2008 Max Men, F1A line and Impluse Hook

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    Following is a reply to Dave Edmonson about the recent Maxmen contest. JIM

    Dave– this was M&K’s first extensive use of spectra line. yes the smaller size for more speed but they like the stiffer line for use with the impulse hook. I’ve been using Finn spectra 130lb with 30 foot of Russian rod for some time– switched to the stiffer Russian leader when I started my relatch hook development. This weekend I used for the first time the spectra with 30 foot of 300 lb Dacron covered spectra line (kite leader). This was Dalls’ (my son) prefered set-up. I saw no significant difference.

    I went to M&K impulse training class– I had initial success but ran into no-hook release problems so I flew conventional models at MM. So on Saturday I went to training camp– M&K also made some impulse hook adjustments to reduce the line pull at 80degree from 7 kg to 6 kg. Interesting enough, Andrew Barron and I measured the force at 90 degrees to be 22 kg. Sergey says the 80 degree is more realistic. So as I had more non-releases, the harder I ran and pulled but the less the hook released. Knowing that the jr flyer, Oliver Cia is able to release the impulse hook, it finally occurred to me the problem was I was not that I was not pulling hard enough or running fast enough but rather I was NOT releasing the line at the bottom of the pull down. For years the pull down and quick hand up and release of the line has worked for the standard hook– for the impulse, it is required to get a clean release at the bottom of the pull. Sergey mentioned he had flights were the line rubbed past his body after release causing a non-release.

    Andrew also suggested a user defined safety open timed window that will make the release less critical. M&K will be making this change shortly. Last night I went to M&K technician training— they provided the cable and training for me to re-program the M&K timer, so in the future, I’ll be able to help the USA flyers. Jim Farmer also got his M&K model going last weekend with the lastest program load solving his problem.

    So after 3 clean releases I had to leave for the banquet prep. The next day I was flying F1H getting a new model trimmed and tuckered out and so fly did not fly an impulse model on Sunday. I hope to do some testing here in the week few weeks to verify my mastery of the impulse launch– more to come.



    I am interested in this “window” that Andrew suggested. I am planning to ask him at our weekly build meet tomorrow but it is supposed to snow soon. (too sudden a change from enjoying Lost Hills weather).

    I went through a very similar experience of non-releases, except it took a bit longer due to a zoom-rudder setting. I happen to like a towing style where I fully bring the model around and launch straight up. When I was flying with Andrew’s settings, the model kept going right and I had no idea what was going on. I went through countless launches where the model veered, and RDT. I tried pulling harder but that ended up with a broken towline (using 80lb spectra). The only way to release was when the model ended up way off to the right and I had no choice but to let go of the line at high tension. I did realize at that point how to release the model.

    It was at the Southwest FAI Challenge in Las Vegas where Jim showed me there was a zoom rudder setting straight in the MTK program. It was looking at me the whole time! After that, I had no trouble launching.

    At Patterson, I had an interesting incident where a tiny stick was wrapped around the middle of my towline which I couldn’t reach. In the middle of my acceleration for launch, the line happened to cut through the stick, making the towline longer by a small amount. However, this caused a sudden tiny change in line tension. This immediately caused the internal safety latch to relatch. There was no way for me to release the model as the model was already above 45 degrees and I didn’t have enough distance to repeat the acceleration phase to unlatch the safety latch. I did not realize this at the time of launch and went off with the line still attached.

    From these experiences, I am assuming that the hook is very sensitive at the line tension at which the safety-latch unlatches. I am not sure if the time the safety-latch stays unlatched can be user adjustable but I’m looking forward to future updates.




    This is an interesting discussion although I’m not used to all the terms you are using. I want to ask Jim why he has moved away from the relatchable hook he was using at the MM last year ? I have started using this type of hook, ie traditional tensioned hook with servo latch and feel that it works well. Having seen and read descriptions of the inertia hooks in circulation they to me just seem too complicated for any benefits they might give. For example, any hook that is not connected directly to the rudder must used a non-proportional or timed zoomed function which requires a lot of practice. Any comments ?

    Of course Oliver thrashed me at the MM so perhaps I should change although the thermal doesn’t know you are using interia hooks !



    My current view on the relatching hook vs impluse hook:

    The swing (pivoting) latch was problematic– servo force could be overcome in a model heading down wind condition. The Lindberger / Stamov “Stupid Hook” (up-down latch pin) does not have this problem. Pierre Brun solved our swing hook problem with a small knotch at the top of the swing latch that engages the circle adjustment screw to prevent this un-intentional towring release.

    So why change to impluse hook?
    1. I determined that I had roughly dropped as many maxes due to the relatch hook (granted most before the open latch solution) has I have saved with a relatch hook. These drops / problem were 99% in strong wind /thermal conditions.
    2. My factory sponsors “bribbed me with a loaner fuselage / stab at the Ukrainian WC last summer.

    3. The answer is in my “head space” while towing. I’ve concluded that for a calm model, the relatch hook is good, to be able to go around again to get the “perfect launch” when thermal selection- awarness is not critical. I still have and use my reltach hook in an extra long and long early round models.
    Where I got in touble is going around again in wind/ strong thermal conditions. For me, the time from deciding to abort and go around, keeping the hook forward for the relauch (1-3 seconds depending of setting) least the model bunts– the model is moving very fast usualy to the right and before I know it I’m looking at the stab raising above the wing as I sprint like a mad man down wind. It took several of these to figure out the servo was being overloaded and the tow ring was slipping off.
    Similar, while towing a relatch, when I hit a gust, I have to ask– Did that open the hook? and so to be safe have to keep the hook forward- not a big deal but it does de-focus the decision making.

    4. So with the impluse hook, you can pull as hard as you want without thinking about unlatching. Even with my low tow time with impluse hook, I find when I’m is trouble, I can pull hard to speed out of the way of less skilled sportsmen who dare come into my space and even in the classic left to right model down wind race, I can pull hard, get zoom rudder to come in to turn the corner.

    5. Down side? Watching your model thermal upward with the line is a real bummer– really hurts the flying focus. So for me, unless I get to the 6 sigma confidence level for unlatching at launch, my final decision is still open.


    Peter Brocks


    How does the M&K impulse hook work? Is there a picture or sketch how it functions?

    Thanks, Peter



    Thanks for that explaination; I see your points. I use the Vasy hook which can’t be overloaded and has the advantage (in my opinion) that you don’t need a rudder servo. As yet I haven’t tried this hook in the wind (and its not as if we haven’t had any here since LH, struth !) so I’ll find out about the problems soon enough. I tend to agree that the use in calm conditions is probably more sensible but with a timed gust filter that will soon be in the BMT (EoB idea) then some of the premature unlatch possibilites in the wind may be sorted.

    I guess its horses for courses with each method having some good points. I’m due to write a paper for the BMFA FF Forum so any further thoughts would be welcome.

    Sponsors ! What are they ?



    In preparing for the SCAT annual, I made a new line of 150 lb spectra with a 30 foot 1/8 dacron leader but instead of a loop I used a 1 inch dia wood ball from a craft store. I put two opposing flats on the ball so it would fit in the reel.

    The idea was to have a physical feel difference to help develop the habit of releasing the line at the bottom of the pull down.

    This worked well thru test and 6 rounds. Only one non-release in practice but that was with an intentional “soft” pull to see were the low end of the pull envelop was.

    I was flying high thru 6 rounds, flew both the short and long model. 7th round is pain full– nice conditions but dark clouds on the horizon. Rene and I went down wind– several model in a large piece of air and I got out of control and tangled Rene– we raced down wind and untangled but by that time the thermalling models were high and both Rene and I let this piece go and headed back up wind. I tested a piece of air that Rene let go, seemed to be good so decided to launch– did not get the pull I was getting in these conditions and the model did not release but then it did not climb- in fact it sank and I easliy recovered the line. Renes’ good judgement paid off and the air developed- he launched and looked good but I was too far away to get it. Now the clouds are closing in the breeze is picking up. I feel what I think is firm air, decide to go, started the pull a bit early, the model stayed to the left, I double pumbed the launch trying to get it around—as soon as I did release the wood ball I knew it was a non-release. The breeze took it so I had to RDT it for an attempt. It started to rain and Peter Allnut came to povide a VW Bus protection and ride. The hard DT broke the aft bunt arm. My 2nd attempt with a standard short model ended up in the ground– have not gotten a zero in some time– humbling sport.

    Final thought. I am greatly encouraged with the impluse models. The wood ball did much to develop a new release habit.

    I did determine the out of control on the impluse model was due to being over declaged in the straight tow position– OK for calmer conditions but leads to tip fall off in turbulence / wind.



    Forgot– Rene won the next morning 10 minute FO with over 7 min. Graet Launch, firm air beautiful glide. JIM


    I have made great progress with the impluse hook– flew the last contest with three different impluse models and had no “non-releases”. Had only one in practice but knew it when I released. The small wood ball instead of the classic loop has provide the tactal habit re-formation— release at the end of the pull and not “throughing the loop up” as I had done for 30 years. Stay out of the way of the ball- it is moving fast at release.

    Still flying with the orginal M&K set up– that is I have not gotten the software change that will put a small delay from high load activation time to the stab up / hook saftey release time.

    I am still looking forward to the time delay software. I understand it will be ready for testing in a a couple of weeks. I’m thinking only .1 to .2 sec is all thats needed to provide more margin in turbulant conditions or stumble that could result in a reduction in tension causing the saftey to re-arm resulting in a non-release of the towring.

    I have repeated a differnt towing situation with the impluse models. Towing the model over head and up wind in lift– the model will continue to pull up wind into the ground! Very strange in deed. I have not sat down yet to draw it up, but I think it has to do with different rack angle of the two hook designs. I have learned to react– just like a down wind thermal situation– have to run toward the model and tug the nose around. It’s happened several times so it was not a single freaky condition.

    Any other M&K impluse hook sportsman encountered this situation? I do believe I saw Sergie M. do this at the MaxMen this year but was not smart enough to recognize it and question him about it.

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