Ventris Scratch Build

What's sacrilege?

That makes me dizzy, lol!

Bruiser said:

I've been following your build. I'm interested in how cutting stencils out with the cricut works for you. Are you going to use the letters or are you going to make a paint mask and paint the letters on?

I do enough scale builds that I like to keep my sport rocket schemes pretty simple. Did you see my gooney build from a Baby Bertha
View attachment 396279

Anyway, I don't know if I am going to put "VENTRIS" on this rocket or not. I'm thinking it over. No decals actual came with the kit but they were available for an extra cost I guess. Mark at Sticker Shock also had some vinyl for them and the word "VENTRIS" was included. After I put the color on I'll decided if it needs anything more.

-Bob

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As far as the masking/cricut goes, I just picked up some frisket made by Oracal on the internet, the same maker of the popular vinyl that most of us use.
I've only used it once so far but paint wise it worked great!
However, it left bad adhesive residue everywhere I masked...MAJOR pain to remove!!!
The base color paint (white) was "Rust-Oleum" "Gloss Protective Enamel"....dried for about 2 weeks...
The color sprayed over that was "Dupli-Color" "Acrylic Enamel Multi-Purpose Coating" in royal blue on my Argent.

I would like to give it the benefit of the doubt that it was the un-cured white that caused the adhesive residue, but after the residue was removed, the white paint surface was still perfect.....if it was a reaction to the adhesive/uncured paint, the paint surface would have been "mottled" by the adhesive.
Looks more like the adhesive was affected buy the solvents in the sprayed coat (blue duplicolor).
I may now have 40 Square feet of worthless masking frisket.....

As far as to your question....masking/painting vs stickers/vinyl goes...
It all depends.....do you want to clear coat and have a mirror finish?,
Is it small markings/letterings or large symbols/insignia?,
Is it a small diameter rocket (2" or less) or larger?

Do you use an airbrush/spraygun?.....

Too many variables....

But standard Oracal 651 vinyl is .025" thick, pretty thick if you want to make mirrors....lots of sanding over the vinyl and recoats of clear to level up (and lots of extra weight from the extra paint) and more work than it's worth for small rockets and small embellishments...

Masking/spraying has the potential to lay a thinner coat that takes less "leveling up" for the embellishments prior to clear coat.
Rattle cans can completely eliminate that advantage....

All depends on your intent/rocket/budget/resources....

I have been using the Cricut stencil vinyl with Rustoleum 2X paints. I find there is some type of reaction that happens. If you try to pull the vinyl off after just a few minutes the paint will "stretch" with the vinyl. It is very strange. The longer you leave it on, the less it "pulls" the paint.

I was just wondering if you have experienced the same?

-Bob

With rustoleum 2x, I wait a day before doing any manipulation

Saturday I was able to do some wet sanding and took care of the two short hairs, the two small runs and a few "fish eye' kinda things and re-sprayed the Gloss White. Monday I masked off the fins and painted them Colonial Red. This morning I masked off the checkerboard areas and painted the Gloss Black on.



I used Tamiya masking tape for the first time and I am happy with it. The edges cam out nice and I didn't have any of that weird stuff going on that happens when I use the Cricut stencil vinyl.

Now I need to work on the transition, payload tube and the nose cone.

I am thinking about cutting out a small "VENTRIS" paint mask with the Estes Logo to put on a fin but I don't know. Maybe just an Estes logo... I'll see after the payload area is done.

-Bob

Funny, I usually leave the estes sticker off when I put decals on

True craftsmanship to be able to mask and paint the roll patterns that way.
I would have used home printed decals.
Cuz I'm lazy.
Laters.

My transition, payload tube and nose cone must be cursed because I keep running into paint issues with them. The transition and payload tube are finally done after the third try at painting them Navy Blue. I sprayed the nose cone yesterday and the paint went on well but when I looked at it I saw it has several (like 8) hairs on it. They must have come off me when I was spraying, damn cats I spray in a container at my office to avoid that problem at home but now they are following me. Gonna have to wet sand and try again. I'll have to tack cloth myself too, lol! I wonder if they are fighting me because they wanted to be black...

I have started looking at 29mm motors for it and I saw a few Aerotech Economax motors that may work well. They are the F67-6W and the G74-6W. I tried to run a sim in OpenRocket with them both but the F67-6W is not in the list of motors. What do you do then? I did run the sim with the G74-6W and it was a little high for me right now. I don't yet have a chute release and I have not set up the rocket for dual deploy yet either. I did pick a motor from the list that had close to the same total impulse as the F67 and ran it. Is that about the best way to get a sim?

-Bob

To elaborate slightly:
1) In OR go to Edit->Preferences, then in the "General" tab point to a folder where you will store your own thrust curves. I put mine on Dropbox so it's available on all my machines where I run OR.

2) To add a new motor, go to Thrustcurve.org and search for it. Then take the .rse or .eng file and save it in the folder specified above.

You should now see the new motor listed in OR when you go to select a motor.

I did go to thrustcurve.org and it is there. Thanks for elaborating on how to get it into OR. I'll do that tonight so I can run the sim. It's similar in total impulse to the F26 but the other numbers are quite different. It'll be interesting to see how they play out performance wise.

-Bob

Bruiser said:

but the other numbers are quite different

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Those number differences are very important as you get into higher power motors. Hopefully your learning won't be expensive

Higher thrust motors -> Better stability off the rail -> faster top speed (will fins survive?) -> higher drag (lower altitude)
Lower thrust motors -> less drag (higher altitude) -> easier to track -> lower speed off rail (can it lift rocket safely?)

(also, pay attention to the fact that the "average thrust" in the motor name is not always indicative of how the motor performs. The F67 is actually pretty close to average mostly. The F26.....is not)

So computer "black thumb" me was able to get it into OR and it's showing 1,386 feet. That's quite a bit higher than I was wanting for a first flight. The .ork file has the rocket at 15.4 ounces. I think mine is heavier than that so I will gather up all the pieces and get a weight tomorrow.

-Bob

Ha-ha ork file! I don't know how anyone could build this rocket and come in at 15.4 ounce with motor.

Ok, mine was "scratch built" but I used Estes pro tubes, coupler, transistion, nose cone, parachute, shock cord, motor mount tube and retainer. Basically the only non- Estes pro series parts where the plywood parts; the fins, three centering rings and three baffle plates that I installed in the coupler. The baffle plates are the only parts I added. Oh, and six plastic rivets to hold the payload section together.

So get to it, right? What did mine weigh? My Ventris is tipping the scale at 17.2 sans motor. The Aerotech F67-9W comes in at 2.8 ounces so that would push my total weight up to 20 ounces. I'll adjust the weight in OR tonight and see what happens to that 1,384 foot altitude OR was giving me at 15.4 ounces I haven't adjusted a weight yet but it shouldn't be to hard to do...

-Bob

Product page for the Ventris showed 15.6 oz. So you're 1.6 oz heavy. That's not really that bad. You've got some extra plywood in there and who knows if your plywood was denser than the stuff used in the kit.

To adjust the weight, just select the Sustainer and override the mass and you're good to go. Might wanna override the CG while you're at it.

Neil,

Checking the cg is a good idea too. So glad you're around to point these things out. It came out to be 18.5 inches from the rear so I'll check that against the OR file as well.

Three plywood disks with holes in them shouldn't weigh too much and neither should the plastic rivets that hold together the payload section for now. Should I actually get feeling froggy enough to make it a dual deployment rocket, those pins will change... Anyway, you mentioning the cg also reminded me that my payload section is longer than standard. The standard size is 6.5 inches and mine is a little longer at 9 inches. I had contacted another TRFer how had built a Ventris and he suggested I make the payload area longer if I am thinking about setting it up for dual deploy so I did. Anyway, that's a little more weight and a little here and a little there adds up

I am editing this because as soon as I posted it my curiosity got the best of me. I weighed the 6.5 inch long section of payload tubing that I have and it came out to .83 ounces. So I divided that by 13 to get the weight of a 1/2 inch section of tubing and multiply those results by 5 to get the weight for a 2.5 inch section which came out to .32 ounces. Add in some weight for cwf, primer and paint but I don't know how much. Shoot, I just realize I should have done this with the 9 inch long finished tube on the rocket. Stand by...

Ok, the 9 inch payload tube weighs 1.39 ounces. Divide that by 18, multiply that result by 5 and come up with .386 for the 2.5 inch section of finished tube compared to .32 of bare tube. Anyway, there is almost .4 ounces of the extra weight.

Writing of the payload area I realize that I haven't posted a pic in a while so here is a pc of it. It is held together with Dorman plastic rivets. They are the type you insert, then push the center in and three fingers spread out on the inside. To remove them you have to unscrew the center before you pull them out. I didn't want to glue the payload area together because I think I may change this rocket over to dual deployment sometime in the future. The transition is long enough to house the electronics for the dual deploy.



All I have left is the clear coating and to actually rig up the recovery system. It is all just sitting in the rocket right now. I'm not sure about the clear coating as I'm just a little taken aback by this mornings weigh in. I think I'll decided after I see what the sim says tonight.

-Bob

After updating the file with the new parameters the sim shows right at 1,100 feet with the F67-9W.

Here's the final shot:



-Bob

Bruiser said:

After updating the file with the new parameters the sim shows right at 1,100 feet with the F67-9W.

Here's the final shot:

View attachment 398107

-Bob

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That paint job looks AWESOME! Nice work. I read through this thread and saw where you were having some troubles with paint "blistering" shortly after hitting the rocket.

That can happen for a few reasons, but usually it's due to the first coat(s) not having fully cured. Another culprit can be incompatibility in the paint compounds (which can even occur between different colors of the same brand and type of paint). The only thing that I've found in years and years of painting rockets and other things that will help get you around the blistering if you've got fully cured base coats is to go very light on the newer (different colored?) topcoats. Let them cure, then do another light topcoat, and so on.

I, like everyone else, wants to get as much paint on as i can to avoid lots of coats, but the directions on the can (every can I've ever seen) say to do multiple light coats. Sometimes we just need to do it a different way... :-|

Again, very nice on the paint work! S

Thank you SammyD for your kind words.

My biggest problem with paint was getting hair on it while painting. I did get a couple of fish eye looking things but that could have been caused by some dust or some such thing. ThHe runs were from me trying to cover over where I picked a hair off with the tip of an x-acto knife

I've had a few problems with 2X but the problems on this rocket had nothing to do with the product. They were all because I don't have a "clean" room to paint in

-Bob