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All Forums >> RC Airplanes >> RC Jets >> RE: sport jet scratch build
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RE: sport jet scratch build - 12/13/2006 3:14:16 PM   
Bob R2



Posts: 504
Joined: 6/20/2004
From: , TX, USA
Status: offline 		Next is assembly of the composite shells to the frame. Hysol (what a great invention) is applied to the formers and longerons. The right and left shells are held in place with masking tape and clothes pins. After cure, the top surface is taken down flat to the basswood longerons with carving knife and sandpaper, and a cap is glued to the top of the boom structure. The top surface is shaped to the desired contours. A flat floor for the fin is carved into the top surface, and the holes for rudder servo lead and fin spar box are cut.

When the outer surface is ultimately glassed, the structure will be a glass/balsa/glass sandwich with c/f reinforcement. Very strong and very rigid. A modern (sort of) composite structure with old school construction methods.

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       Post #: 26

RE: sport jet scratch build - 12/13/2006 4:10:03 PM   
mick15



Posts: 809
Joined: 4/2/2002
From: essex, UNITED KINGDOM
Status: offline 		Hi bobber
I did a scratch sport jet if you are interested, didn't want to hijack the thread

M

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       Post #: 27

RE: sport jet scratch build - 12/13/2006 4:18:02 PM   
Bob R2



Posts: 504
Joined: 6/20/2004
From: , TX, USA
Status: offline 		Thanks Mick, I'd like to take a look later today. If it is not on RCU, I'd appreciate a link.

Bob R

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       Post #: 28

RE: sport jet scratch build - 12/13/2006 4:39:26 PM   
Bobman


 

Posts: 278
Joined: 1/16/2002
From: Alden, NY, USA
Status: online 		Bob,

Nice job! Unfortunately scratchbuilding is becoming a lost art form.

An off topic question.... can you give me some details on your building table? I'm in process of building my new shop and am looking for ideas on a moveable table like yours. My concern is keeping it flat when moved, or at least keeping the adjustments to a minimum. I've used hollow core doors mounted stationary on frames with good success for years, but would prefer something larger & one piece (4x8) that I could move around the shop when required.

Thanks!

Bob K.

_____________________________

Jet Black R/C Models www.JetBlackRC.com
Authorized SkyMaster ARF-Plus Dealer /Jetcat Dealer

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       Post #: 29

RE: sport jet scratch build - 12/13/2006 11:52:40 PM   
Bob R2



Posts: 504
Joined: 6/20/2004
From: , TX, USA
Status: offline 		Hey Bob,

That table is just a piece of mdf flopped on top of my Jet cabinet saw and extension. The end over the saw is very flat, but the opposite end over the extension is not. I have another bench, which is fixed, with a glass top that is shimmed to flat.

Bob R

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       Post #: 30

RE: sport jet scratch build - 12/14/2006 4:20:10 PM   
Bob R2



Posts: 504
Joined: 6/20/2004
From: , TX, USA
Status: offline 		The fin is traditional built up construction with some c/f on the spar.

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       Post #: 31

RE: sport jet scratch build - 12/16/2006 12:53:18 AM   
Bob R2



Posts: 504
Joined: 6/20/2004
From: , TX, USA
Status: offline 		A few pics of the components blocked up. I'm far enough along with the build that I can now imagine jet noises to keep my motivation up.

This will be my last post for a while. The holidays and a work project will slow things down a bit.

Have a good holiday,
Bob R

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       Post #: 32

RE: sport jet scratch build - 12/16/2006 9:33:27 AM   
john agnew


 

Posts: 1688
Joined: 1/29/2004
From: glasgowScotland, UNITED KINGDOM
Status: offline 		Bob

Congrats. on a great looking model, very quick work too! Your workshop looks a bit underequipped though, I think you need some bigger machines!

John

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       Post #: 33

RE: sport jet scratch build - 12/16/2006 3:31:06 PM   
Bob R2



Posts: 504
Joined: 6/20/2004
From: , TX, USA
Status: offline 		Thanks John. Actual build time has been more like four weeks scattered over a couple of months, so not nearly as quick as the pics would imply.

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       Post #: 34

RE: sport jet scratch build - 1/3/2007 11:31:53 PM   
Bob R2



Posts: 504
Joined: 6/20/2004
From: , TX, USA
Status: offline 		I was able to make a little more progress over the long weekend.

Next up is the pod portion of the fuselage which will be built clamshell fashion. Right and left side temporary formers are glued to a piece of scrap aluminum laying around the shop. The side and bottom pieces are cut from sheet balsa and the inside surfaces are laminated with glass or c/f. The side and bottom pieces are then glued to the temporary formers. Finally, balsa strip planking is applied to the portions of the pod with compound curvature.

I hope my wife doesn't hear that I've been on line talking about "strip planking".

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       Post #: 35

RE: sport jet scratch build - 1/3/2007 11:39:02 PM   
Bob R2



Posts: 504
Joined: 6/20/2004
From: , TX, USA
Status: offline 		The right and left sides are rough sanded and trimmed, then they are popped off the aluminum backbone. The temporary formers will be removed and a bit more glassing will be done on the inside surfaces. Once the clamshell halves are glued together, the outside surfaces will be glassed. This will produce a glass/balsa/glass sandwich shell with c/f reinforcement.

Time to fire up the lathe and turn a foam nose piece.

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       Post #: 36

RE: sport jet scratch build - 1/4/2007 3:40:35 AM   
Boomerang1



Posts: 832
Joined: 6/24/2005
From: Sydney, AUSTRALIA
Status: offline 		Looking good Bob, a bit more shapely than mine. Yours is looking like a Jaguar, mine a bit like a Volvo!
A friend has a P-70 in a Boomerang, sweet engine. It replaced a Jet Joe, now that left a bitter taste in his mouth! - John.

_____________________________

Distributor for: Nothing! So my posts can be unbiased.

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       Post #: 37

RE: sport jet scratch build - 1/4/2007 2:08:34 PM   
Bob R2



Posts: 504
Joined: 6/20/2004
From: , TX, USA
Status: offline 		Thanks John. The P70 was previously in my 23 lb BobCat Comp and pushed it around OK, so it should do OK in this airframe. I was hoping to keep things light enough that I would have a 1:1 thrust to weight ratio, but that ain't going to happen. If the plane survives the test flights and the vertical performance isn't up to expectations, I may consider a motor swap - perhaps a Falcon.

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       Post #: 38

RE: sport jet scratch build - 1/5/2007 2:04:15 AM   
Bob R2



Posts: 504
Joined: 6/20/2004
From: , TX, USA
Status: offline 		Foam blocks are glued up around a central shaft, then chucked up in the lathe. After a few minutes with various cutting tools and a few sanding blocks, the nose takes shape. A check fit on the fuselage shows a decent transition of contours, but a bit of tweaking of the nose shape is needed. Ultimately, the foam block will be glued on, glassed, then dissolved out with lacquer thinner.

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