BVM F-4
 

I was wondering what is the best way to controll the gear. What are you guys using for the valve and how do you deal with the up assist cylinder?

Should I go with the stock set up or if there is a better way?

Thanks,

Chris

RE: BVM F-4
 

I suggest you don't change anything and go with what's recommended as it works every time you hit that gear switch.


Good Luck !!

RE: BVM F-4
 

I would add a caution to the above. I added a Clippard needle valve, two actually on for up one for down, with tiny non return valves to give total control over the nosleg retraction speed. This is vital to avoid an out of sequence situation as the air micro switch triggered by the noseleg closes ALL doors and this must not happen till the mainlegs are up and locked.

On my AirWorld Hawks I have added these needle vlaves to the JetTronics gear controllers to give total speed control of the gear operation, magic !

Regards, David Gladwin.

RE: BVM F-4
 

Or as an alternative, you can use a gear/door sequencer. I was having a problem with the doors interfering with the gear during retraction (since the doors are not held open with positve pressure with the air micro switch method). I use the Mini Hobby unit in conjunction with a second air valve to hold the doors open and with plenty of delay to allow all three gear to retract prior to the doors closing. It's a little more hardware but it simplifies the sequence setup and virtually eliminates the aggravating "partial/jammed retract" issue during flight.

Craig

RE: BVM F-4
 

I am a new BVM F-4 owner......I have mine set up like Craig has described, and as I have done on my other planes in the past......I use Tom Cook's JMP sequencer with (2) JMP Valves, using JR 351 servos to drive them.....takes up minimal real estate on one of the component boards just in front of the junction of the right and left limbs of the inlets.....

I use the longer, 5 second sequencer delay on the doors, programmed simply with dip switches in the JMP unit......system works perfectly every time, as it has on many of my sport planes in the past.....

As far as the up assist cylinder, I just have mine T'd into the main cylinder line.....

I have added a single Robart restrictor to each of the gear door closing lines to prevent them from slamming shut.......

RE: BVM F-4
 

Thanks guys. I never used electronic sequencers before, think I'll give it a go. Interesting thread on 2.4 W/sequencers as I'm going to be a convert when my 12X arrives...

Tom, I thought I read in an old RCJI about the up assist jamming the unlock on the mains and some sort of fix with another valve. I'm sure not keen on this if it's not nessesary.

Chris

RE: BVM F-4
 

David, Where can I order the Clippard valves you speak of?

Thanks,

Chris

RE: BVM F-4
 

I used the Jet Tronic gear door sequencer and the BVM Hi-Flow valves on the 3 BVM F-4s I have owned with no problems. I had a small problem on my first BV Phantom several years ago when the Jet Tronic timer wasnt set long enough. It was an easy fix. I use wheel collars to restrict the air in the up/down motion.

RE: BVM F-4
 

Chris:

My air lines, one for up gear and one for down gear come off the retract valve in the usual way.......

The up-gear line enters the wing root, goes into a T with one limb going to the single up-gear port on the up-assist cylinder and the other goes to the up-gear port on the main cylinder....

There is no down-gear port on the up assist, so no connection there....

The down-gear line comes off the main cylinder, going back to the other port on the retract valve......

The only other lines are up/down for the inner doors and the brakes.....

I don't use any restrictors on the gear lines, only on the door-close lines.....the weight/inertia of the gear in the F-4 keeps them from really slamming up or down......

I use the Clippard valve setup with the nose strut controlling the gear doors on my Kingcat nose gear door.....but with that system as BV diagrams it, if you want to be sure the door stays open in the slipstream on a F-4 or F-100, it is best to use a separate tank, pressurized to about 40 PSI for the door-open line......then when you command gear up, the full pressure of say 100 PSI on the door-close side will overpower the 40 PSI and allow the door to shut.....

Sounds a bit complicated and it is......additionally, with that setup, you have to slow the gear valve servo way down......It's the system BV has been using since back in the Maverick days at least.......it is simple in the sense that it only requires the 1 gear retract valve and a Clippard valve.....

IMO, much easier to go with one of the sequencers on the market, along with the two valves.....they are not expensive and they do the job.....I have used both JetCat and JMP......It would be nice if a UP-2 or UP-3 would work that I had on my Bandit.....I tried, but never could get enough air to move and get the timing of the doors right on the Phantom......I do use the UP-6 brake valve on my Phantom.....

RE: BVM F-4
 

I have used two old robart valves, two servos and the Jomar sequencer for years on my F-4. The up assit cylinders will prevent the mains from unlocking unless you use some kind of restrictor. BV recommended using a wheel collar a hundred years ago when I built mine and that has worked perfectly for me. One note on the F-4 if one of your mains gets hung up on the gear door and it will happen from time to time you will notice the trim change. It's a great airplane.

David Reid

RE: BVM F-4
 

I got all my Clippard stuff from the UK dealer but Clippard have dealers world wide. All their parts are on their excellent site at www.clippard.com and they have all the pneumatic parts we could desire, prices very reasonable, inc air line.

The flow control needle valve is MNV1 and the check valve MCV1

I used the system EXACTLY as per BVM but with the addition of thie regulated nosegear and after the first flight the nose travel speed (up and down) was set, it is affected by air loads, and the gear operated flawlessly ever after.

The needle valves allow VERY precise control of travel speeds and as well as the F4 nose I use them to control the gear and speedbrake travel speeds on my big AW Hawks, again with excellent results and they just screw into the Jettronics valves on the exhaust side.

Strange you guys should raise the F4 this weekend , I have just finished repairing mine after some flameout damage (fail -safe finger trouble, the Pagasus HPES is flawless) like the real thing, it didnt glide too well with zero thrust and almost full tanks ! Engine running tho it is a fabulous machine !

Being modelled on the F4J I have installed a scale slotted tailplane, looks great and has no affect on handling.

Regards, David.

PS Food for thought. Perhaps BVM could do with the F4 what they did with the F86, enlarge it by about 25 % for Olympus or JC 200 or even twin power to compete with machines such as those from Air World and Skygate and even C-ARF with the Mig 29 and A4 . With its really excellent scale profile, superb ground handling and quite docile flight characteristics (being basically a delta it has no nasty tendencies if you get the speed low). Could be the BVM flagship and with so many F4s having seen service around the world it would have very real appeal and probably be very succesful commercially for BVM. How about it Bob ?

RE: BVM F-4
 

Thanks very much for all the input, it's very much appreciated. A real wealth of field experience here. I will have more questions. One that comes to mind right now is the CG. Do I plan my install on being tail heavy? Also the CG itself I see has been moved to 12 3/4. Is this optimum or can it be moved further back?

DavidR, Those wheel collers and grub screws may seem crude as restrictors but once set up they sure are reliable. My Aggressor only gets about three flights a year but the retracts are always flawless.

Patrick, What size Dan Gill chute do you use? 14 or 16 inch?

David G, The slotted stab is that cut into or added on to the leading edge? Mine will be a AF C model, perhaps without? I have not got any documentation yet and have still not settled on the subject yet.

Here's where I'm at:

RE: BVM F-4
 

I did mis-speak again.....I do have a couple of Robart restrictors in the retract lines in addition to the door-closing lines......

RE: BVM F-4
 

Chris,

12 3/4 is optimum and should not be difficult to achieve with batteries (or a little extra lead) in the nose. Oddly, this is one airplane that does not fly as well with even a slightly forward CG. I suppose you could experiment with moving it aft a little, but I would suggest going with what is proven.

Just a reminder, the 12 3/4 is along the leading edge, not straight back along the wing root.

Craig

RE: BVM F-4
 

Chris

It looks like you have done an excellent job on your phantom. I just finished re-plumbing mine with two high flow BVM valves and the jet-tronic gear sequencer from Jet Cat USA. BVM rep Ad Clark came up with the idea and it works great. What paint scheme are you going to do?

Justin Sands
BVM rep

RE: BVM F-4
 

Justin

I started off with a showtime 100 scheme then I dont know what happened but now I'm into an AF cammo scheme...that could all change though!
I did commit to the nose fairing (showtime 100 has none) and sprayed some green paint before adding the diverters.... wont keep me from going Navy....??

RE: BVM F-4
 

Chris,

The Chutes are approximately 20" in diameter and you can purchase them from Dan Gill (Details4Scale), Justin Sands or Phil Nuza. I have bought chutes from all three guys and all are nice!

Where did you get your chute spring?

Also................if you are interested in the extendable nose strut I can get you the guy's number out of New York that makes them. They are sweet!

RE: BVM F-4
 

Patrick, My kit is an early DF version and it came with all the parts for the chute including the spring.

Yes I would be interested in the nose strut. If it's available, definitly a must have!

Thanks, Chris

RE: BVM F-4
 

David, great job with the stabs.
They look awesome .... and a lot of work !!!


Jack

PS: Hope BV read your wishes regarding a big F-4...... I need one too. LOL.

RE: BVM F-4
 

Since we are on the F-4 subject, let me ask you guys a question:

I am building a new one to replace my Supersonic Eagle.
I have to transport the plane back and forth from the field disassembled (no wings), since it doesn´t fit in my car otherwise.
To make the process of installing the wings easier, I am considering to hinge the bottom access panels and have them opening as doors.
Hinges will go on the inner side. Also, the panels could be held closed with a couple or three little magnets.
I think the hinges should be offset type.

What do you think? Have somebody done it?

Any help and suggestion would be appreciated.

Jack

RE: BVM F-4
 

Hey Jack
I have not heard of anyone doing it that way but could you mount them like the belly pan on a bandit is mounted. Poly ply tabs front and back with a couple poly screws?
I understand the reason for speed of removal but I would be afraid they would blow or get sucked open with magnets.
What squadron are you doing?
I think a larger F4 would also be great, but this bird is one heck of a hot rod.
We have three under construction.

RE: BVM F-4
 

Hi Kelly:
I am repeating the scheme of my old F-4.
This is a picture of her last flight a couple of years ago.

Jack