# Thrust plates?

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#### ttabbal

##### Well-Known Member
I'm evilly plotting to do an L3 certification flight next summer. The kit is on the way, Wildman Ultimate Darkstar. I'll do a build thread on it once I get more parts so there's something to show. For now I have a question. I like the look of the thrust plates that are out there. While I don't doubt The Wildman or his kit, I like the look and idea of the plates. Other than some weight on the tail, which I'll sim with and ensure CG is good on the real thing, are there downsides to be aware of? The cert flight will be on 75mm, so I'll have a 98mm Aeropack retainer and a 98-75 Aeropack adapter in there.

#### ColumbiaNX01

##### Red blooded white American male
Thrusts plates are great. In reality not necessary needed. For example a rocket with through the wall fins. A rocket with 3 fins; 6 fillets on fin tabs and motor tube. 6 fillets on the inside on fin tabs and airframe. Then have 6 fillets on the outside. Plus foam the fin can with expanding foam. Do all that locks everything in, job done. It is not going anywhere. I built a full scale fiberglass Amraam this exact way and flew it on a O3400. Do what you want but not required.

#### fyrfytr310

##### Well-Known Member
I love the plates Mike Fisher has made for me. In fact we are working together on a 5"x98mm unit right now!

#### Titan II

##### Well-Known Member
Love mine. The little extra weight is not necessarily bad. This particular rocket is properly balanced without adding anything to offset the plate. A bonus is 12 perfectly aligned and threaded holes for the Aero Pack retainer.

#### fyrfytr310

##### Well-Known Member
Love mine. The little extra weight is not necessarily bad. This particular rocket is properly balanced without adding anything to offset the plate. A bonus is 12 perfectly aligned and threaded holes for the Aero Pack retainer.
Your bonus is my primary lol. Nothing causes me more stress than drilling all those dang holes which have to be pretty precise...

#### OverTheTop

##### Well-Known Member
TRF Supporter
If you use an Aeropack-style MD retainer and put the thrust at the front of the motor tube the thrust plate doesn't have to take any thrust at all.

Then it can just look good.

#### fyrfytr310

##### Well-Known Member
If you use an Aeropack-style MD retainer and put the thrust at the front of the motor tube the thrust plate doesn't have to take any thrust at all.

Then it can just look good.
View attachment 306483
Do you have any build threads with the MD retainers in use?

#### OverTheTop

##### Well-Known Member
TRF Supporter
Do you have any build threads with the MD retainers in use?
Here you go (beer is for scale):

http://www.ausrocketry.com/forum/viewtopic.php?f=6&t=4612

I also used the same method on my Velociraptor R. It keeps the back of the airframe less in compression, which I think is not a bad thing, given how much better composites are in tension vs compression.

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#### ttabbal

##### Well-Known Member
Your bonus is my primary lol. Nothing causes me more stress than drilling all those dang holes which have to be pretty precise...
I can do it, but I don't LIKE to do it... I'll admit, that is one reason I'm considering adding one. The cost isn't that much on a project of this size, and in theory anyway, I could swap it around if I make more 6"/98mm rockets, and who doesn't want more of those?

I don't think it's required for safety etc, the rocket will hold up to the forces I have in mind, no N2000 or similar. Though I expect it could handle that. My reasons for being interested are..

1) Bolt the retainer on, easy stuff...

2) Looks..

3) Distribute the thrust load. While not required, it seems like the "right" way to do it, all other things being equal.

It sounds like weight is the only downside people see to them, and cost. But if I'm going to burn $350 just to fly it once, I can cough up another$70 for the plate to make assembly easier and to add to the looks of the bird.

Is there some reason to avoid putting the thrust on the plate and/or body tube that I'm missing? It seems like it would be better than the shear force on the MMT/CR/Fin joints.

#### fyrfytr310

##### Well-Known Member
Other than what you have already stated/observed, none that I can think of.

#### OverTheTop

##### Well-Known Member
TRF Supporter
Thrusts plates are great. In reality not necessary needed.
Whut?

The top statement is correct

#### rharshberger

##### Well-Known Member
Thrust plates can be lighter than foaming the fin can which is a plus in my build theory, yes they look good. Their most important functions though are to transmit the thrust directly to the airframe along its strongest axis and to reduce loads on the CR to airframe joint and fin fillets (why put heavy fillets and heavy foam in if it can be built lighter), they also protect the rear of the airframe from damage.

#### cherokeej

##### Well-Known Member
Your bonus is my primary lol. Nothing causes me more stress than drilling all those dang holes which have to be pretty precise...
Y'all might consider investing in a set of transfer punches. They make the job considerably easier.

#### neond7

##### Sky Pirate
TRF Supporter
I have used the SCP thrust plates on a few of my builds.

I do wish they came in more colors, but they still look really sharp and fit the Aerotech flange perfectly!

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#### NateLowrie

##### Well-Known Member
I'm evilly plotting to do an L3 certification flight next summer. The kit is on the way, Wildman Ultimate Darkstar. I'll do a build thread on it once I get more parts so there's something to show. For now I have a question. I like the look of the thrust plates that are out there. While I don't doubt The Wildman or his kit, I like the look and idea of the plates. Other than some weight on the tail, which I'll sim with and ensure CG is good on the real thing, are there downsides to be aware of? The cert flight will be on 75mm, so I'll have a 98mm Aeropack retainer and a 98-75 Aeropack adapter in there.
I made the thrust plate for my Formula 200. 8" to 98mm and it weighed 1.6 lbs, which is about 1/3 of the weight foaming the fin can would be. It had mounting holes for the 98mm aeropack and worked out really well. I am actually thinking of producing a line with integrated motor retention so you wouldn't need the aeropack. Would that be something you would be interested in?

#### ColumbiaNX01

##### Red blooded white American male
They do serve a purpose, but on 98% of rockets dont need if built a certain way. yes, for those super high thrust motors then a thrust plate is extra insurance. I used a thrust plate on a O3400 5" airframe. Looking back was it necessary for success, no but just looked slick.

#### ttabbal

##### Well-Known Member
I made the thrust plate for my Formula 200. 8" to 98mm and it weighed 1.6 lbs, which is about 1/3 of the weight foaming the fin can would be. It had mounting holes for the 98mm aeropack and worked out really well. I am actually thinking of producing a line with integrated motor retention so you wouldn't need the aeropack. Would that be something you would be interested in?

That's a nice looking plate. I would be interested in one with motor retention, so long as I could use or was provided an adapter for 98-75 so I could use the motor I have in mind. I my case the plate would need to be 6" to 98mm. I can get exact measurements for ID/OD next week when the kit gets here, or I'm sure Wildman has them.

That's another point I hadn't considered, weight vs foaming the fin can. And since I haven't bought the foam yet, that helps balance the cost.

#### Lowpuller

##### Well-Known Member
What are the little things sticking out between fins on that gold fin can?

#### Bat-mite

##### Rocketeer in MD
What are the little things sticking out between fins on that gold fin can?
Looks like a taped-off rail button to me.

#### Nick@JET

##### Well-Known Member
I also did for easy installation, great product - Nate's looks great too. My Ultimate QCC (started as a darkstar) came in at 72 lbs loaded on the pad - thrust plate not going to affect the weight unless you look at saving weight on every component and go with that attitude. I prolly could have save 3-5 lbs if I would've started with that attitude but my rocket isn't an Altitude buster - I want to see the entire flight so wasn't worried about weight

#### Nick@JET

##### Well-Known Member

There is a sexy factor but that wasn't my reason.

#### NateLowrie

##### Well-Known Member
That's a nice looking plate. I would be interested in one with motor retention, so long as I could use or was provided an adapter for 98-75 so I could use the motor I have in mind. I my case the plate would need to be 6" to 98mm. I can get exact measurements for ID/OD next week when the kit gets here, or I'm sure Wildman has them.

That's another point I hadn't considered, weight vs foaming the fin can. And since I haven't bought the foam yet, that helps balance the cost.
I am actually looking at a line of plates. I will get back to you in a few days with cost.

Regarding the plate, another plus is it makes the backside of the rocket a lot easier to assemble especially if you are using the flanged aeropacks.

#### Fearoflightning

##### Well-Known Member
I will be building an ultimate wildman for my L3 and was wondering the the same thing as OP, but I plan to eventually fly an N10,000 in it. I imagine the thrust plate will become far more necessary for flights like those, but how much more necessary? Also, what different building techniques would I need to use to withstan the N10,000 without a thrustplate?

#### NateLowrie

##### Well-Known Member
I will be building an ultimate wildman for my L3 and was wondering the the same thing as OP, but I plan to eventually fly an N10,000 in it. I imagine the thrust plate will become far more necessary for flights like those, but how much more necessary? Also, what different building techniques would I need to use to withstan the N10,000 without a thrustplate?
If you build the wildman the way it's specified in the instructions it will handle the N10,000. You can use a thrust plate for added insurance, but it's not strictly necessary.

#### Nick@JET

##### Well-Known Member
Thats just simply awesome Nick. What kind of clear coat did you put over that?
Thanks - Automotive clear (mixed 4:1 with same maker hardener) over Duplicolor Pearl white rattle can - purchased from Napa applied with an HVLP paint sprayer @ 20 psi.
I haven't polished the booster yet - not sure if I will so there is serious orange peal. With white base not as noticeable. If you end up using apply Wet, don't mist it on like I did. I'm no Nathan but am enjoying making my bigger birds look better

#### Binder Design

##### Well-Known Member
I love the plates Mike Fisher has made for me. In fact we are working together on a 5"x98mm unit right now!
Thanks! I'm able to leave them thinner because I use steel threaded inserts and don't need to rely solely on the aluminum. And the threads won't wear out if you have to switch your retainer back and forth between rockets. And I can dye them any color or polish them. I can even do splash anodizing for a bit extra. Just don't ask for red.

Special order only, you supply tubing specs. Too many different tube sizes to try to stock these in every size.