North Coast Rocketry LaserHawk build...

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James Duffy

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A couple of years ago Matt Steele of North Coast Rocketry sent me a review copy of his LaserHawk kit. I've been remiss in getting this one to the top of the build pile, but it has finally bubbled to the surface. To begin with, here's a quick in-box review of the kit I whipped up not long after receiving the kit:

[video=youtube;r4qE2S_kuCo]https://www.youtube.com/watch?v=r4qE2S_kuCo[/video]

In reviewing the parts and instructions it is clear that finishing will be greatly simplified if we paint as we go along. For instance, the main airframe is constructed from three sections of tubing which correspond to the lower white section, the middle red section, and the white upper payload section. Also, masking and painting the side boosters would be a bit of a pain if we were to attach them first. So, we'll be departing from Matt's suggested build sequence a couple of times.

Our first step will be to shape and sand the fins. My trusty twenty-year-old Black & Decker Mouse sander will be pressed into service for this step. The leading and trailing edges will be rounded off, while the tip surface will be squared off. The plate surfaces are then sanded.

IMG_3195.jpg

More later,
James
 
Our next step will be to glue up the centering ring/engine mount assembly. I made a decision to glue up the centering ring "cage" assembly separately, then slide the completed unit onto the engine mount tube.

IMG_3196.jpg IMG_3197.jpg

Medium CA was used to tack up the cage assembly, while 5-minute epoxy was used to mount the cage onto the engine tube.

More later,
James
 
Pretty standard stuff at this point as the airframe components come together. First, the cage assembly is glued into position with epoxy, taking came to make sure that the fin attachment positions are correctly aligned and free of any excess glue.

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A fin is dry-fitted into place to make sure that everything is in alignment. Note that the fins are not attached at this point; we're simply making sure that the cage is properly positioned.

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After the cage sets up for a few minutes an additional epoxy fillet is applied to the aft centering ring.

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The forward coupler is glued into place.

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Next, we turn our attention to the forward payload section. A bulkhead plate is glued into another section of coupler. A Q-tip swab was taped to a popsicle stick so that the fillet on the interior of the coupler tube could be smoothed out.

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The bits of forward bolt eye hardware are installed, and a dot of epoxy is placed on the threads to make sure that the assembly does not come apart. The coupler is then glued into the forward payload tube (sorry, no photo).

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More later,
James
 
A minor deviation from the kit instructions: rather than loop the shock cord mount through the two holes in the forward centering ring, the mount will instead go through one of the holes and then around the motor tube. Here's a pic:

IMG_3204.jpg

I'm sure that the method specified in the directions is plenty secure, but wrapping the recovery attachment point around the motor tube has always given me a warm, fuzzy, secure feeling.

James
 
The fact that the LaserHawk has two big, fat, simulated strap-on boosters pregnant with potential begs the following question: who would NOT convert this model to fly as a big, nasty, clustered beast?

The answer in this dojo: not us.

Matt has designed some laser-cut mounts for the simulated boosters that are, I'm sure, perfectly adequate for their intended unpowered application. Here's a shot of the parts that come with the kit:

IMG_3207.jpg

However, we plan on equipping this rocket with 24mm motor mounts in each of the boosters, and don't want to run the possibility of the attachment points breaking under power. So, we're going to equip each booster with a more robust full-length attachment method. This isn't going to be anything fancy or complicated, just a strip of 1/8" x 1/4' basswood that runs the length of each booster.

First step is to mark the locations for the strips to be attached. A Great Planes bar sander is used to extend the attachment locations down the length of each booster.

IMG_3205.jpg

It's a shame that these bar sanders have become scarce since the Hobbico financial woes began. Hopefully they will reappear under the new owners of the Great Planes brand, Horizon Hobby: https://www.greatplanes.com/accys/gpmr6170.php

More later,
James
 
A bit of epoxy is used to glue the basswood mounting strips to each of the strap-on boosters, and a bit of tape is used to hold everything together until the adhesive cures.

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James
 
Just coated the fins with diluted Elmers white wood filler, and used up the last of that stuff that I had on hand. The only place that I've been able to get that locally is Walmart, who seem to have stopped carrying it. That discontinuance leaves me with exactly zero reasons to ever go to Wally World. Fortunately, Amazon carries the product. Eventually Amazon will be the only source for everything, I guess.

We'll sand these out tomorrow and hit them with some primer.

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More later,
James
 
The fins have been sanded, then attached to a handling stick with a few drops of CA.

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Next, the coupler ends of the fin can and payload section were masked off. Using Rustoleum grey automotive primer, all of the airframe and fin components were then sprayed with three coats of primer. These components are all a bit large for my hobby spray booth, so my wife's horse trailer was used as an ad-hoc spray facility.

Here's everything primed and drying outside.

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We'll let this cure for a couple of days and then sand everything out. Astute viewers will note that nothing has yet happened with the nose cones. We have something special in store for them. There will be fire.

More later,
James
 
Fire.gif

Unless you're building with composite parts, chances are that the nose cones used for most mid- or high-power projects are molded from polypropylene plastic. In practical terms that's the same stuff used to make milk bottles, and it is notoriously difficult to get paint to stick without a generous application of voodoo. I'll share some of my personal voodoo for this task here.

First, some background. Years ago I commissioned blow-mold tooling to create the V-2 airframes for the Bumper WAC models flown by Matt Steele, Tony Reynolds, Jim Filler, and myself in FAI competition from 2010 through 2104. To help recover the cost of the tooling I marketed a styrene version of the V-2 kit (there's a link in my sig below). The problem was that the easy-to-paint styrene airframe used in that kit was far too heavy for FAI scale altitude models, so I had the molder run off a handful for the airframes using polypropylene instead of styrene. With the "milk bottle" airframes in hand I was given a crash course in painting and gluing PPE components by the kind folks at the molding plant.

In short: the stuff is tough to paint, but not impossible. Polypropylene is used extensively in the auto industry for exterior components such as bumper covers. There, they chemically alter the surface of the parts using flame, then follow that up with adhesion promoters. We're going to do the same here.

First, check out this short video on flame treating:

[video=youtube;l-R2lDEocDc]

The application of flame to the surface converts the outer layer of the plastic from paint-phobic plastic molecules into a paint-groovy surface. I use a handheld propane torch just like the one shown in the video above. (I seem to recall paying about $15 for the rig at Home Disappointment.) Our HP nose cones are thick enough that they can withstand a quick flame pass without melting or distorting. The trick is to keep the flame moving, and to not allow heat to build up and store in the plastic structure.

IMG_3216.jpg

It just takes a minute or so to flame treat a cone. Once it has been through the fire, so to speak, Duplicolor Adhesion Promoter is applied in three light coats, allowing just a couple of minutes between each coat. I buy the stuff at the local Advance Auto Parts:

https://shop.advanceautoparts.com/p...-cp199/7140919-P?searchTerm=adhesion+promoter

After the third coat goes on you'll want to begin to spray the color coats within the next 5-10 minutes. The adhesion promoter works a bit differently than traditional primer coats, as we want it to still be tacky so that it can cross-link with the color coat. Let it dry for a day or so, and you're done.

IMG_3217.jpg

More later,
James
 
Last edited:
...

In short: the stuff is tough to paint, but not impossible. Polypropylene is used extensively in the auto industry for exterior components such as bumper covers. There, they chemically alter the surface of the parts using flame, then follow that up with adhesion promoters. We're going to do the same here.

First, check out this short video on flame treating:

[video=youtube;l-R2lDEocDc]https://www.youtube.com/watch?v=l-R2lDEocDc[/video]

The application of flame to the surface converts the outer layer of the plastic from a paint-phobic plastic molecules into a paint-groovy surface. I use a handheld propane torch just like the one shown in the video above. (I seem to recall paying about $15 for the rig at Home Disappointment.) Our HP nose cones are thick enough that they can withstand a quick flame pass without melting or distorting. The trick is to keep the flame moving, and to not allow heat to build up and store in the plastic structure.

View attachment 343414

It just takes a minute or so to flame treat a cone. Once it has been through the fire, so to speak, Duplicolor Adhesion Promoter is applied in three light coats, allowing just a couple of minutes between each coat. I buy the stuff at the local Advance Auto Parts:

https://shop.advanceautoparts.com/p...-cp199/7140919-P?searchTerm=adhesion+promoter

After the third coat goes on you'll want to begin to spray the color coats within the next 5-10 minutes. The adhesion promoter works a bit differently than traditional primer coats, as we want it to still be tacky so that it can cross-link with the color coat. Let it dry for a day or so, and you're done.

View attachment 343415

More later,
James

Nice. I knew about adhesion promoter but not the flame treatment. My wife's gonna love that new toy ! :wink:
 
The primed parts have all been sanded down, then hit with color coats. I've decided to embrace some elements of the factory paint scheme (white and red on the main airframe), while going my own way on others (yellow instead of black on the strap-ons). The fins will get a Nike-like fluorescent paint treatment after the white undercoat has had a couple of days to cure.

IMG_3219.jpg

More later,
James
 
After allowing the paint on the various airframe components a couple of days to dry we can begin gluing the bits together. First, the fin can is inserted into the main airframe tube. Next, the mounting locations for the strap-on boosters are marked.

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We don't want to glue the boosters directly to the paint, so a thin surface layer consisting of the paint and outer glassine layer of the tube is removed. This was easy to do, as all that is required is a quick pass with a sharp #11 blade, then peeling the layer away.

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With a secure mounting surface created, epoxy is applied to the joint and the whole assembly is stabilized until the adhesive can set up.

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We're in the home stretch now!

More later,
James
 
With the strap-on boosters in place we'll next turn our attention to the markings, as these will be easier to apply before the fins are mounted. Instead of the kit-supplied markings we'll be using some vinyl left over from a circa-2001 Little Joe project, along with a couple of bonus markings from a more recent 4"-diameter Black Brant IIIB project. (Pro tip: throw all of your leftover decal bits into a box or binder, as you never know when they might come in handy.)

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A pair of temporary tape flags are attached to the airframe tube at the forward and aft positions for the markings, and centerline alignment markings are then placed on the tape. Similar markings are placed on the carrier sheet for the vinyl markings, then the vinyl is placed on the rocket.

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The vinyl is burnished into place, then the carrier film is carefully peeled back.

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The spare Black Brant markings are then applied to the strap-on boosters. Note the ruler that has been inverted and placed into the gap between the strap-on and the main airframe to provide a bit of alignment guidance.

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More later,
James
 
Our last tasks will be to install the rail buttons and fins. The rail buttons are first, taking advantage of the fact that we marked their locations using the centerline established in the same step where we marked the installation points for the markings. Next, we glue the fins into place one at a time using epoxy.

Note that we're not using an external fillet, as we wish to preserve the scale-like appearance of the model. Besides, there is plenty of internal structure to provide to provide strength. I know that this decision will upset many of you. I feast upon your indignant tears.

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Here's the aft end with all four fins installed. Note that we've also installed an Estes 29mm motor retainer, as they are cheap and easy to install. (We'll also be installing 24mm motor mounts and retainers in the strap-on boosters as soon as some centering rings arrive in the mail.)

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More later,
James
 
And here's the (almost) completed model! In addition to installing the motor mounts in the strap-on boosters when the parts arrive, I may also add some additional scale-ish markings. Come see it fly at next weekend's Austin Area Rocketry Group launch!

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I highly recommend the kit, BTW. Thanks to Matt Steele of NCR for the review copy!

James
 
Hi @James Duffy I know that this thread is over a year old now, but I'm wondering if you added the 24mm motor to the strap-on boosters? I'm considering purchasing this model and would also like to make it a cluster rocket. You did such a great walk-through of the build, that I'd love to hear your thoughts on adding the additional motors.
 
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