5.5" Cherokee-D L3 build thread for rharshberger

[rharshberger]

US Composites has 5.7 oz / 3K CF @ 1yd x 42 plain weave for $16.50. I picked up a couple lengths of this and I like working with it. It works great on fins.
It is under the Discounted Carbon Fabrics section sixth item down.

Good catch, my initial uses for the CF will be painted anyways so the appearance of the weave is not as important. US Composites is one of my favorite vendors and I love working with the 635 Med Epoxy Resin/Hardeners

 

[rharshberger]

This evening's work was a pretty quick one, laminating the coupler stiffener with 2 wraps of 6oz FG (Bondo 499, from Home Depot) it should be just enough under the ID of the Loc 5.38 couplers for them to slide over the stiffener (a little sanding may be necessary). The ends of the stiffener will also be the shoulders for the Av-Bay bulkheads to seal against. The stiffener is a section of 5" mailing tube from OfficeMax. I tried a new to me technique of tacking the edge of the FG cloth to the tube with a light spray of 3M 77 spray adhesive, then using a bondo spreader to apply the epoxy so far it looks really good, in about 3 hours or so I will check to see if its set enough to trim the excess from the ends. The mailing tube OD is normally .0625" by my measure smaller than the Loc 5.38 couplers ID so with the two wraps of FG it should hopefully be a sliding fit still. The whole thing is really a bit beefy but I am not super concerned about the weight, glassing added about 5ozs to the (70g FG and 80g epoxy) to a tube that already weighed about 11ozs, I am estimating that after trimming the stiffener should be about 16ozs or so. The line on the tube is simply a reference so I know when it has made a complete revolution, the wraps start and finish points are almost perfectly on top each other.

 

[rharshberger]

Parts for the Av-Bay cut and ready to assemble (except the bulkheads). Switch/Static port band, couplers, stiffener, and doublers for stiffener shoulder that bulkhead snugs against to seal. Tomorrow maybe I will assemble the Av-Bay section. Still need to cut the access hatch on the switch band. Nice thing about Loc 5.38 airframe is my big hands have lots of room to get inside and work on things. The two wraps of 6oz fiberglass worked perfectly with the mailing tube, the couplers slide over it with just a bit of drag, which should be about right for a thin layer of epoxy. Due to the nice fit I can put the switch band on after joining the couplers which will make cutting the hatch nice and easy. The second picture from the left shows the relationship of the parts, and the fourth from the left is with a coupler left off for a different view.

 

[rharshberger]

Fin template is ready, will cut the fins later today. Yesterday I ordered vac bagging stuff from ACP sales, End Grain Balsa sheet from Fiberglass Supply, and Carbon Fiber fabric from Soller Composites.

As the fins are only ~9" span I didn't feel that a spoke to the center of the leading edge was necessary. The spokes and edges are 1" and the corners are 5/16" radius (I have a 5/8" sanding drum). The root edge has a 1.5" solid section, fins are roughly 16.25"x9".

The triangular cutouts will be filled with end grain balsa sheet and then everything sanded smooth and then 2 plys of 5.9oz CF twill applied to each side of the fin. It will be a shame to cover up the beauty of carbon fiber, but the fins will be painted white.

 

[RocketFeller]

Fin template is ready, will cut the fins later today. Yesterday I ordered vac bagging stuff from ACP sales, End Grain Balsa sheet from Fiberglass Supply, and Carbon Fiber fabric from Soller Composites.

As the fins are only ~9" span I didn't feel that a spoke to the center of the leading edge was necessary. The spokes and edges are 1" and the corners are 5/16" radius (I have a 5/8" sanding drum). The root edge has a 1.5" solid section, fins are roughly 16.25"x9".

The triangular cutouts will be filled with end grain balsa sheet and then everything sanded smooth and then 2 plys of 5.9oz CF twill applied to each side of the fin. It will be a shame to cover up the beauty of carbon fiber, but the fins will be painted white.


View attachment 283510

That looks great! The cutouts will be filled with balsa, are the spokes going to be birch ply? What is the thickness?

 

[rharshberger]

That looks great! The cutouts will be filled with balsa, are the spokes going to be birch ply? What is the thickness?

Yes its 1/4" aka 6mm Baltic Birch ply (not the 12 ply stuff, but still good Baltic Birch). The main reason for doing the fins this way is to play with some new techniques, losing a bit of weight is a bonus, and the fins will also be a bit stiffer this way. So far the rocket sims out just short of mach and the original un-modified fins were strong enough, but I like working with composites so chose to do it this way.

 

[Onebadhawk]

Holey smokes man,,
Geez,, how did I mange to miss this thread..
Rich,,
You do some incredible meticulous work man..
This thing is coming out absolutely gorgeous...
I saved the site that makes wood gear templates,,
way too cool,, I loved the rotisserie too...lol...
I'd sure love to see this beast fly,,,
When ?? Where ?? Airfest ??

On the money Rich,,
Beautiful work man...

Teddy

 

[rharshberger]

Holey smokes man,,
Geez,, how did I mange to miss this thread..
Rich,,
You do some incredible meticulous work man..
This thing is coming out absolutely gorgeous...
I saved the site that makes wood gear templates,,
way too cool,, I loved the rotisserie too...lol...
I'd sure love to see this beast fly,,,
When ?? Where ?? Airfest ??

On the money Rich,,
Beautiful work man...

Teddy

I wish Airfest was close enough, but the plan is to fly Memorial Day weekend at Fire in the Sky the annual big launch for the Washington Aerospace Club.

 

[kcobbva]

You really do make everything look so easy Rich. Always enjoy following your threads and learning from your techniques. Too bad you aren't at Ft. Belvoir still; would love to learn those techniques in Person; alas TRF is a great second method! Thanks for all you continue to share.

 

[rharshberger]

You really do make everything look so easy Rich. Always enjoy following your threads and learning from your techniques. Too bad you aren't at Ft. Belvoir still; would love to learn those techniques in Person; alas TRF is a great second method! Thanks for all you continue to share.

There are days I wish I was still at Ft. Belvoir, I have some good memories of my time there. Back then our favorite hangout was Bennigan's at Springfield Mall, of course if I was still at Belvoir I would have 23 years in the Army, instead of 5.

On to today's update:

The Av-Bay section in the left-most photo was actually done about a week ago (maybe even two weeks). The bulkplates for the Av-Bay have been routed to create a step to help seal the Av-Bay, the shoulder they sit on has been doubled to provide a wider sealing surface and a "rope" of poster tack will be used to make an airtight seal. Why poster tack?, its cheap and easy to replace and doesn't form a real strong bond, I may use a 5" Oring too, both methods are still options at this point. Third photo from left is just a shot of the bulkplate in place.

Center photo, the fins are roughed out on a section of 6mm Baltic Birch plywood, the fourth from left photo is after the initial shaping of the exterior and the interior cut-outs are layed out. I used a 5/8" Forstner bit to punch the corner radii (plural for radius iirc). I then used a jigsaw to cut the inner sections out leaving about 1/8" waste off the lines. The semi-final shaping of the cut-outs was done on the drill press using two different sized sanding drums a 1.5" and a 5/8" to just kiss up to the line, then a Great Planes aluminum sanding tee/block with 120 grit to take out the line. The last photo is the Av-Bay with the vent band dry-fitted, during the next week or so I hope to find time to finish the Av-Bay now that I have all the hardware on hand. The Av-Bay is 15" long and 5" ID, its huge, total length of the unit in the last picture is 22".

Edit: added an additional photo to the lineup (the sixth photo from left).

 

[pyrobob]

Very nice work once again Rich!

 

[K'Tesh]

Love the fin cut outs Rich! Nice work!

 

[kcobbva]

That's awesome work with a jigsaw! Did you use a guide or freehand? VERY straight lines from the pictures.

 

[rharshberger]

Thanks guys, the balsa sheet should be in today or tomorrow, and Soller composites is shipping the CF today.

 

[Onebadhawk]

Geez,,
You sure do some meticulous work Rich,,
Those fins look like they were cut out on a CnC machine,, lol..
Absolutely beautiful man...

Teddy

 

[rharshberger]

The end grain balsa panel arrived today, and was immediately put to use. The stuff cuts easily with a sharp xacto knife (red one in picture). The fin is simply laid on top the balsa sheet, a pencil used to scribe a line around the edges of the triangular cutouts, pattern taken off, then a straight edge and knife to cut the balsa to near exact size. The triangles are then moved over to the belt sander for some very quick (VERY QUICK) removal of excess right up to the pencil line. The balsa can be slightly compressed so if its a hair oversized it still fits. To protect the top of my table saw (its the second flatest object in the shop) I put a bit of plastic wrap under the fin and glued the panels into place. The back of the panels have a mesh scrim binding the pieces together. I covered the glued fin and panels with some more plastic wrap and placed the flattest object in the shop on top of them, a small granite surface plate (its also one of the heaviest non-machinery items in the shop). I will wait until tomorrow and get a weight on the pre-laminated fin, prior to adding the panels the skeletonized fins weighed 6.1oz each (172grams approx). The assembled fins should require a light sanding to flush the panels with the fin, as the balsa stands just about a 1/32" proud.

 

[Onebadhawk]

Holey smokes Rich,,
Georgous work ,,,

Rich,,
Why do you say the granite slab is flatter then the table saw top ??
What make table saw ??

Teddy

 

[rharshberger]

Holey smokes Rich,,
Georgous work ,,,

Rich,,
Why do you say the granite slab is flatter then the table saw top ??
What make table saw ??

Teddy

The table saw is a Grizzly 1023RL 5hp, the table on it is very flat, the granite slab is actually a granite surface plate and according to Grizzly is held to plus or minus .0001", I don't think the saws table is that precise.
Edit: Its actually the bottom of the plate that is seen in the picture above.

 

[Nick@JET]

Beautiful workmanship! Are you doing this to just remove weight?

 

[rharshberger]

Beautiful workmanship! Are you doing this to just remove weight?

Nope, for fun! The weight savings might be 25%. I forgot to weigh the fin before skeletonizing so I will have to go with the original OR weight for a solid fin which was about 13 or 14oz each.

 

[rharshberger]

The OneBadHawk harnesses arrived today for this beast. A 25' 7/16" tubular kevlar 2 loop harness and a custom Teddy Special, a 30' three loop also 7/16" TK, but with a 24" Y-harness sewn into the booster end for attachment to the zipperless booster. I did z-fold the 3 loop in my standard method that I use to reduce the chance of tangling, and slow the extension of the harness a little.

 

[kcobbva]

Looks really sharp Rich.

 

[Onebadhawk]

Rich thank you so much man,,
That really is a great pic of a properly done Z fold...
I've never seen a pic that makes it so clear..
Both ends on each bundle must come out from the tape on the same side..

Rich, If I get the chance later do you mind if I hijack that pic for my site..

Teddy

 

[rharshberger]

Rich thank you so much man,,
That really is a great pic of a properly done Z fold...
I've never seen a pic that makes it so clear..
Both ends on each bundle must come out from the tape on the same side..

Rich, If I get the chance later do you mind if I hijack that pic for my site..

Teddy

Go ahead Teddy, I have no problem with you using the photo.

 

[rharshberger]

Ok, all three fins now have their end-grain balsa panels, the Carbon Fiber from Soller Composites arrives tomorrow. After tomorrows club pre-launch planning meeting, I hope to be able to cut the skins and get them ready for vac bagging the fins on Tuesday. In the process of cutting the panels, I found the easiest way was to cut them with an Xacto knife and dress to final size with a Great Planes Easy Sander (I have both the 5.5" and 11" versions) with 120 grit sandpaper. After inserting the panels they were a little proud (a little thicker than the plywood), so using the 11" sanding bar again with 120 grit the panels were sanded flush with the ply skeleton. The panels were cut very slightly oversize for the most part and lightly pressed into place (a very light compression fit), the small gaps seen are less than 1/16". One panel I did glue them in first, but on the other two I did not and will allow the epoxy to do the job instead. My goal is to start the assembly of the fin can/booster section by Friday, as we have a club launch Saturday.

 

[rharshberger]

Busy day in the shop today. I had most of a day off due to no sitter for the kids (for part of the day) and being the only one with paid time off in the family, these kind of days fall to me. But it had a bright side.

First up was cutting the motor tube. My technique is to score the tube with my 10" compound miter saw with a 60 tooth blade (its what I have, otherwise I would use a higher tooth count), the saw has a sacrificial fence that is tall enough to support the tube, and a stop block is placed at the short end of the tube so that as I rotate the tube the cut stays straight. Once I have scored most of the way through the tube I finish the cut with an Xacto knife. The raw cut is seen in the second picture, before sanding clean.

Then its on to peeling the glassine, normally I start at the tip where a spiral ends. However as can be seen in the 4th and 5th pictures getting it to start peeling took a bit, in the 6th picture the glassine started peeling smoothly only occasionally tearing. The last photo is of the peeled tube ready for the centering rings.

 

[rharshberger]

March 9th...the continuation (my 14month old daughter required my full attention, and then use of me as a mattress for a 30min nap).

Next up was the parts for the fin can anchor points and their reinforcement. The aluminum is an unknown grade of .125" material (I've had it so long I can't remember what it is). The centering ring is 12mm Baltic Birch ply (cabinet grade not aircraft ply), there is a 6mm Baltic Birch ply reinforcement glued to the CR and an aluminum spreader plate contoured to match the radius of the CR. The 1" Belt/8" Disc combo sander is probably my most used tool for CR's and Bulkheads (I also have a 4" Belt/6" Disc combo right next to it). The aluminum parts were cut out using a jigsaw and shaped on the belt sander, except for the inside radius which was done with a drum sander in a drill press. As will be seen in the next post the zipper less anchor points are going to be tight to the wall and will be angled a bit to allow attachment of the quick links ( I probably will switch the 5/16" forged eyebolts for 1/4" ones as the 5/16" aren't really necessary).

 

[rharshberger]

And some more....

Dry fitted parts of the zipperless fin can, the second picture shows just how tight the spacing is, hence the reason for the change to 1/4" eyebolts as soon as I get down to Tacoma Screw again on Friday.

I tend not to use a stainless steel on rockets that won't be flown a lot, the eye-nuts are galvanized and overkill for this project as is the B7 grade all-thread with matching nylock nuts. They eye-nuts will be
point of failure if anything.

The last three pictures are kind of self explanatory, the Carbon Fiber arrived Monday so today I cut the panels for the fins, thinking tomorrow about cutting some half fin pieces and quarter fin pieces to add additional thickness between the root and half span/quarter span points. The blue tape was stuck to my shirt prior to placing on the CF, just visible in the last photo is the Fiskars Rotary Cutter used to cut the CF and my wife's cutting mat.

 

[rharshberger]

Wiring schematic for the av-bay. I am so happy NAR changed the requirements for switching.

 

[kjkcolorado]

Wiring schematic for the av-bay. I am so happy NAR changed the requirements for switching.

View attachment 284547

Just curious. Why a LiPo for the Quark, but a 9V for the RRC3?