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DERIVATIVE, New 2X2

Old 08-08-2013, 08:32 AM
  #201  
MTK
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Originally Posted by MTK
I've got16 flights on Delta this far. Primarily set-up flights, getting Delta tuned. Still have a little ways to go but it's flying very well. This model makes melook good even with almost no practice

With the built in reduced throttle, it is easier to manage the awsome power of the 55. But even with it detuned I find I seldom need more than half throttle. The sound it makes is really cool...akin to aHonda motorcyclerather than an Harley.I'll try to taskBobbyto take video this weekend at the PokeURnose contest.
Rather than making another Delta, I decided to install the OS33 in place of the DLE55. The big block is just beating the hell out of the airframe and I would rather enjoy Delta's flying character than hang it up as an experiment. The 55 is better suited to an all wood airframe or a bit more heavily built airframe. I have a Giant Kaos in mind for the DLE....about 1600 squares and 95" wing span, 92" length, and around 15 pounds...

BTW- has anyone had problems with Horizon's service this summer? I've got Delta's 12X transmitter in for repair going on 4 weeks and nothing. I know they have it; the lady that answered the phone told me it was received in early July.

Last edited by MTK; 08-08-2013 at 08:35 AM.
Old 08-25-2013, 04:53 PM
  #202  
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Retro fit complete. The 33 fit easily of course. Did some more work on the soft mount reducing vibes to the airframe, although the 33 was okay before.

I had estimated about a pound of weight loss. Actual was 13 ounces. So delta weighs 10# 3 ounces, very sporty....hope to re maiden later this week.
Old 09-23-2013, 12:16 PM
  #203  
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Well, with 3/4 of a pound removed from the nose and changing nothing else, the plane flies tail heavy...DUH!! In retrospect, there is very little weight to move that will shift CG enough to matter. Here's where the Electric folk have a huge advantage where they can shift the battery BRICK just a couple inches and make a difference

Hate the thought of putting dead weight back into the nose of the thing. BUT, I just might do that temporarily to keep the crate flying and breaking the OS in. I also hate to hack into the fuse and move the wing tube. I decided not to do that.

In order to remove the weight from the nose I have a newly designed wing in mind that will buy me 1 1/2 inches in CG location (aft location from its current location that is). This direction makes lots more sense than slicing and dicing the fuselage.

Of course when another fuse is molded at some point all this becomes moot
Old 10-01-2013, 02:15 PM
  #204  
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Originally Posted by MTK
Photos of the gear details
Hi Matt,
I wonder if you could detail, briefly even, the lay up for these struts - cloth weight/quantity ,core materials etc.
Weight per strut only - if you have it.
I will have to make a set for my new model - a little shorter than normal as they will be placed very low down.
I really like your approach with these.

Brian
Old 10-02-2013, 08:58 AM
  #205  
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Originally Posted by serious power
Hi Matt,
I wonder if you could detail, briefly even, the lay up for these struts - cloth weight/quantity ,core materials etc.
Weight per strut only - if you have it.
I will have to make a set for my new model - a little shorter than normal as they will be placed very low down.
I really like your approach with these.

Brian
Brian,

I use clam shell molds for all of my landing gear and propeller lay-ups. I slightly overstuff the mold to make certain of 100% coverage, unless I am making hollow cores. Overstuffing is simpler and heavier of course

Lay-up is as follows:

First off, 2 layers each side of a strut (8 pieces total) 3K carbon cloth, typically plain weave, BIAS CUT. What I do is first put the two layers of cloth together and wet the cloth with epoxy between layers of plastic wrap. I roll the assembly with a small roller to distribute the epoxy evenly and remove excess. The cloth becomes easy to manage and cut exactly to the shape I want prior to placing it in the mold. Plastic wrap is easy to remove

Then a predetermined amount of full length carbon rovings, 3k also (because I have it handy, but other heavier grades will work just as well, but use less plies) wetted and rolled between layers of plastic, same way as the cloth, is made and laid down over the cloth. Then I build thickness with shorter rovings with special attention at the strut to fuse knee and the strut to wheel axle knuckle.

Then I add carbon fill in the middle of the clamshell

The clam shells are aligned and bolted together. Any excess epoxy squeezes out and the carbon fill will if I overstuffed too much.

Hollow gear legs are a whole nother type of construction, similar but different, that I won't go into.

The struts I show on Delta (Derivative) weigh between 44 and 45 grams each. Pants weigh 12-14 grams (2 3/4" wheel) and aluminum axle about 4 grams. The wheel pants already have all the hard points installed, nuts and ferrules installed, and carbon cloth reinforcements installed in the mold, fully aligned in the mold. Fully painted and RTF each complete gear without wheel weighs around 2.4 ounces.

The mount in the fuse is really simple. It starts by building a 1/64" ply box around the fuse knee, using each gear leg as the male mold. Then on I add 2 1/32" birch ply layers over the box, while it is still mounted onto the gear leg. This assures a perfect fit when installed in the fuse. Then I wrap the box with carbon roving 20 times with 3K roving and epoxy, and let that cure. Needless to say, the gear leg must be waxed and PVA'd lest you want a stuck together assy. I have also use teflon tape before as release with good results. The assembly of both struts, fuse mounting boxes and mounting pins is done on the bench first to fit everything. Once I'm satisfied, holes are cut in the fuse and the ply-carbon boxes are installed, with the gear in place to assure alignment.

The landing gear area in the fuse has 3K cloth applied first of course, with a doubler layer in the immediate area of each hole cut out. The doubler overlaps about 1" all around. Total weight in the fuse is about 1 ounce but this could be reduced a bit and depends on the area covered.

Good luck with it and hope that clarifies the essential points
Old 10-02-2013, 10:21 AM
  #206  
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Still watching...thanks for the updates.
Old 10-02-2013, 11:01 AM
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Hi Matt,
Thanks.
Your weights are good and it looks strong - yet flexible.
Just one or two questions ;
What do you mean by 'carbon fill' ?
Is that some wood at the root ?

Brian

Last edited by serious power; 10-02-2013 at 04:26 PM.
Old 10-02-2013, 05:44 PM
  #208  
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Originally Posted by serious power
Hi Matt,
Thanks.
Your weights are good and it looks strong - yet flexible.
Just one or two questions ;
What do you mean by 'carbon fill' ?
Is that some wood at the root ?

Brian
Brian,

Carbon fill is chopped carbon cloth, roving, whatever is too small to be used whole. I cut it about 1/8-1/4" lengths and mix it with epoxy to a thin peanut butter consistency. This mix is the fill. Some people will use glass here and that works okay too.

The mounting boxes or sockets if you will that house and support the struts at the fuse are made of a/c birch plywood. Once that's done, the sockets are wrapped with carbon roving to about 45K-60K filaments and allowed to cure. Then the sockets are fitted into the fuse holes with gear in place and pinned down to assure perfect fit, and epoxied with more carbon fill all around. The sockets are trimmed flush and painted to match the fuse.
Old 10-03-2013, 03:08 AM
  #209  
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Hi Matt,
I wasn't very clear re the wood - sorry.
See the pic ;
Old 10-03-2013, 06:40 AM
  #210  
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Originally Posted by serious power
Hi Matt,
I wasn't very clear re the wood - sorry.
See the pic ;
I understand.....Photos don't always do justice.

Your arrow is pointing directly at the strut's tang. The idea is to have a long enough tang to reach the opposite fuse side. The tangs of both struts slide past one another, interlocking. But the main load is still carried by each mounting socket through which each tang is slid. A snug fit between each strut and each mounting socket is of prime importance to assure rattle free performance over time. This is the key advantage over the Wist Model method, on which my technique is based. There is no other mounting hardware required to secure each strut; just the friction between strut and socket......

Each tang is pinned on the opposite fuse side. The easiest pins to use are 4-40 or 2mm bolts secured into blind nuts. I've tried just pieces of music wire before and it was iffy. Each mounting socket has room inside to accommodate each tang tip. The pin goes through each tip locking each strut laterally so they can't move side to side. The sockets on the other hand lock each strut so they can't move neither up or down nor to the rear. Sockets carry and transfer landing and t/o loads to the reinforced fuse side.

We'll continue until it is clear..... Once you do one this way, you'll know and immediately appreciate the logic of the Wist Model engineer that devised it. It's brilliant solution, exceedingly light, simple to actually make and is self aligning once the epoxy has cured. And no screwy screws (other than the pin which carries no load) to ruin your day
Old 10-03-2013, 08:06 AM
  #211  
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Matt,
Ok , I'm getting there.
I see how it all works - clever !!
So is there a wood core in the tang ?
It looks like you removed the carbon on the compression side.

Brian
Old 10-03-2013, 08:49 AM
  #212  
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Originally Posted by serious power
Matt,
Ok , I'm getting there.
I see how it all works - clever !!
So is there a wood core in the tang ?
It looks like you removed the carbon on the compression side.

Brian
Brian, tangs are made from carbon rovings at present. But nothing sez we couldn't place a strip of 2mm balsa in there. Just got to make sure that there is enough roving surrounding the balsa to keep flex low. Tang thickness is about 3.5 mm in my current mold.
Old 10-03-2013, 10:20 AM
  #213  
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Matt,
Thanks.

Brian
Old 06-26-2014, 05:21 PM
  #214  
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Originally Posted by MTK
Well, with 3/4 of a pound removed from the nose and changing nothing else, the plane flies tail heavy...DUH!! In retrospect, there is very little weight to move that will shift CG enough to matter. Here's where the Electric folk have a huge advantage where they can shift the battery BRICK just a couple inches and make a difference

Hate the thought of putting dead weight back into the nose of the thing. BUT, I just might do that temporarily to keep the crate flying and breaking the OS in. I also hate to hack into the fuse and move the wing tube. I decided not to do that.

In order to remove the weight from the nose I have a newly designed wing in mind that will buy me 1 1/2 inches in CG location (aft location from its current location that is). This direction makes lots more sense than slicing and dicing the fuselage.

Of course when another fuse is molded at some point all this becomes moot
Decided to move the wing tube instead. It turned out to be straight forward But that is not without its drawbacks. Reducing the tail moment by even a small amount (1" in this case) could compromise yaw damp.

Plane flies well enough but it's a bit on the average side now. It also displays a rather strange behavior of pulling to canopy immediately following a half roll in an up vertical line. That's indicative of not enough downthrust or enough +wing incidence and +stab incidence. Trimming continues now that I have finally gotten full use of my hands again.
Old 06-26-2014, 06:03 PM
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Interesting stuff Matt, the pull to canopy only occurs on vertical up lines?
Old 06-28-2014, 04:32 AM
  #216  
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Originally Posted by RonMcCormick
Interesting stuff Matt, the pull to canopy only occurs on vertical up lines?
Ron, actually the power on up line is fine. The issue (slight) is felt imediately following the half roll. My vectors are slightly off in the new configuration with wing 1" further aft. I'll work it back, But I wanted to capture the actions such that others might benefit.

It's obvious to me that the first model set-up with the DLE55 and forward wing position, albeit much heavier than now, was a much much better flying airplane. About as close to the best model I have ever flown as I have experienced. Dave Lockhart's Bravo a few years ago was another really memorable plane.

Soooooo, I will be rebuilding a new, lighter stab as a pull-pull set-up, removing the twin servos from the tail and removing about 4 ounces overall from thetail too. That should allow me to bring the wing back to it's forward location. That will mean a longer tail with it's groovier, more directionally stable character. And at just an ounce or two over 10 pounds, it will fly even better than before.

Rather than foan cores I decided to use the foam as a template in Bob Hunt's lost foam technique.
Old 06-28-2014, 07:38 PM
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Gotcha, thought I missed something. Have a link to Bob Hunts lost foam technique?
Old 06-28-2014, 09:10 PM
  #218  
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Originally Posted by RonMcCormick
Gotcha, thought I missed something. Have a link to Bob Hunts lost foam technique?
The technique is straight forward. Bob has described it on his Stunt column in MA a few times. It builds up from balsa spars and ribs. I was visiting with Bob recently and he suggested I try it his way, so I will and see for myself.

The sequence is as follows:
First, you need a foam core and husks. Heavier density than the typical wing core will work better as tooling material. 3lb density foam would be much better and last longer
Then you determine rib spacing and cut the foam core into pieces chordwise only with that spacing in mind. In new stab, spacing is 1.625".
Then you use the core sections as rib outlines
You will need to cut two sets of ribs of course
Work in as many lightening holes as you can muster in the ribs
Then lay the bottom sheet in the lower husk and start laying in the ribs. The foam sections are laid in accordingly holding ups and spacing the balsa ribs until the glue dries
The foam is then removed, and any additional reinforcements, sockets, elevator hard points, etc., are laid in
Then the top sheet is installed and top husk is laid over the top of the assembly.

When dry cut elevators (ailerons etc) and face them. Or it might be easier to lay down carbon veil or Japanese tissue over the semi complete surface, then cut

Bob tends to mold his LE and it's simple thing to actually do, if you have an accurate foam core. Molded LE saves weight and is more accurate than carving a balsa stick. I've been molding LE's of control surfaces for example, for a long time.....

I will take some snaps of the process as I go through it. It is labor intensive and isn't for those that want instant gratification of course but the weight savings are significant.
Old 06-29-2014, 05:57 PM
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Very interesting, looking forward to photos.
Thanks Matt
Old 06-30-2014, 02:55 AM
  #220  
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Looking forward to more info and photos of this Matt.
Old 06-30-2014, 05:43 AM
  #221  
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I have several sets of foam stab cores that were CNC cut years ago from 1/2 lbs density foam I had sourced. I sent the foam to the cutter and he proceeded to cut incredible cores....extremely accurate with a fully radiused LE. The core itself weighs only 11 grams, however, the ribs (10 ribs on each stab half) weigh less.

Molding the LE around the foam was straight forward...just spritzed 1/16" sheet with Windex and formed it around the LE with tape. Then held it there with the husks until dry. The LE's are as accurate as the foam core is. The final fitting is done on the stab half.

Bob does his differently: he cuts a block of foam into the shape he wants using only LE templates. He releaves the mold of the sheeting thickness. He wets the balsa and inserts it into the female cavity, following it up with the male piece. Then he squeezes the mold together pushing the male piece into the female and lets it dry. The point is that there are a few ways to mold a wing or stab LE. The two I discussed are a good start.
Old 06-30-2014, 10:30 PM
  #222  
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Hello Matt

Difficult for me to understand everything that is written!
Is what you mean? see photos of geoffroy plane named Graviton.
Claude

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Old 07-01-2014, 06:50 AM
  #223  
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Originally Posted by papaone
Hello Matt

Difficult for me to understand everything that is written!
Is what you mean? see photos of geoffroy plane named Graviton.
Claude

Hi Claude,

No that isn't the technique, BUT what you show in the photos will work. Many many years ago, Hal DeBolt described this same method in his "Solution" build plans. I built the Solution (a 60 sized pattern model) using Hal's wing crutch method (that your photos show) around 1977 or 1978.

Bob Hunt's Lost Foam technique is different and it doesn't use foam ribs; balsa ribs that are hollowed out are just as light but stronger, stiffer. Both techniques can build an accurate surface

Having built the individual crutches under each rib back then, I remember it was a lot of work. It seems to me the Lost Foam method has been easier. There are several good sources for cutting foam cores using CNC cutters. In my opinion you will get a better, more accurate product if the LE was cut at the correct radius by the CNC cutter. Also, you will have to sacrifice one panel when using the Lost Foam technique, because you need to make the tooling needed. One shouldn't get emotional about cutting up a foam core and losing 30$. Done right and from denser foam, the tooling will last several stab or wing builds so the lost money is miniscule in the long run......

The end result will be lighter that a foam-balsa composite but will be strong enough for the job.

BTW- Bob showed me his latest Stunt model and I wish I had taken a photo to show all of you. Made from molded balsa, an outstanding build. It is a large model for Stunt at around 60 inches of span, with two electric motors driving. The completed model fully covered in carbon veil and ready for primer,(with no equipment), weighed in at about 26 ounces. That is extremely light and with the carbon skin, strong enough for Stunt!
Old 07-01-2014, 08:19 AM
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Hi Gang,
I just tagged up with bob hunt, and if you email a request to him at [email protected] he wills end you 2 or 3 emails with large, production quality PDFs of the entire "manual" for the Lost Foam method.
Yes, Bob also sells compete fixtures and fully built wings/tails. Oh yes, and Matt is not exaggerating when he says it's spectacularly nice and light work.
Regards,
Dean Pappas

Last edited by Dean Pappas; 07-01-2014 at 08:22 AM.
Old 07-01-2014, 10:16 AM
  #225  
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Hello Matt

Thanks for the informations.
I'm fond of building technique. So I found this notices :
http://www.aeromaniacs.com/pdf/Bob%2...ing%20Wing.pdf
http://www.modelaircraft.org/files/1049G-Fast.pdf
Claude

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