Folks,

After a very long time, spent time building a balsa model and this thread is because of this experience. There are few basic topics I wish to put up to the members for discussions

1) Balsa vs Foam
The finish of foam model - even if covered with cloth/PU etc. is very different from the finish of a balsa model. The controls have a different degree of rigidity. So does this make an impact on the flight characteristics?

The choice of glue vis-a-vis engine
I have noticed that IC engines vibrate a lot as compared to the brushless motors. Now, does this vibration have an impact on the joins? For example, a wood join using Fevicol would have different holding capacity and longevity as compared to a join using Feviquick (CA). So if this is a cause for concern, then the choice of glue becomes important, but then again there is a weight issue to consider. So what are the options and/or tradeoffs?


regards
Pankaj

ps. We often lament the lack of meaningful discussion on this thread, now let us see if this thread get attention amidst all the commercial activity that goes on.

Pankaj, I agree that Balsa flies better. This has been my own experience. Nonetheless, corro and foam models do fly well enough for up to intermediate flyers, and offer a decent trade-off viz. ruggedness, cost, ease of building and repair

On glues, for wood I would use cyano, except for joints subject to more stress and/or vibration where I would use epoxy. On corro, I use SR 998 or Araldite SR. Limited experience with foamies, but I have used a combination of foamsafe glue and a hot glue gun.

With adhesives, keep the layer thin and even, and don't worry too much about the weight. No point in having an extra-light plane that falls apart

Quote from: sanjayrai55 on September 10, 2013, 02:43:26 PM
On glues, for wood I would use cyano, except for joints subject to more stress and/or vibration where I would use epoxy.

How does one differentiate where there is more or less vibrations? Once the IC starts, the entire model vibrates.
The question on glue, was more from the ability of the joint to remain joined :-)

In very limited experience with balsa, i have seen that cyno sticks fast within seconds, but just with some jerk it, fall apart or leave the joints. Whereas fevicol takes time but sticks for longer time..

In extensive experience with balsa, there are different types. One is soft, and very absorbent. Cyano works great on this, but you have to use slightly more. The other is hard, and does not absorb much. This with cyano will form a very thin adhesion layer, and 'can' pop open, but it has never yet happened to me - the balsa breaks first.

Old stickfast type glues work great on wings and tail - they are not methanol resistant, and cannot be used wherever nitro fuel may contact

On vibrations: any, and I mean any, reasonably designed nitro plane will have very low amplitude and frequency of vibration except in the immediate vicinity of the engine. Your question is superfluous, being adequately answered earlier.

Quote from: sanjayrai55 on September 10, 2013, 07:21:30 PM
Your question is superfluous, being adequately answered earlier.

The comment is quite harsh. Wonder what prompted it. Then there are discussion on "why people are afraid to post"

My apologies if you found it harsh. I merely like to be precise.

I don't think your comment 'Then there are discussion on "why people are afraid to post"' is warranted - it appears to be a personal attack on me and my character. As every week I receive on an average 2 or more PMs asking for help, which I reply to the best of my ability, it is a strange aslant accusation.

Incidentally, I have taken the trouble to post replies to your queries, in good faith. Lack of appreciation is not unexpected, nor do I reply expecting this appreciation, but crassness leaves a bad taste in the mouth.

Two points.
#1. As mentioned in the first post, i was wanting to have a discussion on the topic from all scratch builders on their choice of materials. When i had started on this journey, simple things were difficult for me to understand. That time i do remember likes of Anwar, Sai, Izmile and host of others pitching to clear doubts and that too with patience for a newbie. Topics like these may have been covered in other forum, but the idea was to put an effort in building a knowledge base here as well. From that perspective, I have been posing questions to get fellow builders to respond.

#2 while i appreciate your posts and willingness to help, still felt the comment was harsh and unprovoked. If you felt that you had adequately addressed a question earlier, you could have chosen to ignore my question or pointed that it has been done so.

Reading your comment, one thought came go mind was a thread on why people do not post so i had posted my comment. Last thing a newbie would want to hear is a more experienced hobbyist making a comment about a question being superfluous.

Personally in my professional world, I like being a mentor where i need to be patient while imparting knowledge. If you don the mantle of a mentor, then I guess you cannot be judgemental about your pupil's intellect.

Pankaj

Adding materials for boats here... like pankaj...I had tough time selecting material for  boats.

Balsa: my personal experience. . Boat does not need this expensive material to build. Further more it needs all the treatment as fiberglassing. Again the motor and stuffing tube vibrations can be felt All over the body.

Sunboard: very rigid. Although heavier than Balsa sits the purpose well. No need top waterproof this material as well.Absorbs motor vibrations very well. Needs to be reinforced at places of hardware installations such as rudder.
Foam : easy to build. But needs to be fibreglassed. Drawback.... internal surface Also needs epoxy treatment before hardware installation.

@Rooster. Can Sunboard take in vibrations of Glow engines?

Havent used engines so far...so cannot comment on this.

I used 5MM Coro to complete my first flying wing and it vibrates and gives lot of sound even with a small Emax cf 2812 motor. switched to a 10x7 prop and the whole body doesnt even remains in shape, went out of trim in flight. Just got a used Highwing balsa model from one of my friend with JBA 46 engine and found the vibrations are quite less with the same 10x7 prop. so in my opinion, balsa is best for Glow. but Coro is fuel resistant.

Rooster boss! Long time no see

I have observed that Sunboard does have a tendency, albeit minor, to absorb water and swell. As we normally paint it, it is not a problem.

V2 Eagle; I've built 6 corro models, 2 nitro (46 & 55) and four electric. Never experienced a vibration problem yet. I do use a ply (8 mm upwards) firewall, and use Fevicol SR 998 or Araldite SR (Rubber based adhesives which flex slightly)

Oh, talking about corro; it comes with a very thin layer of silicon mould release agent (part of the manufacturing process) This should be removed. Some people 'flame' it off, I use fine grit sandpaper + a wipe with NC thinner.

Pankaj, I have read through your diatribe and failed to see what you are trying to state that you haven't already. If having the last word is important to you, so be it.

Calling Anwar/Moderator. Please delete my posts #5 and #7 and this one. I do not think it is worth preserving these posts.....

Sanjay Sir, should try your recepie with coro, i use Anabond and never experienced any pop open problem, and my problem with coro is more of sound and flex, the vertical fins flutters a lot in flight, reinforcement isnt even worth . any ideas?

Put wooden skewers in the flutes. 2 are enough for the vertical stab. No flutter. Flutter is distinct from engine-caused vibration. The ailerons are particularly susceptible. Trim the corners. You will find details on spadtothebone.net in 'tips and tricks'