AJ/JW .020 Firebaby Jr. Pretty neat

I haven't had a chance to put it together yet Robert.  Nut and bolt construction retains the wing and I'm not great with those little 2/56's but I will get to it and post a weight.  Those metal weights are heavy, I 'm not sure it would get off the ground with all attached, would act more like a plow I think.  




A clone is a must.  But this time Hobby Lobby balsa!!!!! No more making do.  1/16" fuselage with external ribbing.  I'm still thinking about a decal for the wing, big one split in half and applied.  A chunk taken out of the leading edge. A wedge of balsa and food coloring to match maybe.  Box end says with .020 Cox Eng $4.98.  Control lines once attached but the engine shows no signs of ever being fueled.  





Wen stuff.

That is a new one on me the Jr. never heard of it . A lot of weight up front , did any instructions come with it ? Bee interesting to see where the CG is when put together . Hard to read https://www.worthpoint.com/worthopedia/vintage-jim-walker-american-junior-3766318702
Just as i thought ((( "Variable CG". The engine mounts with three steel plates (weights) to provide a forward CG making the Firebaby Jr. a stable basic trainer. As the novice pilot develops his skills the weights can be removed one at a time to cause the little plane to become more maneuverable. It works! ))) from the site

This guy says he has the plan but no pic > https://www.model-plans.co.uk/jim%20walker.htm

getback wrote:This guy says he has the plan but no pic > https://www.model-plans.co.uk/jim%20walker.htm

Thanks Eric. I have plans, yellowed with age but readable.

Scans:

I may have just enough 1/16" to do it. Box repair etc. I have no steel sheet but I do have aluminum which would be easier to work for the clone.

Roberto, I wonder why in the design they carried out placing so many iron counterweight plates...perhaps a cost issue to modify the matrix to make a fuselage with a longer nose moment??
I have worked in design companies and many times, due to cost reasons, they decided to solve "a problem" by making an "adjustment" to a piece, instead of fundamentally modifying the design matrix. Could this be the case?
Flying with all that weight up front doesn't seem like a good idea to me, an impact would be much more serious for the engine, potentially compressing it due to inertia and breaking some of its parts...just thoughts...

Flying with all that weight up front does not make much sense to me either.  I don't think it would get off the ground as they are very heavy and the wing area so small.

The idea is, as you get better at flying remove steel plates one at a time shifting the CG further backwards making the plane more maneuverable but less stable.  

Bob

The box is nasty but repairable. First thing is to remove the masking tape. A warm Monokote iron works good. Just heat it up and pull it off at zero angle back over itself. It will leave a sticky residue. Howard Feed-N-Wax removes it. Citris base Orange oil.





I can get all the clone pieces cut from a sheet of 1/16" left-over balsa. The comparison to the P-26 is kind of laughable but it does referance it on the box.

Building in camber for a clone.  A couple of coats of sanding sealer well dried then wet the top of the wing with water, clamped and let dry for a couple of days.  Block sander curve a good substitute for the real thing.  





Scanned to water slide decal paper.  All I have.  Will try vinyl backed later if it doesn't work.  1/16" won't do for the fuselage, has to be 1/8th or better even if the plastic is more like 1/16th.  Seam it at the fuselage which I will rib like the original, firewall support etc..  Still thinking about the small dihedral of the original.  Slight bevel of each wing, 1/4" supports at the wingtips, weight in the middle, epoxy - maybe.  Belly pan will back up.

Way to go on producing that cambered wing Bob!….I think hanging it and weighting it may be a good way to get the dihedral…. A big part of the plane’s character and possibly flying IMO….. Will take a little fiddling around with to get the camber and dihedral to agree….Graphic looks good too…. It maybe can even figure in to help the wing hold its shape… Subscribed to your project!!…. I gotta try building a Firebaby wing replica when I get time!!

rdw777 wrote:Way to go on producing that cambered wing Bob!….I think hanging it and weighting it may be a good way to get the dihedral…. A big part of the plane’s character and possibly flying IMO….. Will take a little fiddling around with to get the camber and dihedral to agree….Graphic looks good too…. It maybe can even figure in to help the wing hold its shape… Subscribed to your project!!…. I gotta try building a Firebaby wing replica when I get time!!

I cut out a new fuselage out of 1/8th" balsa, perhaps the hardest close grained balsa that I have ever seen. Beggars can't be chooses and about all they had on hand at the time. I had to rough cut it out with the jig saw, an Exacto would never cut around those curves.





I'm thinking about just cutting a slot for it and sliding it in rather than complicating it with a detached belly pan. It would require a remote wing mounted bell crank rather than the mid-ship bell crank position of the original.

I have a little problem.

The scan of the wing is ok N/S but off E/W. The wing measures 14 1/2 inches E/W but the decal scan is just 14". It did not scan one to one but close, probably due to the way I held it on the scanner. I could not close the lid on the wing due to its dihedral and camber not wanting to do damage.

I could shorten the wing to 14" but I don't want to do that. I think I will just add black treading to either side of the fuselage to cover the discrepancy if I can't come up with something else.




More scientific assembly......................






When I added the second coat of Minwax to the wing (its water based) it removed all the camber. Reintroducing it with a third coat. I need to add ribbing and firewall supports, then everything gets painted red. I'm too chicken to cut out the windshield, I would botch that for sure.

Meanwhile, the radiator on my Rx-7 is leaking..................................

That Estwing has been my finish hammer for 42 years. It will be 43 in August. I actually repaired the leather and did a refinish.

Ken Cook wrote:         That Estwing has been my finish hammer for 42 years. It will be 43 in August. I actually repaired the leather and did a refinish.

Ah Ken we do love those hammers.  It has a nice "swing" to it, so well balanced.  I could really get into hammers.  The one on the right belonged to my Dad, the tapping hammer came from my wifes uncle's estate, and the ball peen was one I used to beat on my old 1937 Ford coupe.  15/16 year old with a $80 flat head V8, chicken farm money.  I could tell stories.  Guy's girls and gas!



Fixed the leaky radiator.  Wasn't the radiator but the small bypass hose off the bottom elbow.  Now I remember that I just slipped it on without tightening the clamp.  Groan!

Bob,

This one is turning out so cute!

Consider Minwax's Clear Lacquer Sanding Sealer once you run out of the water base stuff...unless the water base stuff is also fuelproof. The clear lacquer isn't and must be top-coated. I just treat it like nitrate dope.

944_Jim wrote:Bob,

This one is turning out so cute!

Consider Minwax's Clear Lacquer Sanding Sealer once you run out of the water base stuff...unless the water base stuff is also fuelproof. The clear lacquer isn't and must be top-coated. I just treat it like nitrate dope.

Thanks Jim, I will look for it. Always willing to try something new.

After a final sanding everything will get a couple of coats of red paint. Including the top and bottom of the wing. I want the top of the wing to be really smooth so I can move the decal around a bit if necessary. It's going to be touchy getting the two haves intersected and aligned. Were I smart, I would get my son to do it.

Got to make up my mind, a new can of Krylon or one of my half empty red high engine heat reds. Thinking the latter.

Weight? I'm always eager to compare clone vs. original. Remember this thing came with four heavy metal nose weights which I will substitute with 1/16" balsa just for looks.

Wow Ken. Estwing hammers from $44.50 12 oz to $223.96 16 oz.

rsv1cox wrote:

Weight?  I'm always eager to compare clone vs. original.  Remember this thing came with four heavy metal nose weights which I will substitute with 1/16" balsa just for looks.  

I'd like to know the weight difference without the weights, if you would...please. And thank you!

I'd also like to know how much each metal ballast weighs. Who knows...the weight may be the same as a trimmed large fender washer.

Along with weights another interesting measurement would be how much does it change the balance point as weights are subtracted …. Would be interesting to see what the manufacturer thought would make it more maneuverable…

rdw777 wrote:Along with weights another interesting measurement would be how much does it change the balance point as weights are subtracted …. Would be interesting to see what the manufacturer thought would make it more maneuverable…

Interesting.  I could not get it to balance on the knife edge, I had to turn the pivots 90 degrees.  I can not imagine this flying with any of those weights, much less four of them.  Fake balsa weight on the nose, perfect balance.



1.25 oz



2 oz.

Wow Bob, Is that your clone in the last photo?…. Looks like you got it spot on!!…. Everything lines up great.. Color match, Wing graphic, Even the fake weights, Nice touch … The external bracing on the fuse adds a lot to the replica….. Well they would have wanted it very nose heavy with all the metal weights in place…. Probably would balance shortly behind the engine….. Maybe not a deal breaker but seems it would be very sluggish….

rsv1cox wrote:

Interesting.  I could not get it to balance on the knife edge, I had to turn the pivots 90 degrees.  

Bob. Try putting it on the balance rods upside down. My PT19 wouldn't balance right side up, but was fine flipped over.

Thanks TL, I'll give it a try.  After about five minutes of trying to get it to balance on the knife edge I gave up.  

Thanks Robert, not my best effort (I'm saying that a lot lately ).  Lot's of little things that bother me, hurried to finish as like you I have other things in the fire.'

The ribbing really make the model, but I did not get it right.



I did get some box repair started at the same time.






Edit

I tried it TL, on the knife edge.  In that position it balances at 3/4" behind the leading edge.  Pretty good I would say.  I could fly it as is on maybe 15/20' lines.  No big deal if I return it to scrap balsa, that's where it came from.  Biggest expense is the printer ink used in making the wing decal.  



I do like the added color on the horizontal stab pictured on the box. It adds detail but the model itself does not have that application.

Bob