HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Oct 25, 2014, 12:06 PM
Registered User
United States, CT, Oxford
Joined Jan 2009
235 Posts
Build Log
DCU/Jetmart F-14 Twin Jetfan 90 build

Have had the same projects on the bench for far too long now, and was tried to looking at them. So it's time to look at something different! Pictures are a few weeks old, so I'll post a bunch of pictures to get up to date

Not in a hurry to get this done, want to savor the build F-14 has been a long time dream, the new SM just aren't an option for all of us. Costs more to build than my truck, and no place around here to fly it! The smaller size, and electric power is a little more realistic

Detail in the glasswork is awesome! What an awesome kit, but oh how I wish it was 1/9th scale instead of 1/10.

Jumped around as I just wanted to get the gear in, will let the pictures do the talking
70 ragtop is offline Find More Posts by 70 ragtop
Reply With Quote
Sign up now
to remove ads between posts
Old Oct 25, 2014, 12:34 PM
Registered User
United States, CT, Oxford
Joined Jan 2009
235 Posts
The instructions refer to the plans, which I don't have. Like most every Jet fan in the 90's, I had a set of MAN plans, and a set form Hobby Barn. Sold the Hobby Barn set long ago, but still have the MAN set. While you don't really need them, kinda nice to actually pull them out for reference
70 ragtop is offline Find More Posts by 70 ragtop
Reply With Quote
Old Oct 25, 2014, 12:44 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
5,988 Posts
I also have set of plans from M.A.N. Actually cut out all the formers years ago, foolishly thinking I could do it as prop job!! How dumb I was then!

I'll keep an eye on this project.
CoolerByTheLake is offline Find More Posts by CoolerByTheLake
Reply With Quote
Old Oct 25, 2014, 12:55 PM
Registered User
United States, CT, Oxford
Joined Jan 2009
235 Posts
One thing I'm not happy about is the pivot mount for the horizontals.

Looking for some input on this one

The whole plane fly's on the tail, no control surfaces in the wings. Large surfaces, high torque servos. That said, look how the instructions have you gluing pivot tube into stab.

Cut a slot in bottom skin to accommodate tube, position tube and fill with epoxy and microballons. Repair balsa skin you cut out, and add kelar on outside of balsa.

Will it work, I guess. I would much rather have carbon fiber between the foam and skins, and have the pivot tube in a hard balsa block to spread the load into the skins a little better.

The root end of the stab is a large balsa piece. While I don't want to drill a hole in the tube, I would like a cross bar glued in between the stab and balsa block. Think that would spread the twisting load a lot better. Thinking of brazing a metal strip to the tube, which would then be exopied in place between the core and root end balsa, in addition to stock cross rod.

Thinking of cutting slot thru both skins for a hard balsa block. Pivot rod in that block. Carbon fiber on both sides tieing block to skins

Thoughts??
70 ragtop is offline Find More Posts by 70 ragtop
Reply With Quote
Old Oct 25, 2014, 01:06 PM
Registered User
United States, CT, Oxford
Joined Jan 2009
235 Posts
Reality sets in
Kit has been sitting in the box for years. Over the years, I feel sure it was taken out and admired, then put back in the box. Well, it wasn't sitting quit straight, and the packing material on top has taken it's toll

During the build, once you have the wing angles set, the kit used the retracts and inlets to lock it all together. The inlets get glassed to the fuse and then to the wing box, tying everything together. My opinion, this setup relies on the fans being stuck in the ducts to add some rigidity to the inlets.

I went back and started checking things like I should have in the first place. The wing box is tipped to the left, with a slight twist. The weight of the packing materials has pushed the top down over time, so the hatch won't fit.

Not the end of the world, just need to do a little work. Add to this the fact the fans are smaller than the inlets, so they won't be there to add any rigidity to the inlets.
70 ragtop is offline Find More Posts by 70 ragtop
Reply With Quote
Old Oct 25, 2014, 01:36 PM
Registered User
United States, CT, Oxford
Joined Jan 2009
235 Posts
Also noticed with the wing box locked down, the back of the fuse flexs a lot when you simulate roll load at the stab pivots. This is obviously due to the fact there is minimal formers, and the fact the large section over the fans is removable. With all the FEJ flutter/flex issues, this just screams FIX ME!

This with the items I metioned above, has me thinking a combo of light weight formers, and some CF, to stiffen it up, and lock it all togehter. If the hatch has enough alignment pins, that should actually stiffen it up quite a bit. Toying with the idea of modding the hatch so the center section is fixed in place, with hinged sides, like the Yellow F-14s did it. Would give it a spine down the middle on the top side, but would be right where I would want to put one set of batteries

I did some materials experimenting when I was repairing my P-38, and found a layer of carbon on both sides of a piece of 1/4" foam board was unbelievably strong, and very light. I only used dollar tree foam, so it wasn't strong enough for use as the core crushed, but it was very impressive nevertheless

Just ordered up some Depron, and plan to do some more experimenting. I'm thinking a combo of lite ply, depron, and carbon skinned depron formers should be plenty the stiffen it up, without adding toooo much weight

Plane with flying surfaces and gear already weighs 10# Add servos, wing swing mechanism, actually building it, glass, paint, fans, ESCs, and 7# of batteries, will be real lucky to get it in the 23-25 range

Having the same argument with my self Jetfan 90s, or 120S?? Right now, just want to keep the weight down as much as possible so it's the 90s
70 ragtop is offline Find More Posts by 70 ragtop
Last edited by 70 ragtop; Oct 25, 2014 at 01:48 PM.
Reply With Quote
Old Oct 25, 2014, 04:47 PM
A-4 nut!!
skyhawk's Avatar
Vancouver B.C.
Joined Apr 2002
4,665 Posts
This plane is an absolutely beautiful model - and it has preformed very well as designed.

I think going to 90mm fans is a huge mistake.They are going to be way to small, and if you did get it to fly (Big if in my mind) - it would take a ton of power and only get so-so performance.

Go with the Electric dynamax conversions as they would be a drop in fit, or some sort of 120mm fans (evf's or similar) but you would still have to mod the ducting.

A lot of engineering and time went into the design of this model and for the most part it was good. The plane also had good performance on the OS91's. (I believe the turbine versions were coming in at just over 30 lbs! and still preforming well. I would not worry about the weight too much)
skyhawk is offline Find More Posts by skyhawk
Last edited by skyhawk; Oct 25, 2014 at 05:01 PM.
Reply With Quote
Old Oct 25, 2014, 04:50 PM
A-4 nut!!
skyhawk's Avatar
Vancouver B.C.
Joined Apr 2002
4,665 Posts
While the aft fuse is not horrible like the FEJ plane - it could use a little stiffening up.

Go to this webpage - it's got good info of the construction and what he found after 33 flights (on the maintenance page) and the fixes he came up with.
http://www.hawaiijets.com/aircraft/f14/f14-df.htm

BTW - Did you just recently buy this from Ontario?
skyhawk is offline Find More Posts by skyhawk
Reply With Quote
Old Oct 25, 2014, 06:38 PM
Pursuit of Happiness
Ron101's Avatar
Brentwood, California
Joined Jul 2007
7,272 Posts
cool project! I vote for bigger fans too
jetfan 120's, Tam jets Dynamax conversions, vasa 120, Stu Max 110's

Tams making some big planes fly on 90's but I still like the biggest fan you have the FSA for
Ron101 is offline Find More Posts by Ron101
Reply With Quote
Old Oct 25, 2014, 07:08 PM
Registered User
United States, CT, Oxford
Joined Jan 2009
235 Posts
Quote:
Originally Posted by skyhawk View Post
While the aft fuse is not horrible like the FEJ plane - it could use a little stiffening up.

Go to this webpage - it's got good info of the construction and what he found after 33 flights (on the maintenance page) and the fixes he came up with.
http://www.hawaiijets.com/aircraft/f14/f14-df.htm

BTW - Did you just recently buy this from Ontario?

I did, about a month or two ago

Studied that website forwards and backwards!

Did you build one of these? Always looking to learn from what other experienced!
70 ragtop is offline Find More Posts by 70 ragtop
Last edited by 70 ragtop; Oct 25, 2014 at 07:21 PM.
Reply With Quote
Old Oct 25, 2014, 07:19 PM
Registered User
United States, CT, Oxford
Joined Jan 2009
235 Posts
Quote:
Originally Posted by Ron101 View Post
cool project! I vote for bigger fans too
jetfan 120's, Tam jets Dynamax conversions, vasa 120, Stu Max 110's

Tams making some big planes fly on 90's but I still like the biggest fan you have the FSA for
That's the catch, it doesn't have the FSA on the inlets for a 5" fan. I wrote numbers downstairs, and I think it was around 13 sq in on the front part of the duct. I'll add correct numbers later, but check out how small the front looks compared to the back where it opens up for the Dynamax's.

Not saying I'm not thinking 120s, because I am. You really don't think a pair of 90's pushing 10-11 lbs each with crazy Eflux won't push this thing right along? It still looks draggy, but nothing like the Phantom. If it behaves with the wings back, might actually be pretty slippery
70 ragtop is offline Find More Posts by 70 ragtop
Reply With Quote
Old Oct 25, 2014, 08:00 PM
A-4 nut!!
skyhawk's Avatar
Vancouver B.C.
Joined Apr 2002
4,665 Posts
Quote:
You really don't think a pair of 90's pushing 10-11 lbs each with crazy Eflux won't push this thing right along?
No.
Its not just the efflux - but you need the volume as well. There is only a certain amount you can reduce - and personally, I think it's got a little out of hand. It's fine for the old designs that crammed the biggest fan in the smallest airframe (like some of the Yellow or JHH kits) as when they were designed 30 or so years ago - the technology was very limited (.65 engines and really low thrust) You needed the big fan just to get enough to taxi around. Nowadays the (nitro) planes are better designed.

As I said before - smaller fans could do it - but at a certain point you need to dump soo much power into the fan to get it to do anything - it's more efficient to use a larger fan with less power.

If - in theory, you could get 10 lbs thrust out of say - a 65mm fan - would you do it? No - because you wouldn't be moving enough volume to push you through the sky.

10 lbs from 65mm is not the same as 10 lbs from 127mm.
skyhawk is offline Find More Posts by skyhawk
Reply With Quote
Old Oct 25, 2014, 08:02 PM
A-4 nut!!
skyhawk's Avatar
Vancouver B.C.
Joined Apr 2002
4,665 Posts
Quote:
That's the catch, it doesn't have the FSA on the inlets for a 5" fan.
Maybe not perfect - but this plane has been time tested to work very well on the dynamax/OS91. Even single engine performance was not really that bad.
skyhawk is offline Find More Posts by skyhawk
Reply With Quote
Old Oct 25, 2014, 09:49 PM
Registered User
JetMang's Avatar
San Diego, California, United States
Joined Feb 2002
2,515 Posts
Ragtop,

Lucky you to have this kit! We have an f-14 thats the same size (was built for the movie top gun, never kitted) and I think twin high power 90's are about perfect for the airframe size. I plan to build one some day and plan to power with twin 12s 90 setups. Just my 2 cents. 90s will be lighter and get better flight times for the same capacity packs compared to 120s. It's only about 74" long at 1/10 scale. at 1/9 scale I could see 120s making more sense. The key will be though having clean inlet ducting obviously and ensuring the structural rigidity.


Chris
JetMang is offline Find More Posts by JetMang
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Sold DCU/Jetmart Black Bunny F-14 "VX-4" VF-142 built by Ronnie York" owner of DCU/Jetmart ShockWave Aircraft - Electric - Jets (FS/W) 8 Aug 26, 2014 10:09 PM
For Sale DCU/Jetmart Black Bunny F-14 "VX-4" VF-142 built by Ronnie York" owner of DCU/Jetmart ShockWave Aircraft - Fuel - Jets (FS/W) 3 Aug 02, 2014 04:49 AM
Sold DCU f-14 little joe Aircraft - Fuel - Jets (FS/W) 0 Jun 15, 2014 01:05 PM
For Sale DCU Jetmart F-14 bigfrank330 Aircraft - Electric - Jets (FS/W) 12 Oct 29, 2012 05:31 PM
For Sale Jetmart DCU F-14 NTIMID8R Aircraft - Fuel - Jets (FS/W) 6 Jan 04, 2012 12:26 AM