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View Poll Results: Model platform
Delta 89 57.79%
Non Delta 65 42.21%
Voters: 154. You may not vote on this poll

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May 17, 2011, 08:29 PM
bwoollia's Avatar
I like it. I don't believe that there are other blended ogive delta sport EDFs out there.
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May 17, 2011, 10:50 PM
Registered User
LuvEvolution7's Avatar
yeah, I think we could work with that shape. could be interesting.
May 18, 2011, 06:16 AM
Scale Modeler
Concordefan's Avatar
Originally Posted by boredom.is.me
I just got to thinking. What about a blended wing...like the sr71.

I made this when I was younger so excuse the cartooniness. I say narrow down the wings and give it an overall smooth job.

Looks close to how Testor Models did F-19 Stealth Fighter's rendition in mid 80's before F-117A was disclosed. I'd go with blended wing Ogival design.....
May 19, 2011, 02:38 PM
Registered User
frank40's Avatar
The poll should expire today and the result is 22 to 16 in favor of a delta design. So now we have a platform to work with. I think that 5 days is to long for future Poll's so I suggested they will be set to 2 days from now on.

Things we need to deside:

Naca inlet/Normal inlet
Canards/non Canards
Shape of delta
All speed/ sportlike

Did I miss anything.

I think ones we have these desistions on plase, it will bee easier to move on.

Rich. I have been trying to finde some more material on the Naca duct, but there is not a lot to finde. But i do have one questions. If the effectiveness is greater than a normal duct, dose it not only mean that the inlet areal should bee smaller.
May 19, 2011, 03:21 PM
Registered User
LuvEvolution7's Avatar
I think you covered it all Frank.

here's my thoughts on wing shape............ogival delta is really optimized for high speed flight and also high lift/high alpha/high weight. in other words, it fits inside the shock wave at speed, but is also the right shape to fully utilize the LE vortex during slow speed flight. deltas often fly at higher AOA's than other aircraft and at heavier loads. since we know that the LE vortex can spill off the tips of the wings without doing any work at all, the ogive delta gives shape to the LE and therefore moves the LE vortex further back on the flying surface of the outer panel. this makes more use of the vortex and is therefore able to lift higher weights at higher AOA's. we don't have to worry about this at model size, so it's more about looks than functionality. so I guess we have to decide if ogive is a better look than the a plain delta, double delta, etc, etc. the other thing to consider, is that ogive will be more difficult to make than any other type, which will add to the overall weight. I love the look of the ogive, but at some point, you've got to compromise somewhere.

as far as sport or speed, I think that deserves another poll. at the very least, we need to figure out who requires what. for me, sport is more than fine, since I don't enter speed contests. on the same token, I think it's also wise to invest some time into both ends of the spectrum, so that all are catered to. perhaps a compromise of both ends of the spectrum, while retaining good characterists over that broad spectrum of inbetweens.

as we've discussed before, delta's bleed speed because of the upturning of control surfaces on the TE, which causes drag and loss of total available lift, so we've either got to find a way to minimize that effect without canards, or we've got to add canards to counter that effect almost completey. either way is fine for me, as I'm not particuarly interested in all out speed per say.

for NACA inlets, you would still need full area that the fan requires. the only way you don't, is at really high speeds which we won't be seeing, where the ram effect starts to take place. we're talking speeds approaching and beyond Mach 1. so, it's got to be designed for the environment in which it's going to live and perform at its best. this means you've got to have full area. NACA inlets with full area would be absolutely enormous, which is why I had suggested a combination inlet that utilizes both pitot and NACA style ducts. some of the intake area would be recessed into the fuselage and the remaining would be the bulk of the pitot inlet. this would also benefit us by reducing total frontal cross section, thus better air penetration due to less overall drag. as speed climbs, the pitot inlets would have less affect, while the NACA duct would become more effective. this is of course, if you have the inlets in the correct fuselage position to begin with. NACA inlets won't work unless you have them in a postion of constant area increase. for example, at the junction where the nose has come to its widest point of the fuselage. if you put it a little further astern, you lose the effectiveness of the duct. all things to consider.
May 19, 2011, 03:54 PM
I'm slow but I'm expensive
Ken Lilja's Avatar

Ram recovery

According to the textbooks I used to teach A&P classes, inlet pressure should go positive at .1M to .2M. Somewhere between 70 - 140 mph. These textbooks could very well be wrong.
May 19, 2011, 05:30 PM
Life begins at transition
Anyone measured the intake pressure in the static condition for an EDF? Once you know that, it's very easy to calculate the speed at which intake pressure will become positive.

Mind you, at all speed pressure recovery should be taken in to account, even cars do it for cooling (at 60mph, not M.9)
May 19, 2011, 05:41 PM
Micro Boat Forum Founder
boredom.is.me's Avatar
As far as making the actual aircraft, that is relatively easy with a cnc machine and a block of foam. If precision is needed to prove a design, I say use a machine that wont add any variables to make the aircraft. I am sure someone in this thread has a machine.

A 2" thick 4'x8' sheet of wallboard (white eps) is only $22. A 1" sheet is only $12.
May 19, 2011, 05:44 PM
Micro Boat Forum Founder
boredom.is.me's Avatar
I have an idea for my wing. I'll get started on it tomorrow in school. I'll create a general design, then let you (everyone) nitpick at it.
May 20, 2011, 01:20 AM
Registered User
LuvEvolution7's Avatar
awesome boredom. can't wait to see it.

ken & Odysis......................you guys are both spot on with the speed. this style of inlet does indeed go positive within that speed range. you should start to see recovery rates of 90+% at 60-100 and beyond. before that, the pitot inlets would be providing all of the pressure recovery ahead of the inlet. at speed, the NACA inlet takes effect and the recovery takes place inside the duct itself. I believe this will be a great advantage to going faster with an EDF...............and of course, the fact that frontal cross section is reduced, which will reduce drag too. both win win I believe. I must be on to something, because the designer of the Cyclonebird chose the exact style combined inlet for the exact same reasoning. I discussed it with him after I proposed it on this thread and it turns out we are/were on exactly the same page.

it's kinda scary that someone is/was thinking like me. LOL.
May 20, 2011, 02:35 AM
Registered User
frank40's Avatar
The Poll should bee stoped now, dose any of you know how stop it. Can't make a new poll as long as the old poll is on.

Man you guys know some great stuff Glad I started this thread, learned some new stuff
May 20, 2011, 09:12 AM
Registered User
frank40's Avatar
How would a ogive delta trapezoid wing work, any ideas? Can we combine this tree, I was thinking the TE should be trapezoid.
May 20, 2011, 09:21 AM
Micro Boat Forum Founder
boredom.is.me's Avatar
Wouldn't it be something like what I proposed?
May 20, 2011, 09:35 AM
Micro Boat Forum Founder
boredom.is.me's Avatar
Before on top, after on bottom. Does anyone object having the intakes on top?
May 20, 2011, 10:10 AM
Registered User
LuvEvolution7's Avatar
the problem of intakes on the top, is that they are usually in a location where the fuselage starts to taper towards the rear. if this is the case, then you can't use a NACA/pitot combination inlet. it just won't work. other than that, intakes on top isn't a bad idea, especially if you plan on it being a belly lander.

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