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Old Jan 12, 2010, 01:10 AM
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St.Catharines, Ontario
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Build Log
7th Scale Jaguar Build

well, I said I would start the build thread, so here goes

as stated in the title, this a 1:7 scale Sepecat Jaguar that I am scratchbuilding. this has been in the works for a few months now and I feel like I've come a long way in a short while. I chose this project because there just aren't any out there. there's a turbine version by Christen Diffusion of Fance, a small one by Green Air Designs in the UK and a few one off's here and there. the only true scale one is the afore mentioned Diffusion jet and it's fairly pricey I might add. I have had a love of the mighty Jag since I was a kid and my build skills have finally caught up with my dream to have one.

the first thing to do was to get a 100% scale outline. this proved difficult, as most 3 views available are "off" in certain areas and others are "off" in other areas. so it's been a difficult process to get it right. I finally settled on an old airfix model that I purchased and used a contour pin guage to get my formers correct. at 1:72 scale, I chose every 5mm, which equates to every inch and a half at 1:9 scale, so there's a former at every inch and a half of fuselage. I will be building my parting board right into the fuselage plug using two pieces of warp free 1/8th inch ply, that will form a spine. I can then seperate the spine after I've added my foam, filled and sanded. then glue the spine to a bigger board and that will make my plug. I believe I will use sand and epoxy for the mold, but I am open to other suggestions if you have any.

I had gotten to the foam stage but once together, I realized that the shape just wasn't right, so I scrapped it and re-did the entire fuselage formers and spine outline. now I am happy with the shape and I have the foam pieces cut to glue into the formers. I will post pictures of this once I have them all glued in place.

the airplane will have the airfoil section this is used on the full size Jaguar. it is the NACA 65A-006 and will be a fairly fast airfoil. the only changes I will be making is to increase the thickness to 7% at midspan and 8% at the tip. this will give me the clearance I need for the wing mechanics. I am building two wings at the same time...........one scale with full span flaps and spoilers for roll control and one with half flaps and ailerons. this will be the wing for test flights and the scale wing will be tried later.

the Jaguar would not be the Jaguar without those awesome looking landing gear and, those will be reproduced at a % of scale. in other words, they won't be completely scale, but will look and operate as the full size do. they have a twist as they retract and have several drag/sway links for rough field operation. I believe this will translate well for our grass flying field. the biggest problem to overcome was the angles of the gear. there are two angles from the side and 3 from the front. then there are two angles to the main pivot point. these have all been painstakingly reproduced and I have the few extra grey hairs, bald patches and lousy eyesight to prove it. LOL. they will be driven by a screw jack system and have sequenced gear doors, or doors on another channel...........I'm still undecided. the screw drive will basically be a 3.6 volt chordless screwdriver, driving a machine screw with a plate and threaded hole. this drives two links that are attatched to the gear legs. end points are established using micro switches. I've seen this done before and it works extremely well and is light. a servo simply activates the switch in forward or reverse.

the Jag will also have two position air brakes, a provision for a drag chute and possibly a provision for a working tail hook. this will be dependant on weight of course. the cockpit will also be mostly scale..........the seat and panels will be scale size and position, but I will leave it at that for the test flights and if I kit it, it will be sold like that and be up to the builder to add or leave the details out.

as of this point in time, motivation will be via twin 70mm fans........I am going with WM400 MKII's. the inlet area is perfectly sized for this, or single 90mm, so I decided on twins for some extra WOW factor. LOL.

so, that's where I'm at at the moment. I will take some pics tomorrow of the scale outline and the main gear mock up model I made and I will post them. I hope others will be as interested in this build as I am.

Rich
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Old Jan 12, 2010, 03:03 AM
smithy
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Cornwall, UK
Joined Dec 2004
524 Posts
Hi Rich, best of luck with this build, one of my fav aircraft. Takes me back to RAF Germany in the eighties, seeing Jags flying out of Laarbruch. All we need now is a Phantom FGR2 and Harrier GR3 to go with your Jag! Looking forward to seeing some pics.

Phil
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Old Jan 12, 2010, 03:42 AM
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St.Catharines, Ontario
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now that would be something, wouldn't it? don't give me any ideas though......my wife is already mad enough about losing her dining room table at the moment. LOL. I'm going to need a house with a garage, or I might end up divorced. I suppose it wouldn't be too difficult to mod an existing F4 to an RAF spec aircraft with the Spey engines and the different nose cone. would be interesting for sure. the Jag looks really cool sitting up on the wall though. it's quite large at 1:9th scale.

length: 64 inches without nose pitot tube
wingspan: 36 inches

Rich
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Old Jan 12, 2010, 03:50 AM
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Canada, ON, Mississauga
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Now this will be quite innovative and unique project to do, i have a tiny place in my heart for Jags and can't wait to see it take shape, I'm in the game!!.


Sam
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Old Jan 12, 2010, 04:00 AM
smithy
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Cornwall, UK
Joined Dec 2004
524 Posts
Just curious Rich, are you going for a scale wing planform? When i was looking at doing a Jag the wing area came out to be relatively small resulting in quite a high wing loading. What sort of all up weight are you looking at?

Phil
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Old Jan 12, 2010, 04:04 AM
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Canada, ON, Mississauga
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Quote:
Originally Posted by LuvEvolution7 View Post
my wife is already mad enough about losing her dining room table at the moment. LOL. I'm going to need a house with a garage, or I might end up divorced. it's quite large at 1:9th scale.

length: 64 inches without nose pitot tube
wingspan: 36 inches

Rich
Hey don't get Divorced Ok!, bring it to my shop, i have more then enough room for your project, no i'm not kidding, i'm serious if you need space to work. Only down fall will be commute plus whenever hours you want to work on it, you will have to come here. My modeling tools are available to you or you can bring yours....No rent charged to you!...haha


Sam
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Old Jan 12, 2010, 04:58 AM
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St.Catharines, Ontario
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thanks Sam. the Jag would look really cool next to that Herc. so far, my wife has been pretty understanding. hey, she married me knowing this was my hobby!!!!!! hahahaha. oh well, she'll only have to put up with this for a few more months........at least that's what I'll tell her anyway. LOL. I might just take you up on that offer though. depends where you are. I'm assuming a commute might mean you are a few KM away from me. LOL.

Rich
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Old Jan 12, 2010, 05:01 AM
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Phil. I'm doing two wings side by side. one is completely scale and one is slightly overscale. both use the scale airfoil root and bump up a few percent toward the tip. I'm counting on a few extra ounces of lift. if it doesn't work, I have another airfoil to try, the wing is being designed as a removable module, so it won't be difficult to re-design if need be.

Rich
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Old Jan 12, 2010, 05:21 AM
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Canada, ON, Mississauga
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Quote:
Originally Posted by LuvEvolution7 View Post
thanks Sam. the Jag would look really cool next to that Herc. so far, my wife has been pretty understanding. hey, she married me knowing this was my hobby!!!!!! hahahaha. oh well, she'll only have to put up with this for a few more months........at least that's what I'll tell her anyway. LOL. I might just take you up on that offer though. depends where you are. I'm assuming a commute might mean you are a few KM away from me. LOL.

Rich

You are welcome Rich, i'm for sure few KMs from you in Huttonville area, slightly north of Hwy 401 between Winston Churchill Rd and Mississauga Rd area. It's Gr8 she is a understand lady, i'm happy to find my girl who loves planes and especially my models too, so i consider myself blessed in this regard.


Sam
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Old Jan 12, 2010, 10:41 AM
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Watching with interest. I would like to do a plug someday but only have a rudimentary idea as to how to go about it. So, don't spare the details.

My only concern is the choice of air foil. I'm not sure a scale air foil works well at the Reynolds number your wing will be generating but you may have already researched this point.

Regardless, I'm signing on. There are very few of us scratch builders around to keep the true modeler's fire burning.
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Old Jan 12, 2010, 12:02 PM
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St.Catharines, Ontario
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well Larry, I'm right there with ya. LOL. this is a sharp learning curve for me, for sure. I've only ever glassed small pieces with varying successes, which is why I'm hoping the more experienced guys will sign on and correct my mistakes. LOL. I want this project to be a success and possibly share it with others if successful. I believe I can produce a good product and offer it to others, if they want it. the main concern is to make something I am proud of and the rest is a bonus. the size is perfect for me, but if this is successful, the sky is the limit as far as size is concerned. I would have no problem making larger planes. in fact, I've already started thinking ahead for a twin XPS powered Jag..................that's not a good thing, or maybe it is. LOL.

as far as the scale wing and the reynolds numbers concerned, I will admit that I have absolutely no idea how it will perform. I can tell you this though............the full size airfoil is modified somewhat and is a little flatter on the upper surface than the lower. the NACA 65A-006 as plotted, is a symetrical airfoil and I'm hoping it will work. if it doesn't, I will deffinitely try another foil. I already have a few chosen and will go to those, if the scale one doesn't work. I'm not using any fancy computer programs for design. this is all old fashioned, pencil and paper and using my brain to access eveything I ever learned in college as an A&P tech. I knew I'de use it again at some point in my life, so it wasn't all wasted money. LOL. the way I look at it, scratchbuilding is a journey. sometimes it's not a fantastic journey, but one well worth it, that not many venture into. that being said, I've got my fingers crossed with the scale airfoil.

Rich
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Old Jan 12, 2010, 12:20 PM
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one thing I am up in the air about, is the wing, vertical and horizontal stabilizor construction method. I've drawn out a plan for built up construction, but I could be swayed to go with foam core. just wondered what everyone's thoughts are on this. the tailplane is full flying and the vertical is traditional with rudder. also, can anyone offer information on the best setup and materials for the full flyings stabs? the full size is a taileron setup, so I'm thinking two servos in the tail driving each half. I've never done a plane with full flying stabs, so I'm deffinitely open to suggestion for construction, materials, setup, etc. the full size looks like it's pivot point is around 23% of MAC and the pivot bar is roughly the same angle as the leading edge. this makes sense to me, but again, I am completely open to suggestion. what do modellers use for the pivot assembly?............are there pillow block bearings available at this size, or is there a way to make your own? I'de like this to be done right and no play or slop in this vital assembly of the plane. thanks for any info.

Rich
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Old Jan 12, 2010, 12:31 PM
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man, the questions keep pouring from my mind, but I have one in regards to intake ducting............if I use a 5mm wide, 2:1 elipse at my inlet, the throat size is 2,760mm squared. I can always play around with that if need be. the duct will be basically 2 feet long to the fan face and then about 8 inches from the fan to the exhaust. I don't have a lot of room to play with as far as angles and fan position are concerned, so the shape is the best compromise. my question is this............with the dimensions given, at what point in the duct should the area increase to the size of the inner dimension of the fan case? as mentioned before, I will be using twin WM400 MKII's for power. do I want to increase to that size as soon as possible in the duct, or leave it till the last possible second? again, I am completely open to suggestion, since I have no experience with this at all. thanks.

Rich
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Old Jan 12, 2010, 01:09 PM
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Regarding the duct, make any dimensional transitions as gradual as room allows. Abrupt expansion/contraction is never a good path where fluid dynamics are concerned.
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Old Jan 12, 2010, 01:41 PM
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United States, CA, Lodi
Joined Feb 2001
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This will be a really cool model. I love those videos where they plop them in on the highway.

I wouldn't be worried about the wing nearly as much as the inlets. They are really small compared to the size of the fuselage. If you get that part working well and that crazy landing gear, the rest will be easy!

Steve C
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