Ventris SRB

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I'll miss the December LUNAR launch at Snow Ranch. It will be with me at a future TCC or LUNAR launch if you are in the SF Bay Area.
 
Shuttle, hmmm... Interesting to think about. It would be small, probably would need to cant the SRB engines a bit to make up for the weight and drag on the front side, auto release at main ejection charge, either free flight with gentle spiral turn or super mini R/C for controlled flight. Going to need a whole launch crew to keep track of all that. But it could be doable, hmmm...
 
I've ordered and received all the necessary pieces/parts to start building my version, but it'll have to wait until after the holidays... I'm booked for the next three weeks with work and a short trip home to Indiana to visit family.

I don't know anything about the LUNAR launch system. I've got a Heavenly Hobbies Tri-Pad Max and LightSword II Controller with a 12V Gel Cel battery (None of which I've used yet, unfortunately). I wonder if I can create a similar clip whip?

To maximize the chance of simultaneous ignition, 3" long Quest igniters were inserted into each engine nozzle and taped in place. They were attached to a 3-head igniter whip (from Dog House Rocketry - now showing discontinued) which was connected to the LUNAR launch pad system.
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Awesome!
I've brainstormed about something like this on more than one occasion. It's nice to see a working design, the self detaching boosters I mean.
Job well done. I applaud you sir. And I may copy your design sometime down the road. Lol

Mikey D
 
Hey! Mikey Likes It! (How many TRFers remember that ad?)
 
What size rail did you use for this? I've got a 1/4" x 6' rod that I've used on my MDRM and a NCR Laserhawk, but the rod whip was so bad on the Laserhawk that it ripped out the lower LL, so now I'm looking into using rail for larger MPR. I bought some MakerBeam rail a while back on Amazon, I think it's 1010 x 1500mm, which seams small (and short) to me. I've never used rail so I'd appreciate any feedback/direction.
 
The clubs in my area have both 1/4" rods and 10x10 rail. Not familiar with MakerBeam rail but it looks a lot like 80-20 T-slot aluminum rail (https://www.8020.net) that is most popular. Rail lengths vary and I look for at least 6 feet in length.

The Ventris SRB with the F-15/D-12 combo is a bit slow at lift off and, with no guarantee everything will light at the same time, having extra length is added insurance it will start out going up straight. The rail also provides some extra stability, keeping the rocket from rotating. This is really important given the play in the boosters.
 
Thanks. I'll have to order a 6' section eventually. I don't have any clubs within a 2.5 hour drive.
 
I gathered up all the requisite parts and will start construction of my version of your Ventris SRB. :wink:

I've had some thought of making the SRB/Main guide rails in two shorter segments, an upper and lower on each, rather than the one long section as you did. But then again, I suppose it could induce the chance for some binding at separation, and maybe I shouldn't mess with what works (KISS). Regardless, my build will be almost an exact carbon copy of yours. Do you think it's worth doing a dedicated build thread on? :confused2:
 
I gathered up all the requisite parts and will start construction of my version of your Ventris SRB. :wink:

I've had some thought of making the SRB/Main guide rails in two shorter segments, an upper and lower on each, rather than the one long section as you did. But then again, I suppose it could induce the chance for some binding at separation, and maybe I shouldn't mess with what works (KISS). Regardless, my build will be almost an exact carbon copy of yours. Do you think it's worth doing dedicated a build thread on? :confused2:
My personal take in this situation would be to tack on to this thread, unless Mr. G. objects, or unless you *want* to do a full build thread (which is always your prerogative). If you stay here, I'd just focus on the SRB-related highlights. Strap-on boosters are interesting and not at all routine, so even if you duplicate Mr. G's design I for one would still be interested in seeing how it goes for you.
 
I'll probably tack on here as you suggested, as long as Mr. G doesn't object. The only parts I don't have are the rail-button standoffs from Dog House that he used. I guess I'll have to fabricate something from 1/4" plywood for that.
 
I just did a Google search for Dog House Rocketry and the link I found only had electronics components.:confused2: I think I could fashion something easily enough with 1/4" ply.
 
They sold their inventory to either Binder design or Mac performance. Whichever of those have rail buttons, you can email them for the standoffs.

I bought a pair for my Ventris before D-house went out.
 
Binder Design bought doghouse. Just email Mike. He is a great vendor, and he usually responds quickly.
 
Thanks guys. I'll look into it. I did some work on my SRB's this weekend, but until Mr. G chimes in with his approval, I'll refrain from posting photos to this thread. As I get further along I may decide to start a new thread if I haven't heard from him.
 
Well, alrighty then!

Parts!
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Once I cut the Booster engine tubes to length (6"), I epoxied on 24mm Estes retainers, and marked where I was going to glue the lowest centering ring. I took a cue here from Mr. G's build. One of his Boosters came in a little hard on its tail and split the BT slightly when the nozzle bell got jammed into it. My intent is for the nozzle bell (shower head) to rest against the lower centering ring for more strength.
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I have card stock rings and wood rings. I'm a little worried about all the weight near the aft/exhaust end, so I used the card stock rings as the lower rings assuming they are lighter, but I don't really know that.
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But the nozzles have to be slipped on before the centering ring, from the top down, then I had to invert the whole assembly in order to get it all snugged up against the retainer.
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And then the top centering rings.
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Once all the centering rings were dry and secure, the motor mounts were glued into the Booster BT's. But not before I added CA to both ends of the tubes for added rigidity.
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A vertical line was drawn as the guide for glueing on the 3/16" H-channels.
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I started to measure and cut the channels, but I soon realized that perhaps the product I bought wasn't quite the same as what Mr. G had used. My plastic wasn't very rigid (Styrene vs. ABS) and I was afraid that I wouldn't be able to glue it on straight, and that would cause binding. So I had to go online and order the right stuff.
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So I'm stuck there until I get home Wednesday night. The new H channel should arrive at home by the time I get there.
I started thinking ahead to how I want to finish this rocket, and I want to give it the appearance of a scale bird. I drew some lines on one SRB to visualize my ideas.
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Here's where I left off until I get home.
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Mr. G, did you add nose weight to your Ventris? It seems to me I'm adding a lot of weight aft. I'm not sure where the original CG is in comparison to the CP, but I'm concerned.
 
The Ventris is really long and with the larger diameter payload section and nose cone at top, it is nose heavy, even with the boosters. Open Rocket shows the center of gravity four calibers ahead of the center of pressure. And that's without the threaded rod or camera. Mass with the two D's and an F was 1.87 lb. and the CG was at 31.2 inches. So I don't think you have to worry about being tail heavy.
 
That's good to know. Thank you. I haven't really figured out how to use simulators yet. I'm old school, which is easier to do with smaller rockets... If it looks about right, launch it.
 
Killing a little time this morning at work and playing around in "Paint", working on a Logo that I'll try to airbrush onto the payload bay when I get to that point.
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I get home tonight for 7 days off, so hopefully I can get some more work done starting tomorrow. Of course, I'll have household chores and other running around to tend to also while I'm off (hoping to get some other models flown this weekend), which is why I tend to build more at work - I have more unused time and I'm captive to my office. :eek:
 
The shock cords for the Boosters are #100 Kevlar cord attached to the upper Centering Ring with approximately 3x the BT length of 1/8" flat elastic attached to that, then to the NC. I used a length of Coffee Stirrer straw glued to the inside of the Booster BT, below where the NC shoulder sits and ran the Kevlar through it. My thought is, from what I've seen/experienced, is that when the Kevlar is anchored deep in the BT, it tends to cause a zipper, whereas the Estes teabag style mount tends not to do this, so gluing the straw up near the top of the tube, it should act like an anchor point and eliminate zippering, without being in the way like the teabag can. That's my story and I'm sticking to it. :wink:

I don't have any absolute plans yet for my payload bay, other than my JLA2, but I wanted to make sure there was plenty of room inside for anything I decided upon in the future, so I cut off the upper shoulder of the transition, and the shoulder of the NC creating a LOT more usable space. The transition was then glued into the payload tube with epoxy. I'm still thinking through how I'll attach the NC for flight. I'm leaning toward tiny screws and blind nuts. Hopefully today I can get to work on that.

I've also shaped my fins and coated them with Aerogloss Balsa Filler prior to sanding.

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I still haven't received the "H" channel I ordered, so I can't do much more to the boosters until I do. My booster NC's are balsa, and quite porous. This is how they look after three heavy coats of Aerogloss Balsa Filler. I think they could still use another coat.
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I turned my attention to the Payload Bay since I had nothing better to do. I'm going with more of a scale rocket theme so I'm adding corrugated vacu-form wraps (Apogee), as well as some 1/2 round banding (Evergreen).
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Only the banding is glued on at this point.

I'm also strongly considering a way to mount my Sony Action Cam.
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That last photo shows how if I were to cut a groove out of the Payload Bay BT, the camera lens would be external and looking down. I could build some sort of cradle out of 1/8" Ply maybe. It would add 89 grams, plus whatever the mount might weigh.
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Woohoo! I got my Plastruct "H" channel in the mail today!

Ok, so the Booster BT's are 12" long, so I cut the channels to 11" long (6 pieces total). I also cut the stops from scrap pieces (4 total). Then sanded those to match the contours of the respective BT's.
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Then it was time to glue everything on. I used 30 minute epoxy, applied with the edge of an epoxy brush to keep it to a minimum without too much squeeze out. I used scrap pieces of "H" channel to maintain an even gap on the booster pieces.
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I made balsa fairings to go in front of the forward/main rail stops on the Ventris BT.
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