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10/23 Raptor Video

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Volzalum

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Nov 22, 2019
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Technical observations/ questions on the 10/23 Raptor video:
1. Observation - The nylon tufts appear really stiff compared to yarn ones.
Question - How much flexibility is needed to be able to ascertain the flow behavior?
2. Observation - As mentioned in the video, there appears to be turbulence near the hull on the canard.
Question - Is turbulence near the canard/hull joint normal?
3. Observation - As mentioned in the video, there is turbulence at the landing gear hull opening. There also appears to be a suction into the slot at the tuft near the N on the leading edge of the slot (though it could just be hidden in the shadow and flowing straight).
Question - How much turbulence is expected on other retractables in similar positions?
4. Observation - The wheel well covers are held by a single layer of tape.
Question - Are there any examples of where a smooth flat surface similar to this was taped and released due to failure of the tape?
5. Question - Were there other observations of note in this video?
 

WINGITIS

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Not sure which video you are referring to..?

BUT here is another people may not have seen yet.....!

IT FEATURES THE FULL TAKEOFF RUN, not just the last part as on the Raptor website......

 
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pictsidhe

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Peter has a new video out.


Looks like the next test will have aluminium sheet taped over the wheel wells as well as an altered c.g. Yep, changing several aero things.
Lots of very long tufts have gone on.

In a comment in another video, he said that the main wing airfoil is a NACA 6 series. I'm no expert, but I am under the impression that canards are rather picky about airfoils, needing low Cm?
 

proppastie

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looks like removed stall strip, in front of the wheel wheel
 

flywheel1935

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Keeping things 'Technical'
I would have used styrene and tape, to fill the wheel wells. much safer ref prop damage !!!
As an aside, I wonder what the gear legs weigh? as fixed gear with GRP/Composite legs could save a load of weight. It's good enough for Cirrus.
 

wsimpso1

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Moderator Mode ON

In the recent past, the moderators have closed two threads on the Raptor. Why?

We only did it reluctantly. We attempted to keep the threads within our principles on hba.com. There were many instances of citing the CoC, deleting posts for violations, communicating with individual members, and in general attempting to remind us all that piling on and personal attacks were inappropriate here. While all of this was going on, the tenor of individual posts treaded the line of unacceptable, and the entirety of the threads took on as unacceptable and intimidating a tone as if personal attacks were still allowed. This too violates the principle of hba.com being a welcoming place where we can discuss homebuilt airplanes and ideas involved with them. When it became the whole thread, we deleted large numbers of posts and then locked the thread.

So, what can we do about this?
  • Any one individual post must stay within the code. If a violation of the CoC occurs once in a while, we delete posts and issue warnings, same as we always have.
  • Piling on, repeating points already made, and mass focusing on any individual's actions are not acceptable. This is intimidating and clearly violates our principles too. Just because your post, by itself appears OK, does not mean that its contribution to bigger thread is acceptable.
The moderators will delete posts, issue warnings with warning points, discuss the violations off-line where the members desire, and as long as the thread remains generally within our principles, it shall remain open. When the thread drifts into an intimidating cycle, we will quickly close threads, and consider banning individuals.

There are many ways of writing about airplanes, their features, the interactions between features, airplane handling, risks, etc, and then how to fix it without getting into personalities. Likewise there are many ways of writing about design and development processes, either in single posts or in the accumulation of posts. In particular, I want to remind folks that drafting a post, letting it cool for a few hours, and then re-reading and editing it with our principles expressed in the CoC for our little piece of the internet will go a long ways.

Billski
 

rbarnes

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Technical issues I noticed in the latest video:

1. Post intercooler air inlet temps at 190* going into the engine. It's been my experience that anything over 160* is reducing power significantly
2. An ambient air temp probe was placed downstream of the radiator to see air temps coming out of the radiator. During the run air temps dropped post radiator. That seems to me that there is no air flow through the radiator at all.
 

pictsidhe

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Technical issues I noticed in the latest video:

1. Post intercooler air inlet temps at 190* going into the engine. It's been my experience that anything over 160* is reducing power significantly
2. An ambient air temp probe was placed downstream of the radiator to see air temps coming out of the radiator. During the run air temps dropped post radiator. That seems to me that there is no air flow through the radiator at all.
On an SI, high IAT is bad news. Diesels don't care so much, if raised EGTs are not a consideration. They do mind the density drop from high temps. That run only had full power for 8 seconds before the engine was throttled back. TIT seems to be gone from the log.
Radiator exit temperature suggests either that he has a massive air leak, or that the core is too small. Could of course be both. I didn't see the ambient temperature, but it was probably 60s judging from my recent NC weather. Details like that are required for proper analysis.

Edit. Radiator exit temp is probably rather cool because the engine is not up to temperature and the thermostat is still closed! A longer run is needed...
 
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pictsidhe

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Apollo's thoughts on main wing airfoil selection.
Cozy uses E1230, like the Long-EZ. The velocity started out with the E1230, but had an early wing redesign after having deep stall issues. I think only the planform was changed.
 

proppastie

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The prop will not like those alloy sheets if one comes off in flight!
I used this tape on a leaking fuel cap on the Mooney .....very difficult to remove and clean....really really strong tape/glue....seems like a the seal is an un-cured rubber .....looks the same but I really do not know.
 

BBerson

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The tufts cannot measure "laminar" flow conditions mentioned in the video. Laminar flow breakdown can sometimes be crudely seen with a smooth coat of kerosene and talc or something. Kind of messy, I like to watch the evening dew on a clear night evaporate at takeoff.
The tufts only detect turbulent or separation. The tufts cause turbulent flow so cannot show laminar. Often these words are confused.
 

flywheel1935

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Formula 1 Race cars use a greenish airflow fluid in testing ( at speeds over 200mph) to see what the air is doing, guess its water based as its cleaned off before the race. As it exists there must be a supplier somewhere.
 

WINGITIS

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Apollo's thoughts on main wing airfoil selection.
Cozy uses E1230, like the Long-EZ. The velocity started out with the E1230, but had an early wing redesign after having deep stall issues. I think only the planform was changed.
Thanks Pixtsidhe and Mark.

But I would like to know what the Canard airfoil is to model it in conjunction with the main wing.

He mentions the AOIncidence of the canard in the video and I want to see what the relative lift/area values are with a view to understanding the pitch oscillations present in the "First Flight" video.

Cheers
Kevin
 

Mike0101

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Formula 1 Race cars use a greenish airflow fluid in testing ( at speeds over 200mph) to see what the air is doing, guess its water based as its cleaned off before the race. As it exists there must be a supplier somewhere.
It's called flo-vis in those circles ->Link Paint
 

fly2kads

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Formula 1 Race cars use a greenish airflow fluid in testing ( at speeds over 200mph) to see what the air is doing, guess its water based as its cleaned off before the race. As it exists there must be a supplier somewhere.
Dick Johnson used cheap automotive motor oil, with food coloring added, for his sailplane flight testing. In the photos accompanying his articles, you could see the laminar, transition, and turbulent zones pretty clearly.
 
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