Yet another 5" Jart build thread - M power

When I first saw the picture of the 5 inch Jart right after the Wildman's Black Saturday sale I thought "Doh! I should have bought one of those". Thankfully about a week later Tim realized he had some units leftover from the sale and posted a message here on TRF. This time I did not hesitate and bought one.

So why do I want to do another build thread on a 5 inch Jart? Manny is already describing his "Jart meets N-10,000" project, others have very nice build threads on their Jarts as well...

Because I want to do it a little differently. The parameters for this particular project will be as follows:

1) Fly a 5" Jart on an M motor
2) Set it for dual deployment
3) Keep the same size. No extensions, no fin mods (except for some reinforcement)
4) Fly it at Thunderstruck 4.



To be continued... :smile:

nh4clo4 said:

1) Fly a 5" Jart on an M motor

Click to expand...

This will be cool. :grin:

I am so subscribed !!

nh4clo4 said:

3) Keep the same size. No extensions, no fin mods (except for some reinforcement)

Click to expand...

:cry::y::confused2:

:rofl:

I know... A build thread is worthless without pics.

The subject as I received it:


More tomorrow.

PS: Double Doh! I just realized the thread title only says [5" build thread] instead of [5" Jart build thread]. Moderator, if you have a chance, could you make the correction? Thanks.

nh4clo4 said:

PS: Double Doh! I just realized the thread title only says [5" build thread] instead of [5" Jart build thread]. Moderator, if you have a chance, could you make the correction? Thanks.

Click to expand...

You can fix that, yourself. Go edit your first post, then when the editor comes up, click "Go Advanced" and it will give you the ability to edit the subject.

-Kevin

Going to need an awfully skinny "M" reload to fit that mount.

And a lot of nose weight.

(and yes, I know you knew that)

s6

troj said:

You can fix that, yourself. Go edit your first post, then when the editor comes up, click "Go Advanced" and it will give you the ability to edit the subject.

-Kevin

Click to expand...

Well, that was easy.

Thank you sir.

Note: I will not try to make this an all-encompassing build thread, or try to capture every single step of the build, I simply wanted to share something that is a little different and share some of the madness err... I mean some of my ideas.

With that being said, let's get going. I was initially thinking a 5-grain motor, but after receiving the kit and looking at the nose cone dimensions more carefully, I am beginning to believe I can fit a 6 grain in there and I just so happen to have an M-2150 red in my motor box One of the benefits of this swap, if I can make it happen, is to reduce the need for nose weight since the motor would extend pretty much all the way to the tip of the nose cone. :dark:

So the 6-grain will be the ultimate goal, with a 5-grain as an alternate option.

So first step is to get rid of the motor mount and centering rings that came with the kit. Then take the 3 inch MMT and associated centering rings I had ordered separately from Tim and get to work. The motor mount tube I had ordered was 24 inches long, but due to the configuration I have in mind, I have cut it as shown below. I will use the top section to make an av-bay that will slide over the motor. This should make more sense later.


As you can see I received centering rings that were on the large side. They were loose enough to wiggle from side to side as seen in the attached picture. Don't panic. This can be easily fixed. Just insert three small pieces of cardboard equally spaced around the MMT so that the gap is uniform around the tube. Tack in place with 5 minute epoxy, then cut off the little cardboard tabs. Once this is done I did a fillet using JB Weld.

Now to the fins.

Since I could hit Mach 2 with the M-2150 I have decided to open up the fin slots and glue the fins on the motor mount outside of the rocket, This will allow me to do some fin tip to fin tip reinforcement and then re-insert the assembly into the airframe.

I can already hear CJ scream " You don't need to do that. Injecting internal fillets would be strong enough and much simpler. Aaargh." :rant:

I know. Fillet injection would probably work, but my gut tells me there is a risk of fin flutter at Mach 2 with these swept-back fins. I could also have done some T2T reinforcement over the airframe once the fins are glued in, but I didn't want that look. Since I have a black Jart I wanted to minimize the presence of other materials over the airframe as much as possible.

So, I slid the MMT into the airframe and measured the excess of fin tab. What extends past the airframe is not how much you want to keep. This tells you how much you want to cut off. Measure that distance and then remove that form the tab depth.



I did cut off the tabs last night and tacked the fins on the MMT. Next will be the reinforcement.

nh4clo4 said:

I know... A build thread is worthless without pics.

The subject as I received it:
View attachment 112901

Click to expand...

Wait a minute.... the 5" Jart comes in black?!?!?!?!?! All the pictures I have seen thus far were normal green fiberglass... I may have to rethink this...

T-Rex said:

Wait a minute.... the 5" Jart comes in black?!?!?!?!?! All the pictures I have seen thus far were normal green fiberglass... I may have to rethink this...

Click to expand...

There were ten black ones, all are gone.

Chad
Tim twisted my arm and I purchased the last Black Jart 5 at this time unless Tim gets more black tube. That's the story I told my wife anyway. I may not build it as a Jart. I have a design in mind for the 5" parts.
Gary

crossfire said:

Chad
Tim twisted my arm and I purchased the last Black Jart 5 at this time unless Tim gets more black tube. That's the story I told my wife anyway. I may not build it as a Jart. I have a design in mind for the 5" parts.
Gary

Click to expand...

I know how Tim twists... Russ W might have the last one known, thanks to ordering confusion he ended up with two - I'm anxiously awaiting to hear what he plans to do. We now return you to your regularly scheduled build...

Mini update.

I added an eyebolt at the tip for shock cord attachment. Todo that, simply unscrew the metal tip, tap on the machine screw to remove the retaining disk, and replace the machine screw with an eyebolt of similar size. Done. I also glued the nose cone shoulder in place.

What is more exciting is that I have received my decals from Mark at stickershock23. :w: . I will paint the fins and the nose cone tip in yellow, leaving the rest of the rocket black. Mark made a decal set in two colors, with the main logo in yellow (going over the black body) and the smaller logos in black since they will go over the yellow fins. Schweeet.

Chad I think I heard Russ say he will keep both of them. Lucky guy.
gp

nh4clo4 said:

I know... A build thread is worthless without pics.

The subject as I received it:
View attachment 112901

More tomorrow.

PS: Double Doh! I just realized the thread title only says [5" build thread] instead of [5" Jart build thread]. Moderator, if you have a chance, could you make the correction? Thanks.

Click to expand...

Dang! How'd you get a black one!?


Good luck with this project! I'm looking forward to it!



Braden

Fin reinforcement was accomplished in a relatively standard fashion: Clean the fins to remove the sticky stuff, sand the MMT, CRs, and fins with 60 grit sandpaper. Clean with denatured alcohol.

Once that was done the fins were tacked to the MMT using 5 minute epoxy. Then I added fin fillets using thickened West System epoxy.

Before the fillets were completely hardened, I did my T2T reinforcement. One layer of 5.7 oz CF and one layer of 2 oz fiberglass. The 2 oz. fiberglass has a tight weave and will facilitate finishing, since I plan on painting the fins.

Trim the excess material, and voila!

Now I have one solid chunk consisting of the MMT, CRs, and fins. We will place this back in the airframe a little later.

UPscaler said:

Dang! How'd you get a black one!?


Good luck with this project! I'm looking forward to it!



Braden

Click to expand...

I did nothing special. I just got lucky.

Really.

nh4clo4 said:

Fin reinforcement was accomplished in a relatively standard fashion: Clean the fins to remove the sticky stuff, sand the MMT, CRs, and fins with 60 grit sandpaper. Clean with denatured alcohol.

Once that was done the fins were tacked to the MMT using 5 minute epoxy. Then I added fin fillets using thickened West System epoxy.

Before the fillets were completely hardened, I did my T2T reinforcement. One layer of 5.7 oz CF and one layer of 2 oz fiberglass. The 2 oz. fiberglass has a tight weave and will facilitate finishing, since I plan on painting the fins.

Trim the excess material, and voila!

Now I have one solid chunk consisting of the MMT, CRs, and fins. We will place this back in the airframe a little later.

View attachment 113314View attachment 113315

Click to expand...

Claude,

Looking really nice! Exciting build so far; and looking forward to watching a screaming flight at Tstruck!

Very nice!

-Eric-

nh4clo4 said:

Fin reinforcement was accomplished in a relatively standard fashion: Clean the fins to remove the sticky stuff, sand the MMT, CRs, and fins with 60 grit sandpaper. Clean with denatured alcohol.

Once that was done the fins were tacked to the MMT using 5 minute epoxy. Then I added fin fillets using thickened West System epoxy.

Before the fillets were completely hardened, I did my T2T reinforcement. One layer of 5.7 oz CF and one layer of 2 oz fiberglass. The 2 oz. fiberglass has a tight weave and will facilitate finishing, since I plan on painting the fins.

Trim the excess material, and voila!

Now I have one solid chunk consisting of the MMT, CRs, and fins. We will place this back in the airframe a little later.

View attachment 113314View attachment 113315

Click to expand...

WOW those are long and pointy.

Nice build. Have you or anyone got to the point where you are adding nose weight. Just wondering how much is needed?
Thanks
Gary

Wow interesting build, still trying to figure out that if the rocket AF is 24" the NC is around 20" (much less at the inside taper point where the 98 mm case will hit) and the 98 - 6 grain motor case is around 44" how you will get this in with no extension. Please post more photos and build descriptions. Sounds like you are doing the dual deploy Gizmo approach (ala the “donut hole” Avbay, except you are adding also the “donut hole” nosecone) it seems like it will be a challenge with the space to get two altimeters/battery’s, drogue. main, and shock cords in there with the 98-6 grain and also tracking if you ever want to find this again . Please keep us posted can’t wait to see more of this. If I can some how get a hold of a 5” Jart I may also be crazy enough to try this approach as well.

jolevich said:

Wow interesting build, still trying to figure out that if the rocket AF is 24" the NC is around 20" (much less at the inside taper point where the 98 mm case will hit) and the 98 - 6 grain motor case is around 44" how you will get this in with no extension. Please post more photos and build descriptions. Sounds like you are doing the dual deploy Gizmo approach (ala the “donut hole” Avbay, except you are adding also the “donut hole” nosecone) it seems like it will be a challenge with the space to get two altimeters/battery’s, drogue. main, and shock cords in there with the 98-6 grain and also tracking if you ever want to find this again . Please keep us posted can’t wait to see more of this. If I can some how get a hold of a 5” Jart I may also be crazy enough to try this approach as well.

Click to expand...

It is actually a 75mm, 6 grain motor. Casing length is around 34-35". The 98 mm 6 grain would be well into N motor category.

More to follow today.

crossfire said:

Nice build. Have you or anyone got to the point where you are adding nose weight. Just wondering how much is needed?
Thanks
Gary

Click to expand...

Not quite there yet. However, with the motor extending well into the nose cone I might not need any nose weight. The long 6 grain motor will help shift the CG forward.

Back to the build. I was able to get several small things done this weekend...

What I have described in this build thread so far is is somewhat standard. Now we get into the part of the build that is a little more unusual. The av-bay. The av-bay will be built around the section of MMT I removed earlier (post #9).

Parts:

3.75 inch section of MMT
1 centering ring
2 Ravens with Power perch.
2 backplates for the Ravens
1 1-inch section of coupler tube
Misc. items (such as glue, wires, spacers, e-matches, screws, chips, beer, etc&#8230

So, below we have the basic components. Normally I mount the Ravens on a sled, with the screws going down through the altimeter mounting holes, the spacer, then the sled. This time around I will have the screws go through the backplate, then the spacer, then the altimeter mounting holes. Therefore the nut will be on the altimeter side of the assembly. The screws and the spacers will be glued to the backplate, and the backplate will be glued to the MMT.

Here you see the arrangement that will receive the altimeters. I prefer to use nylon spacers instead of the small pieces of wood that come with the Power Perch. This is a mix of 1/8 and 5/16 inch spacers.

Once I have the elements positioned correctly I glue the screws and spacers in place. Next I will trim the screws (the ones I had are on the long side and would interfere with the airframe) and epoxy the backplate on the MMT. Always insert a nut on the screw before you trim it. The threads always get a little messed up during the cutting, so you can "fix them" by unscrewing the nut. In the pics below you can see the nuts placed on the screws. I have marked the screws with a permanent marker before removing the Ravens. The masking tape on the backside was to ensure the screws would not fall off while I was test fitting the assembly.

nh4clo4 said:

Manny is already describing his "Jart meets N-10,000" project,

1) Fly a 5" Jart on an M motor
4) Fly it at Thunderstruck 4.

Click to expand...

Okay, so mine won't meet an N10,000 for a long time, probably MWP (that's if I'll have time with school and everything).
Mine is probably going to fly at Thunderstruck as well, and probably with a 6G M840 White (because I've had it sitting in my motor box for a while too). I think we should drag race, because it is going to fly without the extension for that flight...

nh4clo4 said:

Before the fillets were completely hardened, I did my T2T reinforcement. One layer of 5.7 oz CF and one layer of 2 oz fiberglass. The 2 oz. fiberglass has a tight weave and will facilitate finishing, since I plan on painting the fins.

Trim the excess material, and voila!

Now I have one solid chunk consisting of the MMT, CRs, and fins. We will place this back in the airframe a little later.

View attachment 113314View attachment 113315

Click to expand...

One question Claude, did 'ya bag it? Interesting approach, mine is similar except I'm only doing outter lays of carbon because I didn't want to widen the fin slots. Tim did give me one of the black Jarts, but I told him what I was going to punish it with and he took it away and gave me a normal one

Manny
Whats the CP on the Jart 5???
Thanks see you at Bong
Gary

nh4clo4 said:

It is actually a 75mm, 6 grain motor. Casing length is around 34-35". The 98 mm 6 grain would be well into N motor category.

More to follow today.

Click to expand...

yes,I now see. I just figured with all the JART upscaling of motors going on when you stated a 6 grain I assumed 98. The gods smiled on me today and I was able to get an unobatianium 5" JART shipped out to me, and I do have this 98mm 4 grain case sitting around in my shop...... Keep the build photos going. Thanks