Hydra Sanhawk?

Ed Brown posted this picture on the Facebook Model Rocketry Fanatics page:


So . . .
Is it a HYDRA SANDHAWK or,
HYDRA SANHAWK?

To see the entire build from Finish to Start: CLICK HERE


Here's another face card misspelling:
The Fliskits MECURY REDSTONE

I'm not making fun of these mistakes. I worked in a print shop for years! These things happen. At a glance, it reads correctly. Your mind can fill in a missing letter.
If you've printed up one thousand full color face cards on heavy gloss stock, it'd be a shame to throw them away over a spelling error.

Rocketarium Hydra Sandhawk Finished

I was happy with the build and look of the finished Hydra Sandhawk.
This BT-60 based model is tall and impressive.
The nose cone mask was a challenge but turned out well.

The staging on this one is different with a 24mm D in the booster and a 18mm engine in the sustainer.
The small booster fins require almost one ounce of clay in the nose cone for stability.

I didn't care for the supplied peel and stick decals. When set in place the gray boltheads were almost translucent. These decals weren't difficult to draw up and print at home.
This kit did have some masking and paint challenges, as most scale models do.
Down the road I'd like to try a build of the Rocketarium Jayhawk.

Rocketarium Hydra Sandhawk Build Part 23, Decals

I glued the card stock pieces on after painting so they aren't sealed.
I applied two coats of Future acylic with a Q-tip.

The bolt decals I made are water slide and I didn't want the card stock to swell up.

I cut the booster decals width short on one side. The width of the clear backing was cut this way on all the decals.
This gave me a spacing reference when the clear coat was set right next to the attachment piece.

I knew the booster decals weren't applied on top of the fin attachment pieces, but to the side.
I started setting them down on the wrong side! I didn't realize they went near the root edge of the fin and not on the body tube.

Here's how they should have been applied - 
Enlarge the picture and look for the bolt heads on the gold fin root edge.

Rocketarium Hydra Sandhawk Build Part 22, Booster Fin Attachment Pieces

Here's the mask for the booster fins.
They are sprayed gold.

The fin attachment plates on the booster are narrower than on the sustainer.

Scrape away the paint and glue in place with white glue.

A band of aluminum trim Monokote was applied to the top and rear.

At the rear do a rough trim with a sharp blade and any remaining can be sanded off even with the end of the tube.

Here's how the model looks before the decals are applied.

The booster fin attachment plates will be brush painted gold.

Rocketarium Hydra Sandhawk Build Part 21, Fin Attachment Pieces

The instructions give you two choices to make a double layer of card stock for the fin mounting attachments.
I simply glued the back and folded over the card. I dried flat in a book.
You could cut out sixteen pieces then glue and stack them. Folding, gluing and cutting seemed easier.

I set the double thickness card stock piece next to the root edge to mark the gold area for paint removal.
A smaller area than the attachment piece was scraped away down to the body tube.

Each fin attachment piece was pressed against the Sharpie barrel to put a slight curve in it.
This will better fit the curvature off the body tube.

The fin attachment pieces were attached with white glue.
There is no paint on the upper stage fin attachment pieces, they are white on the finished model. I might "seal" the faces of the pieces with some white glue applied with a Q-tip.

Gluing the attachment pieces on after the gold paint is applied gives a sharp color separation, better than you might get by complex masking.

Rocketarium Hydra Sandhawk Build Part 19, Gold Mask and Paint

The fin mounting attachments would normally be glued on before painting. It would be very hard to mask around the attachments.

I'll simply glue them on after the gold is sprayed.

Here's the mask for the gold.

I'm using a Q-tip again to soft burnish the Scotch tape masks along the root edges.

The tan plastic wrap are cut up grocery bags.





The first try was an old can of gold Krylon.
I had bad masks on half of the taped edges. It didn't release at the tape edge like the Rustoleum 2X I was used to. The paint seemed to rip and pull as the tape was pulled up.

I had to sand off the ridge and respray with a new can of Rustoleum 2X gold. This second try gave me a much better clean line.

Rocketarium Hydra Sandhawk Build Part 18, Nose Cone Mask

This is the nose cone mask for the lower flames.
While the face card art shows red above and dark red below, the online picture shows orange and brown below. I went with the online picture.

The Scotch tape segments are in place around the nose cone.
The masking tape strip on the left was a guideline so the base of the flames would be somewhat straight.

At the base of the nose cone is a darker brown, a mistake on my part. the paper wrapped around the BT-60 tube holder slid up over the nose cone base before the orange was sprayed. It should be covered with the brown primer coat.

This brown primer color was from an old can of $1.00 Walmart paint.

Here the Scotch tape mask is being removed. The lines came out very clean.

Before the paint totally cures some of the rough edges were pushed back into the brown side with the flat side of a knife.

There was a paint ridge on the brown side.
Instead of sanding it off and risking removing the paint, the ridge was  pressed down with the back barrel of a Sharpie pen.
I didn't rub back and forth, I simply rolled the smooth pen barrel over the ridge flattening it out slightly.

Rocketarium Hydra Sandhawk Build Part 17, Nose Cone Mask

Here's the only picture I could find online showing the hand painted flames on the nose cone.

That picture was rotated and blown up to the BT-60 diameter of 1.637" wide.

The "flames" were traced and copied into an approximation of the area width, shown at the top.
Going around the nose cone, it looked like there were eight "high flames" and eight "low flames".

This is all a guess, the original flames were hand painted so I'm just going for close.

The flame pattern was printed out.
The print was taped to the outside of my patio door to make a poor man's light table.
The door was shut and clear tape layed over the print on the inside of the glass.
Everything was cut out with a #11 blade.
The strip was cut into sections at the top of the flames.

Rocketarium Hydra Sandhawk Build Part 16, Fin Gluing

Here's the booster section ready for the gray primer filler spray.
The fin lines are masked and a piece of tape covers the vent holes from the inside.

The same was done on the upper body.
The fins are glued 3/32" from the rear of the body tube. A wrap of tape (blackened with a Sharpie) was rolled around the rear for a reference.

After the first fin was glued on, a paper wrap gave me the height for the leading edge tips.

Paper wraps were also used on the booster for height reference.

Here's how the booster was masked to keep the engine mount clean.
Masking tape pieces were stuck sticky side in around the end of the booster tube.
An engine casing on a dowel was inserted into the mount.
Paper towel pieces were stuffed in the recessed.
White undercoats followed.

Rocketarium Hydra Sandhawk Build Part 15, Payload Bay

There is a longer rectangle left on the fin mounting sheet. This is used to fill the gap on the split tube of the payload.
A two piece laminate wasn't quite thick enough to be even with the to surface. I ended up using a three piece stack and would sand it down to surface.

The three layers of 110 lb. card stock were glued in place using white glue.
The strips were glued long and trimmed off even with the end of the payload section.
To stiffen it up, a layer of CA was applied with a Q-tip. This makes the surface hard and easier to sand without any raised paper fibers after sanding.




After drying the filler strip was sanded with 400 grit on a block.

CWF filler followed with a final sand.

After a spray of primer filler, the patch is almost gone.
A smooth sanding and one more coat of primer should fill it in.

Rocketarium Hydra Sandhawk Build Part 14, Payload Bay

Jumping ahead to Step 10:
The raised surface of the payload bay is made by gluing a piece of body tube over the top of the sustainer body.
The short length of BT-60 is split and wrapped.
Mark a straight line with an aluminum angle.

Cut and split the tube using the aluminum angle as a guide line.

The cut was opened and the edges sanded clean over the edge of my sanding block.

Apply glue over the top of the sustainer tube and wrap the split tube over it. Quickly wipe away any glue in the open split area.

The tube was wrapped with rubber bands to apply pressure while the glue dried.
Before setting aside to dry be sure the tube ends are even. The glue is slippery and the split tube could move.

Rocketarium Hydra Sandhawk Build Part 13, Vent Hole Drilling

The inside edges will be rough. You'll need to toughen these up to sand off the edges.

A Q-tip was dipped in some medium CA glue and swabbed around the inside of the drilled hole.

Some 400 grit was wrapped around another Q-tip in a cone shape.

Turn the sandpaper in the hole to smooth and "round" it out.

Rocketarium Hydra Sandhawk Build Part 12, Vent Hole Drilling TIP

1/4" diameter vent holes are drilled in the booster side walls.
The instructions say to drill a 1/8" hole first then enlarge it to 1/4".

TIP: You can make a "drill" out of a 1/4" diameter brass tube.
The inside wall of the tube was filed to a sharp edge using a half round file.

This sharp edge works pretty well to cut a 1/4" hole through the tube wall.

Take an extra moment to center the tube before starting to drill.
Spin the tube until you start to scratch the outside layer. Remove it and check to be sure it is centered. If the circle is positioned correctly, continue the drill.
The tube will want to collapse in so go slowly. It's easier to drill a hole when you can apply some finger pressure on the inside tube wall. You can't reach the inside of the BT-60.
After drilling through the outside continue through the interior BT-50 engine tube wall.

Here's how the tube will look after drilling through both sides of both tubes.
We'll clean up and strengthen the edges in the next post.

Rocketarium Hydra Sandhawk Build Part 11, Booster Mount

I used a dowel to set the glue inside the body tube for the engine mounts.

A line of glue was to be set 2 1/2" from the end. That is the position of the forward ring when the mount is slid in place.

The inset picture shows how I set the glue line just before the forward ring. The dowel was marked just inside of the 2 1/2" mark. This way I know the ring will go through the ring of glue.

For now, glue was only applied for the upper ring.

The mount was slid into position, I used the flat side of my sanding block to be sure the tube ends were even.

The inset picture shows the front end of the booster. The tube ends are even on both sides.

The rear ring got a fillet of glue applied drop by drop on the end of a rounded dowel.
Set a drop in the seam and smooth it out using the rounded dowel end.

Apply more glue drops until the fillet is all the way around the ring joint.

Clean up any excess glue using a Q-Tip.

Rocketarium Hydra Sandhawk Build Part 10, Booster Fin Replacement

Look at the booster fins on this picture shown earlier on the blog.
Those booster fins are very thin.

The fin stock in the kit is 1/8" thick.
That works great for the upper stage  fin taper, but the booster fins would look clumsy.

I wanted to cut new fins from 1/16" thick ply but didn't have any at hand.
I did have some very dense 1/16" thick balsa.

Here's one of the new thinner fins on the right.
It looks larger than the thicker original, but it is the same size.

Rocketarium Hydra Sandhawk Build Part 9, Sustainer Fin Shaping

From this picture found online you can see the fins wedge shape on the outside edge.
The leading edge looks like a rounded knife edge.

The small booster fins look very thin, much thinner than the 3/32" thick fins in the kit. I might buy some thin plywood to get them to a closer scale profile.

I drew a center line down the leading edge of the fin.
A wedge shape was drawn on the outside edge.

This line was drawn with a fine point Sharpie. The lines were drawn quickly so no ink would soak into the fin. The fins will be painted white and I don't want black ink to bleed through the white paint.

The leading edge taper was sanded first, almost to the center line.
220 grit sandpaper was used on a sanding block.

The leading edge was sanded first then the sides flattened.
Setting the fin surface on the block you can see the convex side that needed to be sanded flat.

Here's the first fin fully tapered.
I marked the root edge with a "M" for "master".
This fin will be used as a "guide" for shaping the other three fins.
Try to match the thickness of the leading edge when shaping the other three.






Next to a untapered fin:
On the left is the root edge, on the right is the outside edge.