X jet scratch build
05-26-2008, 04:34 PM
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X jet scratch build
Another scratch build commenced a few months back. I'll put up a few pics as the build progresses for those interested in this kind of stuff.
It is a sport jet loosely styled after some of the mid 50's X jets. It gives me an opportunity to build a circular cross section fuse which I've wanted to do for some time.
90" oal
30# target weight (I never make my targets, but maybe this time)
1330 sq in
35# turbine
It is a sport jet loosely styled after some of the mid 50's X jets. It gives me an opportunity to build a circular cross section fuse which I've wanted to do for some time.
90" oal
30# target weight (I never make my targets, but maybe this time)
1330 sq in
35# turbine
05-26-2008, 04:41 PM
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RE: X jet scratch build
The fuse was fabricated using molded balsa shells with glass and c/f both sides to form a composite structure. I did a thread with a bit of detailed discussion on the composites forum. I'll post few pics here as well.
http://www.rcuniverse.com/forum/m_7123475/tm.htm
http://www.rcuniverse.com/forum/m_7123475/tm.htm
05-26-2008, 05:07 PM
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RE: X jet scratch build
The fin and turtle deck structure carries load, so it is also a composite structure, but formed differently than the fuselage shells.
05-26-2008, 05:18 PM
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RE: X jet scratch build
Bob and www.flyingfoam.com supplied the foam cores. Excellent work as usual. Had to prop the cores against the fuse and make jet noises.
05-27-2008, 03:15 PM
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RE: X jet scratch build
Bob, I have a couple questions. Is there a reason you put your balsa sheeting in the pattern that you did? I have always followed from the leading edge straight back, and you did one piece that way and the rest perpendicular to the fuse. Is there some free strength for weight gained there?
I have always cut back on the foam 3/8 both sides and installed 3/8 balsa edges for hinges. Is there an advantage to the balsa blocks you preinstalled in the foam? I assume there is cause you did it...
You put in balsa for your conrol horn, what type of horn are you going with? I have always been scared to use balsa and have been putting 1/4 5 ply for that.
Are you using carbon tissue over the gear well? My latest wings I put unidirectional carbon there and it did not work like I thought it would when I tested it
I'm thinking of going with Kevlar there, for no other reason than I have tried pretty much everything else, and I have a lot of it here.
Looks awesome as always!
I have always cut back on the foam 3/8 both sides and installed 3/8 balsa edges for hinges. Is there an advantage to the balsa blocks you preinstalled in the foam? I assume there is cause you did it...
You put in balsa for your conrol horn, what type of horn are you going with? I have always been scared to use balsa and have been putting 1/4 5 ply for that.
Are you using carbon tissue over the gear well? My latest wings I put unidirectional carbon there and it did not work like I thought it would when I tested it
I'm thinking of going with Kevlar there, for no other reason than I have tried pretty much everything else, and I have a lot of it here.Looks awesome as always!
05-27-2008, 03:19 PM
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RE: X jet scratch build
Great job as usual, congrats! this technique for rounded fuselages looks excellent.. need to try it for a unusual scale jet one day of this!
Enrique
Enrique
05-27-2008, 05:53 PM
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RE: X jet scratch build
Hey Sean, the answer to all your questions is this: artistic license. 
Seriously though, I like to have the sheeting grain aligned with both the leading edge and the trailing edge. The ailerons and flaps should have more torsional and bending rigidity if the grain is aligned with the trailing edge, but your method obviously works quite well. The blocks for the hinges provide a bit a more surface for the epoxy to grab (I use the large dubro flat hinges), but it may be overkill. As for the horns, I make my own out of G10 which then get glued into a deep slot in the block. I use either 3.5 or 5.7 oz c/f cloth above the wheel wells - works well. See you at the field.
Jim, it will be a one piece wing - I know, arghh. There will be c/f reinforced spar joiners and glass and c/f over the wing joint. Access to the turbine will be through the wing saddle area.
Steve, SJN, Jim, Enrique, Paul, and Gary - thanks for the kind words.
Seriously though, I like to have the sheeting grain aligned with both the leading edge and the trailing edge. The ailerons and flaps should have more torsional and bending rigidity if the grain is aligned with the trailing edge, but your method obviously works quite well. The blocks for the hinges provide a bit a more surface for the epoxy to grab (I use the large dubro flat hinges), but it may be overkill. As for the horns, I make my own out of G10 which then get glued into a deep slot in the block. I use either 3.5 or 5.7 oz c/f cloth above the wheel wells - works well. See you at the field. Jim, it will be a one piece wing - I know, arghh. There will be c/f reinforced spar joiners and glass and c/f over the wing joint. Access to the turbine will be through the wing saddle area.
Steve, SJN, Jim, Enrique, Paul, and Gary - thanks for the kind words.
06-03-2008, 05:58 PM
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RE: X jet scratch build
Tested G10 control horn tear out strength in solid balsa block. Pulled 80 pounds force without failure. Equivalent to 700+ in oz torque at servo.
06-03-2008, 06:04 PM
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RE: X jet scratch build
Time to sand. Jet air filtration unit is mounted on a castered stand. Can be moved near the work and catches the majority of balsa dust.
06-04-2008, 06:21 AM
#23
RE: X jet scratch build
Two things Bob, last year I started using 10 dollar Box fans with 3to 5 dollar HVAC 20x 20 filters on the back of them. Homemade "Jet air filtration" at very low cost. Set it up just as you did with yours, close to the work, picks up A LOT!
PS, yes, you can use it in your home as well!
I love love love the fish hook test on the control horn!
PS, yes, you can use it in your home as well!
I love love love the fish hook test on the control horn!
06-04-2008, 11:40 AM
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RE: X jet scratch build
Hi Bob,
Your project is looking great!!
Question for you. In post #7 what kind of hot wire bow are you using for the hole cutouts with a top and bottom template? I've been using just a wire between two handles for quick insertion into the holes.
Thanks,
Greg
Your project is looking great!!
Question for you. In post #7 what kind of hot wire bow are you using for the hole cutouts with a top and bottom template? I've been using just a wire between two handles for quick insertion into the holes.
Thanks,
Greg