Simple Decision Tree - Excel Spreadsheet

I have read many threads on priming and they all seem to start with, ?I have read many threads on priming??

The variety of concerns and opinions, which include: environmental, health, strength/durability, longevity, etc., offer too many options for the first time builder.

As a first time builder, with my RV-9A Empennage about to arrive this week, I will need to decide on a primer very soon.

To help myself and others in this quest, I think it should be a simple task to create an Excel spread sheet with simple criteria.

For example:
What humidity level do you live in? Dry, Average, Wet.
How much effort will you put into the process: Low, Medium, High.
Environmental Concern: Kill all who interfere, will bury larger animals, care about neighbor?s well.

The Excel spreadsheet should also consider weighting the personal choices. For example, are environmental concerns or gross weight your biggest effort.

In my case: High salt/wet environment, I don?t have the time, don?t care about weight, but my neighbors do have wells. So the spreadsheet should give me a high score on:

Yellow self etching sprayed on all interior surfaces.*

This should be an easy enough task to create if someone with extensive primer experience works with someone who knows Excel. .

John Edwards
RV-9A ? Empennage (on the Fed-Ex truck)

* Does that seem right?

A partial list, please add to the list:

Environmental Concern: Low, Medium, High
Ease of Application: Low, Medium, High
Weather: Dry, Medium, Moist
Salt in Area: Low Medium, High
Water Wells: Yes/No

On the other page of the Excel Spreadsheet:

No Primer Needed
<List of all primer options>

I can say I understand Excel very well and would be more than willing to work with someone on this but I am not sure I quite follow your idea yet.

If I understand right you want to have some kind of score that can be used to determine what type of primer to use. Is this assumption right?

If so, are you wanting to use your Low, Medium, High rankings to score? Then there would be a range of scores for the various types of primer. Whatever the score is you would then look at the range for these various primers to see which one to use. That is what I am envisioning this spreadsheet doing from your post.

It would be very simple to set up as far as the spread sheet is concerned but it will take a great deal of knowledge about the various primer solutions to come up with the appropriate scoring of the primers. The key is in the "judgement" of the primer expert as to what qualifies as easy to apply, environmentally friendly, toxic/non-toxic, etc..

If my math is correct, that's "only" 27 options for a poll (which sounds like a lot but isn't so bad imho). You might create a poll right here on VAF.

That Sounds Great

RVbySDI said:

If I understand right you want to have some kind of score that can be used to determine what type of primer to use. Is this assumption right?

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Yes, that's what I had in mind. On one side, you would have the various factors that would influence your decision: quality of protection needed, ease of application, health concerns, protective equipment needed, environmental concern, price, etc. The user would give a weight to each factor: Don't Care (0.0), Low Concern (0.8), Medium Concern(1.0), High Concern(1.2).

On the other side would be the list of Primers. Each would have it's own score on each of the above factors. (Primer expert needed to set these, say on a score of 0-10). There would be a total score column for each Primer.

The calculation would be something like:

Ease of application: User selects High (1.2 weight). Each Primer's ease of application factor (1-10) is multiplied by the weight and added to that Primer's total.

At the end, each Primer would have a total score and it could be sorted.

The final product's numbers could be tweaked for years on this forum and new Primers added. It should not be considered definative by any means, however, it would give a starting place to look at the top three for example. It would be an excellent starting point for newbies like me, and cut down on Primer related questions to the group.

John Edwards
RV-9A - Empennage

All well and good, but...

Primer is an emotional subject. I have found that whenever you try to create a spreadsheet to make a decision for an emotional choice, if the spreadsheet does not give you the answer that you wanted, then you just ignore the spreadsheet, and choose what you were going to choose in the first place. The spreadsheet is only there to make you feel good about the decision that has already been made.

I want to see one person who fills in the spreadsheet and says "you know I wasn't going to prime everything, but now after I see the numbers, it looks like I had better order some more paint..."

I don't want to hinder your project, but let's be honest.


Tracy.

But what about me?

thallock said:

Primer is an emotional subject.

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True, and no matter how accurate the results of the spreadsheet, many would berate its findings.

The purpose was for people like me. I don't have a clue on what Primer to use. And if I ask online, I will start yet another Primer war. I was looking for a more scientific approach*.

Perhaps I would be better off to ask the question and let the comments fly...

My future RV would be tied down where there is a constant warm, moist, salt air breeze. I am worried about protecting myself from heavy metal, and I don't want to contaminate my neighbor's water wells. What should I do?

John
RV-9A - Empennage

* Physicist/Software Engineer - worked on Shuttle, Hubble, Mars Reconnaissance Orbiter, Mars Phoenix Lander (soon to launch), F-22, Trident, etc.

For your personal knowledge perhaps the spreadsheet would be a little too much to develop to get the answers you need. There are all manner of opinions on this subject so reading the threads in this Primers section may be more useful.

Here is what I have done. Since I was not interested in the complications associated with the two part sprayer primers many have used here, I went with the NAPA 7220 Self-etching rattle can primer (MarHyde is another brand of rattle can primer that many are using).

I chose the NAPA 7220

• because I found it on sale 1/2 price

• because it is easy to use

• because it does not present problems with setup and mixing

• because it is easy to use

• because I do not have to set up any elaborate spray booth for it

• because it is easy to use

• because I do not have to worry about mixing toxic chemicals

• because it is easy to use

• because I do not have to worry about cleanup of equipment

Oh, and did I mention that

• it is easy to use

Perhaps there are positives for using the two part spray with your paint gun type of primers but for my needs and desires the rattle can primer did what I needed it to do. YMMV. Good luck with your decision but whatever you decide, keep building.

Ok, John, as usual, it looks like I need to appologize, again.

I think what you are doing is a good thing, and I should not try to hinder what you are trying to accomplish with the spreadsheet. When chosing whether to prime or not, and if so, then what product to use, it is important to do the research, gather as much info as possible, and then make an informed decision. Whatever tool you use to help make that decision is not that important, it's the process of gathering the information and laying it out in front of you so you can make the decision that is important. A spreadsheet is as good as anything for this.

The problem is how you assign the weights to the spreadsheet. This is the gut feeling/emotional part of the process. There's nothing wrong with that, and the spreadsheet helps to point out what you think is important. So, it is a good tool to use.

As an example, look at what RVbySDI has done. He has a simple spreadsheet with 6 entries, each of which have a weight of 1, except for "because it is easy to use" has a weight of 5. Obviously, "ease of use" is important to him. Did he make the decision to use 7220 because it is easy to use, or did he make the decision because all of the positives taken together said 7220 was a good choice, and ease of use was high on the list? Doesn't matter, he made the decision based upon his own criteria, and the info that he gathered. I would, however, question his process, just a little, since there are no negative entries, but that's for RVbySDI to worry about .

So carry on, and sorry if I sounded like I was trying to discourage you from doing the spreadsheet. I think the spreadsheet is a good idea, and you should finish it and then publish it here, so others can use it.

Cheers,
Tracy.

thallock said:

I would, however, question his process, just a little, since there are no negative entries, but that's for RVbySDI to worry about.

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The negatives were not listed because . . . Ok, well I was trying to be a little bit humorous with my post. Maybe I should be a little more serious and explain my reasoning better.

It was important for me not to spend an extremely high amount of time and effort planning, setting up, spraying, cleaning up every time I needed to prime something. The rattle can method was truly the best choice for that. There are negatives such as perhaps the rattle can self-etching primers may not be as strong as the two part processes (although there is definitely a great deal of debate on that). Perhaps it may be more expensive (then again maybe not). Or, a myriad of other negatives that were weighed. However, it is true that the real decision was made as much on the ease at which I could apply the primer as was anything else. Since I am one of those individuals that does live in the Midwest, am one that does plan to have a hangar over my baby whenever it is not performing and am one that does not intend to subject my bird to adverse weather conditions unless it is absolutely unavoidable, then I felt the self-etching rattle cans would provide very adequate protection while allowing me to prime without a great deal of headaches.

I hope that helps to clarify my decision making process. Again as I stated in my original post: I don't think building the spreadsheet would be that difficult to do at all. The real power in the spreadsheet will be in the spreadsheet's ability to depict an accurate representation of the true value of each decision point. As Thallock has pointed out, these decision points will have some emotional aspect that will need to be factored in as well as some method to have some meaningful weight given to any other "technical" factors. Those things can only come from the "user" of the spreadsheet. If it comes from some pre-assigned "expert" and his/her judgments of the value of the various factors, the user of the spreadsheet will have to be willing to accept that "experts" weighting of the values.

2 part vs. rattle can

Has anyone taken parts primed with the etch/alodine/prime method and parts primed with a self-etching rattle can and left them side by side out in the elements for any appreciable amount of time? It would be interesting to compare two pieces of scrap which were primed with each method and left outside for about a year.

I remember about 10 years ago I was looking for some material property for work and I ran across a test report comparing the corrosion of various metals after 1, 2 and 5 years of exposure to the elements. The test pieces were bolted to posts right on the beach, I think it was somewhere in Florida. I can't remember whether or not they were primed. I'll look through my old files and see if I can dig it up.

John
Planning to build an RV....someday
VAF #130

Steve,

I too meant my comment to be humorous, but I forgot the happy face. Happy face has been added. Sorry.

Tracy.

You may be overcomplicating this decision, as many engineers like myself tend to do. Priming everything sounds like a lot of work when youre in front of the computer thinking about it, but its really a non event. Youre going to buff out the scratches in the aluminum anyway, therefore the first step of roughing up the piece is already done. Next you wipe it down with acetone..which takes seconds. And finally you shoot it with some primer. I use Marhyde self etching primer (rattle can) from Wicks Aircraft. This stuff works very well and should provide enough protection until we run out of crude oil. I spray outside in the summer and inside in the winter. Regarding health concerns, I bought the nicest paint/dust mask that Homedepot had for sale $40. It has dual filters and it seems to work great. Well thats my 2c's, good luck on the plane.

Rob

You're Right

rph142 said:

You may be overcomplicating this decision, as many engineers like myself tend to do.

Click to expand...

Yes, you're right, after looking at the variations in opinions (with humor appreciated), I?ve probably over analyzed it. It?s frustrating for a newbie, and I was just trying to help out the next person.

I?m now looking at getting a web site up and running for my build log, and if I do get a spreadsheet up and running on this topic, I will post it there. I will need to decide on exterior primer/paint in a few years anyway.

BTW, I decided on the primer I will be using, rattle-can Tempo self etch Zinc Chromate. Just because I think the yellow will look cool.

I appreciate eveyone's help...

John Edwards
RV9A - Empennage (inventory complete)