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Author Topic: TLGs... are DTs an absolute must?  (Read 1690 times)
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Jimmy JFlyer
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« on: February 22, 2017, 10:19:30 PM »

Hello folks,
After getting my start in RC DLGs I now have a hankering to try my hand at building a balsa TLG. I am not really wanting to get overly technical and would rather not do one with a DT. But is that a bad idea? Sounds like that answer is yes from what I have seen and read so far. I haven't yet found a TLG plan w/o one and have seen a lot of posts mentioning any good flying TLG will be a goner. I guess my real question is whether or not there is a beginner style simple TLG that is more for fun than serious air time?
Now I am really just a bit intimidated about DT's as I don't really know much about them and really just want to toss a good enough TLG for some fun. I suppose if they are that simple I would build a TLG with one. I just only have balsa and am on a serious budget so spending much on materials is not an option. Of course unless the stuff nec for a DT is silly cheap. I am actually saving the pennies for an rc scratch built foamy DLG so was hoping to just grab some balsa and build something I can toss while wtg for saving up for the DLG's electronics.

Any help/advice will be greatly appreciated.

Regards,
Jimmy
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NormF
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« Reply #1 on: February 23, 2017, 03:21:13 AM »

A good introduction to FF tip launch is Stan Buddenbohm's Easy 24. No DT, simple, basic design. You can purchase the kit and/or plan. Buying the kit is a lesson in proper wood selection, very important for a successful build. Stan's catalog is here: https://www.amaglider.com/static/sciolympia/stan-stuff-2014.pdf

Later, when you have invested in a prime piece of glider wing stock, carbon fuselage and a lot of work, you will want a DT! Stan can help you there also. He does hold the world record in that event!
Norm
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Yak 52
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« Reply #2 on: February 23, 2017, 06:38:10 AM »

Hi Jimmy,

You certainly don't need a d/t to fly FF hand launch but you will almost certainly lose a model one day - just when you have it nicely trimmed Cheesy If its a low investment model then that may not be a problem. You will need a bigger field than you'd use for RC models though, unless it's flat calm.

Making a simple model won't cost you much but a good one uses careful wood selection, a carbon boom and a suitable varnish for finishing. Ideally you need low density quarter grain wood (work out what you've got?) Fishing rod booms can be quite good these days but depends on having a source (I get broken sections from the local tackle shop which can be surprisingly good.)

The actual d/t timers can be a simple viscous damper and some fishing pole elastic - not that expensive in the greater scheme of things. However to engineer the model to d/t (usually break back style now) takes a few bits and pieces, some light ply, a few fittings and probably some epoxy.

Have a look at some of the plans here:
http://www.discuskid.com/tlg-plans.html

And a build here: http://peterboroughmfc.org/membersmodels2014/06-DLG-MickPage.htm

I would also say - don't get too bogged down in the detail. A simple model made with the wood/boom you have and no d/t will still be fun and a learning process. Just build to the basic outlines and angles of these plans and make some effort sanding a good airfoil. The more refined models may be of interest down the line.

You may also enjoy catapult gliders - a simple one is serious fun for the time and money involved.


Jon (slowmatch on RCG)

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dephela
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« Reply #3 on: February 23, 2017, 06:42:33 AM »

There is another advantage to having a DT on a TLG other than the obvious one. Trimming will no doubt take time, many launches and of course provide much fun through the life of the plane. Without a DT there are opportunities in the early trimming phase to damage or destroy the plane, a DT can be set to deploy early enough to prevent this. During subsequent trimming flights the retrieval time can be seriously reduced by using short DT's, the walking distance is reduced, trim flights can even be made while travelling across the length of the field!

Two last reasons and maybe the best, you can enjoy tossing your plane without fear of losing it while just enjoying its flights or, opportunities are endless for learning to pick the right air and the right time to toss!

DEnnis
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Dennis
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« Reply #4 on: February 23, 2017, 07:29:33 AM »

Back when competitive FF DLG's (TLG stands for towline glider, and I will never use that term in reference to a hand launched model) were a relatively new thing, Carl Dowdy showed up at a Raeford contest with a beautifully built 36" model with no DT because "it's just an experiment to see if it will work". I seem to remember it going OOS on the third flight.

Besides, there's no reason not to use a DT if you order Stan's fuselages. They're pricey, but everything is ready to go, and it sure beats what you pay for an R/C DLG fuselage these days ($120-150).
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USch
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« Reply #5 on: February 23, 2017, 10:17:45 AM »

If you are tight in the moment you can always build a fuse and sniffer tube DT. The fuse can be home-made (dont remember right now the how's), so the only cost is a rubber band  Smiley
The sniffer tube will be in the same place other's have a timer.

Better than nothing,

Urs
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Starduster
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« Reply #6 on: February 23, 2017, 11:48:40 AM »

Really, there's a simple question you have to ask yourself when it comes to DT vs. no DT:

Am I going to be unhappy if the airplane is lost?

If the answer is yes, put a DT on it.

I've built every one of my HLG's with no DT. But I'm not very good at building or flying HLG's
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« Reply #7 on: February 23, 2017, 12:52:30 PM »

OK I am gonna be the idiot who has to ask a dumb question and Josh and I went around on this a while back. We get a lot of brush fires here in central Florida especially in the dry windy season. Has anyone ever heard of a DT starting a fire? I know the idea of the snuffer tube, and the fuse should be snuffed out by the time the plane hits the brush, but what if?
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Starduster
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« Reply #8 on: February 23, 2017, 01:07:07 PM »

OK I am gonna be the idiot who has to ask a dumb question and Josh and I went around on this a while back. We get a lot of brush fires here in central Florida especially in the dry windy season. Has anyone ever heard of a DT starting a fire? I know the idea of the snuffer tube, and the fuse should be snuffed out by the time the plane hits the brush, but what if?

I've never actually heard of it happening, but I believe that Fuse DT's are illegal in CA for that very reason.

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danberry
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« Reply #9 on: February 23, 2017, 02:24:28 PM »

OK I am gonna be the idiot who has to ask a dumb question and Josh and I went around on this a while back. We get a lot of brush fires here in central Florida especially in the dry windy season. Has anyone ever heard of a DT starting a fire? I know the idea of the snuffer tube, and the fuse should be snuffed out by the time the plane hits the brush, but what if?

Nope
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« Reply #10 on: February 23, 2017, 02:57:48 PM »

OK I am gonna be the idiot who has to ask a dumb question and Josh and I went around on this a while back. We get a lot of brush fires here in central Florida especially in the dry windy season. Has anyone ever heard of a DT starting a fire? I know the idea of the snuffer tube, and the fuse should be snuffed out by the time the plane hits the brush, but what if?

Crabby, I can't remember if I ever mentioned this to you, but a prominent flier ripped me a new one many years ago for using fuse DT's to save money. He made it very clear in public over the years after that my existence was slightly less offensive than raw sewage for refusing to stop using fuses. Setting that aside, he insisted that fires have been started by fuses and that at least one club had lost its field over this issue. Given the discussion here, I'd be very interested to see this fact checked. Do we have any answers on it?

I've actually been trying to get away from fuses (though the cost of a good DT still puts me off) for tactical reasons. Having to light a fuse definitely is a hindrance at times, especially with the amount of demo flying I do these days.
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USch
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« Reply #11 on: February 23, 2017, 03:49:20 PM »

Has anyone ever heard of a DT starting a fire?

Never heard of a fire and I can assure you that in summer it gets really hot and dry over here, very similar to Florida.
BUT
we, as modellers, discourage the use of fuses because of the above reasons.
Officially we are to few to be noticed by the law and there is no control whatsoever.
Another cheap idee, somewhere on HPA is a description how to build a silly putty timer from scratch, a few leftover pieces of aluminium tube, one gram of silly putty and half an hour of work and you have a non burning DT timer.

Urs
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« Reply #12 on: February 23, 2017, 04:14:44 PM »

I believe the Detroit Cloudbusters lost access to the Ford Test Track in the 70s or 80s due to a fire started during modeling activities.  However, I think it was NOT a fuse, but a rocket motor - or even a car that started the fire.  This can be verified/corrected, if someone wants to really know.

I do use fuses as they have given me the least hassle and seem to be the most reliable.  However, I would like to switch to viscous timers.  I will be experimenting with viscous timers with a spring pull this year.  Mechanical seem to be more reliable than viscous, but even the lightest are 3 grams or so.

Back to the thread - Starduster hit the nail on the head.  DTs are NOT absolutely necessary, but you risk losing your model without one.  I have lost models WITH DTs, but every time it is because I CHOSE NOT TO activate the DT.  Sometimes, merely building a DT into the model is enough to ensure it never flies away - either by fate or by making the plane too heavy.  We have a joke - if you don't put on a DT, the model will fly away; if you do, it will never come close to needing the DT.  (Maybe we just don't build good enough!)

--george
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Crabby
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« Reply #13 on: February 23, 2017, 04:57:07 PM »

I have a silly putty DT but I never got around to building something that needed it. Can anybody vouch for the reliability of the silly putty timers? I guess I am gonna do a bench test for the "H" of it. Josh I don't think St. Peter has the DT users on his check off list. You may want to call the Vatican on that though and let me know right away... I am nearing my P-30 period.
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« Reply #14 on: February 23, 2017, 05:12:28 PM »

I have a silly putty DT but I never got around to building something that needed it. Can anybody vouch for the reliability of the silly putty timers?

Crabby, I built one to Tmat's design a while back but I could never get it to work - maybe the putty was the wrong type (hard to source silly putty here in the UK) I was put on to the tiny viscous dampers by PeeTee and have never looked back since - much easier for me anyway and the small ones are very light. I'll dig out the part number or pop one in the post for you if you're interested.

Jon
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dephela
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« Reply #15 on: February 23, 2017, 05:21:17 PM »

I use homemade silly putty DT's in all my DLG's and cat's. I still have all my planes so I guess the timers have never failed!

Dennis
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Dennis
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« Reply #16 on: February 23, 2017, 05:34:01 PM »

Getting back to your question... NormF's recommendation to use Stans' kits is the way to go, but you can also get smaller catapult/HLG kits from Retro RC. Assuming you want something easy to build from limited materials, if these kits are too pricey then try either Pit's Krazy Katz W in the plans gallery or if you can source 2mm or 3mm cf tube try Tmat's Scaredee Cat 12" design. These size models are quick to make, have no dt and will get you into the arcane art of sanding aerofoil sections in balsa. They will also start the process of learning to trim a free flight model glider and that will help with any RC dlg models you build in the future. You may also, like me, never get further than clg as they are so much fun.

There is a huge amount of knowledge on this site about building and flying dlg, clg and hlg but it is better to get something into the air, no matter how short the flight, because only after trying the options does all the expertise offered begin to make sense. I'd recommend that you have a read of the build logs for the two gliders mentioned. Good Luck.

Ian
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« Reply #17 on: February 23, 2017, 06:37:12 PM »

OK I am gonna be the idiot who has to ask a dumb question and Josh and I went around on this a while back. We get a lot of brush fires here in central Florida especially in the dry windy season. Has anyone ever heard of a DT starting a fire? I know the idea of the snuffer tube, and the fuse should be snuffed out by the time the plane hits the brush, but what if?

Crabby, I can't remember if I ever mentioned this to you, but a prominent flier ripped me a new one many years ago for using fuse DT's to save money. He made it very clear in public over the years after that my existence was slightly less offensive than raw sewage for refusing to stop using fuses. Setting that aside, he insisted that fires have been started by fuses and that at least one club had lost its field over this issue. Given the discussion here, I'd be very interested to see this fact checked. Do we have any answers on it?

I've actually been trying to get away from fuses (though the cost of a good DT still puts me off) for tactical reasons. Having to light a fuse definitely is a hindrance at times, especially with the amount of demo flying I do these days.

I call absolute BS on the fire started by DT fuse issue-it's one of those rural myths I guess. I have 50 years of FF experience-and still use them-though not exclusively-and over the decades i've fought tooth and nail against various well meaning but ill informed individuals who have tried to get them banned. When you really starting digging-no one can produce concrete, verifiable evidence of it occurring-its always "well I heard of an incident'..."I heard that..."... "such and such a club had a fire" etc etc. I've deliberately tried to start grass fires (under closely monitored test conditions) with DT fuse on dry grass-it simply doesn't work-you get a bit of charring thats all.  My standard of proof for DT fuse starting a fire is as follows: a model with lit DT fuse on board is seen to land-and a fire is observed to break out in the exact same spot within 15-20 minutes.   Direct cause and effect-nothing less...If you can't meet that standard of proof then I suggest your claims simply are not credible.  Now I can easily accept fires caused by cigarette butts, spilt fuel, hot motor bike/car exhausts [I've seen both of the latter first hand-some here may remember the big grass fire at Lost Hills during the 93 World Champs]-etc etc-but you're really testing credulity when you blame DT fuse.

  Now NZ is not California...and it definitely is not Australia-where DT fuse is absolutely banned-and even in NZ it gets hot enough and dry enough for local government to institute total fire bans in various regions at various times over the summer-and I have no issue with these-and if one is in place then you can't use DT fuse-I've even as CD imposed such a ban myself at the WC events in Omarama when due to the hot dry NWers the local area fire risk was much higher than normal-but for most situations DT fuse is a useful option in the appropriate class of model-and all DT fuse models should be fitted with snuffer tubes (compulsory under NZ rules!)-and I can state with absolute certainty that I've lost less models through DT fuse failure than from DT timer failure over the past 50 years.

 ChrisM
 'ffkiwi'
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NormF
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« Reply #18 on: February 23, 2017, 06:52:42 PM »

I don't know of any Calif fields that ban fuse DT, nor fires started from fuses. We have had field fires from cars parked over tall grass and lately, carbon models dropping onto and shorting power lines. I think first freeflights should not have DT's so the beginner experiences the awe of an out of sight flight, then the realization you lost your plane!

Norm
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« Reply #19 on: February 23, 2017, 06:53:33 PM »

Effective October 28, 2011

SEC. 96.1.305.5. ROCKETS, MODEL AIRCRAFT AND SIMILAR DEVICES.
 
 Section 305.5 is added to the California Fire Code to read:
 
 Sec. 305.5 Rockets, model aircraft and similar devices. Rockets, model airplanes,
gliders and balloons powered with an engine, propellant or other feature liable to start or
cause a fire shall not be projected into or across hazardous fire areas without prior
approval of the fire code official. 
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« Reply #20 on: February 23, 2017, 07:16:37 PM »

Here are a few random thoughts on DTs. I am not sure they are on point.

I mostly fly in California and I have never flown with a fuse DT.  I have used viscous timers, mechanical times and electronic timers in my DTs. Each has advantages and disadvantages.

Apart from the fire issue, and the legal issue in California, I have wondered about the weight of a fuse in the tail end of the model where it is most frequently mounted, next to the stab.  That's the precise location where I don't want extra weight.  On top of that, most of the fuse burns away, and most of its weight disappears.  Can't this change the CG? Thus it would seem to me that if you put in 180 seconds of fuse into a snuffer at the end of the fuselage of an airplane trimmed to fly with a 90 second fuse, won't some aspect of the flight performance be adversely affected?  I guess the weight of the fuse doesn't matter on big OTR models like Miss Canada Sr. but it seems to me that it would make a difference on a MAXOUT X Embryo, for example.  So then you have to mount the fuse near the CG on smaller models. 

A friend of mine said his wife would no longer accompany him to contests after she lit his model on fire.

Good models can be lost to thermals even after their DTs have activated.  For example, I had a wonderfully trimmed Pathfinder CLG from Stan Budenbohm.  Its DT definitely activated after it got a max. The tail feathers were cocked at almost 90 degrees and the model was flopping around, like a fish out of water, and still going up, as I viewed it through binoculars.  It was never to be seen again.

An effective combination that ups the odds of retrieval is a DT plus an on-board RF tracker.  I like to use both.  I am not so much concerned about the cost of the model. A P-30 can be built for less than $30 worth of parts and materials. I am more concerned with the loss of investment in the time it takes to build a model and get it well-trimmed.  Also, the best flying models are the ones most likely to be lost without a DT.

I have seen Stan use an RDT on his HLG.  After a nice tip launch, and a beautiful transition, he pushes a button to bring his model down in a short amount of time, rather than wait for what would be a very long glide (almost always the case with Stan's gliders).



 
   
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applehoney
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« Reply #21 on: February 23, 2017, 08:06:02 PM »

>  seems to me that it would make a difference on a MAXOUT X Embryo, for example.

Good observations, Cal.  

I've  used (and still use) fuse d/t's for some 70 years on models of all sizes, from Embryo 'up'  -   have never noticed a trim change at any time when using longer fuses for fly-off's, etc.

The only d/t system that gets lighter in operation....   Grin
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« Reply #22 on: February 23, 2017, 08:16:50 PM »

>the Ford Test Track

I flew several times in the Ford track in the 80's .. interesting place, especially if  model went into the trees that were immediately outside the banked curve.     I heard that the facility was lost to outsiders when an individual drove his car around the track on some occasion ( not necessarily model-related) and rolled it down the banking.    True or not?  No idea.
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Jimmy JFlyer
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« Reply #23 on: February 23, 2017, 10:35:45 PM »

wooo hooo what a discussion!  Grin
Thanks everyone for chiming in. I have to admit I have learned a lot from this thread about DTs that's for sure. And thanks for the links. I particularly enjoyed going through "Stan's Stuff". $38.00 for a shipped Easy 24 kit is seriously tempting but unfortunately the pinching the pennies thing wins out. May just get a plan though and take a shot at picking the right wood. I do have various thickness, weight and grain balsa I got from A2Z before they went poof. I might just have what is needed to do the Easy 24 without getting anything else.
Ahhh having to be a cheapo sux!  Roll Eyes

Hey Yak52... I mean Jon... I mean slowmatch... I didn't know you were... YOU. lol As soon as I can afford those batts w/charger and connectors I will get your CANDy DLG finished. Can NOT wait for that. That is what i am pinching for. But in the mean time I want to build and toss something as I just can't wait. I used to build scratch built foamies like mad until RL kicked in and had to step away for a while. So now the itch to build needs scratching and the itch to throw something does too.

Any recommendations on any of the known plans in the gallery that are similar to the Easy 24 in simplicity as a beginner TLG? Yes I know I might loose it if I go without a DT. I am thinking building, trimming & short flights will be good for now. I see Stan's Stuff doesn't incl viscous DTs. What is the preferred source for those? Might check LHS as they have a lot of FF items. I suppose I would use them if they are not to much.

Thanks again folks for your advice and help.

Regards,
Jimmy
« Last Edit: February 23, 2017, 10:47:25 PM by Jimmy JFlyer » Logged
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« Reply #24 on: February 23, 2017, 11:57:35 PM »

FAI Supply and Volare products both have the viscous timers.

If you fly these things during a time that thermals are around..... they will thermal.
The Dyno Mite is a good start.
These planes are easily r 60 -90 seconds without a thermal. A DT can help you even if thermal acivty hasn't arrived.
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