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blackshire
03-10-2011, 05:41 PM
Hello All,

In Reply #4 to this YORF thread (see: http://www.oldrocketforum.com/showthread.php?t=6216&page=1&pp=10&highlight=SpaceLoft ) about the Estes Educator bulk-packaged scale kits of the UP Aerospace SpaceLoft sounding rocket (see: http://www.estesrockets.com/rockets/educator/001793-up-aerospace-spaceloft ), Shamous wrote:

"This is not a good replacement kit. The Gnomes were a great kit. The Up A kits black tube is almost impossible to see the pencil line. But the worst thing about them is that the fin units almost always fail. The plastic cement releases due to heat and needs to be regluded after almost every flight. This was not the case with the Gnome."

I ordered one of the 12-kit SpaceLoft bulk packs, and I found the cause of the fin unit problem that Shamous noted (and there is a very simple, "builder-implementable" solution for it). There is also a very simple solution to the "pencil problem" (please see below).

The barrel ("fin can") of the plastic fin unit fits rather loosely over the BT-5 body tube, which requires a thicker (and therefore weaker) layer of tube-type plastic cement to be applied to the body tube in order to bond it to the inside walls of the fin unit's barrel. This is why the fin units come loose as Shamous observed. Here's the remedy:

Cutting out one or more small strips of self-adhesive label paper (or masking tape) and then applying them to the body tube where the fin barrel goes will build up the body tube's outside diameter so that the fin unit barrel can be cemented in place using a much thinner and stronger layer of glue. Regarding the "pencil problem":

The kit instructions do specify using a white pencil to mark the black body tube, but there is a way to use an ordinary black (graphite) pencil and see its marks on the black body tube. Holding the body tube at a grazing angle to the incident light makes the shiny black graphite pencil marks visible.

I hope this information will be helpful.

Bill
03-10-2011, 06:39 PM
One way to get a decent paper to plastic bond is to rough up the glassine coating on the tube, then apply a liberal coat of tube-type plastic cement to the tube where the fin can will go. Let it dry. Then apply more glue and join the parts. Allowing the initial application of glue to soak into the paper makes a bond possible.

The instructions do not say where to get a white pencil. While browsing in the notions department of Hobby Lobby in search for materials to build an A helicopter model, I noticed a mechanical pencil with white leads. If someone in the household engages in sewing or quiltmaking, buy one of these as a gift and borrow it when needed.


Bill

blackshire
03-10-2011, 10:33 PM
One way to get a decent paper to plastic bond is to rough up the glassine coating on the tube, then apply a liberal coat of tube-type plastic cement to the tube where the fin can will go. Let it dry. Then apply more glue and join the parts. Allowing the initial application of glue to soak into the paper makes a bond possible.Agreed, and I apologize for not including that suggestion--for *all* balsa part/body tube and plastic part/body tube glue joints, it's always best to "sand the shine off the body tube (only 'just')" at the part's or parts' bonding spot(s) on the tube, so that the glue can soak into the paper fibers.

With the Estes SpaceLoft kit, though, the gap between the inner walls of the fin unit's barrel and the body tube's outer surface is wide enough to make it worthwhile to build up the body tube's diameter with self-adhesive label paper or tape--the thick "bridge" of glue that is needed otherwise is more easily broken loose.The instructions do not say where to get a white pencil. While browsing in the notions department of Hobby Lobby in search for materials to build an A helicopter model, I noticed a mechanical pencil with white leads. If someone in the household engages in sewing or quiltmaking, buy one of these as a gift and borrow it when needed.Indeed--white pencils are a bit of a specialty item, but not rare. *But* if one doesn't know where to get them, they might as well be as rare as matzoh ball soup in Saudi Arabia. :-) Fabric stores and craft stores (and possibly the fabric sections of department stores) carry white pencils.

Jerry Irvine
03-11-2011, 08:29 AM
Why not put masking tape or tape stickers on the inside of the fin and lug barrel (maybe even at the factory) and use white or yellow glue and forsake crappy plastic glue all together?

Jerry

:confused:

http://www.v-serv.com/usr/USRchutesticker.jpg

blackshire
03-11-2011, 11:05 AM
Why not put masking tape or tape stickers on the inside of the fin and lug barrel (maybe even at the factory) and use white or yellow glue and forsake crappy plastic glue all together?I had thought about that, but since children in schools and youth groups are the main builders of the SpaceLoft kits (Estes only sells them in 12-kit bulk packs with classroom guides) and because its BT-5 size fin unit is so small, it would be less difficult for them to build up the body tube at the attachment area with label paper or tape.

(For plastic part/body tube joints, I've had good results with UHU Bond-All glue, as its slightly rubbery consistency when cured allows it to flex. When I built the old-style Quest Starhawk and Antari kits [the ones that used the MPC/AVI Tomahawk fin unit that the short length of yellow motor tube was glued into using plastic cement], the UHU Bond-All worked like a charm.)

Shreadvector
03-11-2011, 11:14 AM
Plastic cement is not allowed in many schools (fumes, etc.), so Quest uses friction fit for their fin cans. AND, they have a secret tip not included in the instructions: apply a very small amount of white or yellow glue to the body tube and then slide the friction fit fin can onto the tube. The glue will lube the fin can as it slides on and when the glue is abosrbed into the paper body, it will make it swell and that will grab the fin can a bit better. There is no glue bond between the fin can and tube, it just increases the friction as a result of the swelling.

Jerry Irvine
03-11-2011, 11:22 AM
Fred describes a form of swedging. I have not seen the Quest part, but Estes could do something similar by having the wide end of the barrel be at the rear like a Maniac/1340 fin unit and put glue at the base of the tube and it will form a slide preventer, since all forces are rearward and small.

My idea which Blackshire seemed to miss, probably because he is a horse not a human ( :) ), was to put a tape disc or rectangle on the INSIDE of the plastic part NOT on the outside of the paper part. I suggest it be a factory operation after removing the flash from the parts.

The sticker glue sticks just fine to plastic, the paper sticks just fine to the paper tube and you have a perfect adhesive usage, not some hack with plastic glue.

Since it is my unique idea, they should print my web address on every sticker. :D

BTW the Gnome can be updated/fixed the following way:

Gnome 2 (Irvine variant)

- Trash the engine lock

- Stick the tube out the rear of the fin unit about 1/4". Have the motor stick out the rear of the motor tube 1/4-1/2". Use a single wrap of external tape to retain the motor from ejection. I suppose you can keep the stupid thrust ring.

- Increase the tube length 50-100%.

Done. Valid, even faster motor waster kit. Lower cost too!

Red pencils are common. Think, people!

Jerry

blackshire
03-11-2011, 11:45 AM
Plastic cement is not allowed in many schools (fumes, etc.), so Quest uses friction fit for their fin cans. AND, they have a secret tip not included in the instructions: apply a very small amount of white or yellow glue to the body tube and then slide the friction fit fin can onto the tube. The glue will lube the fin can as it slides on and when the glue is abosrbed into the paper body, it will make it swell and that will grab the fin can a bit better. There is no glue bond between the fin can and tube, it just increases the friction as a result of the swelling.Indeed--after test-fitting the "new-style" Starhawk fin unit on the body tube, I usually apply a thin line of white glue to the tube, slide the fin unit onto the tube with its molded-in launch lug over the line of glue, and then rotate the fin unit to spread the glue onto the tube. Since the glue isn't being used to form a bond but simply to create a friction-fit in this case, even Elmer's School Glue (which isn't as strong for building rockets as Elmer's Glue-All) works fine for attaching the "new-style" Starhawk fin units.

blackshire
03-11-2011, 12:14 PM
Fred describes a form of swedging. I have not seen the Quest part, but Estes could do something similar by having the wide end of the barrel be at the rear like a Maniac/1340 fin unit and put glue at the base of the tube and it will form a slide preventer, since all forces are rearward and small.

My idea which Blackshire seemed to miss, probably because he is a horse not a human ( :) ), was to put a tape disc or rectangle on the INSIDE of the plastic part NOT on the outside of the paper part. I suggest it be a factory operation after removing the flash from the parts.I appreciate the equine acknowledgement. I didn't miss your idea (which is an excellent one). In fact, when I received my SpaceLoft kits bulk pack and found that their fin units fit rather loosely on their body tubes, I decided to use the old tape strip method (utilized in the Estes Streak, X-Ray, Constellation, and other rocket kits that required/require balsa nose cones or balsa adapters to be glued into mylar body tubes or clear plastic payload tubes using white or yellow glue) for gluing on the fin units in my SpaceLoft kits.

I just didn't mention it because the children who usually build the SpaceLoft kits may not have the manual dexterity (or tweezers) to apply tape strips inside such small fin unit barrels. Also, the children who build the SpaceLoft kits in schools and youth groups will already have tube-type plastic cement on hand. (Some of my kind [particularly Standardbreds] can pace as well as trot, but I don't presume that *all* of us can.)

I also agree with your suggested modifications to the Gnome kit.

Jerry Irvine
03-11-2011, 12:18 PM
I used to modify my Phoenix Birds which had a plastic fin unit, to take G motors reliably. Glue a 1/2" long tube on the OD of the airframe tube at the rear and seat the fin unit against that. The glue is superfluous at that point.

The Estes variant of my method could be a 1/4" - 1/8" tube that fits just over the BT-5 at the end for the fin unit to seat against. One in front to capture it too might not hurt.

On my own designs, that front tube is where you glue the launch lug instead of having a big fat heavy molded one, and a launch lug "dongle" like Estes uses. The ridge is in the boundry layer.

Jerry