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RE: Turbine or EDF
Thank you for the comments on the flying.:D I have to say I was supprised about the performance of the 12s setup as it had plenty of go and vertical performance even at 20lbs and hopefuly will have a nice afternoon to test the 15s setup.
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RE: Turbine or EDF
ORIGINAL: smchale Kirk, have a good trip across country. Can't wait for you to be in the same time zone! :D |
RE: Turbine or EDF
Hi Kirk,
Congratulations on finding that candy store! Just be careful, kids eating too much candy can get sore tummys! ;) Tim |
RE: Turbine or EDF
ORIGINAL: jfetter ORIGINAL: stumax Actually, longer inlets/shorter exhaust is a more efficient way to go for a number of reasons: <SNIP> Maybe you can reaffirm they are the best choice by helping me out with a static thrust question. We know on an Electra we see 14.25 lbs installed thrust using the stock BVM inlets (granted, they are huge and the inlet-to-FSA ratio is 106%) and the 5612 fan on 12S. When you take the same power plant and put it in the Bandit with the longer inlets (and 96% inlet-to-FSA ratio as calculated by RD), we see only 11.65 lbs. The Efflux also drops from 212 to 191, now is that solely to be blamed on the smaller inlets and lower inlet-to-FSA ratio or do the swept inlets get part of the blame? Likewise do they perform any differently in the air once you start shoving air into them? Thanks, Jack Jack, inlet size is very largely responsible for static thrust, as is the size of the radius on the inlet lip. This is especially true for tractor fans, as they create a region of very low pressure in front of the rotor in the static condition. Consider this region of low pressure acting on the inlets. If the inlets are larger, they have more surface area, and the net force reaction from the low pressure acting on this surface area and higher atmospheric pressure acting behind the inlets, creates a lot of thrust. Usually, the efflux velocity is a better indication of how well the fan is performing, as you can calculate thrust by integrating efflux velocity across the face of the exhaust. In you case, you are seeing a drop in efflux velocity, which will be due to the smaller inlet size and the longer inlets. This will disappear as soon as the aircraft starts moving. Once in flight, the dynamic pressure will be captured at the face of the fan and everything will be sweet. BTW, the Bandit's inlet area is smaller than 96% for the EVF, I would have thought? Can you take a photo from the front with a 6" rule in plane with the inlet? |
RE: Turbine or EDF
Hi Tim,
Man, that's the truth. I'll have to limit myself to few meets. Kirk |
RE: Turbine or EDF
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I received the BVM 80 inch F-86 today. I measured the intake opening and it is 93% of the FSA (fan sweep area) of the TF-8000 fan. I'll have to wait until I get to the East Coast so I can get inside the fuse to see if I can fit the fan/intake ducting but so far, it's looking promising. The Flite Metal is too shiny for my taste (not very realistic) and it's a little rough, but I can always recover it.
Kirk |
RE: Turbine or EDF
Hi Stu
Thanks for the info. After flying it on 15s today the performance is awesome. Jack and I are both really happy with the overal so far. |
RE: Turbine or EDF
ORIGINAL: k_sonn The Flite Metal is too shiny for my taste (not very realistic) and it's a little rough, but I can always recover it. Kirk I think some of the guys hit the flite metal with some #0000 steel wool to dull it down. This give the differing panels a different look just like in the big ones. The steel wool would knock the shine off. You could leave some areas (small panels) shiny to get the contrast between the panels, or if you didn't like the shiny at all, you could do the whole jet with #0000 and go up a grade or 2 of super fine steel wool for the other panels for a more realistic look. Tim. |
RE: Turbine or EDF
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Hi Tim,
Thanks for the tips. That's different than the way I've done it in the past. I'm going to give it a try. The way I approach finishing Flite Metal is to wet sand it with 400 grit in one direction, then sand a few panels 90 degrees to the surrounding panels. It's a lot of work but looks great in the end. Here's a couple photos of a Mustang I built a few years ago. Kirk |
RE: Turbine or EDF
ORIGINAL: k_sonn I received the BVM 80 inch F-86 today. I measured the intake opening and it is 93% of the FSA (fan sweep area) of the TF-8000 fan. I'll have to wait until I get to the East Coast so I can get inside the fuse to see if I can fit the fan/intake ducting but so far, it's looking promising. The Flite Metal is too shiny for my taste (not very realistic) and it's a little rough, but I can always recover it. Kirk Jack |
RE: Turbine or EDF
ORIGINAL: stumax Jack, inlet size is very largely responsible for static thrust, as is the size of the radius on the inlet lip. This is especially true for tractor fans, as they create a region of very low pressure in front of the rotor in the static condition. Consider this region of low pressure acting on the inlets. If the inlets are larger, they have more surface area, and the net force reaction from the low pressure acting on this surface area and higher atmospheric pressure acting behind the inlets, creates a lot of thrust. Usually, the efflux velocity is a better indication of how well the fan is performing, as you can calculate thrust by integrating efflux velocity across the face of the exhaust. In you case, you are seeing a drop in efflux velocity, which will be due to the smaller inlet size and the longer inlets. This will disappear as soon as the aircraft starts moving. Once in flight, the dynamic pressure will be captured at the face of the fan and everything will be sweet. BTW, the Bandit's inlet area is smaller than 96% for the EVF, I would have thought? Can you take a photo from the front with a 6'' rule in plane with the inlet? My own calculations show 71cm² (86% inlet-to-FSA ratio) whereas Ralf calculated 86cm² (96% inlet-to-FSA ratio), Bobs fan wants air and it seems BV knows his own product because he told us the Bandit inlets were to small, he was right in that we'll get very respectable performance but not Electra performance. In the end I'm more than happy and we're not done experimenting but I think my measurements may have been accurate (I used the square area of an oval for base calculations, I think Ralf traced onto paper marked in cm²). I'll take a shot of the Bandit inlets when I track down my metal rule (8-year-old!)... Jack |
RE: Turbine or EDF
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ORIGINAL: jfetter Recover?! Are you insane?! This thing is oh so pretty... Jack Kirk |
RE: Turbine or EDF
Deleted ... double post.
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RE: Turbine or EDF
Although this post has drifted a bit from my original question I've found it very educational.
Thank you guys. |
RE: Turbine or EDF
Kirk, you aren't kidding when you said they used the wrong tool. seems crazy to work so hard to prep the surface for FM, only to apply it like that. If there is anyone who can fix it, it's you! How do you think you can remove it? Heat to soften the glue? Is the wing and stab a composite like the fuse...ie, will the FM be removable without damaging the surface? I'd say outfit it with the EDF gear you want, fly it, then take advantage of the wonderful ( [:o] ) east coast building season to refinish it. Can't wait to see how you progress. Btw, you should start a new thread with this...
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RE: Turbine or EDF
I'll start a new thread when I get to my destination. Going off line tomorrow. See you guys in a week.
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RE: Turbine or EDF
Kirk, Have a safe trip getting here to MD and email me when you are in town so we can do the meet and greet thing at my shop. I got an email from the Land of Purple that my EVF Powered P-80 kit will be here when I get home from work tomorrow. YEA man thanks family for the B-day present!. Funny that you are going to do the TF8000 conversion as I was just thinking that just might work for my 80" F-86 if I kept it light. I have one that's NIB in my shop and I just got the fuel tanks and bypass for it last week. So now I have everything except the cockpit before I start it. I have to decide should I do the EVF P-80 first or the F-86 80" ,my F-86 60" is in primer I just ran out of time for painting it before the fall weather got here. See you soon We'll get all the jet guys together somehow before the season starts back up at Fentress you'll love it there if you can make it 8000' x 100' strip!!!!!!!!!!!!
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Ron, was good meeting you in Hamburg. Let me know how the F-80 looks. I'm waiting on mine :)
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RE: Turbine or EDF
Bob it was great meeting and talking to you as well. The kit boxes (2) arrived at lunchtime today without a scratch on them and my wife was shocked at how big the boxes were getting them into my shop for me; even though she saw the finished plane at Hamburg. I just inspected the kit as the packing list requires incase anything is missing or damaged and I am really mad! The prefabrication, of the flying surfaces, plans, instruction book and glass work is done so well (as usual with BVM products) that I have very little to build. LOL!!!!!!!!! This looks like a great update to the origanal T-33 kit I built years ago for JPX T-260 power when turbines first came out. You'll love it I'm sure. Even the drop tank ez-air system is included with the EVF kit. All I am waiting on now is the retracts as they were still backordered when the kit was shipped but you don't need them to start the build.
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RE: Turbine or EDF
Ron, thank you buddy for the update. It'll be a pleasure building the plane I'm sure. Since we know its a great flier and performer it's a plus as far as the build. It's always nice to know that after all the work building and detailing etc. that the finished product is worth the effort. :)
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