I am not ready to fill yet but wnen i do i will post the quantity put in.

FlyEng

My Feedback: (5)

Thanks. My Viper has the two main tanks and the factory smoke system. Does take a bit to rotate and even a 1/2 inch move in cg will make it easier to rotate and the simplicity of a single tank is desirable to me.

barger

I measured and it sits roughly 3/4 " behind front edge of intake.