Hi- I'm building a LOC Stovi with the 29mm mount option, and am turning the transition into an av bay for dual deploy because I don't hate myself enough, apparently. Where should I place my static ports? If I go at the top, with the narrower OD, my controller is quite a bit lower than that (Eggtimer Quark). I know not to go on the transition, and to give space after a transition, so now i'm thinking of lower down, but there exists weird compression and expansion pressures as the air equillibrates to the larger BT diameter. What's the typical approach?
Location of static ports when AV bay is a transition section
- Thread starter soopirV
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So, adept Rocketry indicates that static ports should be 4 calibers behind the nose cone, which I read as a transition. This means my static ports should be on the fore (narrow) end of the transition...If my bay is tight, I guess it doesn't matter, since it will feed/respond to the the pressure at the sampling ports.
Nytrunner
Pop lugs, not drugs
I agree with placing them ahead of the transition. I did that on my electric Ventris, and will repeat it on my electric Argent (both have T-bays).
For what its worth, the Ventris' performed fine with the forward vent holes, and a larger switch access hole on the transition itself.
The '4 diameters behind the nose' comes from design theory for Pitot-Static tubes. It's the minimum distance from the nose where you can place the the static pressure ports to gather data that will be accepted for analysis. That's one of the reasons I'm not comfortable with HED. because by the nature of the nose-coupler bays, that guideline is violated. But, you aren't gathering scientific/engineering data during HED, you just need 'good enough' pressure behavior for deployment, and many have had successful outcomes with HED.
For what its worth, the Ventris' performed fine with the forward vent holes, and a larger switch access hole on the transition itself.
The '4 diameters behind the nose' comes from design theory for Pitot-Static tubes. It's the minimum distance from the nose where you can place the the static pressure ports to gather data that will be accepted for analysis. That's one of the reasons I'm not comfortable with HED. because by the nature of the nose-coupler bays, that guideline is violated. But, you aren't gathering scientific/engineering data during HED, you just need 'good enough' pressure behavior for deployment, and many have had successful outcomes with HED.
rharshberger
Well-Known Member
The static ports will do their job just fine at apogee wherever they are located on the transition, however the data will be pretty noisy due to the turbulent air flow. I have used several alts in transitions and nose cones and the data curve is always ugly, but the altimeter does its job.
I'm using a non-recording alt, so I don't mind noise as long as the deployments happen where they're supposed to.
H_Rocket
Death by Powerpoint
On my Expediter, I use the same arrangement and the static holes are just forward of the tapered section punched through the shoulder. I'm not that much of a data person in rockets so a noisy download does not bother me. The MAWD works perfectly.
That's great data, thanks- did you use shear pins in the drogue section (the larger of the two diameters)? I'm concerned about drag separation, particularly with high thrust motors. I did a ground test with 3 2-56 nylon screws, and had success at 1g of FFFg smokeless, which I think will be fine since the 29mm CTIs I'll be flying come with 1.2g charges, that will be drilled as a redundant deploy. I ask because it seems maybe to be overkill on a cardboard rocket, but I'm a belt-and-suspenders kinda guy...
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