4 Bladed Props

Post by **dougl33** » Thu Dec 23, 2004 5:45 am

I thought it was Ronald McDonald. 1986 33 Bertram FBC Queen Elizabeth

Post by **Admin** » Thu Dec 23, 2004 8:44 am

quote:Originally posted by dougl33 I thought it was Ronald McDonald. 1986 33 Bertram FBC Queen Elizabeth Mmm, McHerman burgers! David Sumich Bertram33.com Forum Administrator

photo finish · Post by **photo finish** » Fri Dec 24, 2004 7:34 am

that is one big bug.....i am glad florida bugs dont have claws. Tim Stamm Photo Finish 1981 33' Bertram FBC

photo finish · Post by **photo finish** » Mon Jan 24, 2005 3:48 pm

nibral vs bronze I know nibral is stronger and wont ding or bend as easily as bronze but beyond that is there any other reason to justify the extra cost? Tim Stamm Photo Finish 1981 33' Bertram FBC

franklyprice · Post by **franklyprice** » Tue Jan 25, 2005 3:02 am

Tim, I know that when you go from aluminum to stainless(with smaller ,performance boats)you gain a noticable difference in performance. The reason is the stronger material allows thinner blades and they cut through the water better, blah,blah,blah. As far as bronze VS nibral? I don't think they take advantage of the material in this way, my impression is that it is just a little less likely to fail, probably a little less likely to corrode also. My boat came new with federal "equipoise" (bronze)and works fine. But someday , if I convert to diesels, I'm going for the nibrals. The fish will love looking at them. Frank Price

Bompapen · Post by **Bompapen** » Sun May 15, 2005 9:24 am

Hi I have a Convertible with 454 1.9:1 Trans. I install 4 blade 19x17 no cup props. The engines pass the max rpm by 200. Then I cupped, never try WOT. But my cruisse at 3200 20K to 21K. I personally dont like the cup. I take the props to the shop and make it to 19x18 no cup. I can test the boat next month and see what happen. David Vila

photo finish · Post by **photo finish** » Sun May 15, 2005 3:19 pm

why dont you like the cup? Tim Stamm Photo Finish 1981 33' Bertram FBC

Bompapen · Post by **Bompapen** » Wed May 18, 2005 1:50 pm

Hi Tim I dont like the cup because, When I paint the Prop the cup is filled with primer and antifouling and I lost about 1.5 Kt at cruissing speed . The other propellers I test (19x18 3 blades cup) adding 1 inch of pitch and eliminate the cup (19x19 no-cup) give me very close the performance and I lost less than 1 Kt when I painted . My boat cruisse faster at the same RPM and load . David

photo finish · Post by **photo finish** » Thu May 19, 2005 8:49 am

David , if the props are carefully painted that should not affect the cup....i personally do not like painting the props .i know alot of people reccomend that here in florida but the fact is the paint wears off quickly and unevenly .i would rather jump over and clean them now and then.also before you blame the cup make sure you are comparing apples to apples ...i can get a 1.5knott difference if i am going with the tide or not or wind or even if my windows are open or not. good luck, Tim Tim Stamm Photo Finish 1981 33' Bertram FBC

Bompapen · Post by **Bompapen** » Thu May 19, 2005 1:39 pm

Tim I dont like to paint the props too but here in the tropic the fouling is incredible heavy. I use ablative paint to the hull and hard epoxy to the metals. That way my props keep the paint longer. One time I not paint the props and in two weeks they look terrible, have vibration and lost a lot of performance. My friend is an owner of a prop workshop. We launch the boat after full bottom paint with the 19x18 cup no paint props, around 11:00 AM. I test the boat with 1/2 fuel tank, full water, all the regular stuff and two people including me. I measure the speed in calm water side wind with a GPS at 3200 rpm and get 22.6 KT max. We change to the spare twin props 19x18 cup but painted and test about one hour later with same load and conditions. The results 21.2 KT max. We change back to my redone 19x19 no cup painted original props, that my friend work and paint when I test the boat. The result 21.9 litle more than four hours later from the first test. I am very technical guy, the success of my bussiness depend on that . When I modify and test an engine I must do with same conditions for have the best real results on it. I do that for 19 years. By the way the windows of my boat still close during all test. David

photo finish · Post by **photo finish** » Thu May 19, 2005 3:01 pm

sounds like you know what you are doing..its very interresting that you lost 1.5knotts with the paint...just curious...was the rpms the same in all of the tests? Tim Stamm Photo Finish 1981 33' Bertram FBC

Bompapen · Post by **Bompapen** » Thu May 19, 2005 5:10 pm

The RPM was the same on all test on the tachs. When I buy the boat have a 3b 19x19 cup props but the rpm not reach the manufectured specifications. My friend tell me to eliminate the cup for gain that 200 rpm I need, I dont follow his advise because all boaters I know tell me to leave the cup. I ask he to do my way and not tell him why , you know is a good friend. A year later when paint the bottom, I tell him why I decide not to eliminate the cup, he insist to do this long test, I agree and use my best knowledge for have the best result on it. After we finish the test he told me why this happend. No matter how carefuly you paint a prop, the paint not accumulate at the edges. Each hand of paint and primer add about 0.010 inch. You have to paint at least two coats of primer in opposite directions and do the same with the paint. When you finished you added close to 0.15 inch of not smooth paint and the cup lost its original angle. I asqued him for what is the cup. The cup is for give you more speed at top end. I care for cruissing speed not top. He explained is better have a litle more angle all the way of the blade than a sharp at the end. Other advantage is at the dock, more pitch give you better response at same low rpm. The cup not work at that rpm. I am not an expert in props but I am very motivated to gain the best performance in everything and learn more every day. Tim I will test my new 4 blade next month, I buy from second hand almost new. They was 19x17 cup and change to 19x18 no cup. Let see what happend and I let you know. I join this forum for give and recieve any help or experiences that may help from other members . Thanks for any advise David Vila Bertram 33 FBC 1985

franklyprice · Post by **franklyprice** » Fri May 20, 2005 1:10 am

Tim, David definately thinks about props. Between the two of you , we couldn't get a better prop test for 33 berts in any magazine. I also doubt the factory ever did as much testing of different setups. How cool is that? Keep the info coming guys! Frank Price

CB35 · Post by **CB35** » Fri Jun 24, 2005 4:14 pm

Props work better with a cup, period. Also in most cases on these older boats three blades work better than four. I heard a lot of crap from prop salespeople about putting 4 blades on my 35B. Finally I told one guy I would only if I got an extra knot at 2450 rpms. I did I would pay for all the work if I didn't he would pay. No Deal was his answer. I talked to lots of guys with 35B's with four blade porps and not one can match my numbers. Either cruise or WOT. By the way my boats still turns the numbers Bertram put in the owners manual. I don't know about the 33B's I found out Bertram put a lot of work in setting up the 35B's with Cats. Oh one more thing Nibrals are the only way to go. They will give you an extra kt or so over bronze Federals. Never paint a prop with a brush. That has got to be one of the dumbest things I have ever heard. If you are in tropical waters with lots of growth just fall over the side every month with a green pad and do a little work. Charlie

Bompapen · Post by **Bompapen** » Thu Jun 30, 2005 12:49 pm

Work better, In my case cruise at the lower plane speed in the Atlantic Ocean with an average of 4 to 6 foot waves. Thats four blade give to me. I install longer tabs have a new 5.5kw D compact gen over the strainers in the front of the engines .Later a new 4 blade props. I can plane my boat 200rpm less with close to 2kt less speed than the 3 blades with the same setup on the boat. Thats is work better to me because I use my boat 99.9% of the time at cruise speed and half of that time directly to that size of waves.The 4 blade work better than 3 because have more DAR in the same DIA. Is more efective row with 4 small oars than 3 big. They have better balance and more even force with less stress to the blade . The cup not work well at low rpm for me. I still have my boat out of the water making full outside gelcoat job. When I launch the boat I can test the new setup. If I dont paint the props, In one month I can find shels in my props. My marina is very dirty and the closest beach is 20 min away. I have my boat since 1991 believe me I try everything. David