Hydra (Semroc) 54 MM Upscale Build

[sodmeister]

This is a very enjoyable build ,I like very much ,it`s going to be a great looking upscale !

Nice work on the lathe BTW !

Cheers

paul T

 

[gary7]

This is a very enjoyable build ,I like very much ,it`s going to be a great looking upscale !

Nice work on the lathe BTW !

Cheers

paul T

Thank You!

 

[bradycros]

This is a very enjoyable build ,I like very much ,it`s going to be a great looking upscale !

Nice work on the lathe BTW !

Cheers

paul T

Yes, nice work.

 

[gary7]

Time consuming is all I can say here. I lied about wrapping sand paper around your 4 inch airframe. Will work ok with balsa, but not so much with basswood. It is harder. So I used my oscillationg spindle sander to get it down to almost done. Only have a 3 inch spindle so had to rough fit it several times to avoid taking off too much. Finished the rounding on the sandpaper wrapped airframe then.

After rounding the blocks, I cut the tips to shape on the band saw then did some more rounding and shaping. Doesn't look too bad now. Still some tip shaping to do with some epoxy clay or sanding or probably both. Got all 6 of them cut and rounded to match the 4 inch airframe. This is the only filler block on which I got the tip shaped tonight though.

I have to decide if I want to use epoxy clay to final shape the tips or glue the two pieces together then sand them down. Either way will work, just have to decide which way is less time consuming. Will probably glue them together then sand the tips down. Problem with that, if I do too much, the entire piece will be wasted and I'll have to start a new one from scratch. About 2-3 hours of work. Can you tell I'm thinking about this process even as I write about it?

 

[dpower]

Looking good Gary. I looked at those pod cones for a long time before, but still didn't see the issue. I was also wondering how you'd tie together the strakes, fins, and ring. It's tough to figure out how long to make the fin tabs, since they'll fit deeper if beveled, maybe that's where the sim comes in? This is way bigger stuff than I fly, but it seems like this ring fin structure will be very strong, so I'm curious why the glass is necessary? Just an experience / gut-feel thing?

Hmm, a bandsaw, that sure saves time on a fin beast like this!

Oh, and I vote for rounding all the fin edges, it'll give it a more finished look IMHO, and be a bit more resistant to paint chips. Are you surface mounting the small fins?

I'm curious about all this stuff, as I have a much smaller upscale in the works. I may just have to head down to Thunderstruck to see yours up close!

 

[Woody's Workshop]

Looking very good Gary.
I'm just curious, what spindle sander do you have in the pic above?
Does it oscelate? I need to replace mine combo unit in the wood shop
and have been looking at a few different models.
Thought I'd ask you what your's is and you opinion on it, if you don't mind me asking.

Woody

 

[gary7]

Thanks Paul and Woody.

Yes the smaller ringtail fins will be surface mounted. The ringtail is about 1/8 inch paper, a Menard's concrete tube. This one layer of 1.5 oz wrap will just give it a little more protection. I'll continue to show what I am doing and state my reasons for it if I think about it at the time.

Rocksim takes all the work out of the project as far as calculations are concerned. I just have to do the labor.

You are welcome to see it at Thunderstruck, if I can get it done! And if I don't, then I'll bring my current Hydra to Thunderstruck to fly if I don't crash it this weekend! I may take both to Thunderstruck anyway.

Re the spindle sander? Just a cheap Wilton I picked up about five or so years ago. Got it on sale for about $85 then. And yes, it is an oscillating sander. It has served me well with the little use I've have with it.

 

[gary7]

Take another look at this aft end drawing of the Hydra. Notice all the points of contact of each pod to the central MMT. The pod pairs have been glued with Titebond II. I am also using Titebond II to attach the pairs to the central MMT. For those epoxy users out there, there has been plenty of discussion on this forum regarding the use of epoxy vs. wood glue in high power construction and surely, this will reignite those discussions among some. But I am of the opinion that if a joint is going to fail or a MMT is going to blow thru on a J or K motor with wood glue because the paper comes apart, the centering rings break or due to some other wood/paper failure, I can't see how it will not happen with epoxy as well. Same applies to these pod joints.

To quote some forum users (if they don't mind) :

troj: We built a rocket using Titebond II, and flew it on a Q motor. The rocket's failure wasn't due to the adhesive used...

kenstarr: Everything for a particular purpose. for wood-wood or paper or porous materials, where shear forces are involved, wood glue is great stuff. (And I'm a huge fan of expoxy). I learned early on a sturdy fin epoxied to a paper tube tears off just as nicely as wood glue.

luke strawwalker: I've SEEN wood/white glue strength EASILY surpass that of the materials it's bonding... once your glue joint is stronger than the paper or wood it's bonding, it's pointless to worry about anything stronger...

cjl: If it's a wood to wood, wood to paper, or paper to paper joint, I'd go with wood glue. Epoxy will work fine, but wood glue will weigh less and work just as well.


Having said all that, I am still considering the TTW attachments of the main fins at the pod/MMT joints with epoxy. Haven't decided, yet.

Since winds here today will be gusting to about 25, we'll probably cancel our local launch so I have a lot that will get done today. My "to do" list is long and full, better get with it. Will post results of today's work with pics later.

 

[gary7]

First pic shows my Rockler gluing rubber bands. Very nice to hold this together while the glue dries.

Next is a close up of the fillet. Can't put fillets on the inside of this part of the rocket. A concern? Yes, but I think we'll be ok here the way it is. The most critical glue area I believe will be at the TTW fin attachment. There will be plenty to secure the pods at those points. The front part of these pods also have a glue joint at the pod cones, to the upper main air frame as well so I am not really that concerned.

Next pic shows the central MMT sticking out ~ 1/2 inch, just enough to secure the Aero Pack motor retainer.

Final pic shows glue up of the pod 1/2 cones to the filler blocks.

Decided to do all this glue up first so I can work on glassing the 10 inch ring tail, route the fins and anything else I can get done today.

 

[qquake2k]

Final pic shows glue up of the pod 1/2 cones to the filler blocks.

Decided to do all this glue up first so I can work on glassing the 10 inch ring tail, route the fins and anything else I can get done today.

Hey, where'd you get the cool looking red and black clamps?

 

[gary7]

Hey, where'd you get the cool looking red and black clamps?

I think I got them at Lowes.

 

[qquake2k]

I think I got them at Lowes.

Are they spring clamps or squeeze clamps? I have some Irwin Handi Clamps, and need more, but they're EXPENSIVE! I've been trying to find a less expensive alternative.

 

[gary7]

https://www.lowes.com/ProductDispla...gId=10051&cmRelshp=req&rel=nofollow&cId=PDIO1

 

[o1d_dude]

Yup. Bessey clamps. I have four of them in my traveling tool bag.

 

[gary7]

It's not that I don't like it, just never have actually seen someone do it so have to rely on pics on this forum. With my little experience, it hasn't been lots of fun.

I am giving this ring one wrap of 1.5 oz glass with West Systems. If after both inside and outside aren't as stiff and strong as I want them to be, I'll just wish I had done another layer. Can you wrap glass over existing cured glass if I do want to do that? Maybe I'm trying to talk myself out of it.

Didn't know what to do with the extra hanging off the edge. Tried wrapping it over and sticking it inside but it didn't wand to stay there. So, I'll trim it off when it's dry and spot the edges with some CA.

Here is my 10 inch ringtail on my "ringtial glassing jig". It consists of two, 2 inch foam board circles stuffed inside to help support it and which slide over a left over piece of 1 inch pvc, then clamped in my Triton multistand. These fun tools make all the difference, if you know how to use them.

Boy, I have discovered that it takes longer to post a build thread than it does to actually build the rocket!

 

[gary7]

Got all 18 strakes, fins and more strakes sanded today, down to 320. Took a couple of hours doing it by hand. Tried rounding some edges on left over ply stock on the router but could never get it the way I wanted it so I sanded those by hand as well. Decided on the gently rounded leading and trailing edges but again, it isn't going to make much difference on this beast. It might look a little prettier tho. Hmm, like my other Hydra, I intend to paint this black and silver-gray giving it a military look. "Pretty" fins?

I am using 1010 rail buttons on this thing. Once again, take a look at the aft end Rocksim graphic and see the placement of the buttons on one of the pod cones at the 12:00 position. I have never been confident about the practice of screwing rail button screws into 1/4 inch plywood. I made these rail button anchors or "non-centering-non-ring" circular blocks out of solid red oak. They are nearly 1 inch thick and weight about 36.5 grams. Not alot really for this rocket. I know, some may say all that added weight here and there adds up, but so be it. I'm building this for looks and to get it off the ground then safely recover it. It isn't intended to win a performance contest.

These will give me very solid anchors in which to place the rail button screws. That is unless some one looking here can give me a good engineering reason not to do it this way. It just seems with the way they will have to guide this rocket under the power of a K700, these larger anchors will be more secure inside the pod they are attached to. Maybe I should sand or plane them down, make them a bit smaller or drill out a little of the center? Nah. Not yet.

Got little done today but in a way, still alot too with all the sanding I had to do. Think I'll go glass the inside of the ringtail then call it a day. Monday will complete what I can on the pod cones and get them attached. If time permits, will also cut main fin slots in the ringtail. Hopefully can get the main fins and ringtail on by Tuesday, finish the strake attachments by Wednesday or Thursday and start priming Friday! Hey! I just might get this thing done in time to fly at Thunderstruck!

 

[gary7]

Can't put fillets on the inside of this part of the rocket. A concern? Yes, but I think we'll be ok here the way it is. I am not really that concerned.

Well, sort of.

I have a way to better secure the pods to the main, central MMT. It is something I'll have to work on while paint and glue are drying. Thought someone might take issue with this. For those who did, you'll be relieved. At least, I'll be relieved with the resolution to the inside pod fillets or lack thereof.

I call them "pod reinforcing rods". If you look at this aft end Rocksim graphic, you'll notice I have added something. See those squares? Those actually represent round (or perhaps triangular) dowels that will be glued in place at those three positions which are inbetween the main fins and will run the length of the pods. Triangular rods would offer the most glue contact. Besides that, the round dowel diameter would not be a standard size so turning it would be required. Ripping triangles on the table saw would be easiest to do as well. That will do the job!

 

[gary7]

Got home from work and trimmed then sanded the ringtail. No, it didn't turn out as nice as one would hope leaving me less than completely satisfied. But again, this is a military rocket, not a rocket for the Girl Scouts. Nor is my name "grimracer". For those of you who have not seen Mike Z's rocket work (and here), well see them at Thunderstruck. In a word, beautiful. Besides, I am willing to sacrifice the lack of beauty inside the ringtail to get it done in time to fly at Thunderstruck.

As discussed in the last post this morning, I decided to reinforce the joints between the central MMT and the pods. These triangular rods or dowels were relatively easy to do. After two trial versions that were too small, these fit very well.

I had some stock pine and although would have preferred poplar, thought these will work just fine. I also thought the length as seen will be enough. Final pic shows them dry fit in between the pods and central MMT.

Let's get um glued in then cut main fin slots in the ringtail.

 

[Woody's Workshop]

A little tip to make things go a little faster on build threads.
Take your pics and take notes, really good notes.
Then when it's in primer and your waiting for the primer to dry and in between coats, do your posts.
I have one ready to post, but where I live I can't put any primer on until Spring comes (Hopefully just a couple weeks away now). And if you have to do tape lines you have to wait at least 24 hours to tape, then it requires wet sanding with 600 grit w/d sandpaper. After all said and done, couple nice coats of clear coat. Another light wet sanding with 1000 grit, apply the decals (water slide especially) and about 4 good coats of clear and it buries the decals so they don't peal and gets rid of the decal edges.
You can even re-wet sand with 1000 grit after a few days and add another couple coats of clear for a glass smooth finish over the decals.
Doing custom paint jobs as an auto body tech for years has taught me much in finishing, just applying it here on this here rocket stuff.
Maybe I'm going a bit overboard, but if I'll never be able to afford engines, at least they will look good in the rack for the next generation to launch.

 

[gary7]

First, thanks for the tip Woody. I appreciate your comments. But I feel compelled to continue working then posting the progress the way I have been doing it. It keeps me honest and makes me think things thru even more than I have!

Forgot I had to complete the pod cones so worked on those instead of cutting fin slots.

Remember the tips were somewhat square? Had contemplated how I would correct that. Ended up doing it the same way I did on my first Hydra, took them to the disc sander. I may be getting older but still have steady enough hands to give the half cone tips a nicer look, tapering them then finishing the job with 120 grit. They look ok. Maybe, just maybe, even grimracer would be proud!

 

[gary7]

It isn't really drudgery, it just seems that way. One has to wait so long in between the setting or curing.

I decided (finally) to use epoxy on the main fin attachment. I don't have a laser cutter so had to cut the fins on my bandsaw and the ringtail fin slots with my dremel tool. So there are small areas, lots of small areas, where a crack of light (what kind of metaphor is that?) shines around the fin. Epoxy will fill and seal those areas better. Besides, where the fins meet the ringtial, epoxy is required anyway since the ringtail has been glassed. For now, the only epoxied area is where the fin tab meets the central MMT. When cured, I'll move on to the next one, then the last one. Afterwards I can secure the remainder of the contact points with epoxy.

The first two pics again show my fin alignment jig, now trimmed to actually fit the rocket, in place and holding the fin while allowing time for the epoxy to cure. You can really begin to appreciate the way this might look when it's done.

The last pic shows how I marked the ringtail for the main fin slots. Did it the same way I marked the pod tubes (see post #8) except this time I used blue painters tape. Once you have the tape as long as the circumference is, you can take it off, divide it into three equal lengths by pencil marks, then reapply it. Next just mark your slots and cut them. Of course always check and recheck before making any cuts. Remember the old saying? "Measure twice, cut once".

 

[gary7]

But I almost did!

Took a piece of paper towel, taped it to the end of a stick and smeared Titebond II inside the pod tube that will hold the forward rail button.

I had basically asked for anyone with a reason not to use this block to let me know why I shouldn't. No one did so here it is going in. I dry fit the aft block as well. That will be glued in right after the fins are done.

I put the forward block in now because I didn't want to run into trouble later, after the fins were in place and epoxy inadvertently dripped into that pod thereby making it more difficult to get in. With the drouge bay attached, the block had to go in from behind.

Always mark your work for reference later. The "x" was placed inside the MMT to remind me where the rail button blocks are and of course, onto which pod the rail buttons will be mounted after painting.

Did I forget about drilling a hole into the aft block since the ringtail is now in place? Of course I did. But not to worry, I'll figure out how to fix that. Tomorrow. Any suggestions?

 

[gary7]

Found something to do while the main fin epoxy dries.

The main fins have pods on the tip. They don't do anything but make the rocket look a little more cool and of course, have a tendency to pop off if the rocket hits the ground just right, even when epoxied on.

Anyway, in my mind there were three choices for these. I want them to be 1/2 inch diameter. Loc 1/2 inch launch lugs are about 5/8. BT5 is about 1/2 and this dowel I turned is also about 1/2 inch. Could have saved time buying a dowel but enjoy the work so I turned it. BT5 would just be too soft and flimsy on this rocket. The Loc LL while only 5/8 inch, was aesthetically unappealing to my eye. So I turned them.

See the dowel on my Jet mini. I measure smaller dowels while turning with an open-ended wrench which matches the diameter I want. It's just easier than trying to keep a caliper gauge adjusted.

BTW, I figured out how to drill a hole in my aft rail button block (see my last post). Will show you how when we get there.

 

[gary7]

More detail about the fin pods. For those of you who turn, I'm not very good with a skew so I used this gouge to round over the tip and part the waste from the fin pod.

I then marked the length of the point of attachment of the pod to the main fin. Next, sanded those areas flat and just wide enough to have complete edge and therefore better contact with the fin. Look closely at the 3rd pic, you can see that flattened area.

For now, they are tacked on with Titebond II. When dry, I'll finish up these joints with epoxy, both rough securing and the creation of a small fillet.

This rocket will have a military silver/gray airframe and pod color, the fins and ringtail will be dark gray, all the half pod cones and main cone will be black. These pods however will provide the only other color contrast on the rocket, RED!

Back to work.

 

[Grimracer]

Well. well...

Ambitious and very well done Gary.

I would be honored to return the favor (Red Hot Chilly Pepper) and help you at the pad the day you put this bad boy up!

Very very nice! Can not wait to see it fly!

Grimracer

 

[gary7]

First of all, thanks to my good friend Mike Z.

The main fins are on as are the main fin pods. Could not resist putting on all the other stuff, the strakes and pod cones, although they are all only dry fit in this picture.

Total height now of the booster/drogue bay as you see it is about 46 inches, span diameter about 23 inches. Also still have to attach the small ringtail fins, 9 of them. I believe the original Hydras have 12, four each between the main fins. I like the symmetry of only nine, each matching the strakes in between the pods. Besides that, there are three fewer to attach!

Please pardon the messy dining room. Not asking you forum junkies for the pardon, I'm asking my wife.

 

[dixontj93060]

Please pardon the messy dining room. Not asking you forum junkies for the pardon, I'm asking my wife.

My wife would have already kicked me out of the house if I even thought about using the dining room table to build rockets!!!

 

[gary7]

My wife would have already kicked me out of the house if I even thought about using the dining room table to build rockets!!!

Yea, but I built the table too so she will not say too much about that. It's just the mess in general. Or was that what you were thinking about?

 

[dixontj93060]

Yea, but I built the table too so she will not say too much about that. It's just the mess in general. Or was that what you were thinking about?

Not the mess. It's just in our house "everything has its place" (wife's rule, not really mine) and rockets and dining room just don't mix.

 

[Woody's Workshop]

Not the mess. It's just in our house "everything has its place" (wife's rule, not really mine) and rockets and dining room just don't mix.

I will agree 100%.
Leave something laying around, and it dissapears.
And nobody seams to what happened to it.
That's why I have a little corner of the basement with MY computer, and a place to build rockets and the like.
Then I have the Wood Shop.
And for the gardening stuff, tractors and man stuffs I have a pole barn.

She's happy, don't complain, and stuff of mine don't mysteriously dissapear. :bangpan: