"Buck style" bellcrank failed after 300 flights

[Brett Buck]

Has anybody notified Tom?

  I am going to try to contact him tonight, probably. If there is an issue with a particular batch, he might be able to track it down. It's not like these things are made in the thousands.

   Brett

[Paul Walker]

  I am going to try to contact him tonight, probably. If there is an issue with a particular batch, he might be able to track it down. It's not like these things are made in the thousands.

   Brett

Yup, they should be rated FC1.  Serialized and traced!  He should know what mine they were dug from, and the exact alloy and temper.

 

[frank williams]

Is that the up line or the down line?  Its a little unusual to have the pushrod off the bottom of the bellcrank.  Is (was) the flap horn pointing down or up?

[Paul Pomposo]

Would someone be willing to bench check one of these bellcranks as is and see how many pounds it takes to get this to delaminate and buckle like it did here. This will be a concern for all of us.

[jim gilmore]

Looking at the buckeling I wonder if the actual buckling was caused on impact and the actual cause of the crash was maybe just the glue joints shearing. And the major bending resulted during the impact ?

[Howard Rush]

Several planes, 1000s of flights, no failures. One of mine has 4000 flights over 5 years. I often fly in 15 mph wind, like today.
Will continue to use as is from Tom Morris.

Would someone be willing to bench check one of these bellcranks as is and see how many pounds it takes to get this to delaminate and buckle like it did here.

You both seem to assume that they are all the same.  That may not be something one would want to assume.

[Mike Haverly]

I've been using this system for the last ten years on many airplanes and never had one fail.  I make my own per Brett.  I bought one from CLC that was manufactured by aforementioned vendor and tossed it out because of low quality.  The lead outs were crimped instead of wrapped, as advertised and the hole was off center in the bushing.  The bushing was also too short.  At first I was going to just change the lead out cable to what I wanted and install a new bushing but the whole assemble began to separate.  This is not a bash on the vendor, there are plenty of satisfied customers with no issues.  Instead I just made a new bellcrank.

Just sayin.

Best to check fabrication against design specs.  Maybe I just spent to much time in manufacturing.

Really sorry to hear about your loss Chris.

[Chris Cox]

Hi Chris

Really sorry to hear about your loss.  It certainly was a good flying airplane.

I use Brett's bellcrank's in my model's as well, but built to Brett's specificifations and using high grade aircraft aluminum. One of my bellcrank's was the victim of an "incident" in an aircraft with 100 flights on it.  That bellcrank now resides in last year's model with near 600 flights, and still going strong.  I can not imagine it failing, but hey, crap sometimes happens.

I can understand why you do not wish to use this type of bellcrank again, so rather than trying to talk you into something you are not comfortable with, thought I would suggest using the bellcrank system I believe Paul Walker is still using.  Paul uses the old Windy nylon (Delrin?) 4"  bellcrank.  Paul slots the ends for the leadout loops and uses a 4-40 bolt with a nyloc nut, same as you did on your failed bellcrank.  I used the same setup for many years with no issues. I could send you a picture if my less than stellar description isn't working for you.

I'll look forward to seeing you at the Nat's again next year with a shiny new airplane.

Chris

[frank williams]

I still wonder if this isn't an artifact of the crash.  Chris, was this indeed the "up" line?  Coming downhill in the hourglass, the controls are neutral, pulling from a neutral position, so we are saying that the "Netzeband wall" (hinge moment) is what did this? We're talking about a 12 to 15 lb. pull, 20 at most. I'm not convinced that this was the failure.

[Steve Fitton]

Clearly it should not have failed and Frank makes some excellent points.  I have trouble thinking it is impact damage when the photo shows the balsa core of the bellcrank is not smashed or caved in, only the tip of the balsa core is missing.
 If as Brett points out the materials were too soft, though, maybe it is possible it yielded at 1/10th the load of Brett's test article.

It would be interesting to come up with a way to test the remaining arm of the crash bellcrank and see what measurements could be obtained.

[Chris_Rud]

Hi Everyone,

Wow I never thought we would open an FAA investigation.

I have enjoyed reading everyones comments and possible causes of the failure. When I got home I took a few pictures of the crank. See below.

A few observations:

1. I have flown that plane a lot and it was my 7 flight that day and the 302 flight of its life. I document all flights on my phone. It was very clear to me that something failed in the inside turn of the hourglass. And no other parts of the control system had been damage.

2. The damage was caused inflight and not from impact. I know this since there is no scrape marks on the end of the crank, it was bent slightly toward the handle and as Steve pointed out the balsa was intact. (see photo)

3. The glue joint was faulty. There was no adhesion on one side and minimal adhesion on the other. (see picture)

The crash felt as though the plane started to turn and then stopped. I felt as the controls had locked up. My first thought was the leadout clips had stuck or something but I couldn't believe that after 300 flights with the leadouts in the exact same spot that this was the cause. When I looked at the bell crank I new that was the issue. At first I thought it was the up line and the buckling alone had been the culprit causing it not to complete the turn. But as some have pointed out it was not the up line. I know believe that the culprit is the fact that the buckling caused the bellcrank to go from being just over 1/8  think to 1 3/8 thick and the bell crank caught on something and stopped it from turning (the wing is only 2 inches thick on the outside.) Though I can't say exactly what it caught on (best guess is the epoxy hardened foam on the center joint) because there wasn't much left in the center section and I burned the wood parts after the crash...

In the end I think its safe to say its not the design of the crank and an issue with the construction of this one. Whether there are others like it I don't know...

-Chris

[Tim Wescott]

Wow I never thought we would open an FAA investigation.

Well, this is serious stuff!  I mean -- burning 777's in Los Vegas is just daily news, but a crashed stunt plane is important.

I just can't believe that's 6061-T6 aluminum.  AFAIK, 6061-T6 would have cracked at the tight bends, and that surface finish looks more like soft aluminum to me at any rate.

If you have some soft aluminum to compare it to please do so, or toss the thing in your flight kit and show it to Brett at the team trials (assuming that someone manages to push a satisfactory airplane into your hands).

[Ward Van Duzer]

Is there no one available that can test the hardness of that damaged aluminum? Certainly not me, but it shouldn't be such a big deal...


W.

[Tim Wescott]

Is there no one available that can test the hardness of that damaged aluminum? Certainly not me, but it shouldn't be such a big deal...

That's why I suggested Brett.  Anyone who's been around a few different alloys could do it, but I don't know who's close to Chris that has that experience.

If you can get it close to flat with your bare hands, that's a pretty good indication that it's soft, though.

[Mike Haverly]

That looks regrettably similar to one that I tossed out for poor quality.  Notice the inside of the laminated aluminum is shiny, not dull like it should be if it was prepared.

It may be 6061-T6.  It will usually bend sharply to 90 degrees once.  When straightened it will probably break or at least crack.  It may very well be some lesser heat treat.  70XX aluminum is stronger and probably way overkill and would probably have at least cracked before it bent that far.

Looks to me like bad surface prep and wrong adhesive.

I use a similar product to Brett's.

[Steve Helmick]

Surely, somebody has access to a Rockwell tester and maybe an Eddy Current tester? That would answer some questions, if not all.  Steve

[Mike Haverly]

Steve is right.  Most machine shops, even many small job shops would have a RC hardness tester. 

[Tim Wescott]

Can this Eddy guy tell the difference between two alloys of aluminum?  I guess there is some difference in resistivity between 6061 and 3003 (to pick two at random), but it's not a heck of a lot.

[John Leidle]

  I agree with Mr Bill Johnson,,,,  if I want the best Epoxy I'd use Hysol...  I think it's made by Weld Wood  believe it or not.  But I dout it was the epoxys fault.
    John

[Mike Anderson]

Can this Eddy guy tell the difference between two alloys of aluminum?  I guess there is some difference in resistivity between 6061 and 3003 (to pick two at random), but it's not a heck of a lot.

I think that's a little too subtle    ....   

[Jim Svitko]

Since I would like to make my own bell cranks I am very interested in finding out what happened here.  I do not want to repeat a mistake.

To me, a bellcrank can be viewed as a simply supported beam with a concentrated load at the center.  Bending stresses, etc. can then be calculated.

However, even if the stresses in a beam are below critical limits at a given load, a beam can go unstable laterally if a span is too long and unsupported or there is not enough material to resist the tendency to buckle laterally.  Could that be what happened here?

[John Leidle]

  I have to agree with Frank .

[Bill Johnson]

I have a Brinell hardness tester in my tool box specifically made for testing aluminum after heat treatment. If you want, I'll test it and send you the results. Too easy.

[Brett Buck]

I still wonder if this isn't an artifact of the crash.  Chris, was this indeed the "up" line?  Coming downhill in the hourglass, the controls are neutral, pulling from a neutral position, so we are saying that the "Netzeband wall" (hinge moment) is what did this? We're talking about a 12 to 15 lb. pull, 20 at most. I'm not convinced that this was the failure.

  I really don't dispute his analysis, plus, what to we think it might have hit in the crash to cause this kind of damage? If it didn't buckle in-flight, then you have to find something that rammed into it, end-on, hard enough to cause this damage. If nothing else you might expect a big dent in something else and the forked end of the bell crank flattened out from the impact.

   The only thing that suggests anything else is that the buckling was all the way across the arm. Mine failed by buckling (at very high loads compared to flight) but it left a "wedge" buckled up, as the inner edge (toward the load) buckled and the outer edge remained straight because it was in tension. I did the test at zero deflection, so the fore/aft component of force was essentially zero. Maybe with it deflected that was different.

   Brett

[Steve Helmick]

Can this Eddy guy tell the difference between two alloys of aluminum?  I guess there is some difference in resistivity between 6061 and 3003 (to pick two at random), but it's not a heck of a lot.

Eddy alone doesn't tell you the alloy or temper, but if you have Rc and Eddy tests, you can nail it. So there...  Steve

[frank williams]

Well, I hate to say this but, "Houston, we may have a problem".

I took a NIP bellcrank and applied just a little pressure between thumb and finger and  .... oops it de-laminated very easily.  The other three I have did also.

There also seemed, without too much wiggling, for the two aluminum sides to want to go in opposite directions.

In use I've always wrapped them with kevlar thread ....... I think I did them all.

[Steve Fitton]

Its hard to argue with an experiment like that!  Thank you for sacrificing some bellcranks to shed light on the problem.

[Howard Rush]

It has been said solid aluminum like Fox and Perfect are not strong enough, then how on earth can thinner aluminum and balsa  be stronger?  (that is adding the 2 thin sheets of aluminum do not add up to the thickness of a Fox or Perfect bellcrank)

https://en.wikipedia.org/wiki/Euler%E2%80%93Bernoulli_beam_theory

[Dennis Moritz]

Solid piece. Notched and bushed.


Sent from my iPhone using Tapatalk

[RC Storick]

After seeing Franks post I think if I were to make these 1/16 holes could be drilled every 1/4 inch before lamination and let the epoxy ooze out in the clamp state. That would fix this issue.

[frank williams]

I really didn't set out to sacrifice a bellcrank ....... just picked one up and gently applied a lateral load, one handed between thumb and forefinger.

I plan to redo these with 1/16 in holes along the edge , interlaced with kevlar line, and BVM epoxy. Everything else is good except for the de-lamination of skins.

[Mike Haverly]

After seeing Franks post I think if I were to make these 1/16 holes could be drilled every 1/4 inch before lamination and let the epoxy ooze out in the clamp state. That would fix this issue.

Sure, and be much heavier than need be.  Use the right materials and make like the designer intended.  Also a longer bushing to stop any rocking causing play in the controls.  Franks observation is exactly why I tossed mine in the garbage.

Again, just sayin.

[Chris Cox]

Very interesting and cool stuff Howard.  I'm surprised you didn't call and wake me at mid-nite last night to tell me about it!

Oh yeah, the contest is over....

😇

[Bill Morell]

Sure, and be much heavier than need be.  Use the right materials and make like the designer intended.  Also a longer bushing to stop any rocking causing play in the controls.  Franks observation is exactly why I tossed mine in the garbage.

Again, just sayin.

Why not just send them back to Tom? This is a manufactures defect and I wouldn't lose $ for something I didn't do.

[Brett Buck]

I don't understand all of this.  If it needs to be stronger, then why not make a bellcrank out of steel? 

    Most of the metal in the middle has no useful effect in terms of stiffness, but just adds weight.  The material on the outside gets more effective as you separate it further.

This makes me think of the guy that was collecting money to make perpetual motion machine all because he was a good salesman, not because the machine was even a possibility. 

   So now I am a scam artist and/or incompetent?  Or Tom Morris and I are *both* scheming to cause people's airplane to crash for some reason?  Even if there is a defect in the design, or in the manufacturing, it certainly wasn't intentional. I get exactly *zero* for this, and have provided the plans to whoever wanted them for free. Tom manufactures them and sells them but I am pretty sure it is not to get rich, and it is not intended to sabotage people. What motivation would I have to cause Chris's (or anyone else's) airplane to crash. Particularly since I use the prototype in my NATS-winning airplane for the last 10 years, and another one in my current project?

   Listen, I feel bad enough about this already, but I certainly am not attempting to trick, sabotage, or scam anyone, and I resent the suggestion.

    Brett

[CircuitFlyer]

I'm here to learn from the best of the best.  This has been a very interesting topic thus far.  I've learned:

1) If its damaged - replace it.  Any attempt at a repair is at your own risk (not the designers, the manufactures or the retailers)
2) An ideal installation would allow for inspection from time to time.  Maybe via an inspection hole or even a camera if required.
3) If possible, design an installation that allows for the bellcrank removal without major surgery.

Paul

[Randy Cuberly]

Brett, I apologize, I didn't intend for you to take it that way.   Honestly, I don't see how you can use balsa and not expect to separate.  I have seen many times on a rc plane where ply is laminated to balsa along the nose of the plane and when it separates, the balsa tears or pulls apart.  The glue is not the weak point. 

Anyway, my point in my comment was intended toward the thought that extreme lightness is not going to give extreme strength, like a machine that can run without an energy source.   I don't know, maybe the comment is out of order, sorry.

I have really stayed out of this up to this point because Brett is not only a friend but a highly respected engineer and and in my opinion has designed a very effective bellcrank intended to, as he stated, provide better connection for the leadouts.
The design is sound in my opinion but does require careful assembly and has a couple of very process sensitive items involved in the construction.  First end grain balsa is significantly stronger in shear and compression than normal grain wood.   The endgrain balsa also would provide a significantly stronger bond of the epoxy due to it's more porous and rougher surface.  This provides far more surface for the epoxy to bond to and at this thin section would probably become totally filled with epoxy making the section stronger.

Now to the real problematic part of this assembly process.  Brett mentioned that he applied epoxy to the aluminum surface and sanded it with the epoxy in place.  This provided a non-active surface for the epoxy to bond to by ommiting air that would allow the aluminum surface to oxidize giving a firm bond brtween the aluminum and the balsa.  In Aerospace applications only anodized or in some cases conversion coating such as alodine are specified for bonding aluminum surfaces.  My educated guess in this case after looking at the pictures is that no conversion coating was provided on the aluminum surfaces and being active surfaces they continued to oxidize during the curing process so the epoxy bonded to the oxide which provides a very weak bond.  It then delaminated, probably over a period of time and numerous stresses until the connection between the upper and lower aluminum sheets was non existent and the aluminum buckled under stress.

I also agree somewhat with what Chris said earlier that the buckling could have occurred over time untill it reached a point where the bellcrank snagged on something in the wing.   I further think that the first failure with the pushrod connection was an indication that the delamination had already occurred and was likely a factor in that failure due to movement between the top and bottom plates of the bellcrank.

In closing I believe that this failure was caused by poor process control of the bonding and not really a factor of the design.

Randy Cuberly

[Tim Wescott]

It has been said solid aluminum like Fox and Perfect are not strong enough, then how on earth can thinner aluminum and balsa  be stronger?  (that is adding the 2 thin sheets of aluminum do not add up to the thickness of a Fox or Perfect bellcrank)

If a beam that's strong on the outside and light on the inside can't be strong overall, then how on earth does nearly every bridge and skyscraper in the world stay up?  Not to mention every single full-size airplane and most flying models?

Please answer, because inquiring minds want to know.

[Randy Cuberly]

I don't understand all of this.  If it needs to be stronger, then why not make a bellcrank out of steel?  

This makes me think of the guy that was collecting money to make perpetual motion machine all because he was a good salesman, not because the machine was even a possibility.  

It has been said solid aluminum like Fox and Perfect are not strong enough, then how on earth can thinner aluminum and balsa  be stronger?  (that is adding the 2 thin sheets of aluminum do not add up to the thickness of a Fox or Perfect bellcrank)

Does the manufacturer of the aluminum / balsa bellcrank make good on things like this?  

Rusty,
To be as strong as the laminated bellcrank, a solid bellcrank of the same material would have to be nearly as thick as the laminated one and hence would be much heavier and would not provide the convienent slots at the ends for the line attachment spools without some precision machining.

Simply put the failure mode here is not simple tension but a combination of stresses of tension and bending.  The bending stresses cause compression on one side of the material and tension (or stretching) on the other side.  The farther apart the two sides are the less stress they actually see.  This of course does require the two sides to be firmly attached to each other.  Hence the bonded light material in the center which actually sees very small stresses except at the joining surfaces...in this case the bond between the aluminum and balsa.

The actual failure mode shown in the photos is "Buckleing" or "folding" of the material on the outside of the laminations caused by these combined stresses because the laminations were not joined by the bonding material.

You can google "beam stress" for a technical description of how the stresses are distributed...unfortunately it's got a lot of that nasty old math in the description.    But you can understand the principle if not the math!

Randy Cuberly
PS:  Fox Bellcranks were made from 2024 T4 Aluminum and were fairly strong.  The Perfect Bellcranks were made from 1100 Aluminum and were very weak.

[Paul Walker]

I really didn't set out to sacrifice a bellcrank ....... just picked one up and gently applied a lateral load, one handed between thumb and forefinger.

I plan to redo these with 1/16 in holes along the edge , interlaced with kevlar line, and BVM epoxy. Everything else is good except for the de-lamination of skins.

Frank,

I would HIGHLY recommend that you NOT put any holes in it. That will raise the net stress in the aluminum making the buckling lever lower, not counting the support of the wrap. Simply wrap it with kevlar "string" and cover with a small amount of epoxy.  This is a belt and suspenders approach to a good assembly, but if the interlaminar joint goes bad the kevlar takes over and does the job. As long as the edge doesn't budge, the center isn't going to buckle.

I had a plane with one of these bellcranks from Tom and I wrapped it in Kevlar and there were no issues......Until the bird hit it. Inside the wreckage, the bellcrank was just fine.

Please just wrap it with kevlar.

[PJ Rowland]

Did the kevlar help the bird?

Sorry to hear chris.

Weve ALL lost planes to control failure of some type.

[Brett Buck]

Now to the real problematic part of this assembly process.  Brett mentioned that he applied epoxy to the aluminum surface and sanded it with the epoxy in place.  This provided a non-active surface for the epoxy to bond to by ommiting air that would allow the aluminum surface to oxidize giving a firm bond brtween the aluminum and the balsa.  In Aerospace applications only anodized or in some cases conversion coating such as alodine are specified for bonding aluminum surfaces. 

   I used the process as described. I attempted to delaminate a test part and couldn't do it with my bare hand, and it bent the "fork" where it attached to the balsa. I did get it to come apart with a lot of effort using vice-grips.

    But again, I got it to about 80 lbs with *no balsa at all*, just the pivot and the three screws, before it buckled as described. So I would expect that debonding itself, alone, would cause the problem Chris had. That bent a Top flite into a "u" shape, and pulled about 1/4" each side on a Sig. I also tried to bend it out of plane as Frank describes and could get it to deflect a bit, but not come apart, with the amount of strength I have in my hands.

     There should be tremendous margin in the design, at least a factor of 10, so I am at a loss as to how it could give up so easily.

    Brett

[Randy Cuberly]

  I used the process as described. I attempted to delaminate a test part and couldn't do it with my bare hand, and it bent the "fork" where it attached to the balsa. I did get it to come apart with a lot of effort using vice-grips.

    But again, I got it to about 80 lbs with *no balsa at all*, just the pivot and the three screws, before it buckled as described. So I would expect that debonding itself, alone, would cause the problem Chris had. That bent a Top flite into a "u" shape, and pulled about 1/4" each side on a Sig. I also tried to bend it out of plane as Frank describes and could get it to deflect a bit, but not come apart, with the amount of strength I have in my hands.

     There should be tremendous margin in the design, at least a factor of 10, so I am at a loss as to how it could give up so easily.

    Brett

I would have to suspect that the aluminum material is not as specified (6061T6).  50series aluminum is only about half the tensile strength of that and common hardware store aluminum (1100series) is very soft and only about half of the 50 series (about 15,000psi if my memory serves...which it doesn't sometimes these days).

I'm relatively sure Tom would not knowlingly use any such material but aluminum looks like aluminum and mistakes can occur!

Randy Cuberly

[jim gilmore]

Is it possible that the the aluminum was something like 6061-o by mistake ? o means annealed which is soft.

[John Park]

This thread has opened my eyes to many things I didn't know about bonding aluminium with epoxy.  It just shows, you're never too old to learn something new.  Thanks to all.

[Tim Wescott]

Is it possible that the the aluminum was something like 6061-o by mistake ? o means annealed which is soft.

Possibly -- but an important part of that bellcrank design is the end-grain balsa, and that was done wrong, too.  It's certainly screamingly obvious to me that you can't substitute end-grain wood for balsa with the grain running the length of the crank.  By extension, if someone uses end grain in an application like that where it's obviously so much harder to implement than "board grain" (what is that called?) then clearly the glue joint matters -- and the glue came undone where even well applied hobby shop epoxy would have ripped the wood apart. 

IMHO whoever built Chris's bellcrank (back before 2015, remember this is an old old thread) just didn't understand the reasoning behind Brett's design, yet felt free to change things up.  If that's the case, there'd be very little chance that the changes would be good.

I'm going to reiterate here, since the thread's coming alive again -- in my opinion Brett's original design (strong aluminum, end-grain balsa, strong glue joints) is an excellent of example of mixed-media structural design.  I'm envious I didn't think of it.  Unfortunately, if you don't understand structures, it'll be easy to make something that looks the same but doesn't hold together well.

[Curare]

I would have to suspect that the aluminum material is not as specified (6061T6).  50series aluminum is only about half the tensile strength of that and common hardware store aluminum (1100series) is very soft and only about half of the 50 series (about 15,000psi if my memory serves...which it doesn't sometimes these days).

I'm relatively sure Tom would not knowlingly use any such material but aluminum looks like aluminum and mistakes can occur!

Randy Cuberly

5083-H116 which is the standard aluminium for boat building is pretty close to 6061-T6.

5083 H116 - http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=MA5083H116
6061 T6 - http://www.matweb.com/search/datasheet_print.aspx?matguid=1b8c06d0ca7c456694c7777d9e10be5b

[John Leidle]

   For sure end grain balsa require a lot of epoxy because it  soaks it up like a sive  the guy I worked for in high school tried it as a replacement for foam to stiffen transoms, decks , etc in a boat. not enough presoak on the end grain & you have a dry layup. Which equals poor bond & delamenation. I'll bet a nickel some of the bent , collapsed aluminum is from the crash.
       John L.

[Brett Buck]

As previously noted, my prototypes, and the versions I made to test after this incident, would take the 80 lb pull test with no balsa at all, and I could lift myself off the ground with the complete design as specified. The failure mode of the "no balsa" types were as shown, buckling in the arm , but only at the inside edge, the outside edge was still straight, being under tension.

   It does take a lot of glue - this design was never intended to save weight - and it certainly requires proper aluminum gluing techniques as previously described. My test parts could be delaminated only when I bent one side of the "fork" and clamped it in a vise, and grabbing the other side with vice-grips and heavily pulling on it, while also bending/curling it. Large chunks of balsa remained on the aluminum. Note Chris' picture, one side had a bit of wood/glue stuck to it, the other looks like it came out of the rolling mill minutes earlier- no bond whatsoever, and no apparent surface prep.

    Of the premanufactured versions I subsequently acquired, I performed similar tests, but noted that just trying to assemble them with the hardware provided required forcing the spacers in which started delamination even before a load was applied. The grain ran parallel to the plates, not cross-grain, and they failed around 40 ish lbs much as shown. I also had a few of the early ones where there were large cutouts made to "lighten it up", those failed at very low tension. I didn't test the hardness, but the faces looked like aluminum strip flashing and was much softer and easier to bend.

     Note that I also have one made of .020 titanium face sheets. Cutting that with tools I have in my bedroom closet was a fun afternoon, and provided nothing particularly useful over the 6061-T6 versions.

    Again, I am sorry if anyone had problems with this, particularly Chris. I learned (actually reinforced) a very valuable lesson - *never, ever* cede control of a process or product that I am associated with in any way. The same thing happened with the Infinity plans, they got out against my better judgement, and now I have people building "Infinities" with Trivial Pursuit wings or with "better" features like flat pointy stabs, then complaining about them not flying properly, same with 20FPs - 'no power' - after they toss the muffler "to save weight" and put in ST spraybars. Same with another, er "activity" that got out of my control.

     That's why I am *never* going to publish plans for the Infinity for real, too many people will "fix" it and then complain it doesn't work.

     Brett

[John Leidle]

  I built a bell crank as discussed & I pretty much figured mine is bullet proof. The design is sound providing it is assembled correctly. Different adhesives for different folks I hear some people say,,, when we rebuilt  the Atlas Van Lines unlimited hydroplane that Bill Muncey crashed in in 1981 in Mexico anything structural such as sponsons, deck we used Hysol Epoxy no screws only  clamps , weights & clecos . Layups such as fiberglass parts, fiberglass over the deck we used Systems 3 epoxy. These were not ideas dreamed up by me they were the calculated plan of Crew Chief Don Mock & original design genius by the name of Jim Lacero.  This is a 5,200 pound boat with a 2000 plus cubic inch  V12 Rolls Merlin pounding the water at 185 MPH .
   I doubt sub standard adhesives would hold Brett's design together very long.  I have maybe 75 flights on my bell crank.