Sky Fieri - insufficient space for recovery system?

[DJRNY]

Hello,
I'm not sure where this belongs so I thought I'd try here. I am nearing completion of a LOC Sky Fieri kit and have noticed something troublesome. There seems to be insufficient space to put the recovery system. Has anyone else noticed this with the Sky Fieri (or another rocket)?
The Sky Fieri is a 3.1" kit with a 29 mm MMT. The included recovery system consists of a 36" nylon parachute which seems thick and slippery, I read somewhere that LOC chutes are urethane coated. It also has a 15' 3/8" nylon shock cord, a 9 x 9 flame resistant blanket, and a quick link.
As background, I am building it mostly as per the instructions (see exception below). I installed the MMT with the forward CR close to the end. I installed the coupler 3" into the payload section, but attached it with removable nylon rivets instead of glue (just in case I wanted to do something else in the future).
The booster section has just under 8" from the forward CR to the end of the airframe. With the upper section in place, this leaves only 5" of 3" tube for the recovery hardware. Although I haven't connected everything up, I have been trying to fit all of the above into this space, but to do so I need to pack it pretty tight (not a good idea!), and that is not even with an (optional) JLCR. So I am seeking advice, ideas, and/or the voice of experience.
One option I have thought of is to get another parachute made of thinner nylon. This would add cost but not require any rework, but I am not sure how much space I'd gain. The same thing can be said of going to a 1/4" kevlar shock cord.
Another option I have thought of is to get another coupler, bulkhead, and eye bolt. I could install the bulkhead with the eye bolt about halfway into the coupler rather than at the end, thus gaining up to 3" of space, for example. Again, this is added cost and rework, but less than a chute and kevlar shock cord. This also could gain me the most space compared to my other ideas. Does anyone see a problem with this approach?
Another option is to remove the nylon rivets, push the coupler further into the payload section, and drill new holes and reinstall the rivets. This is a simple no added cost rework. However, I am concerned about how much shoulder there should be to fit the payload section onto the booster section. Currently there is 3" of coupler to slide into the booster section. If I slide it in 1" further into the payload section, that would leave me a 2" shoulder. If I slide it in 1.5" I would have a 1.5" shoulder. I am not sure how much shoulder I need. Currently I can pack everything in and only lack about 1/2" to get a tight fit of the payload section to the booster section, so gaining another inch should do the trick, but with little margin.
I am open to suggestions.
Thanks,
Dave

 

[DigBaddy]

Not familiar with the kit, but did just go look at the instructions. Probably would have been beneficial to chop some off the motor tube, but putting a 29/240 or 360 in this would make it a pain anyways.

Have you tried burrito wrapping the chute and shock cord in the nomex blanket like it would be done for flying? That probably would take up less space.

 

[jmasterj]

Can you take your coupler and flip it around? You'd need to put new holes in the coupler and be able to remove the eyebolt and attach it facing the other way, but it would be no cost a little rework and would gain you most of the coupler's space for your chute burrito.

 

[David_Stack]

You may want to try and optimize how you pack your harness as well. Take a look here for an example:

https://www.rocketryforum.com/threa...-shock-cord-entanglement.179146/#post-2414357

 

[DJRNY]

Have you tried burrito wrapping the chute and shock cord in the nomex blanket like it would be done for flying? That probably would take up less space.

Yes, thanks. I can't say I've exhausted all possibilities but any way I do it it is a tight fit.

 

[DJRNY]

Can you take your coupler and flip it around?

If I hadn't epoxied the nuts and washers..........

So you see no problems with having some of the "usable space" inside the coupler?

 

[DJRNY]

You may want to try and optimize how you pack your harness as well.

I did look at that, thank you. Maybe I am over reacting here. I've not had a rocket before where there was so little space the packing had to be done in a precise and repeatable manor every time. I was trying to think of ways to create more space to have a bit of margin.

 

[mikec]

Unless it's very heavy, a 30" chute, say a TFR thin-mil chute, would take up less space and be sufficient.

 

[jmasterj]

If I hadn't epoxied the nuts and washers..........

So you see no problems with having some of the "usable space" inside the coupler?

Could you mechanically separate them? Or cut off the short section of coupler that holds the bulkhead? Then you just need a new bulkhead and hardware.

And no, no issues there. I have rockets build like that. You make the chute burrito and put it in the coupler, then slide that whole thing into the other tube.

 

[Buckeye]

The booster section has just under 8" from the forward CR to the end of the airframe. With the upper section in place, this leaves only 5" of 3" tube for the recovery hardware.

According to the RockSim file on the LOC website, there is 9" of recovery space from the top centering ring to the coupler bulkhead. You have only 5 inches. My guess is that LOC gave you a body tube too short, a motor tube too long, or both. Verify your parts vs. the BOM.

Other than bitching to LOC about it, my only suggestion not mentioned would be to add a coupler and 4 or more inches of effective body tube.

 

[DJRNY]

Could you mechanically separate them? Or cut off the short section of coupler that holds the bulkhead? Then you just need a new bulkhead and hardware.

And no, no issues there. I have rockets build like that. You make the chute burrito and put it in the coupler, then slide that whole thing into the other tube.

You've given me an idea! I don't have tools to build rockets, but I have tools to build knives! I could cut off the end of the coupler having the bulkhead, loosing 3/8", maybe 1/2" of coupler. I could then grind the bulkhead (with the eyebolt intact) back to the original size and remount it about 3" inside of the remaining coupler. That would reduce my shoulder to maybe 2 1/2", but I am guessing that will be OK. So with a little shop time and $0.00 cost it might get me the space I need. Definitely an option.

 

[DJRNY]

According to the RockSim file on the LOC website, there is 9" of recovery space from the top centering ring to the coupler bulkhead. You have only 5 inches. My guess is that LOC gave you a body tube too short, a motor tube too long, or both. Verify your parts vs. the BOM.

Other than bitching to LOC about it, my only suggestion not mentioned would be to add a coupler and 4 or more inches of effective body tube.

Buckeye - with all due respect are you sure? I don't have a problem contacting LOC if I have my facts straight. I don't have RockSim (for a couple of reasons), but you may have just opened a can of worms.

The BOM on the Sky Firei instructions are kind of sparse, It does say the MMT is 29mm X 12". I confirmed that mine is indeed 12" long. The BOM does not say how long the airframe or payload tube are, just that they are 3.0" (75mm). I did check the OAL and got 45 1/4", which is close to the 45.2" length advertised. So that suggests the airframe length and payload length are correct (BUT - hold that thought).

I measured the airframe ( referred to as the slotted body tube in the parts list) and it is 20" long. I'm not a rocket scientist, but a 20" airframe minus a 12" MMT is 8", minus a 3" coupler comes out to 5", NOT 9". If I had 9" of recovery space I would not have started this thread.

Another thing that didn't feel right from the start of this build is the payload section. Mine is 14" long. That seems disproportionately large compared to the OAL of the rocket.

So it does make me wonder if the kit should have included a 24" airframe and a 10" payload tube rather than a 20" airframe and a 14" payload tube? If that were the case all the numbers would add up and I would indeed have 9" of recovery space, which would be plenty of room for the included recovery gear.

If you (or someone else) could double check that design file for me I would really really appreciate it.

I also wonder if anyone else has a Sky Fieri kit and could check on these things? I could sure use a sanity check!

Dave

 

[mikec]

So it does make me wonder if the kit should have included a 24" airframe and a 10" payload tube

That's what the Rocksim file says. Of course IMHO that would make the payload tube too short, but if you're not doing dual deploy it doesn't matter.

 

[Art Upton]

In the future, don't put the last centering ring on the end of the motor mount tube. I have many rockets where my shock cord is neatly setup between the motor tube and the outer body tube with the last centering ring just above the fins.

 

[jmasterj]

You've given me an idea! I don't have tools to build rockets, but I have tools to build knives! I could cut off the end of the coupler having the bulkhead, loosing 3/8", maybe 1/2" of coupler. I could then grind the bulkhead (with the eyebolt intact) back to the original size and remount it about 3" inside of the remaining coupler. That would reduce my shoulder to maybe 2 1/2", but I am guessing that will be OK. So with a little shop time and $0.00 cost it might get me the space I need. Definitely an option.

I thought about suggesting just that. If it gets short, you're probably better off gluing it into the payload section.

 

[Tractionengines]

Yes, thanks. I can't say I've exhausted all possibilities but any way I do it it is a tight fit.

Organized and tight is the best bet. Dis-organized, and lose, allows things to move and tangle, leading to inconsistent results.

Practice bundling your shockcord. [Z-folds saves some space. Spiral wrapping will squeeze a lot of cord into the minimum space, but is easiest with a tool.] Wrap your parachute tight and exactly the same way each time. Use the same protection devices (deployment-bag, or blanket) Blankets save some space, d-bags save the most. With planning you can eliminate most quick-links, if not use soft-links.

You would be amazed at how little space a parachute in a d-bag, and a well organized shockcord really need.

 

[Buckeye]

Buckeye - with all due respect are you sure? I don't have a problem contacting LOC if I have my facts straight. I don't have RockSim (for a couple of reasons), but you may have just opened a can of worms.

So it does make me wonder if the kit should have included a 24" airframe and a 10" payload tube rather than a 20" airframe and a 14" payload tube?

Yes. The RockSim file shows a booster of 24" and a payload tube of 10." You can also use OpenRocket to look at .rkt files.

By visual scaling off of the 12" motor tube, the image in the instruction sheets also indicates a 24" booster tube, and 10" payload tube. I don't think this rocket was designed for DD conversion, so the 10" booster would make sense.

LOC screwed up your kit.

 

[Buckeye]

In the future, don't put the last centering ring on the end of the motor mount tube. I have many rockets where my shock cord is neatly setup between the motor tube and the outer body tube with the last centering ring just above the fins.

Organized and tight is the best bet. Dis-organized, and lose, allows things to move and tangle, leading to inconsistent results.

Practice bundling your shockcord. [Z-folds saves some space. Spiral wrapping will squeeze a lot of cord into the minimum space, but is easiest with a tool.] Wrap your parachute tight and exactly the same way each time. Use the same protection devices (deployment-bag, or blanket) Blankets save some space, d-bags save the most. With planning you can eliminate most quick-links, if not use soft-links.

You would be amazed at how little space a parachute in a d-bag, and a well organized shockcord really need.

These are all good suggestions, but such tricks should not be needed on an entry level kit. The bottom line is that LOC packaged the kit incorrectly, and thus there is not enough room for the included recovery gear.

 

[Tractionengines]

These are all good suggestions, but such tricks should not be needed on an entry level kit. The bottom line is that LOC packaged the kit incorrectly, and thus there is not enough room for the included recovery gear.

But he has a "built" rocket, so options to get it in the air are what he's asking for.

If he calls LOC I am sure they'll work something out with him for another kit to "make it right", but he still has issue that can be addressed to get flying.

 

[teepot]

I don't know what chute LOC uses so I maybe all wet. The Apogee chutes in the size you are looking for are the thinnest I have seen. And a question. Why a 12" mmt? Is it a HPR rocket?

 

[DJRNY]

Gentlemen,
Thank you all for your help and suggestions. Being a relatively new BAR and new to MPR/HPR I appreciate all the help I can get!
To address a few comments, according to the package this rocket flies on F-H motors, so it is an entry level HPR rocket. The chute is a 36" ripstop nylon with a spill hole. It seems relatively thick (compared to Apogee chutes I have) and feels like plastic, but I read somewhere that LOC chutes are polyurethane coated. I don't plan to convert this rocket to DD, but may want to add an altimeter and/or tracking device in the future. Someday.
All the suggestions for chute and shock cord packing are very helpful, and I need to look into them. But it seems the root cause of my problem is likely the wrong airframe tubes included in the kit, making the recovery volume only 55% of the spec'd space. That's a significant difference. I will contact LOC about it.
Meanwhile, my rocket is about 95% complete, so replacing the airframe is not really an option. I am leaning towards cutting off the coupler, sanding the cardboard and epoxy off the bulkhead, and remounting it in the center of the coupler, thus gaining about 3" of additional space which should bring me up to about 90% of the spec'd recovery space. If I screw this up I can always buy a new coupler, bulkhead, and eye bolt. I may or may not get a thinner chute, but with the additional space and proper folding I think I should be OK.
Again, thanks for boosting me a bit higher up the learning curve!
Dave

 

[4regt4]

Yes. The RockSim file shows a booster of 24" and a payload tube of 10." You can also use OpenRocket to look at .rkt files.

By visual scaling off of the 12" motor tube, the image in the instruction sheets also indicates a 24" booster tube, and 10" payload tube. I don't think this rocket was designed for DD conversion, so the 10" booster would make sense.

LOC screwed up your kit.

I've had to buy and add a small payload section to several kits to give more/better laundry room.

As for LOC messing up the kit, this is EXACTLY what has happened to the PML SWR300 I'm currently assembling. The main body tube is 3" short of what it should be, and the payload section is 3" too long. This is verified by both the .rkt file they provide, and by the photo showing the parts. In the photo, the nose cone is shown inserted into the top tube, and it's laying beside the lower tube. The cone/tube and lower tube are close to the same length. But the tubes supplied when dry assembled like this are not even close to the correct length.

My solution: I cut off 6.5" of the lower tube. Bought an extra coupler and joined what was supposed to be the payload tube onto the main body tube. And the cutoff 6.5" section is now the payload bay.

Hans.

 

[techrat]

So you see no problems with having some of the "usable space" inside the coupler?

That's what I do every time. If I don't have a payload bay, I cut off the bottom end of the Nose Cone and install a bulkhead halfway up the nose cone and use the lower half of the nosecone as additional space if I need it. You can CAREFULLY cut out your bulkhead from the bottom of the coupler and then slide and re-glue it about halfway up and gain your needed 3 inches.

It doesn't cost anything to do, it's just time to do it right. If you know how thick your bulkhead is, just saw off an 1/8" that contains that bit of it, and then peel away the layers of cardboard. Losing 1/8" of a 3" exposed coupler isn't going to make that much of a difference.

 

[techrat]

This is probably why you should dry fit all your parts before assembly. For some reason I guess I'm just of of those folks that can eyeball this kind of stuff.

 

[DJRNY]

As for LOC messing up the kit, this is EXACTLY what has happened to the PML SWR300 I'm currently assembling. The main body tube is 3" short of what it should be, and the payload section is 3" too long.

Thanks Hans. It's an eye opener to learn that kits come with the wrong parts. Another lesson learned!

 

[DJRNY]

You can CAREFULLY cut out your bulkhead from the bottom of the coupler and then slide and re-glue it about halfway up and gain your needed 3 inches.

Thanks techrat, this is what I plan on doing. It's good to know others think it is an acceptable solution.

This is probably why you should dry fit all your parts before assembly

I did dry fit everything to check the fit, and I also checked the OAL. However, I didn't dry fit the recovery gear. Another lesson learned.

 

[waltr]

I am in a similar condition with a LOC Hi-Tech 2.6" kit.
The tube lengths are per the specs but..... I am making this a DD rocket.
Kit comes with a 30" booster and a 10" payload. Just build an Ebay into the coupler and good to go, right? Wrong...
The 10" payload minus the nose shoulder and coupler lengths do not allow enough space for the Main chute plus harness. Aggg...

solution:
Cut 8" off the lower tube and splice this to the payload tube with a coupler (did buy an extra coupler).

Since I make most of my rockets with DD I have learned to first check all the space needed for the recovery gear.

 

[jmasterj]

The 10" payload minus the nose shoulder and coupler lengths do not allow enough space for the Main chute plus harness. Aggg...

Couldn't you just cut the end off the nose cone and put a bulkhead in it? That would get you several more inches of space.

 

[waltr]

Couldn't you just cut the end of the nose cone and put a bulkhead in it? That would get you several more inches of space.

Nose cone space is planned for a GPS tracker, so no, this would not help.

 

[jmasterj]

Nose cone space is planned for a GPS tracker, so no, this would not help.

Wait, why? Aren't you going to need some kind of bulkhead anyway, to attach the tracker to?