PML 1/4 Patriot Build Thread

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ArthurSull

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This will be my first HPR build. Hopefully it will help steer other newcomers in the right direction, as well as highlighting things that I could do differently in the future.

Seems like a good quality kit, Quantum tube is tough and easy to manage. Just needs loads of prep work for epoxy, but that's for later.

I am building this with the piston, but am converting the coupler into an ebay for experimenting with electronics after I certify.
Also adding a closed eyebolt to forward CR for attaching piston strap. I prefer that method to the gluing to MMT method, plus I can remove with quicklink if I want to ditch the piston. Piston strap will be protected with Nomex.

Using a bigger eyebolt for shock cord to ebay/NC attachment as the one that came with the kit was a little flimsy I thought. Will also be using a quicklink and swivel for chute.

Using an Aeropack motor retainer.
 
I decided to the the converting of the coupler to an ebay first.

Adding a stiffy tube inside the coupler, I then measured and drilled the holes for the rods and eyebolts. The forward end of the ebay doesn't come up as far in the coupler as normal, as the rivets are not long enough to fit through the payload bay wall, coupler then stiffy tube.

I wanted the payload bay and nosecone to be removable for easy access to the ebay and for the ability to try dual deploy in the future if I want.

I decided to use plastic rivets for the job, and used graph paper to measure equally around the body.

Also pictured is a 1/8 pressure relief hole in the payload bay. Not totally necessary with the low flight and rivets, but good practice.

IMG_20130725_134924.jpgIMG_20130725_135227.jpgIMG_20130725_142611.jpgIMG_20130728_122936.jpgIMG_20130728_171528.jpgIMG_20130728_171539.jpg
 
Next I assembled the piston.

Did this in the opposite way to how PML state in the instructions, as some articles I have read and some advice on here have suggested (with evidence) that piston ejection systems work better with bulkhead on the aft end as opposed to the forward end of the piston tube.

This makes sense to me, as this is how pistons are in most machinery, plus the ejection charge hits an equal area.

https://www.deltavrocketry.com/piston.htm

Here is also the MMT, with tape used to get the CR level, and with the eyebolt now attached to which the piston strap will be connected via a clibing grade quicklink.

Note how the eyebolt runs perpendicular to the MMT, this is for easy connection to quicklink when assembled in BT. It gives much more room for hands to get in there and play around with the MMT or BT getting in the way.

IMG_20130730_142535.jpgIMG_20130730_142607.jpg
 
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After a dry-fit at the weekend, it became obvious I did not counter in the extra length of MMT tube needed to accommodate the Aeropack retainer whilst still having the bottom CR flush with the BT.

The best I can get it is as pictured, and whilst does not affect the performance of the too much, it does affect the look of the thing :(

An alternative is to have the retainer not fully fitted over the MMT. It would still be bonded well with JB weld, and this way I could get the bottom CR flush with the bottom of the rocket. Not sure what is best?

IMG_20130730_160558.jpg
 
I think the obvious answer is to just go with the aft CR not being flush. At least I can put some strong fillets on there anyway now - or another CR with the hole in the middle big enough to fit over the retainer to make it look nice if I can be bothered to go that far.

Next up is to glue the MMT with forward CR into the BT, and then start on the fins. I will wash the inside of the BT with warm soapy water, and then use a rough sandpaper to get it nice and scratched up ready for the epoxy.
 
MMT is now fitted, obviously with aft CR left out to allow access to glue the fins.

Tape was used on the aft CR to position the MMT properly, and then pulled out using the tabs of tape after glue had set on the forward CR.

IMG_20130730_200006.jpgIMG_20130730_200012.jpgIMG_20130730_221029.jpg
 
Brings back memories for me. It was my first HPR kit as well. Flew like a champ until I lost it.
 
Compared to other photos I am seeing, I sometimes think I am not using enough epoxy for the CRs. I've seen some images where the fillets on the CRs are REALLY coated. Might stick a dowel down there and beef it up a bit.

Saying that, there is epoxy in all the gaps and there are fillets (all be it small ones) so surely any more epoxy would just be extra baggage.
 
I think your epoxy fillets look fine. This is about how mine turn out, and this one has flown on J's. Don't forget, that the fin tabs epoxied to the motor tube will add strength, too.

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IMG_20130803_214130.jpg

So the Patriot is coming along fairly well. Mostly assembled now apart from adding shock cord and chute to piston. The whole thing is heavy!

Little annoyed that the aft CR sits in from the end but I'll just fillet it well. Measure, measure, measure in future!


IMG_20130804_171843.jpg
 
If the aft centering ring was flush and you only had a fillet on the inside you'd lose a significant amount of its strength. As qquake2k pointed out though, most of your thrust gets transferred through the fin fillets on the motor tube.
 
Oh, err, I meant it all along!

But you know, now that I think about it, the only reason I can see to inset them is so you can put fillets around the inside of the body tube, and outside of the motor tube. They both add significant strength, IMHO.
 
Started on recovery this evening.

AS you can see I have a nomex sleeve for the piston strap. I thought about glueing it in place but I'm not sure it needs glueing at all, probbaly best to leave it do what it wants as not to limit the strap or damage with glue (thinking it could make the strap more brittle?)

Used the knot that's advised by PML, not sure what it's called. Was going to use a bowline but thought I'd see how this one looked. Not glued them yet as I'll see what feedback is on knots.

IMG_20130806_204252.jpg IMG_20130806_204230.jpg
 
I don't glue my knots. Have you glued yours in the past?
 
Yeah PML have suggested to glue them. I've not glued mine yet as waiting for advise here, but I would imagine it's going to make them brittle, and more difficult to remove if you need a replacement strap?
 
Yeah PML have suggested to glue them. I've not glued mine yet as waiting for advise here, but I would imagine it's going to make them brittle, and more difficult to remove if you need a replacement strap?

Nylon doesn't suffer as much from gluing, but there's no need to, really.
 
Yeah PML have suggested to glue them. I've not glued mine yet as waiting for advise here, but I would imagine it's going to make them brittle, and more difficult to remove if you need a replacement strap?

That's my thinking as well. I just don't think it's necessary.
 
Used the knot that's advised by PML, not sure what it's called. Was going to use a bowline but thought I'd see how this one looked.
It's a Clinch or Cinch Knot. It's often used to tie fishing line to a hook. I would recommend the "Improved Clinch Knot" just so the tail end is out of the way of the d-ring. Bowline is a good one too. A Surgeon's Loop is great if you're using quick links.

There's your Boy Scout lesson of the day.
 
It's a Clinch or Cinch Knot. It's often used to tie fishing line to a hook. I would recommend the "Improved Clinch Knot" just so the tail end is out of the way of the d-ring. Bowline is a good one too. A Surgeon's Loop is great if you're using quick links.

There's your Boy Scout lesson of the day.

Ah yes of course! The larger scale made me look at the knot in a different way. I'll look into the improved clinch knot too, later. And the bowline for the quick link.
 
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I need some advice.

For the piston strap to CR eyebolt I've used a climbing grade quick link (makes sense as it'll be highly load bearing) and I'm going to use another one for shock cord to bulkhead attachment. (is that overkill? should I just tie it to bulkhead eyebolt?)

Anyway, I'm going to use the loop in the shock cord > quick link > swivel method for the chute, but the swivel I have from Apogee doesn't fit on the quick links. I have a smaller size quick link I could use but it's a cheap one from a DIY store. But I figure it won't particularly take a lot of load as the load will be on CR eyebolt quick link and upper section quicklink at deployment, so this quicklink for the chute doesn't have to be climbing grade too?

What do you think?
 
I only have one PML kit I built and my opinion they are great rockets. I hope to get others.
Jeff
 
I need some advice.

For the piston strap to CR eyebolt I've used a climbing grade quick link (makes sense as it'll be highly load bearing) and I'm going to use another one for shock cord to bulkhead attachment. (is that overkill? should I just tie it to bulkhead eyebolt?)

Anyway, I'm going to use the loop in the shock cord > quick link > swivel method for the chute, but the swivel I have from Apogee doesn't fit on the quick links. I have a smaller size quick link I could use but it's a cheap one from a DIY store. But I figure it won't particularly take a lot of load as the load will be on CR eyebolt quick link and upper section quicklink at deployment, so this quicklink for the chute doesn't have to be climbing grade too?

What do you think?

I only use quicklinks where necessary: if I will be untying a knot to put it in storage, a quicklink would be better there. Otherwise, I just use knots.
 
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