Overbuilding

[uncle_vanya]

I think the best quote I ever heard was in a special on PBS about a bridge being built. The bridge was a large suspension bridge somewhere in the midwest. The engineer was asked about the build and he said:

Any engineer can build a bridge to hold any load. The trick is to
build it so it JUST BARELY holds it within the safety margin.

The point I am trying to make is that optimization of the required flight characteristics vs. the cost/complexity/risk/etc. is very important. Often I think that the tendency is to overbuild without asking what the required characteristics are.

A good example of my complaint is that a large number of Level 1 fliers are being advised to use fiberglass.

A good example of the opposite - are bowling ball lift competitions - here optimization seems to be key to even placing in these competitions.

Don't get me wrong - I am guilty of this myself. I'm just throwing this out to discuss.

 

[uncle_vanya]

BTW... some of my interest in this comes from my father. I learned at an early age that his mechanical skills were more limited by his approach to them than by real limits.

Favorite quotes:

Hand me the corrections. (His word for instructions)

If one is good, two is better. (In reference to building something or medicine or cooking... )

 

[ben]

Originally posted by uncle_vanya
BTW... some of my interest in this comes from my father. I learned at an early age that his mechanical skills were more limited by his approach to them than by real limits.

Favorite quotes:

HAHA I like that "hand me the corrections"

If my dad can't get something to work he says "looks like we don't need (insert item here) that bad"

thanx, Ben

 

[uncle_vanya]

Originally posted by ben
HAHA I like that "hand me the corrections"

If my dad can't get something to work he says "looks like we don't need (insert item here) that bad"

thanx, Ben

In dad-speak those are

spare parts

 

[plasticpaul]

I do believe I am the poster child for OVER CONSTRUCTION !!!!!

This is something that has only surfaced lately and is in part due to our fields ceiling and size. My big thing is when I roll my tubes. I tend to build them pretty stout !!!!!

 

[PopRocket]

One common example of overbuilding is in fin attachments. Is it better to have a fin break upon hitting the ground because it is so firmly attached or to have it simply pop off. The latter is much more easily repaired. Of course ideally the rocket lands gently enough that the fins are unharmed...

 

[uncle_vanya]

Originally posted by plasticpaul
I do believe I am the poster child for OVER CONSTRUCTION !!!!!

This is something that has only surfaced lately and is in part due to our fields ceiling and size. My big thing is when I roll my tubes. I tend to build them pretty stout !!!!!

Yes - ahem... while true you are not the poster child. Your fins are made from 1/8 inch ply and are not fiberglassed with 10oz cloth for a level 1 bird.

Remember - I fly with you! Your fins are also BIG and your birds - while heavier than required are optimized for our field. If you wanted to you could make them thinner and lighter - but then if your rocket failed on a dual deployment and crashed it would probably survive - oh wait, that already happend!

My level 1 bird dropped from a high place and went crunch. But mine was made from paper (cardboard) and not glassed.

 

[BHP]

Originally posted by uncle_vanya
I think the best quote I ever heard was in a special on PBS about a bridge being built. The bridge was a large suspension bridge somewhere in the midwest. The engineer was asked about the build and he said:



The point I am trying to make is that optimization of the required flight characteristics vs. the cost/complexity/risk/etc. is very important. Often I think that the tendency is to overbuild without asking what the required characteristics are.

A good example of my complaint is that a large number of Level 1 fliers are being advised to use fiberglass.

A good example of the opposite - are bowling ball lift competitions - here optimization seems to be key to even placing in these competitions.

Don't get me wrong - I am guilty of this myself. I'm just throwing this out to discuss.

Well said. And I agree.

Overbuilding seems to have become the norm. I've said it many times before that the 'standard' materials used in rockets are very strong in the ways we load them in our rocket flights. Every time we add a little strength we (usually) add weight that then requires a stronger, heavier component to take that load. It's a vicious circle.

Of course there is a place for the high tech stuff but for general sport flying I'm convinced paper tubes and plywood fins are all that's needed.

Build 'em to fly - not to crash.

 

[uncle_vanya]

Originally posted by PopRocket
One common example of overbuilding is in fin attachments. Is it better to have a fin break upon hitting the ground because it is so firmly attached or to have it simply pop off. The latter is much more easily repaired. Of course ideally the rocket lands gently enough that the fins are unharmed...

I'm torn on this one. I like it if the fins don't fall off - and worry about in flight losses - but also landing losses. I have a Blue Ninja that drove me nuts. Every flight it lost a fin. Finally I found a glue that worked but the entire fin attachment methodology drove me crazy. I still have a Rubicon sitting on the sidelines - seven flights lost a fin every time. I finally misplaced a couple and it's sitting around dead in the water until I get around to making some new one's. I think that these are designs that would benefit from improved fin attachments.

My pet peeve... glue.

 

[uncle_vanya]

I would love to do my level 2 project using no expoxy. I know it is possible - at least one level 3 has been done this way.

But - sigh - I'm lazy and sloppy and epoxy works really well to cover up problems in fit. I also like longevity in a rocket and while wood glue is going to work for almost the entire build - the motor mount takes a lot of heat. Wood glue likely would not hold up in repeated flights in the motor mount due to the heat. The fins and other joints should be fine.

My latest HPR bird was built with Polyurethane glue and wood glue except for the motor mount. It flew nicely without any problems on a large H.

 

[SpartaChris]

Funny this discussion comes up. I was just discussing with some friends about using wood glue in a high power build instead of epoxy. Cost isn't really the issue so much as convenience (I have it at home) and ease of use (I don't have to mix it, just shoot and scoot.) After doing some research on my brand (Titebond II), it had an incredible strength rating that rivals epoxy (3750 PSI at room temperature), even after being heat soaked at 150 degrees "overnight" (1750 PSI), which I presume means at least 6 hours.

https://www.titebond.com/download/pdf/ww/IIPremiumTB.pdf

So I have gone ahead with the use of it. I figure that it is going to be stronger than the two components it is bonding anyway, so it should work just fine. The rocket will be flown on a K700 for it's maiden flight and will also use up to an L730.

Construction began this past weekend. I'm not going to be using it for fillets or for trying to bond to fiberglass, but for bonding wood-like products together, it should work fine.

 

[uncle_vanya]

Originally posted by SpartaChris
brand (Titebond II), it had an incredible strength rating that rivals epoxy (3750 PSI at room temperature), even after being heat soaked at 150 degrees "overnight" (1750 PSI), which I presume means at least 6 hours.

https://www.titebond.com/download/pdf/ww/IIPremiumTB.pdf

So I have gone ahead with the use of it. I figure that it is going to be stronger than the two components it is bonding anyway, so it should work just fine. The rocket will be flown on a K700 for it's maiden flight and will also use up to an L730.

Construction began this past weekend. I'm not going to be using it for fillets or for trying to bond to fiberglass, but for bonding wood-like products together, it should work fine.

To clarify - you will use this in the motor mount construction? Cool - I may join you in this idea soon. I have several possible L2 projects cooking and while one may require epoxy (G10 and phenolic aren't going to bond to each other all that well with wood glue) there are others that may lend themselves nicely to this.

Does Phenolic bond well with wood glue?

 

[hokkyokusei]

Originally posted by uncle_vanya

The point I am trying to make is that optimization of the required flight characteristics vs. the cost/complexity/risk/etc. is very important.

"Perfection in engineering is achieved not when there is nothing left to add, but when there is nothing left to take away."

 

[SpartaChris]

I am using it with my motormount construction and to bond my fins in place.

I've never tried it with phenolic, but I imagine that if you sand it a bit, it can penetrate and should work fine.

 

[uncle_vanya]

Originally posted by hokkyokusei
"Perfection in engineering is achieved not when there is nothing left to add, but when there is nothing left to take away."

That's a great quote - it it original?

 

[hokkyokusei]

Originally posted by uncle_vanya
That's a great quote - it it original?

I wish! No, Antoine de Saint-Exupéry. I think I first saw it quoted in a software engineering text book.

Another quote I like is "Make everything as simple as possible, but not simpler" - that's Einstein.

 

[denverdoc]

This is a great thread IMO. Overbuilding is rampant, whats scarier in my opinion that the overbuilding is taking a new direction--buying very exotic and expensive materials that are not needed. Engineering is about getting the job done at a reasonable price point and safety margin. Thers a Deuce thread on HPR that gets into it but is tangentaial. For a mach 3 flight noone will doubt your reasoning for heading straight to CF, get the best grade you can.

But others are advocating for HC/CF fin material for a lazy flier. This makes no sense to me. You gotta heavy rocket based on sonotube, and are thinking honeycomb/CF fins?
John

 

[SpartaChris]

Amen to that! Half the time, Sonotube doesn't even need glassing.

I think folks need to learn how to build for what they fly. If I am going to try and push the envelope with every flight I make, I will certainly look closer at other materials. However, my flight goals are usually bigger/heavier rockets for a slower and lower flight, so I generally use sonotube and plywood and make my nose cones out of foam from Home Depot. You can put together an M powered rocket for less than $100 that way.

 

[BobH48]

Originally posted by BHP
Of course there is a place for the high tech stuff but for general sport flying I'm convinced paper tubes and plywood fins are all that's needed.

Plywood fins? You're overbuilding again!

 

[melvyn]

Originally posted by ben
HAHA I like that "hand me the corrections"

If my dad can't get something to work he says "looks like we don't need (insert item here) that bad"

thanx, Ben

LOL!! Must be a dad thing...

My dad sometimes says "lets look at the destructions".

 

[smurf]

Good thread....here's some of my thoughts on the subject.

1. Durability vs performance. If you are attempting to set a record you only really need to fly once or twice. If it's a sport flyer then you want to fly more than that. If you are flying on the sod fields of the east then straight ply fins are probably good enough...if you fly on the playa out west then the rocket need s to be able to survive a little rougher treatment on touch down. I don't think there is anything wrong with sacrificing a little altitude for durability.....don't get me wrong, I'm not into the flying bricks but building a sport rocket that's on the very edge of a shred every flight is not my scene....I shred enough high performance rockets as it is!

2. Learning. A lot of people pooh-pooh a lowly level one flyer putting a layer of fiberglass on his rocket.....you gotta learn sometime and the rocket with the mighty M motor is probably not the time to give fiberglassing your first shot.

I treat each rocket as a learning experience. I wanted to learn more about carbon so I used it in the construction of a rocket. Now that I know more I only use it where I need the characteristics it gives (the price of cf these days kind of drives you to that anyway)....I only hope that someday I reach the level of carbon fiber artistry some of the people that post here achieve but I would never get there if I didn't "overbuild" a rocket once in a while to develop the skills.


I saw a thread a while back where someone wanted to build a mach buster without using fiberglass (I think he did use epoxy but am not sure). It's cool to try to work down to the absolutel edge of the envelope as far as materials go but that is for record attempts or if you just want to do it as a personal achievement. I build plenty of rockets on the edge but I also want some that I can fly over and over again even after my latest "engineering marvel" just turned into so much colored confetti.

The fun part of this hobby is getting to try new ideas and techniques.

I guess my bottom line is while I don't advocate building every rocket as a flying tank, I also don't think everyone should be on the edge for every flight also. There is a happy medium that is somewhere between.

 

[Stymye]

Smurf,I am totally with you on the durability issue

but I'm not on the idea that we all should learn to fiberglass and eventually "advance" to exotic carbon fiber artistry.like thats the ultimate goal

mabey some people consider that their goal ..but it's not for me

I feel it's harder and more important to learn how to build a light yet strong structure with accurate fit between joints and planning.
thats engineering !

building a cf rocket may look cool but it's not really that hard, you just need the right tools, glassing is easy,again just a matter of the right tools and a bit of know- how.

A person could build a rocket with no glue at all.. now >that< would be far more impressive to me personally. thinking outside the box... bottom line- it's not all about materials

 

[denverdoc]

Originally posted by stymye
Smurf,I am totally with you on the durability issue

but I'm not on the idea that we all should learn to fiberglass and eventually "advance" to exotic carbon fiber artistry.like thats the ultimate goal

mabey some people consider that their goal ..but it's not for me

I feel it's harder and more important to learn how to build a light yet strong structure with accurate fit between joints and planning.
thats engineering !

building a cf rocket may look cool but it's not really that hard, you just need the right tools, glassing is easy,again just a matter of the right tools and a bit of know- how.

A person could build a rocket with no glue at all.. now >that< would be far more impressive to me personally. thinking outside the box... bottom line- it's not all about materials

I agree until the very last sentence, not about materials? It has everything to do with materials. Try making a rocket out of a bed sheet?? The trick is using the right materials and adhesives at the right price to withstand flight stresses. I have long sought a glueless rocket. Estes manages, and I have seen some nuts and bolts cnstruction do fine on big rockets, but that adds weight as well.
John

 

[Stymye]

sorry I meant to say not "all" about materials.
thats what I typed atleast, or meant by that

 

[Bigander]

Originally posted by smurf
Good thread....here's some of my thoughts on the subject.

1. Durability vs performance. If you are attempting to set a record you only really need to fly once or twice. If it's a sport flyer then you want to fly more than that. If you are flying on the sod fields of the east then straight ply fins are probably good enough...if you fly on the playa out west then the rocket need s to be able to survive a little rougher treatment on touch down. I don't think there is anything wrong with sacrificing a little altitude for durability.....don't get me wrong, I'm not into the flying bricks but building a sport rocket that's on the very edge of a shred every flight is not my scene....I shred enough high performance rockets as it is!

2. Learning. A lot of people pooh-pooh a lowly level one flyer putting a layer of fiberglass on his rocket.....you gotta learn sometime and the rocket with the mighty M motor is probably not the time to give fiberglassing your first shot.

I treat each rocket as a learning experience. I wanted to learn more about carbon so I used it in the construction of a rocket. Now that I know more I only use it where I need the characteristics it gives (the price of cf these days kind of drives you to that anyway)....I only hope that someday I reach the level of carbon fiber artistry some of the people that post here achieve but I would never get there if I didn't "overbuild" a rocket once in a while to develop the skills.


I saw a thread a while back where someone wanted to build a mach buster without using fiberglass (I think he did use epoxy but am not sure). It's cool to try to work down to the absolutel edge of the envelope as far as materials go but that is for record attempts or if you just want to do it as a personal achievement. I build plenty of rockets on the edge but I also want some that I can fly over and over again even after my latest "engineering marvel" just turned into so much colored confetti.

The fun part of this hobby is getting to try new ideas and techniques.

I guess my bottom line is while I don't advocate building every rocket as a flying tank, I also don't think everyone should be on the edge for every flight also. There is a happy medium that is somewhere between.

dont know wat u said but amen to that brother!

 

[denverdoc]

Originally posted by Bigander
dont know wat u said but amen to that brother!

Then enroll in some community college courses, its not our problem you dont get it.
JS

 

[agrippo]

I like to build a strong rocket then try to shred it.

Andrew

 

[loopy]

Originally posted by uncle_vanya
I would love to do my level 2 project using no expoxy. I know it is possible - at least one level 3 has been done this way.

But - sigh - I'm lazy and sloppy and epoxy works really well to cover up problems in fit. I also like longevity in a rocket and while wood glue is going to work for almost the entire build - the motor mount takes a lot of heat. Wood glue likely would not hold up in repeated flights in the motor mount due to the heat. The fins and other joints should be fine.

My latest HPR bird was built with Polyurethane glue and wood glue except for the motor mount. It flew nicely without any problems on a large H.

Alot of times now, I'll use wood glue for the initial bond, then fillet with epoxy. Not so much for the strength of the bond, but just because (as you said) the epoxy fills all of the gaps and other problems with the finish. No problems so far!

 

[WillCarney]

On the overbuilt issue, a lot of my rockets are slightly overbuilt.

That has been an advantage on several occasions where my
rocket has come in without a main. My L3 attempt the main failed
but it was overbuilt and only needed repairs. Not bad since it
was 41 lbs after motor burn out and coming down on a drouge.

I also have several rockets I put bigger motors in as well. A 24
mm flying saucer is a good example. I have a flying saucer I put
a 24 mm mount into but it's too big for that size of motors. I
have flown it on a home made G EX motor.

Sometimes overbuilt can be an advantage.

William

 

[denverdoc]

Will,

No doubt. I think the reason some of us (myself, Robert DeHate, others) get so riled over the issue is that it can contribute to failure--in other words when a potentially 20#'er becomes 40, the stresses on everything double during deployment, leading to higher failure rates in many cases. Not suggesting that this happened with your L3. But if can.
John